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docs_md/articles/brachial-plexus-anatomy_da14f802-58b5-447e-b850-2aa139bcb8ad.md
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---
title: "Brachial Plexus Anatomy"
docid: "da14f802-58b5-447e-b850-2aa139bcb8ad"
authors:
- key: "ddcc6243-2b09-4947-b051-fbe736e4cdec"
value: "Blake Riebe, DO"
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name: "Musculoskeletal"
slug: "musculoskeletal"
treeNodeId: "6236c1b2-2af5-420e-99d2-501dc8bc7552"
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name: "Anatomy"
slug: "anatomy"
treeNodeId: "f6e438ae-b8c1-43db-85c5-6c9bfe967bc2"
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name: "Shoulder"
slug: "shoulder"
treeNodeId: "4fe7f631-6d92-4a03-9ed1-b2be9e4a4273"
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name: "Brachial Plexus Anatomy"
slug: "brachial-plexus-anatomy"
treeNodeId: null
category: "Musculoskeletal"
cmeTopicId: "5dd8629f-11cb-45c1-8d7b-6069198d1f5a"
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imageCount: 25
lastUpdated: "04/02/26"
pageDescription: "Brachial Plexus Anatomy"
pageKeywords: "Musculoskeletal, Anatomy, Shoulder, Brachial Plexus Anatomy"
pageTitle: "Brachial Plexus Anatomy | STATdx"
enhancedTitle: "Brachial Plexus Anatomy"
type: "ANATOMY"
references: true
breadcrumbs:
- "Musculoskeletal"
- "Anatomy"
- "Shoulder"
- "Brachial Plexus Anatomy"
---
## TERMINOLOGY
- ### Abbreviations
- Artery (a.)
- Nerve (n.)
- Nerves (nn.)
- Muscle (m.)
- Vein (v.)
- ### Definitions
- Proximal: Toward body midline
- Distal: Toward fingertips
## GROSS ANATOMY
- ### 5 Subsections of Brachial Plexus
- Roots: Most commonly ventral rami of C5-T1
- C5: Dorsal scapular nerve branches directly from C5 root; contributes to long thoracic nerve
- C6 and C7: Contribute to long thoracic nerve
- Prefixed variation: C4-C8 distribution
- Postfixed variation: C6-T2 distribution
- Intrathoracic nerve of Kuntz variation: Sympathetic branch of T2 communicating with T1
- Trunks
- Upper: Confluence of C5 and C6 roots
- Suprascapular nerve, nerve to subclavius muscle
- Middle: Continuation of C7 root
- Lower: Confluence of C8 and T1 roots
- Divisions
- 3 anterior nerves: Innervate flexor muscle groups of upper extremity
- 3 posterior nerves: Innervate extensor muscle groups of upper extremity
- Cords (named for position relative to axillary artery)
- Lateral: Contributions from anterior portions of upper and middle trunks
- Lateral pectoral nerve
- Ansa pectoralis is communicating nerve between lateral and medial pectoral nerves
- Posterior: Contributions from posterior divisions of all 3 trunks
- Upper subscapular nerve, thoracodorsal nerve, lower subscapular nerve
- Medial: Continuation from anterior portion of lower trunk
- Medial pectoral nerve, medial brachial cutaneous nerve, medial antebrachial cutaneous nerve
- Branches
- Musculocutaneous: Terminal branch of lateral cord
- Axillary (a.k.a. circumflex nerve): Terminal branch of posterior cord
- Travels through quadrangular space
- Radial: Terminal branch of posterior cord
- Ulnar: Terminal branch of medial cord
- Median: Terminal branch of confluence of lateral and medial cord
- Key landmarks
- Anterior scalene muscle: Brachial plexus passes posterior to this muscle
- Origin: Anterior tubercle of C3-C6 transverse processes
- Insertion: Scalene tubercle at more anterolateral aspect of 1st rib
- Middle scalene muscle: Brachial plexus passes anterior to this muscle
- Origin: Posterior tubercle of C2-C7 transverse processes
- Insertion: Scalene tubercle at more posterior aspect of 1st rib
- Interscalene triangle: Formed by anterior scalene muscle, middle scalene muscle, and 1st rib
- Subclavian artery also courses within this
- Clavicle: Trunks course inferior to clavicle, divisions are deep to and protected by clavicle
- Axillary artery: Brachial plexus cords are named in relation to this artery
## IMAGING ANATOMY
- ### Overview
- Brachial plexus roots are individually readily visible at resolution of MR
- Trunks, divisions, and cords can often be individually identified, though sometimes blend together depending on MR resolution, patient motion, and other factors
## ANATOMY IMAGING ISSUES
- ### Imaging Recommendations
- Use neurovascular array if available, otherwise flexible body coil can be used
- Bilateral field of view helps to evaluate for asymmetries
- Same-day cervical spine MR exam may assist in identifying pathology unique to patients symptoms with improved resolution of spinal cord
- ### Imaging Pitfalls
- Brachial plexus nerves can be difficult to identify if acute trauma, infection, or aggressive tumor results in significant edema and tissue enhancement in region of nerves
- There are numerous anatomic variations in positioning of brachial plexus nerves
- Most common relationships to axillary artery
- Radial nerve dorsal to axillary artery
- Ulnar nerve medial to axillary artery
- Median nerve anterior to axillary artery
- Musculocutaneous nerve lateral to axillary artery
## CLINICAL IMPLICATIONS
- ### Clinical Importance
- Thoracic outlet syndrome: Compression on lateral, posterior, &/or medial cords by1st rib and clavicle
- High velocity trauma: Can avulse roots from cord or lacerate any portion of brachial plexus
- Parsonage-Turner syndrome: Idiopathic brachial plexus neuropathy
- Nerves may appear normal on MR; denervation of affected muscles helpful in diagnosis
- Traction neuropraxia: Occurs when nerve is forcefully stretched beyond its normal elastic limit
31996311-d772-4ae0-befa-28cb5138de61
## References
## Selected References
1. [Guday E et al: Anatomical study of prefixed versus postfixed brachial plexuses in adult human cadaver. ANZ J Surg. 87(5):399-403, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=27071641%5Bpmid%5D)
## Images
### Graphics: Brachial Plexus
![Graphic shows an anterior view of the brachial plexus.](images/app.statdx.com_image_thumbnail_eda3a360-1702-4fc1-b904-e8c792a9bf84_annotated_false_size_900_quality_90_a3760b07d7ff45e694ef1273ffca9b4a990a4e0d.jpg)
*Graphic shows an anterior view of the brachial plexus.*
![Graphic shows an anterior view of the brachial plexus.](images/app.statdx.com_image_thumbnail_eda3a360-1702-4fc1-b904-e8c792a9bf84_size_168_quality_85_efdbc2d6f7a3e24a42a2594e269839cf80b3692b.jpg)
*Graphic shows an anterior view of the brachial plexus.*
![Graphic shows an anterior view of the brachial plexus.](images/app.statdx.com_image_thumbnail_eda3a360-1702-4fc1-b904-e8c792a9bf84_size_174_quality_85_e1000277b717db931d2d539aa5c0919ee098358c.jpg)
*Graphic shows an anterior view of the brachial plexus.*
![Graphic shows the brachial plexus and retroscapular branches.](images/app.statdx.com_image_thumbnail_f390be04-daf0-43c3-b3e3-a5e2d1dbf925_annotated_false_size_900_quality_90_f1522bed304a4a9f39597d7d7120af7cb0808979.jpg)
*Graphic shows the brachial plexus and retroscapular branches.*
![Graphic shows the brachial plexus and retroscapular branches.](images/app.statdx.com_image_thumbnail_f390be04-daf0-43c3-b3e3-a5e2d1dbf925_size_168_quality_85_e3db2a8c7038c624897fcb95fa9cdf7f261025e6.jpg)
*Graphic shows the brachial plexus and retroscapular branches.*
### Axial T2 FS MR: Brachial Plexus
![The first of 6 axial T2W MR images at the level of C6-C7 shows the brachial plexus nerve roots coursing between the anterior and middle scalene muscles.](images/app.statdx.com_image_thumbnail_bc07b4ef-5cdf-438e-bca9-ffd460765bd2_annotated_false_size_900_quality_90_b9a0cd3af6411bd3cf5b99a7d9715790cb63b9d8.jpg)
*The first of 6 axial T2W MR images at the level of C6-C7 shows the brachial plexus nerve roots coursing between the anterior and middle scalene muscles.*
![The first of 6 axial T2W MR images at the level of C6-C7 shows the brachial plexus nerve roots coursing between the anterior and middle scalene muscles.](images/app.statdx.com_image_thumbnail_bc07b4ef-5cdf-438e-bca9-ffd460765bd2_size_168_quality_85_8fd55e347e1428aa127c4a46cddfcfa4048d8bc5.jpg)
*The first of 6 axial T2W MR images at the level of C6-C7 shows the brachial plexus nerve roots coursing between the anterior and middle scalene muscles.*
![At the C7-T1 level, the brachial plexus roots are easily identified proximally.](images/app.statdx.com_image_thumbnail_5c4df361-33ee-4a5e-843d-e4960bfd1834_annotated_false_size_900_quality_90_8decc58d828a82ab044891665e693d0ab18d90fe.jpg)
*At the C7-T1 level, the brachial plexus roots are easily identified proximally.*
![At the C7-T1 level, the brachial plexus roots are easily identified proximally.](images/app.statdx.com_image_thumbnail_5c4df361-33ee-4a5e-843d-e4960bfd1834_size_168_quality_85_3548f508e48323612fa13e903b7a987941caa27a.jpg)
*At the C7-T1 level, the brachial plexus roots are easily identified proximally.*
![At the T1 level, the brachial plexus roots coalesce into 3 trunks.](images/app.statdx.com_image_thumbnail_1f252b98-ed3d-420e-b0f9-de3b16bf7b9c_annotated_false_size_900_quality_90_99970036cdfbd030e37683c9c81a0b8e43396388.jpg)
*At the T1 level, the brachial plexus roots coalesce into 3 trunks.*
![At the T1 level, the brachial plexus roots coalesce into 3 trunks.](images/app.statdx.com_image_thumbnail_1f252b98-ed3d-420e-b0f9-de3b16bf7b9c_size_168_quality_85_1b5e78c1df520a9e354b85d19d8d6c8686842f26.jpg)
*At the T1 level, the brachial plexus roots coalesce into 3 trunks.*
![At the T1-T2 level, the brachial plexus trunks course through the interscalene triangle. The suprascapular artery and nerve course through the suprascapular notch.](images/app.statdx.com_image_thumbnail_4d237fb2-455b-4bb9-a148-6369245844ab_annotated_false_size_900_quality_90_86475e16187e6fc82d6cc9e841bc91083d23806c.jpg)
*At the T1-T2 level, the brachial plexus trunks course through the interscalene triangle. The suprascapular artery and nerve course through the suprascapular notch.*
![At the T1-T2 level, the brachial plexus trunks course through the interscalene triangle. The suprascapular artery and nerve course through the suprascapular notch.](images/app.statdx.com_image_thumbnail_4d237fb2-455b-4bb9-a148-6369245844ab_size_168_quality_85_a08bb69a120663be9c2728e8a65876ba196abc6f.jpg)
*At the T1-T2 level, the brachial plexus trunks course through the interscalene triangle. The suprascapular artery and nerve course through the suprascapular notch.*
![Axial STIR MR at the level of the mid clavicle shows the suprascapular artery and nerve coursing posteriorly below the supraspinatus tendon. On the patient's right, the inferior trunk splits into anterior and posterior division contributions.](images/app.statdx.com_image_thumbnail_e0c39c08-0964-4908-9252-8b32b7e136ec_annotated_false_size_900_quality_90_6bddd65b9e0b79a7752a604f87bd78c412730293.jpg)
*Axial STIR MR at the level of the mid clavicle shows the suprascapular artery and nerve coursing posteriorly below the supraspinatus tendon. On the patient's right, the inferior trunk splits into anterior and posterior division contributions.*
![Axial STIR MR at the level of the mid clavicle shows the suprascapular artery and nerve coursing posteriorly below the supraspinatus tendon. On the patient's right, the inferior trunk splits into anterior and posterior division contributions.](images/app.statdx.com_image_thumbnail_e0c39c08-0964-4908-9252-8b32b7e136ec_size_168_quality_85_90143d98b86926148941d14d63f3758cef679b8f.jpg)
*Axial STIR MR at the level of the mid clavicle shows the suprascapular artery and nerve coursing posteriorly below the supraspinatus tendon. On the patient's right, the inferior trunk splits into anterior and posterior division contributions.*
![At the level of the mid glenoid, the brachial plexus anterior and posterior divisions course deep to the clavicle bone.](images/app.statdx.com_image_thumbnail_e653c94d-fc95-466b-8f87-c07f671df6b6_annotated_false_size_900_quality_90_990fb8dfbab468670d69e7a95dead54bdd5dc37b.jpg)
*At the level of the mid glenoid, the brachial plexus anterior and posterior divisions course deep to the clavicle bone.*
![At the level of the mid glenoid, the brachial plexus anterior and posterior divisions course deep to the clavicle bone.](images/app.statdx.com_image_thumbnail_e653c94d-fc95-466b-8f87-c07f671df6b6_size_168_quality_85_375b0e9db3c06e3476418178bef3be79b34e8146.jpg)
*At the level of the mid glenoid, the brachial plexus anterior and posterior divisions course deep to the clavicle bone.*
### Coronal STIR MR: Brachial Plexus
![The first of 5 coronal MR images through the brachial plexus from posterior to anterior shows the extraforaminal brachial plexus roots. The middle scalene muscle can be seen as the posterior border of the proximal brachial plexus.](images/app.statdx.com_image_thumbnail_c96733bb-594f-4efd-a677-bbbf45af1434_annotated_false_size_900_quality_90_955efb8ae90cc955141a656c92c2b86efa07335f.jpg)
*The first of 5 coronal MR images through the brachial plexus from posterior to anterior shows the extraforaminal brachial plexus roots. The middle scalene muscle can be seen as the posterior border of the proximal brachial plexus.*
![The first of 5 coronal MR images through the brachial plexus from posterior to anterior shows the extraforaminal brachial plexus roots. The middle scalene muscle can be seen as the posterior border of the proximal brachial plexus.](images/app.statdx.com_image_thumbnail_c96733bb-594f-4efd-a677-bbbf45af1434_size_168_quality_85_4361996a3ff9cbb98e98ccd180e9588a1a7e0176.jpg)
*The first of 5 coronal MR images through the brachial plexus from posterior to anterior shows the extraforaminal brachial plexus roots. The middle scalene muscle can be seen as the posterior border of the proximal brachial plexus.*
![Coronal MR shows the roots proximally and the branches distally.](images/app.statdx.com_image_thumbnail_fa103b94-fe6e-4650-9d4c-e4ff71e29a59_annotated_false_size_900_quality_90_1e3ee75836f3e6d7b5d5fedae57f4466245c6aa7.jpg)
*Coronal MR shows the roots proximally and the branches distally.*
![Coronal MR shows the roots proximally and the branches distally.](images/app.statdx.com_image_thumbnail_fa103b94-fe6e-4650-9d4c-e4ff71e29a59_size_168_quality_85_7b66bbc28308bfd50a9cb679d0d68c560f9869db.jpg)
*Coronal MR shows the roots proximally and the branches distally.*
![The roots of the brachial plexus can be seen in the same plane as the cords and also some of the brachial plexus terminal branches.](images/app.statdx.com_image_thumbnail_a158f5a2-77ae-442b-bd34-fa4f256571f6_annotated_false_size_900_quality_90_045b0d2c954794464a5ca8192c159db51955d74f.jpg)
*The roots of the brachial plexus can be seen in the same plane as the cords and also some of the brachial plexus terminal branches.*
![The roots of the brachial plexus can be seen in the same plane as the cords and also some of the brachial plexus terminal branches.](images/app.statdx.com_image_thumbnail_a158f5a2-77ae-442b-bd34-fa4f256571f6_size_168_quality_85_d040ac0602ad0bbd8f2e46c66f8c23f54b4dc43d.jpg)
*The roots of the brachial plexus can be seen in the same plane as the cords and also some of the brachial plexus terminal branches.*
![The roots converge to form trunks prior to exiting the interscalene triangle. The 3 trunks then form the 6 divisions.](images/app.statdx.com_image_thumbnail_8f1f1ac2-129a-4356-bbba-32cd5d124f46_annotated_false_size_900_quality_90_6d458f2e59bf7cd3a8e5b755dc1135ba479b2ed7.jpg)
*The roots converge to form trunks prior to exiting the interscalene triangle. The 3 trunks then form the 6 divisions.*
![The roots converge to form trunks prior to exiting the interscalene triangle. The 3 trunks then form the 6 divisions.](images/app.statdx.com_image_thumbnail_8f1f1ac2-129a-4356-bbba-32cd5d124f46_size_168_quality_85_ebbb7975e30525f7fe41c0037f7953dbaa4a8e44.jpg)
*The roots converge to form trunks prior to exiting the interscalene triangle. The 3 trunks then form the 6 divisions.*
![Portions of the brachial plexus trunks, divisions, cords, and terminal branches are visible. The 6 divisions form the 3 cords. The 3 cords form the 5 terminal branches.](images/app.statdx.com_image_thumbnail_bb4fdfdc-8fd3-4882-8963-0e84b43c7fd3_annotated_false_size_900_quality_90_8c08e2934c714c1c2a23072109e27b7b77477936.jpg)
*Portions of the brachial plexus trunks, divisions, cords, and terminal branches are visible. The 6 divisions form the 3 cords. The 3 cords form the 5 terminal branches.*
![Portions of the brachial plexus trunks, divisions, cords, and terminal branches are visible. The 6 divisions form the 3 cords. The 3 cords form the 5 terminal branches.](images/app.statdx.com_image_thumbnail_bb4fdfdc-8fd3-4882-8963-0e84b43c7fd3_size_168_quality_85_6feec52357f3f683a87e829b9f0c693365d5b18e.jpg)
*Portions of the brachial plexus trunks, divisions, cords, and terminal branches are visible. The 6 divisions form the 3 cords. The 3 cords form the 5 terminal branches.*
### Sagittal PD MR: Brachial Plexus Nerve Roots
![The first of 12 sagittal T1 PD MR images of the brachial plexus demonstrates the transition from the cervical spinal cord to nerve roots.](images/app.statdx.com_image_thumbnail_29eea65f-c447-4f7d-a829-930aa991ee90_annotated_false_size_900_quality_90_f91f0cbbe7b025dd4f5d2d716b17de3f31671de2.jpg)
*The first of 12 sagittal T1 PD MR images of the brachial plexus demonstrates the transition from the cervical spinal cord to nerve roots.*
![The first of 12 sagittal T1 PD MR images of the brachial plexus demonstrates the transition from the cervical spinal cord to nerve roots.](images/app.statdx.com_image_thumbnail_29eea65f-c447-4f7d-a829-930aa991ee90_size_168_quality_85_fabfeb241d6266741a9f6b7e00436aedfaf41c3d.jpg)
*The first of 12 sagittal T1 PD MR images of the brachial plexus demonstrates the transition from the cervical spinal cord to nerve roots.*
![In the cervical spine, the nerve roots course above the pedicle of the correlate vertebrae, e.g., the C6 nerve root exits through the C5-C6 neuroforamen. The C8 nerve root exits through the C7-T1 neuroforamen.](images/app.statdx.com_image_thumbnail_c17c32f6-157b-4b93-9fce-889d045a0a78_annotated_false_size_900_quality_90_1a7eee497d578e94bc211d85ae3c734f1b5da31c.jpg)
*In the cervical spine, the nerve roots course above the pedicle of the correlate vertebrae, e.g., the C6 nerve root exits through the C5-C6 neuroforamen. The C8 nerve root exits through the C7-T1 neuroforamen.*
![In the cervical spine, the nerve roots course above the pedicle of the correlate vertebrae, e.g., the C6 nerve root exits through the C5-C6 neuroforamen. The C8 nerve root exits through the C7-T1 neuroforamen.](images/app.statdx.com_image_thumbnail_c17c32f6-157b-4b93-9fce-889d045a0a78_size_168_quality_85_6f3993ea7e18713f5609d626f48cfa6b3eb5a202.jpg)
*In the cervical spine, the nerve roots course above the pedicle of the correlate vertebrae, e.g., the C6 nerve root exits through the C5-C6 neuroforamen. The C8 nerve root exits through the C7-T1 neuroforamen.*
![The brachial plexus roots and trunks travel above the 1st rib.](images/app.statdx.com_image_thumbnail_22302c90-2835-4161-918d-83ac1d33aee6_annotated_false_size_900_quality_90_4403f15d6c763a1b1f51ea73766018787561da5d.jpg)
*The brachial plexus roots and trunks travel above the 1st rib.*
![The brachial plexus roots and trunks travel above the 1st rib.](images/app.statdx.com_image_thumbnail_22302c90-2835-4161-918d-83ac1d33aee6_size_168_quality_85_fbec0bfe089dc84cdd5fa008dabe4208be659d8d.jpg)
*The brachial plexus roots and trunks travel above the 1st rib.*
### Sagittal PD MR: Brachial Plexus Trunks and Divisions
![The brachial plexus trunks course through the interscalene triangle. The interscalene triangle is bordered by the anterior scalene muscle, middle scalene muscle, and 1st rib.](images/app.statdx.com_image_thumbnail_ef6d947a-408d-415e-b328-c147428401d9_annotated_false_size_900_quality_90_ae2ee1d2554fc0e4159ca9510e8457f0697e6df3.jpg)
*The brachial plexus trunks course through the interscalene triangle. The interscalene triangle is bordered by the anterior scalene muscle, middle scalene muscle, and 1st rib.*
![The brachial plexus trunks course through the interscalene triangle. The interscalene triangle is bordered by the anterior scalene muscle, middle scalene muscle, and 1st rib.](images/app.statdx.com_image_thumbnail_ef6d947a-408d-415e-b328-c147428401d9_size_168_quality_85_50a206b0b604358d905ab0a5039f2adfb80344ee.jpg)
*The brachial plexus trunks course through the interscalene triangle. The interscalene triangle is bordered by the anterior scalene muscle, middle scalene muscle, and 1st rib.*
![Lateral to the interscalene triangle, the brachial plexus trunks can be identified.](images/app.statdx.com_image_thumbnail_d17b6735-00ee-47cb-b34b-d475a257e581_annotated_false_size_900_quality_90_128851b22d9893169fa57567cfc71b67a33c8511.jpg)
*Lateral to the interscalene triangle, the brachial plexus trunks can be identified.*
![Lateral to the interscalene triangle, the brachial plexus trunks can be identified.](images/app.statdx.com_image_thumbnail_d17b6735-00ee-47cb-b34b-d475a257e581_size_168_quality_85_8bda7faa1acb356abccfa1bc28029b916e0c8810.jpg)
*Lateral to the interscalene triangle, the brachial plexus trunks can be identified.*
![Further laterally, the 3 brachial plexus trunks become the 6 brachial plexus divisions.](images/app.statdx.com_image_thumbnail_c6de8e5f-adcf-4b0a-9518-c5c81ea1c1bd_annotated_false_size_900_quality_90_7aef6bd54010559e250629df013c2d8715f56ccd.jpg)
*Further laterally, the 3 brachial plexus trunks become the 6 brachial plexus divisions.*
![Further laterally, the 3 brachial plexus trunks become the 6 brachial plexus divisions.](images/app.statdx.com_image_thumbnail_c6de8e5f-adcf-4b0a-9518-c5c81ea1c1bd_size_168_quality_85_4e9f8c02497642a78938c6715072f3dad84332d6.jpg)
*Further laterally, the 3 brachial plexus trunks become the 6 brachial plexus divisions.*
### Sagittal PD MR: Brachial Plexus Divisions and Cords
![The brachial plexus divisions are well protected as they pass deep to the clavicle.](images/app.statdx.com_image_thumbnail_8a297a51-7fe5-47d7-9126-569af8f689d9_annotated_false_size_900_quality_90_e2777359306e4cd4c2cd972163dbae234e38ae14.jpg)
*The brachial plexus divisions are well protected as they pass deep to the clavicle.*
![The brachial plexus divisions are well protected as they pass deep to the clavicle.](images/app.statdx.com_image_thumbnail_8a297a51-7fe5-47d7-9126-569af8f689d9_size_168_quality_85_9bfd51e203b926dc9c5effaf96c30556e2c0f015.jpg)
*The brachial plexus divisions are well protected as they pass deep to the clavicle.*
![The brachial plexus cords are named for their position relative to the axillary artery. There are numerous small nerves that originate from the cords.](images/app.statdx.com_image_thumbnail_865abd4d-3f71-46b3-bcab-2ed458bf7951_annotated_false_size_900_quality_90_0e09951696e03b07f8db4adaa921785f29bb0100.jpg)
*The brachial plexus cords are named for their position relative to the axillary artery. There are numerous small nerves that originate from the cords.*
![The brachial plexus cords are named for their position relative to the axillary artery. There are numerous small nerves that originate from the cords.](images/app.statdx.com_image_thumbnail_865abd4d-3f71-46b3-bcab-2ed458bf7951_size_168_quality_85_cfe94008b74a24ca209df359bc0519ba29447d49.jpg)
*The brachial plexus cords are named for their position relative to the axillary artery. There are numerous small nerves that originate from the cords.*
![The brachial plexus cords continue into the upper extremity prior to branching into 5 terminal branches.](images/app.statdx.com_image_thumbnail_46d0af6f-73b7-4721-93a0-f10dd8fe2724_annotated_false_size_900_quality_90_18e7d00fb72d2280f113c46ba3ba4caeba4308f8.jpg)
*The brachial plexus cords continue into the upper extremity prior to branching into 5 terminal branches.*
![The brachial plexus cords continue into the upper extremity prior to branching into 5 terminal branches.](images/app.statdx.com_image_thumbnail_46d0af6f-73b7-4721-93a0-f10dd8fe2724_size_168_quality_85_edc47538efb58668fc18fb6c9fdae16f9b2da856.jpg)
*The brachial plexus cords continue into the upper extremity prior to branching into 5 terminal branches.*
### Sagittal PD MR: Brachial Plexus Branches
![The musculocutaneous nerve travels superior relative to the axillary artery.](images/app.statdx.com_image_thumbnail_7d881a62-f5a1-4872-89e4-15bfd30e103e_annotated_false_size_900_quality_90_1ff250ae2582447dba5458b5e4a1c116ec3ca6d5.jpg)
*The musculocutaneous nerve travels superior relative to the axillary artery.*
![The musculocutaneous nerve travels superior relative to the axillary artery.](images/app.statdx.com_image_thumbnail_7d881a62-f5a1-4872-89e4-15bfd30e103e_size_168_quality_85_f7505c61caa3c1afb483ea555fee55031d46035a.jpg)
*The musculocutaneous nerve travels superior relative to the axillary artery.*
![The musculocutaneous nerve pierces the coracobrachialis muscle.](images/app.statdx.com_image_thumbnail_08d8db78-9f1d-486d-a6b2-3940c704415c_annotated_false_size_900_quality_90_cc4a4e13af08a560f77b6c9a12060e66e9d895ba.jpg)
*The musculocutaneous nerve pierces the coracobrachialis muscle.*
![The musculocutaneous nerve pierces the coracobrachialis muscle.](images/app.statdx.com_image_thumbnail_08d8db78-9f1d-486d-a6b2-3940c704415c_size_168_quality_85_623363929d962c918a124494502812a717ee3ef8.jpg)
*The musculocutaneous nerve pierces the coracobrachialis muscle.*
![The median, ulnar, and radial nerves typically course anterior, inferior, and posterior to the axillary artery, respectively. The axillary nerve courses posteriorly through the quadrilateral space of the axilla.](images/app.statdx.com_image_thumbnail_81c0aa3e-793d-4a9a-9574-de19dceb8878_annotated_false_size_900_quality_90_62dff5098a32d9d57ce63bf407617fdb3bf03c51.jpg)
*The median, ulnar, and radial nerves typically course anterior, inferior, and posterior to the axillary artery, respectively. The axillary nerve courses posteriorly through the quadrilateral space of the axilla.*
![The median, ulnar, and radial nerves typically course anterior, inferior, and posterior to the axillary artery, respectively. The axillary nerve courses posteriorly through the quadrilateral space of the axilla.](images/app.statdx.com_image_thumbnail_81c0aa3e-793d-4a9a-9574-de19dceb8878_size_168_quality_85_5cf3e2163c7fd0bc9feae2b665b38f83359b3393.jpg)
*The median, ulnar, and radial nerves typically course anterior, inferior, and posterior to the axillary artery, respectively. The axillary nerve courses posteriorly through the quadrilateral space of the axilla.*
docs_md/articles/brachial-plexus-lesion_f15c5303-8598-421e-b978-fba4dea2b6a6.md
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---
title: "Brachial Plexus Lesion"
docid: "f15c5303-8598-421e-b978-fba4dea2b6a6"
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---
## ESSENTIAL INFORMATION
- ### Key Differential Diagnosis Issues
- Brachial plexus innervates arm
- C5-T1 ventral rami
- ± minor branches from C4, T2
- Brachial plexus divided into roots/rami, trunks, divisions, cords, terminal branches
- Trauma most common cause of plexopathy
- Stretch injuries → nerve avulsion
- Neoplastic: Metastatic disease > primary
- Metastatic: Direct tumor spread or nodal
- Compresses ± invades plexus
- Inflammatory: Acute → chronic plexitis
- Radiation most common cause
- Diffuse thickening: Consider hypertrophic polyneuropathies (chronic inflammatory demyelinating polyneuropathy, hereditary motor-sensory neuropathy)
- Imaging strategies
- CT: Allows detection of masses
- Look for loss of perineural fat
- MR: Allows detailed evaluation of nerves
- Enlarged, edematous ± enhancing
- Best technique: Multiplanar high-resolution MR peripheral nerve imaging using dedicated surface coil
- Imaging pitfalls
- Too large field of view reduces spatial resolution, compromises visualization of internal brachial plexus architecture
- Technically simpler to evaluate supraclavicular plexus than infraclavicular plexus
- STIR provides more reliable fat suppression than chemical fat-saturated T2WI
- ### Helpful Clues for Common Diagnoses
- **Trauma, Brachial Plexus**
- Most common cause of brachial plexopathy
- Stretch injury: Neuropraxia with swollen nerve
- Most improve
- Nerve avulsion: Pre- or postganglionic
- Infants: Result of traumatic delivery
- Erb (C5, C6, ± C7) & Klumpke (C8, T1) palsies
- Adults: High force, e.g., motorcycle crash
- Imaging
- MR typically study of choice
- Stretch: Enlarged T2-hyperintense nerves
- Preganglionic avulsion: Root absent ± pseudomeningocele, cord displaced, denervated paraspinous muscles
- Postganglionic nerve avulsion: Nerve disruption with distal retraction
- CT myelography shows preganglionic avulsions with absent root
- **Pancoast Tumor**
- Key facts
- Apical lung tumor
- Squamous cell carcinoma most common
- Horner syndrome in ~ 20% of cases from stellate & inferior cervical ganglion involvement at lung apex
- Imaging
- CT: Chest wall invasion
- Loss of fat around subclavian artery
- MR: Infiltration of lower trunk especially
- **Metastases, Systemic, Nodal**
- Key facts
- Most often from breast carcinoma
- Compresses &/or infiltrates plexus
- Imaging
- MR: Enhancing masses compress plexus
- Nodular or diffuse enhancing tissue
- **Radiation Changes, Subacute**
- Key facts
- Uncommon (< 1%); > 6,000 cGy
- Peak at 10-20 months post radiation
- Predominantly sensory symptoms
- Imaging
- MR: Diffuse thickening & enhancement of brachial plexus without mass
- T2 hyperintense, variable enhancement
- **Radiation Changes, Chronic**
- Key facts
- Fibrosis even > 20 years post treatment
- Imaging
- MR: T2 hypointensity; some loss of nerve clarity due to scar
- ### Helpful Clues for Less Common Diagnoses
- **Neuroma, Posttraumatic, Brachial Plexus**
- Key facts
- Result of unregulated nerve regeneration
- ≤ 12 months after injury
- Imaging
- MR: Heterogeneously hyperintense & enhancing nodule in plexus
- **Neurofibromatosis Type 1**
- Key facts
- Plexus neurofibromas rare unless neurofibromatosis type 1
- Imaging
- MR: Symmetrically enlarged, lobulated T2-hyperintense roots
- **Schwannoma, Brachial Plexus,****Perivertebral Space**
- Key facts
- Benign Schwann cell neoplasm
- Clinical issues
- 5% of benign soft tissue neoplasms
- Malignant degeneration rare, more common with multiple schwannoma syndromes
- Development of pain should raise suspicion for malignancy
- Imaging
- T2 hyperintense, ± cystic degeneration
- Moderate to intense enhancement
- Target sign: Central T2-hypointense, peripheral hyperintense signal
- **Fascicular sign**: Multiple irregular, central hypointense foci on T2WI
- **Acute Brachial Plexitis (Parsonage-Turner Syndrome)**
- Key facts
- Idiopathic, viral/post viral, post vaccination
- Bilateral in up to 1/3
- Rapid-onset severe shoulder & arm pain, disabling weakness, early muscle atrophy
- Clinically indistinguishable from hereditary brachial plexus neuropathy, which can be identified with genetic testing showing dominant mutations of *SEPT9*
- Imaging
- MR: T2-hyperintense plexus
- Muscle denervation, then atrophy
- **Acute Brachial Plexitis, Infectious**
- Key facts
- Fever, painful arm swelling, & rapid onset of weakness
- Usually spread of adjacent infection from septic shoulder, cervical spine discitis, or lung infection
- Imaging
- MR: Acute ↑ T2 signal edematous nerves with variable enhancement ± abscess
- Linear ↑ T1 signal due to fatty infiltration
- Look for adjacent structure involvement as clue to source
- MR: Chronic ↑ T2 signal can persist into chronic phase though mass effect decreases
- **Peripheral Neurolymphomatosis**
- Key facts
- Isolated plexus lymphoma **or**with CNS or systemic lymphoma
- Focal nerve → diffuse infiltration
- Imaging
- MR: Smooth thickening, T2-hyperintense enhancing nerve(s)
- **Leukemia**
- Key facts: Infiltration with leukemic cells
- Imaging
- MR: Loss of clarity of plexus elements
- Smooth thickening, T2 hyperintensity & enhancement
- ### Helpful Clues for Rare Diagnoses
- **Brachial Plexus Entrapment (Thoracic Outlet Syndrome)**
- Key facts: Nerves compressed or stretched
- Cervical rib, long C7 transverse process
- Excessive callus from clavicle/rib fracture
- Muscle hypertrophy, e.g., anterior scalene
- Imaging
- MR may show focal T2 hyperintensity
- **Fibromatosis**
- Key facts: Spectrum of disease
- Benign desmoid → aggressive fibromatosis
- Imaging
- Variable: Well defined → infiltrative mass
- MR: T1 hypo- to isointense to muscle, T2 heterogeneous, enhancing
- **Chronic Inflammatory Demyelinating Polyneuropathy**
- Key facts: Acquired, immune mediated
- Sensorimotor symptoms & areflexia
- Imaging
- MR: Diffusely thickened nerve roots
- Enlarged, moderately enhancing nerves
- **Hereditary Motor-Sensory Neuropathy**
- Key facts: Many types & subtypes
- Synonym: Charcot-Marie-Tooth disease
- CMT1: Demyelination & remyelination → onion bulb appearance
- CMT3: Dejerine-Sottas (infantile form)
- Imaging
- Identical appearance to chronic inflammatory demyelinating polyneuropathy
## References
## Selected References
1. [Madhuranthakam AJ: Advanced techniques on horizon for MR imaging of brachial plexus. Eur Radiol. 34(2):885-6, 2024](http://www.ncbi.nlm.nih.gov/pubmed/?term=37624412%5Bpmid%5D)
1. [Meiling JB et al: Parsonage-turner syndrome and hereditary brachial plexus neuropathy. Mayo Clin Proc. 99(1):124-40, 2024](http://www.ncbi.nlm.nih.gov/pubmed/?term=38176820%5Bpmid%5D)
1. [Szaro P et al: Magnetic resonance imaging of the brachial plexus. Part 2: traumatic injuries. Eur J Radiol Open. 9:100397, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=35111891%5Bpmid%5D)
1. [Szaro P et al: Magnetic resonance imaging of the brachial plexus. Part 1: anatomical considerations, magnetic resonance techniques, and non-traumatic lesions. Eur J Radiol Open. 9:100392, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=34988263%5Bpmid%5D)
1. [Fuzari HKB et al: Diagnostic accuracy of magnetic resonance imaging in post-traumatic brachial plexus injuries: a systematic review. Clin Neurol Neurosurg. 164:5-10, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=29145043%5Bpmid%5D)
1. [Lee JH et al: High-resolution imaging of neural anatomy and pathology of the neck. Korean J Radiol. 18(1):180-93, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28096728%5Bpmid%5D)
1. [Cejas C et al: High resolution neurography of the brachial plexus by 3 Tesla magnetic resonance imaging. Radiologia. 58(2):88-100, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26860655%5Bpmid%5D)
1. [Vargas MI et al: Three-dimensional MR imaging of the brachial plexus. Semin Musculoskelet Radiol. 19(2):137-48, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25764238%5Bpmid%5D)
1. [Lutz AM et al: MR imaging of the brachial plexus. Neuroimaging Clin N Am. 24(1):91-108, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24210315%5Bpmid%5D)
1. [Rehman I et al: MR imaging of the brachial plexus. Clin Neuroradiol. 24(3):207-16, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24573785%5Bpmid%5D)
1. [Tharin BD et al: Brachial plexopathy: a review of traumatic and nontraumatic causes. AJR Am J Roentgenol. 202(1):W67-75, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24370167%5Bpmid%5D)
1. [Boulanger X et al: Imaging of the non-traumatic brachial plexus. Diagn Interv Imaging. 94(10):945-56, 2013](http://www.ncbi.nlm.nih.gov/pubmed/?term=23891030%5Bpmid%5D)
1. [Torres C et al: MRI of the brachial plexus: modified imaging technique leading to a better characterization of its anatomy and pathology. Neuroradiol J. 26(6):699-719, 2013](http://www.ncbi.nlm.nih.gov/pubmed/?term=24355190%5Bpmid%5D)
1. [Mikityansky I et al: MR Imaging of the brachial plexus. Magn Reson Imaging Clin N Am. 20(4):791-826, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=23088951%5Bpmid%5D)
## Images
### Selected Images
![Coronal graphic shows cervical ventral rami. C1-C7 roots exit above their numbered pedicle, C8 <img src='img/arrows/CS.png' alt='cyan solid arrow'/> exits above the T1 pedicle, &amp; caudal roots exit below their numbered pedicle. Note upper <img src='img/arrows/WS.png' alt='white solid arrow'/>, middle <img src='img/arrows/WO.png' alt='white open arrow'/>, &amp; lower <img src='img/arrows/WC.png' alt='white curved arrow'/> trunks.](images/app.statdx.com_image_thumbnail_ab2277d7-7045-450c-8dd1-f5c740db2fd3_size_174_quality_85_494e91381441d6d3c533f2df63ee2e8b37d00e7e.jpg)
*Coronal graphic shows cervical ventral rami. C1-C7 roots exit above their numbered pedicle, C8 <img src='img/arrows/CS.png' alt='cyan solid arrow'/> exits above the T1 pedicle, &amp; caudal roots exit below their numbered pedicle. Note upper <img src='img/arrows/WS.png' alt='white solid arrow'/>, middle <img src='img/arrows/WO.png' alt='white open arrow'/>, &amp; lower <img src='img/arrows/WC.png' alt='white curved arrow'/> trunks.*
![Coronal graphic shows trunks recombining into posterior &amp; anterior divisions that form the cords. Note the posterior <img src='img/arrows/WO.png' alt='white open arrow'/>, medial <img src='img/arrows/WS.png' alt='white solid arrow'/>, &amp; lateral <img src='img/arrows/WC.png' alt='white curved arrow'/> cords. Median nerve <img src='img/arrows/CO.png' alt='cyan open arrow'/> is formed from branches of lateral &amp; medial cords. The medial cord forms the ulnar nerve <img src='img/arrows/CS.png' alt='cyan solid arrow'/>. Posterior cord forms the radial <img src='img/arrows/CC.png' alt='cyan curved arrow'/> &amp; axillary nerves.](da5091b8-fd31-48b9-89aa-239dd0c32f0b)
*Coronal graphic shows trunks recombining into posterior &amp; anterior divisions that form the cords. Note the posterior <img src='img/arrows/WO.png' alt='white open arrow'/>, medial <img src='img/arrows/WS.png' alt='white solid arrow'/>, &amp; lateral <img src='img/arrows/WC.png' alt='white curved arrow'/> cords. Median nerve <img src='img/arrows/CO.png' alt='cyan open arrow'/> is formed from branches of lateral &amp; medial cords. The medial cord forms the ulnar nerve <img src='img/arrows/CS.png' alt='cyan solid arrow'/>. Posterior cord forms the radial <img src='img/arrows/CC.png' alt='cyan curved arrow'/> &amp; axillary nerves.*
![Coronal STIR MR shows a large, hyperintense pseudomeningocele <img src='img/arrows/WS.png' alt='white solid arrow'/> at C6-C7, indicating avulsion of the left C7 nerve root. This patient had experienced a prior motorcycle crash.](images/app.statdx.com_image_thumbnail_30c6f9b5-cee2-4a00-bb69-93ff90b0762d_annotated_true_size_900_quality_90_4f80811a7ca9d06a6d8f777e5b80d525c32130c6.jpg)
**Trauma, Brachial Plexus**
*Coronal STIR MR shows a large, hyperintense pseudomeningocele <img src='img/arrows/WS.png' alt='white solid arrow'/> at C6-C7, indicating avulsion of the left C7 nerve root. This patient had experienced a prior motorcycle crash.*
![Coronal STIR MR in the same patient shows a discontinuous, hyperintense, &amp; retracted appearance of the left C7 nerve root <img src='img/arrows/WS.png' alt='white solid arrow'/>, indicating complete avulsion. Injuries to the rest of the plexus nerves are also evident.](images/app.statdx.com_image_thumbnail_f5ae60fa-2806-4992-8632-86a2f53a7eaf_annotated_true_size_900_quality_90_b0810da4c617703f1f202de4f264610b5c244fb6.jpg)
**Trauma, Brachial Plexus**
*Coronal STIR MR in the same patient shows a discontinuous, hyperintense, &amp; retracted appearance of the left C7 nerve root <img src='img/arrows/WS.png' alt='white solid arrow'/>, indicating complete avulsion. Injuries to the rest of the plexus nerves are also evident.*
![Axial CECT reveals a heterogeneous apical lung mass <img src='img/arrows/WO.png' alt='white open arrow'/> invading the posterior chest wall. The anterior margin of the tumor nears the posterior margin of the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>, where trunks of brachial plexus are found. Also note the tumor's proximity to the right vertebral artery <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_2fa40c18-09e3-4d22-ad92-7e23565ef20e_annotated_true_size_900_quality_90_03321d224cea09579f2b142dfd4284276a4fd290.jpg)
**Pancoast Tumor**
*Axial CECT reveals a heterogeneous apical lung mass <img src='img/arrows/WO.png' alt='white open arrow'/> invading the posterior chest wall. The anterior margin of the tumor nears the posterior margin of the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>, where trunks of brachial plexus are found. Also note the tumor's proximity to the right vertebral artery <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Sagittal T1 MR in the same patient shows a superior sulcal tumor <img src='img/arrows/WO.png' alt='white open arrow'/> invading through the chest wall. The anterior limit of the tumor <img src='img/arrows/WS.png' alt='white solid arrow'/> invades the fat pad posterior to the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_529e7728-980a-498e-83c4-3c1a9f299aa8_annotated_true_size_900_quality_90_bffbf79dc5bb2334299955d8ad5761aa700600c1.jpg)
**Pancoast Tumor**
*Sagittal T1 MR in the same patient shows a superior sulcal tumor <img src='img/arrows/WO.png' alt='white open arrow'/> invading through the chest wall. The anterior limit of the tumor <img src='img/arrows/WS.png' alt='white solid arrow'/> invades the fat pad posterior to the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Axial T1 C+ FS MR in a patient with prior breast cancer demonstrates a new supraclavicular mass <img src='img/arrows/WC.png' alt='white curved arrow'/>, the posterior aspect of which abuts the brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/>, which is intensely enhancing. Enhancement from acute denervation change is also noted in the pectoralis major muscle <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_e9984321-2bc6-441d-a501-0c0c11639076_annotated_true_size_900_quality_90_c3f473d65e04c3487d5b7244ee6e6a845b8782de.jpg)
**Metastases, Systemic, Nodal**
*Axial T1 C+ FS MR in a patient with prior breast cancer demonstrates a new supraclavicular mass <img src='img/arrows/WC.png' alt='white curved arrow'/>, the posterior aspect of which abuts the brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/>, which is intensely enhancing. Enhancement from acute denervation change is also noted in the pectoralis major muscle <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Coronal T1 C+ FS MR in the same patient shows marked enhancement extending proximally along thickened plexus cords <img src='img/arrows/WS.png' alt='white solid arrow'/> to divisions <img src='img/arrows/WC.png' alt='white curved arrow'/> &amp; trunks. Both compression &amp; infiltration by tumor are evident.](images/app.statdx.com_image_thumbnail_ddfc83e4-81b9-48a2-8c7a-9d0240a49a52_annotated_true_size_900_quality_90_e0783a967e81f8fa99a94c2487de4e4256f84270.jpg)
**Metastases, Systemic, Nodal**
*Coronal T1 C+ FS MR in the same patient shows marked enhancement extending proximally along thickened plexus cords <img src='img/arrows/WS.png' alt='white solid arrow'/> to divisions <img src='img/arrows/WC.png' alt='white curved arrow'/> &amp; trunks. Both compression &amp; infiltration by tumor are evident.*
![Coronal T1 C+ FS MR shows diffuse enlargement &amp; enhancement of the nerves of the bilateral brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/> due to subacute radiation injury.](images/app.statdx.com_image_thumbnail_59147299-a66c-4256-9c15-ebf605653839_annotated_true_size_900_quality_90_aca13c3189afac7241cfe8db650c81bd513d7918.jpg)
**Radiation Changes, Subacute**
*Coronal T1 C+ FS MR shows diffuse enlargement &amp; enhancement of the nerves of the bilateral brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/> due to subacute radiation injury.*
![Coronal T1 MR shows thin confluence of roots <img src='img/arrows/WS.png' alt='white solid arrow'/> &amp; trunks <img src='img/arrows/WC.png' alt='white curved arrow'/> of the right brachial plexus with homogeneous fibrotic tissue. No mass effect is evident. Note the extensive supraclavicular fat stranding <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_6f3a99d9-3129-4f30-9cb2-edafa29659bd_annotated_true_size_900_quality_90_dee10ec173e2d3a5efad17c1f57ddcc744eb2a15.jpg)
**Radiation Changes, Chronic**
*Coronal T1 MR shows thin confluence of roots <img src='img/arrows/WS.png' alt='white solid arrow'/> &amp; trunks <img src='img/arrows/WC.png' alt='white curved arrow'/> of the right brachial plexus with homogeneous fibrotic tissue. No mass effect is evident. Note the extensive supraclavicular fat stranding <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Axial T1 MR in an infant demonstrates a tubular mass <img src='img/arrows/WS.png' alt='white solid arrow'/> that is isointense to muscle &amp; is located posterior to the anterior scalene muscle <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_6ae38c4e-c72a-4fcb-87e5-ebc3df8d943b_annotated_true_size_900_quality_90_7dee677f0a66cd83ec758466fa9b6461fb65454d.jpg)
**Neuroma, Posttraumatic, Brachial Plexus**
*Axial T1 MR in an infant demonstrates a tubular mass <img src='img/arrows/WS.png' alt='white solid arrow'/> that is isointense to muscle &amp; is located posterior to the anterior scalene muscle <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Coronal T2 MR in a teenager reveals bilateral lobulated, heterogeneous neurofibromas <img src='img/arrows/WS.png' alt='white solid arrow'/> involving each cervical &amp; upper thoracic nerve root. This patient had other manifestations of neurofibromatosis type 1, including intercostal nerve lesions <img src='img/arrows/WC.png' alt='white curved arrow'/> &amp; scoliosis.](images/app.statdx.com_image_thumbnail_b12a976e-6e39-444d-b1d7-b3e45913b262_annotated_true_size_900_quality_90_47b432836a3db5217e08a080bec93ffb9641d5bc.jpg)
**Neurofibromatosis Type 1**
*Coronal T2 MR in a teenager reveals bilateral lobulated, heterogeneous neurofibromas <img src='img/arrows/WS.png' alt='white solid arrow'/> involving each cervical &amp; upper thoracic nerve root. This patient had other manifestations of neurofibromatosis type 1, including intercostal nerve lesions <img src='img/arrows/WC.png' alt='white curved arrow'/> &amp; scoliosis.*
![Coronal T2 FS MR shows a fusiform hyperintense but heterogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> oriented along the course of the brachial plexus. Central cystic degeneration <img src='img/arrows/BC.png' alt='black curved arrow'/> is typical of a schwannoma.](images/app.statdx.com_image_thumbnail_9707fbce-37b8-4e36-a1c9-83dee17eaeef_annotated_true_size_900_quality_90_0394bcef9d279877ae65ab638c511b639a0eff39.jpg)
**Schwannoma, Brachial Plexus, Perivertebral Space**
*Coronal T2 FS MR shows a fusiform hyperintense but heterogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> oriented along the course of the brachial plexus. Central cystic degeneration <img src='img/arrows/BC.png' alt='black curved arrow'/> is typical of a schwannoma.*
![Coronal STIR MR in a young man with rapid onset of shoulder weakness shows hyperintensity &amp; subtle enlargement of roots <img src='img/arrows/WS.png' alt='white solid arrow'/> &amp; trunks <img src='img/arrows/WC.png' alt='white curved arrow'/>. Symptoms resolved over months with antiinflammatory treatment, but no cause was determined.](images/app.statdx.com_image_thumbnail_d94c99e7-4d61-4ac0-8b9c-3e69ef63b2f0_annotated_true_size_900_quality_90_413c180c156f4ea7d1f88418ede9902a7b719721.jpg)
**Acute Brachial Plexitis (Parsonage-Turner Syndrome)**
*Coronal STIR MR in a young man with rapid onset of shoulder weakness shows hyperintensity &amp; subtle enlargement of roots <img src='img/arrows/WS.png' alt='white solid arrow'/> &amp; trunks <img src='img/arrows/WC.png' alt='white curved arrow'/>. Symptoms resolved over months with antiinflammatory treatment, but no cause was determined.*
![Coronal STIR MR reveals bilateral, asymmetric hyperintensity of the brachial plexus with more marked involvement of right <img src='img/arrows/WS.png' alt='white solid arrow'/> than left <img src='img/arrows/WC.png' alt='white curved arrow'/>. Acute plexitis is bilateral in up to 1/3 of cases.](images/app.statdx.com_image_thumbnail_c0d10b00-200f-4098-bee0-744c43657f08_annotated_true_size_900_quality_90_070f069d5c5f3e2c1820c80e75d35bcb9f126be3.jpg)
**Acute Brachial Plexitis (Parsonage-Turner Syndrome)**
*Coronal STIR MR reveals bilateral, asymmetric hyperintensity of the brachial plexus with more marked involvement of right <img src='img/arrows/WS.png' alt='white solid arrow'/> than left <img src='img/arrows/WC.png' alt='white curved arrow'/>. Acute plexitis is bilateral in up to 1/3 of cases.*
![Coronal T1 C+ FS MR shows diffuse enhancement &amp; thickening of the bilateral brachial plexus nerves <img src='img/arrows/WS.png' alt='white solid arrow'/> due to spread of adjacent spinal infection. There is extensive surrounding fat stranding in the adjacent soft tissues, indicative of inflammation. Note abnormal enhancement of the C5-C7 vertebrae <img src='img/arrows/WC.png' alt='white curved arrow'/> related to osteomyelitis.](images/app.statdx.com_image_thumbnail_8e939edd-824b-4b7c-9967-421315b84d2d_annotated_true_size_900_quality_90_20e1829247d29b3fd506b44359ecd3b010e43a61.jpg)
**Acute Brachial Plexitis, Infectious**
*Coronal T1 C+ FS MR shows diffuse enhancement &amp; thickening of the bilateral brachial plexus nerves <img src='img/arrows/WS.png' alt='white solid arrow'/> due to spread of adjacent spinal infection. There is extensive surrounding fat stranding in the adjacent soft tissues, indicative of inflammation. Note abnormal enhancement of the C5-C7 vertebrae <img src='img/arrows/WC.png' alt='white curved arrow'/> related to osteomyelitis.*
![Coronal STIR MR in a patient with systemic lymphoma and a 1-month history of left arm flaccid paralysis demonstrates marked thickening of roots &amp; trunks of the left brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/>. Tumor <img src='img/arrows/WO.png' alt='white open arrow'/> involving the left scapula is also apparent.](images/app.statdx.com_image_thumbnail_76599f97-300e-4750-baf6-88f1ac3f9580_annotated_true_size_900_quality_90_2ec926fddde008560f3cc204eea3c27d54c84d56.jpg)
**Peripheral Neurolymphomatosis**
*Coronal STIR MR in a patient with systemic lymphoma and a 1-month history of left arm flaccid paralysis demonstrates marked thickening of roots &amp; trunks of the left brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/>. Tumor <img src='img/arrows/WO.png' alt='white open arrow'/> involving the left scapula is also apparent.*
![Coronal T1 C+ FS MR in the same patient shows smooth, diffuse enhancement of enlarged left plexus from roots <img src='img/arrows/WS.png' alt='white solid arrow'/> to divisions <img src='img/arrows/WC.png' alt='white curved arrow'/> &amp; cords <img src='img/arrows/WO.png' alt='white open arrow'/>. Intracranial &amp; spinal leptomeningeal recurrence were also found on MR (not shown).](images/app.statdx.com_image_thumbnail_5b13955c-6dec-41eb-9815-e568dad7b60c_annotated_true_size_900_quality_90_dafb4b241ce23de9f63c31af77a40ecd1230f4b2.jpg)
**Peripheral Neurolymphomatosis**
*Coronal T1 C+ FS MR in the same patient shows smooth, diffuse enhancement of enlarged left plexus from roots <img src='img/arrows/WS.png' alt='white solid arrow'/> to divisions <img src='img/arrows/WC.png' alt='white curved arrow'/> &amp; cords <img src='img/arrows/WO.png' alt='white open arrow'/>. Intracranial &amp; spinal leptomeningeal recurrence were also found on MR (not shown).*
![Coronal STIR MR in a child with previous CNS relapse of the anterior longitudinal ligament, new left shoulder pain, &amp; C8 numbness shows enlargement &amp; hyperintensity of C5 <img src='img/arrows/WS.png' alt='white solid arrow'/> through C8 <img src='img/arrows/WC.png' alt='white curved arrow'/> nerve roots. C8 is the largest of affected nerve roots, and the process extended into the trunks.](images/app.statdx.com_image_thumbnail_13e8a5cb-2d99-4dd9-bbd5-d15a44263a86_annotated_true_size_900_quality_90_5136d64eeaf8fc19b64afc45848bdba79e952f22.jpg)
**Leukemia**
*Coronal STIR MR in a child with previous CNS relapse of the anterior longitudinal ligament, new left shoulder pain, &amp; C8 numbness shows enlargement &amp; hyperintensity of C5 <img src='img/arrows/WS.png' alt='white solid arrow'/> through C8 <img src='img/arrows/WC.png' alt='white curved arrow'/> nerve roots. C8 is the largest of affected nerve roots, and the process extended into the trunks.*
![Axial T1 C+ FS MR in the same child at the cervicothoracic junction level demonstrates asymmetric abnormal enhancement of C8 <img src='img/arrows/WS.png' alt='white solid arrow'/> &amp; T1 <img src='img/arrows/WC.png' alt='white curved arrow'/> as they form the lower trunk.](images/app.statdx.com_image_thumbnail_ed0673eb-c910-4fcd-8a52-ec7ca50085e5_annotated_true_size_900_quality_90_1d44fe99530c0a4181ad3ddeba7ffb919126d1b2.jpg)
**Leukemia**
*Axial T1 C+ FS MR in the same child at the cervicothoracic junction level demonstrates asymmetric abnormal enhancement of C8 <img src='img/arrows/WS.png' alt='white solid arrow'/> &amp; T1 <img src='img/arrows/WC.png' alt='white curved arrow'/> as they form the lower trunk.*
![Coronal STIR MR in a patient with prior snowboarding injury &amp; C8-T1 neuropathy shows an abnormally hyperintense C7 nerve root <img src='img/arrows/WS.png' alt='white solid arrow'/> directed toward a heterogeneous mass of the left chest wall <img src='img/arrows/WO.png' alt='white open arrow'/>. C8 &amp; T1 also extend into the mass.](images/app.statdx.com_image_thumbnail_856a95a0-a33a-4863-90f1-293b6b3b7858_annotated_true_size_900_quality_90_1ae7a5d426835cc774d299034f4261c1e050dfef.jpg)
**Brachial Plexus Entrapment (Thoracic Outlet Syndrome)**
*Coronal STIR MR in a patient with prior snowboarding injury &amp; C8-T1 neuropathy shows an abnormally hyperintense C7 nerve root <img src='img/arrows/WS.png' alt='white solid arrow'/> directed toward a heterogeneous mass of the left chest wall <img src='img/arrows/WO.png' alt='white open arrow'/>. C8 &amp; T1 also extend into the mass.*
![Sagittal STIR MR in the same patient shows a healing rib fracture with hyperintense callus <img src='img/arrows/WO.png' alt='white open arrow'/> immediately inferior to the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. Note hyperintensity seen in fat <img src='img/arrows/WS.png' alt='white solid arrow'/> posterior to the artery at the location of plexus divisions.](images/app.statdx.com_image_thumbnail_5eb522a9-943f-4c1e-ac3f-bc1dd8c10551_annotated_true_size_900_quality_90_36e5afd3a5dd2a9a4a24ce3173e64808811c9029.jpg)
**Brachial Plexus Entrapment (Thoracic Outlet Syndrome)**
*Sagittal STIR MR in the same patient shows a healing rib fracture with hyperintense callus <img src='img/arrows/WO.png' alt='white open arrow'/> immediately inferior to the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. Note hyperintensity seen in fat <img src='img/arrows/WS.png' alt='white solid arrow'/> posterior to the artery at the location of plexus divisions.*
![Sagittal T1 MR shows a homogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower neck that abuts &amp; partly surrounds the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/> &amp; compresses the vein anteriorly <img src='img/arrows/WO.png' alt='white open arrow'/>. Brachial plexus divisions are located superior &amp; posterior to the subclavian artery at this level.](images/app.statdx.com_image_thumbnail_c5da5e26-4e20-42dd-93f2-5fec307d95d5_annotated_true_size_900_quality_90_2983916dea81a4572889dcdbc7bed2475b6c4b35.jpg)
**Fibromatosis**
*Sagittal T1 MR shows a homogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower neck that abuts &amp; partly surrounds the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/> &amp; compresses the vein anteriorly <img src='img/arrows/WO.png' alt='white open arrow'/>. Brachial plexus divisions are located superior &amp; posterior to the subclavian artery at this level.*
![Axial T2 FS MR shows marked heterogeneity of a supraclavicular mass <img src='img/arrows/WS.png' alt='white solid arrow'/> that is rounded with ill-defined margins. The middle trunk of the plexus <img src='img/arrows/WC.png' alt='white curved arrow'/> is displaced &amp; slightly enlarged.](images/app.statdx.com_image_thumbnail_125a0865-672b-4d2e-acee-163bb8a1415d_annotated_true_size_900_quality_90_014720fdb012e8e8ac0798f0b667e2f3bf7dc1eb.jpg)
**Fibromatosis**
*Axial T2 FS MR shows marked heterogeneity of a supraclavicular mass <img src='img/arrows/WS.png' alt='white solid arrow'/> that is rounded with ill-defined margins. The middle trunk of the plexus <img src='img/arrows/WC.png' alt='white curved arrow'/> is displaced &amp; slightly enlarged.*
![Sagittal T2 MR in a young man with progressive peripheral numbness, early fatigue, &amp; areflexia shows enlargement &amp; subtle hyperintensity of multiple cervical nerve roots <img src='img/arrows/WS.png' alt='white solid arrow'/>. Note the comparatively normal size of the T1 nerve root <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_79b0bca6-0d75-4935-9647-c60deb7f45e3_annotated_true_size_900_quality_90_1918e97429f318cf4d665deaffe91c6f8b6cd737.jpg)
**Chronic Inflammatory Demyelinating Polyneuropathy**
*Sagittal T2 MR in a young man with progressive peripheral numbness, early fatigue, &amp; areflexia shows enlargement &amp; subtle hyperintensity of multiple cervical nerve roots <img src='img/arrows/WS.png' alt='white solid arrow'/>. Note the comparatively normal size of the T1 nerve root <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Sagittal T1 MR in a patient with Charcot-Marie-Tooth disease demonstrates enlargement of the nerve roots emerging from the cervical foramina <img src='img/arrows/WS.png' alt='white solid arrow'/>. Nerve root enlargement is subtle, as nerves are isointense to muscle, but loss of perineural fat is the key to diagnosis.](images/app.statdx.com_image_thumbnail_bc7bac95-46cc-4027-b793-d3bfc09f2657_annotated_true_size_900_quality_90_ef70f0f79ae5ce2efabd5675e87c18f0a45a1948.jpg)
**Hereditary Motor-Sensory Neuropathy**
*Sagittal T1 MR in a patient with Charcot-Marie-Tooth disease demonstrates enlargement of the nerve roots emerging from the cervical foramina <img src='img/arrows/WS.png' alt='white solid arrow'/>. Nerve root enlargement is subtle, as nerves are isointense to muscle, but loss of perineural fat is the key to diagnosis.*
### Additional Images
![Coronal STIR MR shows diffuse hyperintensity of the plexus relative to muscles &amp; enlargement of roots <img src='img/arrows/WS.png' alt='white solid arrow'/>, trunks <img src='img/arrows/WO.png' alt='white open arrow'/>, divisions <img src='img/arrows/WC.png' alt='white curved arrow'/>, &amp; proximal cords in a patient with prior radiation for breast cancer &amp; progressive left arm symptoms.](images/app.statdx.com_image_thumbnail_3494c3ae-620c-4d01-9c53-1082cf586ba7_annotated_true_size_900_quality_90_18e9fcdd4a2cc3a84e5ecc3eda56703dc754d9b6.jpg)
**Radiation Changes, Subacute**
*Coronal STIR MR shows diffuse hyperintensity of the plexus relative to muscles &amp; enlargement of roots <img src='img/arrows/WS.png' alt='white solid arrow'/>, trunks <img src='img/arrows/WO.png' alt='white open arrow'/>, divisions <img src='img/arrows/WC.png' alt='white curved arrow'/>, &amp; proximal cords in a patient with prior radiation for breast cancer &amp; progressive left arm symptoms.*
![Coronal T1 MR shows a left apical lung mass <img src='img/arrows/WO.png' alt='white open arrow'/> invading through the superior chest wall to involve the left brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/>. Note the normal right artery <img src='img/arrows/WC.png' alt='white curved arrow'/> with surrounding plexus.](images/app.statdx.com_image_thumbnail_b3d76c90-a0d6-4002-8330-28492c373227_annotated_true_size_900_quality_90_0303131c69deb18894617ef839108ac1c69eeeb3.jpg)
**Pancoast Tumor**
*Coronal T1 MR shows a left apical lung mass <img src='img/arrows/WO.png' alt='white open arrow'/> invading through the superior chest wall to involve the left brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/>. Note the normal right artery <img src='img/arrows/WC.png' alt='white curved arrow'/> with surrounding plexus.*
![Sagittal T1 MR in the same patient shows a superior sulcal tumor <img src='img/arrows/WO.png' alt='white open arrow'/> invading through the chest wall. There is a markedly diminished caliber of the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>, which is surrounded by the tumor, indicating tumor infiltration of the plexus also.](images/app.statdx.com_image_thumbnail_7372b483-ebcc-42df-b832-672db8805ab6_annotated_true_size_900_quality_90_7424d663a40af525329ba46d74c87b1281453b37.jpg)
**Pancoast Tumor**
*Sagittal T1 MR in the same patient shows a superior sulcal tumor <img src='img/arrows/WO.png' alt='white open arrow'/> invading through the chest wall. There is a markedly diminished caliber of the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>, which is surrounded by the tumor, indicating tumor infiltration of the plexus also.*
![Coronal T1 MR in a patient with prior radiation for breast cancer &amp; progressive left arm symptoms shows no evidence of a focal mass. The brachial plexus elements <img src='img/arrows/WS.png' alt='white solid arrow'/> are remarkably readily identified, indicating diffuse enlargement of nerves.](images/app.statdx.com_image_thumbnail_8c863612-3acb-4f81-969d-1804edf4a2e9_annotated_true_size_900_quality_90_2b2355e4dafcc282c3a3a0bdb76c630f50d785b0.jpg)
**Radiation Changes, Subacute**
*Coronal T1 MR in a patient with prior radiation for breast cancer &amp; progressive left arm symptoms shows no evidence of a focal mass. The brachial plexus elements <img src='img/arrows/WS.png' alt='white solid arrow'/> are remarkably readily identified, indicating diffuse enlargement of nerves.*
![Sagittal oblique T1 MR in a radiated patient at the level of divisions demonstrates fibrotic tissue <img src='img/arrows/WS.png' alt='white solid arrow'/> surrounding the superoposterior aspect of the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. The subclavian vein should be anterior to the artery, but here it is not discernible due to fibrosis.](images/app.statdx.com_image_thumbnail_ee7d72fb-863d-4f68-b20e-d83af9519083_annotated_true_size_900_quality_90_96d2960a3af29f51834b3e11317782269bd03906.jpg)
**Radiation Changes, Chronic**
*Sagittal oblique T1 MR in a radiated patient at the level of divisions demonstrates fibrotic tissue <img src='img/arrows/WS.png' alt='white solid arrow'/> surrounding the superoposterior aspect of the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. The subclavian vein should be anterior to the artery, but here it is not discernible due to fibrosis.*
![Coronal STIR MR in a patient with known NF1 and plexiform neurofibroma shows involvement of the lower plexus roots &amp; trunks on the left <img src='img/arrows/WS.png' alt='white solid arrow'/> with lobulated, enlarged &amp; hyperintense nerves.](images/app.statdx.com_image_thumbnail_2fef864b-9e67-430c-ab18-549e2e300d2d_annotated_true_size_900_quality_90_feac2f7f1b3ae2415c98844e68dfeaaa5abaa1ee.jpg)
**Neurofibromatosis Type 1**
*Coronal STIR MR in a patient with known NF1 and plexiform neurofibroma shows involvement of the lower plexus roots &amp; trunks on the left <img src='img/arrows/WS.png' alt='white solid arrow'/> with lobulated, enlarged &amp; hyperintense nerves.*
![Coronal T1 MR shows a young girl with chronic left arm symptoms &amp; prominent exostosis <img src='img/arrows/WO.png' alt='white open arrow'/> arising from the medial aspect proximal humerus, which compressed adjacent distal cords <img src='img/arrows/WS.png' alt='white solid arrow'/> in the axilla.](images/app.statdx.com_image_thumbnail_31f7fc95-b128-4491-bbc2-c9e059c92cb5_annotated_true_size_900_quality_90_5164c6f67847947f6aa37a24186f77dc15fc21ec.jpg)
**Brachial Plexus Entrapment (Thoracic Outlet Syndrome)**
*Coronal T1 MR shows a young girl with chronic left arm symptoms &amp; prominent exostosis <img src='img/arrows/WO.png' alt='white open arrow'/> arising from the medial aspect proximal humerus, which compressed adjacent distal cords <img src='img/arrows/WS.png' alt='white solid arrow'/> in the axilla.*
![Coronal STIR MR in a young girl with proximal humeral exostosis <img src='img/arrows/WO.png' alt='white open arrow'/> compressing axillary cords demonstrates hyperintensity in 1 of the distal cords <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_b9418e4f-5ede-4cff-841d-1bd443a47df0_annotated_true_size_900_quality_90_72ac808b5eeda10190a7ffed6b92835b9e7bd2f8.jpg)
**Brachial Plexus Entrapment (Thoracic Outlet Syndrome)**
*Coronal STIR MR in a young girl with proximal humeral exostosis <img src='img/arrows/WO.png' alt='white open arrow'/> compressing axillary cords demonstrates hyperintensity in 1 of the distal cords <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Axial T2 FS MR in the same patient shows enlargement &amp; subtle hyperintensity of exiting <img src='img/arrows/WS.png' alt='white solid arrow'/> &amp; exited <img src='img/arrows/WC.png' alt='white curved arrow'/> nerve roots in the cervical spine. Electromyography showed demyelination.](images/app.statdx.com_image_thumbnail_eef19e74-9481-42b9-b7e5-185ff417d32e_annotated_true_size_900_quality_90_ce7e10e10e650497a355bdbeb7fc0c849ab8f11f.jpg)
**Chronic Inflammatory Demyelinating Polyneuropathy**
*Axial T2 FS MR in the same patient shows enlargement &amp; subtle hyperintensity of exiting <img src='img/arrows/WS.png' alt='white solid arrow'/> &amp; exited <img src='img/arrows/WC.png' alt='white curved arrow'/> nerve roots in the cervical spine. Electromyography showed demyelination.*
![Sagittal T2 MR in the same patient demonstrates similar enlargement of slightly hyperintense lumbar nerve roots <img src='img/arrows/WS.png' alt='white solid arrow'/> filling the neural foramina. (Courtesy L.R. Gentry, MD.)](images/app.statdx.com_image_thumbnail_8d85bdad-8dab-40a5-a879-36fb06e9d263_annotated_true_size_900_quality_90_ab76dbb7aef3d39d5d7bc2c731e05929a760b982.jpg)
**Hereditary Motor-Sensory Neuropathy**
*Sagittal T2 MR in the same patient demonstrates similar enlargement of slightly hyperintense lumbar nerve roots <img src='img/arrows/WS.png' alt='white solid arrow'/> filling the neural foramina. (Courtesy L.R. Gentry, MD.)*
docs_md/articles/brachial-plexus-pathology_b427237e-8f76-436f-9d52-d124e95e2720.md
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---
title: "Brachial Plexus Pathology"
docid: "b427237e-8f76-436f-9d52-d124e95e2720"
authors:
- key: "e764c0d5-3399-4ab6-815f-90d98cc20fb2"
value: "Stefanie W. Y. Yip, MBBS, FRCR, FHKCR, FHKAM (Radiology)"
- key: "ee435a54-df79-4d7a-b78c-b02157eac7f6"
value: "James F. Griffith, MBBCh BAO, MRCP, FRCR, FHKCR FHKAM, MD"
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slug: "musculoskeletal"
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slug: "neurovascular-abnormalities"
treeNodeId: "adc928f5-8882-470a-8a1b-acdbf39d4e74"
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name: "Brachial Plexus Pathology"
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lastUpdated: "11/11/24"
pageDescription: "Brachial Plexus Pathology"
pageKeywords: "Ultrasound, Diagnosis, Musculoskeletal, Neurovascular Abnormalities, Brachial Plexus Pathology"
pageTitle: "Brachial Plexus Pathology | STATdx"
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breadcrumbs:
- "Ultrasound"
- "Diagnosis"
- "Musculoskeletal"
- "Neurovascular Abnormalities"
- "Brachial Plexus Pathology"
---
## KEY FACTS
- ### Imaging
- Examine contralateral asymptomatic side first
- Good side-to-side concordance normally in appearance of brachial plexus
- Though considerable intrapopulation variation
- Smooth & diffuse thickening suggests nontumoral etiology, such as irradiation plexopathy or inflammatory neuropathy
- Focal swelling indicates primary tumor, malignancy, or nodular fibrosis
- **Postradiation plexopathy**: Diffuse enlargement ± hypoechoic fibrotic atrophied perineural fat
- **Traumatic plexopathy**: Swelling of injured nerves
- **Benign neurogenic tumor**: Discrete, well-defined, ovoid hypoechoic mass inseparable from brachial plexus
- **Metastatic infiltration**: Focal, often irregular mass infiltrating neural components without tethering
- **Neuralgic amyotrophy**: Focal enlargement of individual nerves
- **Inflammatory plexopathy**: Diffuse enlargement of affected nerves bilaterally with normal surrounding fat
- **Thoracic outlet syndrome**: Examine from interscalene to infraclavicular region before & after provocative movement
- ### Diagnostic Checklist
- 2/3 of brachial plexus examinations are normal on both US & MR
- US is almost as accurate as MR for identifying & characterizing brachial plexopathy
- If US normal, likelihood of finding abnormality on MR is very low
- Main additional benefits of MR
- Shows foraminal stenosis or intraspinal pathology that may account for symptoms
- Shows parascapular muscle denervation as indirect sign of brachial plexus pathology
## TERMINOLOGY
- ### Definitions
- Brachial plexus extends from ventral rami of C5-T1 roots to terminal branches in axilla
- Brachial plexus comprises roots, trunks, divisions, cords, & terminal branches distal to dorsal root ganglion
- Dorsal root ganglion & preganglionic rootlets are not part of brachial plexus
- **Postradiation plexopathy**: Comprises both early transient radiation-induced plexopathy & later sequelae of radiation-induced fibrosis, due to irradiation therapy for lower neck & upper thoracic malignancy
- **Traumatic plexopathy**: Injury to the brachial plexus from traction, penetrating or direct blunt trauma
- Posttraumatic neuroma: Focal discontinuity proliferation of neural components due to haphazard neural regeneration & connective tissue repair; 2 types
- Neuroma-in-continuity (NIC) continuous with partially transected nerve
- End-bulb neuroma at proximal stump of completely transected nerve
- **Benign neurogenic tumor**: Benign peripheral nerve sheath tumor, e.g., schwannoma, neurofibroma
- **Malignant infiltration**: Breast, lung, & less commonly, head & neck cancer metastasis, lymphoma, or direct infiltration from regional primary tumor
- **Inflammatory plexopathy**: Nontraumatic demyelinating neuropathy due to neural inflammation
- **Neuralgic amyotrophy**: Focal neural inflammatory condition with immunological, mechanical ± genetic predisposition
- **Thoracic outlet syndrome**: Neural or vascular compression typically from fibrous bands or bony compression
## IMAGING
- ### General Features
- #### Best diagnostic clue
- Contralateral asymptomatic or less symptomatic side should always be examined first to allow appreciation of normal anatomy for patient
- Little side-to side variation in neural size & perineural fat normally exists though considerable variation exists across population
- Look for
- Enlargement of roots/trunks/divisions/cords/terminal branches of brachial plexus
- Altered echogenicity of or reduction in perineural fat
- Tethering of neural components
- Focal discontinuity ± neuroma
- #### Location
- Lower cervical region
- Medial to scalene muscles: Roots
- Interscalene triangle: Trunks
- Lateral to scalene muscle & above clavicle: Divisions
- Subcoracoid recess: Cords
- Axilla: Terminal branches
- #### Size
- Should not be > 20% larger than normal side
- Normal cross-sectional areas of trunks: Upper 16.7 ± 2.8 mm², middle 14.0 ± 2.7 mm², lower 13.8 ± 2.6 mm²
- Measurements are a guide only & not widely used
- #### Morphology
- Smooth, diffuse swelling indicates nontumoral etiology
- Focal nodular swelling indicates tumoral etiology
- ### Radiographic Findings
- May show apical lung mass, bony infiltration, posttraumatic deformity or cervical rib
- ### CT Findings
- CT myelography may demonstrate pseudomeningocele due to traumatic dural tear
- 1/5 of root avulsions do not have dural tear
- Dural tear not invariably associated with root avulsion
- May demonstrate rib injury or bone deformity
- ### MR Findings
- US almost as accurate as MR for depicting brachial plexus pathology; main benefits of MR include
- Depiction of parascapular muscle denervation with higher sensitivity than US
- Depiction of preganglionic lesion or foraminal stenosis, which cannot be seen on US
- Thickening & T2-hyperintensity of abnormal brachial plexus neural components
- Signal changes in innervated muscles
- T2-hyperintensity denervation edema
- T1-hyperintensity fatty atrophy
- Postradiation plexopathy: Smooth neural thickening ± clumping ± T2-hyperintensity ± mild enhancement
- Variable effacement of perineural fat planes best appreciated on T1-weighted sagittal images
- Pseudomeningocele suggests root avulsion & high-grade preganglionic traumatic injury
- Benign neurogenic tumor: Well-circumscribed, homogeneously enhancing, oval lesion with smooth margins along length of nerve
- Target sign of central T2 hypointensity & peripheral T2 hyperintensity may be seen in neurofibromas
- Metastasis: Focal nodular mass lesion or focal neural enlargement, T2 hyperintensity of affected nerves, & contrast enhancement
- ### Ultrasonographic Findings
- **Postradiation plexopathy**: Diffuse enlargement ± with hypoechoic fibrotic atrophied perineural fat
- Usually involves > 1 component of brachial plexus, mainly supraclavicular components
- Thickening, hypoechogenicity, & stiffness of subcutaneous & deeper perineural tissues due to fibrosis
- **Traumatic plexopathy**: Swelling of injured nerves
- Focal discontinuity of swollen nerve indicates partial or complete transection
- Best depicted on longitudinal plane
- Retraction indicative of complete transection
- May develop posttraumatic NIC or end-neuroma
- Posttraumatic neuroma resembles nerve sheath tumor & is typically < 2 cm diameter
- **Benign neurogenic tumor**: Discrete, well-defined, ovoid hypoechoic mass inseparable from brachial plexus
- **Metastatic infiltration**: Focal, often irregular mass infiltrating neural components without tethering
- ± hypervascular on color Doppler US
- Often coexistent malignant-type lymphadenopathy
- May need US-guided biopsy to distinguish from nodular fibrosis
- **Neuralgic amyotrophy**: Focal enlargement of nerve
- Suprascapular nerve most commonly affected: Cross-sectional area > 4.2 mm² used as cut-off
- **Inflammatory plexopathy**: Diffuse enlargement of affected nerves with normal surrounding fat
- **Thoracic outlet syndrome**: Scan from interscalene to infraclavicular region at rest & after provocative movement
- Neurologic > venous > arterial compression
- Spectral analysis of subclavian artery & vein
- Subclavian & axillary arteries at rest, axillary artery in abduction
- Focal nerve entrapment ± altered spectral waveform
- Abnormal if flow diminished (peak systolic velocity increases 2x resting value), monophasic, or absent flow
- Reduced flow frequently seen in normal subjects so if abnormal, compare with contralateral side
- ### Imaging Recommendations
- #### Best imaging tool
- High-resolution US with linear transducer
- MR may be able to provide more information on preganglionic nerve roots & infraclavicular region
- MR or CT angiography in neutral & arm abducted position useful in vascular thoracic outlet syndrome
- #### Protocol advice
- Neural components best examined transversely
- Longitudinal plane helpful to show neural transection
- Always examine contralateral asymptomatic or less symptomatic side first
- Provides good indication as to normal appearances of brachial plexus in patient being examined
- Roots, trunks, & divisions examined with arm by side & head turned slightly to contralateral side
- Start scanning trunks in interscalene region, then move medially to examine roots & then laterally to examine divisions
- Cords examined with arm abducted to 90°
- Terminal branches examined with arm fully extended
## DIFFERENTIAL DIAGNOSIS
- ### Cervical Radiculopathy
- Normal brachial plexus US; MR will be confirmatory
## PATHOLOGY
- ### General Features
- Early transient radiation-induced plexopathy due to inflammatory response & small vessel ischemic changes
- Radiation-induced fibrosis occurs due to progressive fibrosis of endo- & perineural tissues
- Inflammatory plexopathy due to variety of causes
- Most commonly chronic inflammatory demyelinating polyneuropathy, multifocal motor neuropathy
- ### Staging, Grading, & Classification
- Neuropraxia represents low-grade (1st degree) nerve injury, characterized by impaired nerve conduction without axonal disruption & intact neural coverings
- High-grade nerve injury characterized by partial or complete nerve transection ± neuroma
## CLINICAL ISSUES
- ### Presentation
- #### Most common signs/symptoms
- Upper limb numbness, pain & weakness
- Sudden onset of unilateral shoulder girdle or upper limb pain suggests neuralgic amyotrophy
- Early transient radiation-induced plexopathy, 3-10 months after irradiation therapy with mild symptoms
- Radiation-induced fibrosis > 6 months to several years after radiotherapy
- ### Demographics
- Younger patients, traumatic injury or primary tumor
- Older patients, postradiation plexopathy or metastasis
- ### Natural History & Prognosis
- Low-grade neuropraxic traumatic injury gradually recovers
- Intermediate-grade traumatic injury gradually heals with mild fibrosis, often with mild residual functional deficit
- High-grade traumatic injury has minimal recovery potential
- ### Treatment
- Supportive ± steroids ± immunoglobulin therapy for radiation-induced fibrosis, inflammatory polyneuropathy & neuralgic amyotrophy
- Surgery for tumor excision or nerve reconstruction
- Primary repair, nerve grafting, nerve ± myotendinous transfer
## DIAGNOSTIC CHECKLIST
- ### Consider
- US is almost as accurate as MR for identifying & characterizing brachial plexopathy
- 2/3 of brachial plexus examinations are normal on both US & MR
- If US is normal, likelihood of finding abnormality on MR is very low
- Main exception is neuralgic amyotrophy, so if this is suspected & US is normal, proceed to MR
- ### Image Interpretation Pearls
- Always examine contralateral asymptomatic or less symptomatic side first
- ### Reporting Tips
- Grade postradiation plexopathy depending on degree of nerve swelling, perineural fibrosis, & clumping
aa716c22-5e6e-436b-9707-b7d80827512f
## References
## Selected References
1. [Yip SWY et al: Ultrasound accuracy for brachial plexus pathology. Clin Radiol. 79(7):e916-23, 2024](http://www.ncbi.nlm.nih.gov/pubmed/?term=38644074%5Bpmid%5D)
1. [Gilcrease-Garcia BM et al: Anatomy, imaging, and pathologic conditions of the brachial plexus. Radiographics. 40(6):1686-714, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=33001787%5Bpmid%5D)
1. [Hsu PC et al: Sonographic pearls for imaging the brachial plexus and its pathologies. Diagnostics (Basel). 10(5), 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32443708%5Bpmid%5D)
## Images
### Selected Images
![Transverse US of the contralateral side in a 56-year-old woman with prior radiotherapy and arm pain shows normal divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> (bunch of grapes appearance). Overlying omohyoid <img src='img/arrows/WC.png' alt='white curved arrow'/> and trapezius <img src='img/arrows/WO.png' alt='white open arrow'/> muscles are also normal.](images/app.statdx.com_image_thumbnail_361ee61c-e56f-4f2b-b4a6-db5ca8fc5a26_annotated_true_size_900_quality_90_0aea7158c8a29af3591c60b7e8effcc8c4a346be.jpg)
*Transverse US of the contralateral side in a 56-year-old woman with prior radiotherapy and arm pain shows normal divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> (bunch of grapes appearance). Overlying omohyoid <img src='img/arrows/WC.png' alt='white curved arrow'/> and trapezius <img src='img/arrows/WO.png' alt='white open arrow'/> muscles are also normal.*
![Transverse US of the contralateral side in a 56-year-old woman with prior radiotherapy and arm pain shows normal divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> (bunch of grapes appearance). Overlying omohyoid <img src='img/arrows/WC.png' alt='white curved arrow'/> and trapezius <img src='img/arrows/WO.png' alt='white open arrow'/> muscles are also normal.](images/app.statdx.com_image_thumbnail_361ee61c-e56f-4f2b-b4a6-db5ca8fc5a26_size_174_quality_85_72a11369e4b54b94200bd0962fc26e1bcbcc9fd2.jpg)
*Transverse US of the contralateral side in a 56-year-old woman with prior radiotherapy and arm pain shows normal divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> (bunch of grapes appearance). Overlying omohyoid <img src='img/arrows/WC.png' alt='white curved arrow'/> and trapezius <img src='img/arrows/WO.png' alt='white open arrow'/> muscles are also normal.*
![Transverse US on the symptomatic side shows thickened divisions with tethering and hypoechoic (&quot;dirty&quot;) intervening perineural fat <img src='img/arrows/WO.png' alt='white open arrow'/> due to fibrosis compatible with moderate radiation plexopathy. The overlying omohyoid <img src='img/arrows/WC.png' alt='white curved arrow'/> and trapezius <img src='img/arrows/WS.png' alt='white solid arrow'/> muscles are moderately atrophic.](images/app.statdx.com_image_thumbnail_95d92ede-2802-4862-a90d-cbe438cedae2_annotated_true_size_900_quality_90_19bf3b2dfe28a66d5df98ff21f6c5c7063ed4a7f.jpg)
*Transverse US on the symptomatic side shows thickened divisions with tethering and hypoechoic (&quot;dirty&quot;) intervening perineural fat <img src='img/arrows/WO.png' alt='white open arrow'/> due to fibrosis compatible with moderate radiation plexopathy. The overlying omohyoid <img src='img/arrows/WC.png' alt='white curved arrow'/> and trapezius <img src='img/arrows/WS.png' alt='white solid arrow'/> muscles are moderately atrophic.*
![Transverse US of the contralateral supraclavicular region in a 68-year-old man with diffuse large B-cell lymphoma and arm pain shows normal divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> alongside subclavian artery <img src='img/arrows/WO.png' alt='white open arrow'/>. Suprascapular nerve <img src='img/arrows/WC.png' alt='white curved arrow'/> deep to omohyoid muscle <img src='img/arrows/BS.png' alt='black solid arrow'/> is normal.](images/app.statdx.com_image_thumbnail_ef61eb29-8bb6-47b5-a975-a113118b1025_annotated_true_size_900_quality_90_03efc6a9d05593fecc780ea0fa7293c6a42f89c1.jpg)
*Transverse US of the contralateral supraclavicular region in a 68-year-old man with diffuse large B-cell lymphoma and arm pain shows normal divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> alongside subclavian artery <img src='img/arrows/WO.png' alt='white open arrow'/>. Suprascapular nerve <img src='img/arrows/WC.png' alt='white curved arrow'/> deep to omohyoid muscle <img src='img/arrows/BS.png' alt='black solid arrow'/> is normal.*
![Transverse US of the same area on the symptomatic side shows focal, mass-like soft tissue thickening encasing the divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> consistent with lymphoma infiltration. The suprascapular nerve deep to the omohyoid muscle <img src='img/arrows/BS.png' alt='black solid arrow'/> is not affected.](images/app.statdx.com_image_thumbnail_48229930-635f-45fc-a8a3-5694b7bf8b76_annotated_true_size_900_quality_90_1f32d56f8317b8a6d56f077141e66c63ed38576d.jpg)
*Transverse US of the same area on the symptomatic side shows focal, mass-like soft tissue thickening encasing the divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> consistent with lymphoma infiltration. The suprascapular nerve deep to the omohyoid muscle <img src='img/arrows/BS.png' alt='black solid arrow'/> is not affected.*
![Transverse US of the interscalene region in a 48-year-old man with chronic inflammatory demyelinating polyneuropathy (CIDP) shows severe smooth enlargement of the superior <img src='img/arrows/WS.png' alt='white solid arrow'/>, middle <img src='img/arrows/WO.png' alt='white open arrow'/>, and inferior <img src='img/arrows/WC.png' alt='white curved arrow'/> trunks. The middle trunk measured 26 mm&sup2;. Perineural fat is normal.](images/app.statdx.com_image_thumbnail_feb3858a-d51b-439d-afc0-10a4d1841019_annotated_true_size_900_quality_90_a1ea7e8b77e641db1299afb068de15609bf063ed.jpg)
*Transverse US of the interscalene region in a 48-year-old man with chronic inflammatory demyelinating polyneuropathy (CIDP) shows severe smooth enlargement of the superior <img src='img/arrows/WS.png' alt='white solid arrow'/>, middle <img src='img/arrows/WO.png' alt='white open arrow'/>, and inferior <img src='img/arrows/WC.png' alt='white curved arrow'/> trunks. The middle trunk measured 26 mm&sup2;. Perineural fat is normal.*
![Transverse US of the contralateral left side in the same patient shows moderate smooth enlargement of the middle trunk measuring 12 mm&sup2; <img src='img/arrows/WO.png' alt='white open arrow'/>, compatible with inflammatory polyneuropathy, more severe on the right side.](images/app.statdx.com_image_thumbnail_0945fa94-a6a3-40e5-9a59-54ba48a0d5c1_annotated_true_size_900_quality_90_d2f4673b2fa1209d107378b64701b1fd09cf2b57.jpg)
*Transverse US of the contralateral left side in the same patient shows moderate smooth enlargement of the middle trunk measuring 12 mm&sup2; <img src='img/arrows/WO.png' alt='white open arrow'/>, compatible with inflammatory polyneuropathy, more severe on the right side.*
![Transverse US of the supraclavicular region in a 23-year-old man with arm pain shows a medium-sized, smooth, well-defined soft tissue mass indicative of a nerve sheath tumor <img src='img/arrows/WO.png' alt='white open arrow'/> arising from the posterior aspect of the divisions superolateral to the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_25d31bbc-8056-45fc-838e-644646466a00_annotated_true_size_900_quality_90_7d2214bf71254859f85ff660286031646112970c.jpg)
*Transverse US of the supraclavicular region in a 23-year-old man with arm pain shows a medium-sized, smooth, well-defined soft tissue mass indicative of a nerve sheath tumor <img src='img/arrows/WO.png' alt='white open arrow'/> arising from the posterior aspect of the divisions superolateral to the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Coronal T2 FS MR in the same patient shows a T2-hyperintense neurogenic tumor <img src='img/arrows/WO.png' alt='white open arrow'/> along the posterior divisions. Mild motion artifact is present. Surgical excision confirmed a benign schwannoma.](images/app.statdx.com_image_thumbnail_a3f6f3e1-44b6-4a9e-a6f0-30de6d2b3a7f_annotated_true_size_900_quality_90_63c649ed9fabad4375f90c809e1db0a4274ad8c1.jpg)
*Coronal T2 FS MR in the same patient shows a T2-hyperintense neurogenic tumor <img src='img/arrows/WO.png' alt='white open arrow'/> along the posterior divisions. Mild motion artifact is present. Surgical excision confirmed a benign schwannoma.*
![Transverse US of the supraclavicular region in a 72-year-old man with axillary swelling and arm weakness shows a large, heterogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> completely encasing the divisions of the brachial plexus.](images/app.statdx.com_image_thumbnail_09a94bfd-b0e9-450e-a3cb-530374a47883_annotated_true_size_900_quality_90_b0ec19abc9e03eee28976435a969f8f1c30bb003.jpg)
*Transverse US of the supraclavicular region in a 72-year-old man with axillary swelling and arm weakness shows a large, heterogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> completely encasing the divisions of the brachial plexus.*
![Color Doppler US of the same area shows moderate hypervascularity within this heterogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> suggestive of a malignant tumor.](images/app.statdx.com_image_thumbnail_6224dfc0-de7b-4bee-8111-fec8af0fe776_annotated_true_size_900_quality_90_d24a6a4693e7508a6889f357d54473e635be795e.jpg)
*Color Doppler US of the same area shows moderate hypervascularity within this heterogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> suggestive of a malignant tumor.*
![Transverse US more distally shows the mass <img src='img/arrows/WS.png' alt='white solid arrow'/> completely encasing the cords of the brachial plexus. Surgery revealed a diffuse large B-cell lymphoma completely encasing the divisions and cords of the brachial plexus.](images/app.statdx.com_image_thumbnail_2a62f11f-e475-4675-9bda-29a8fa29a606_annotated_true_size_900_quality_90_c0acbf63df7a57e89ac35b1745475c071f39f7c3.jpg)
*Transverse US more distally shows the mass <img src='img/arrows/WS.png' alt='white solid arrow'/> completely encasing the cords of the brachial plexus. Surgery revealed a diffuse large B-cell lymphoma completely encasing the divisions and cords of the brachial plexus.*
![Transverse US of interscalene region in a 64-year-old woman with previous left-sided radiotherapy for breast cancer with progressive left arm pain shows severe smooth thickening of the superior <img src='img/arrows/WO.png' alt='white open arrow'/>, middle <img src='img/arrows/WS.png' alt='white solid arrow'/>, &amp; inferior <img src='img/arrows/BS.png' alt='black solid arrow'/> trunks with atrophy of the perineural fat <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_66c1df4a-8a11-4853-8536-5de692401792_annotated_true_size_900_quality_90_822114a8400f6381521cbd4621aa498a93c197cd.jpg)
*Transverse US of interscalene region in a 64-year-old woman with previous left-sided radiotherapy for breast cancer with progressive left arm pain shows severe smooth thickening of the superior <img src='img/arrows/WO.png' alt='white open arrow'/>, middle <img src='img/arrows/WS.png' alt='white solid arrow'/>, &amp; inferior <img src='img/arrows/BS.png' alt='black solid arrow'/> trunks with atrophy of the perineural fat <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Transverse US of the subcoracoid recess in the same patient shows diffusely thickened, partially tethered terminal divisions and cords <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus adjacent to the axillary artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_aab1df35-cadb-4402-a2c9-c09bd1dcd597_annotated_true_size_900_quality_90_0374a12bbbac1575c425694370c9aa8c24fcf16d.jpg)
*Transverse US of the subcoracoid recess in the same patient shows diffusely thickened, partially tethered terminal divisions and cords <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus adjacent to the axillary artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Transverse US in the same patient shows moderate to severe enlargement of the terminal branches <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus along the axillary artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. This is compatible with severe radiation plexopathy involving the trunks to terminal branches.](images/app.statdx.com_image_thumbnail_cc7a768e-414a-4ff6-9ceb-7f6b6c7a660f_annotated_true_size_900_quality_90_d51fc48cd789dff967378c09feb93fd34835863d.jpg)
*Transverse US in the same patient shows moderate to severe enlargement of the terminal branches <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus along the axillary artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. This is compatible with severe radiation plexopathy involving the trunks to terminal branches.*
![Clinical photograph of a 62-year-old man with left arm pain and weakness 20 years after radiotherapy for nasopharyngeal carcinoma shows postradiotherapy skin changes <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_57ffc45b-05ea-4c2a-bc7d-e70d8215a688_annotated_true_size_900_quality_90_617fd67679fb472ab981d87acb0fbc9decfd8f3c.jpg)
*Clinical photograph of a 62-year-old man with left arm pain and weakness 20 years after radiotherapy for nasopharyngeal carcinoma shows postradiotherapy skin changes <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Transverse US in the same patient shows severe radiation fibrosis of the interscalene region with fibrosis of the perineural fat surrounding the mildly swollen trunks <img src='img/arrows/WS.png' alt='white solid arrow'/>, poor muscle definition, and severe dermal- subcutaneous thickening <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_54fa276b-236f-4c7f-b2a2-00af46d0be20_annotated_true_size_900_quality_90_a9bfba97b5356af91c125bdaeb60c820cec1e73b.jpg)
*Transverse US in the same patient shows severe radiation fibrosis of the interscalene region with fibrosis of the perineural fat surrounding the mildly swollen trunks <img src='img/arrows/WS.png' alt='white solid arrow'/>, poor muscle definition, and severe dermal- subcutaneous thickening <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Transverse US of the subcoracoid recess in a 27-year-old male MVA victim with arm weakness shows moderate thickening of the posterior and lateral cords <img src='img/arrows/WO.png' alt='white open arrow'/> adjacent to the axillary artery <img src='img/arrows/WC.png' alt='white curved arrow'/>, suggestive of moderate to severity traction injury.](images/app.statdx.com_image_thumbnail_d693e93f-a5d5-4fbb-ad4b-d1ebcaadeb65_annotated_true_size_900_quality_90_71a2b6d6d4cd3d7cb08420f3488a6021889c7828.jpg)
*Transverse US of the subcoracoid recess in a 27-year-old male MVA victim with arm weakness shows moderate thickening of the posterior and lateral cords <img src='img/arrows/WO.png' alt='white open arrow'/> adjacent to the axillary artery <img src='img/arrows/WC.png' alt='white curved arrow'/>, suggestive of moderate to severity traction injury.*
![Transverse US of the asymptomatic side at the same region shows normal lateral, posterior, and medial cords <img src='img/arrows/WS.png' alt='white solid arrow'/> alongside the axillary artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_ad778d38-0927-46ad-8867-08778f316506_annotated_true_size_900_quality_90_55d756e063dbc27ae0775e16225844f0f2a1dc0b.jpg)
*Transverse US of the asymptomatic side at the same region shows normal lateral, posterior, and medial cords <img src='img/arrows/WS.png' alt='white solid arrow'/> alongside the axillary artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Longitudinal US of the noninjured side in the same patient shows a normal left musculocutaneous nerve <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_99573840-f3af-4e9d-b3a5-3be790ba830f_annotated_true_size_900_quality_90_de403c15feb0d8d2b1ffa3dfd1a0f05cf6584263.jpg)
*Longitudinal US of the noninjured side in the same patient shows a normal left musculocutaneous nerve <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Longitudinal US of the injured side in the same patient shows severe smooth thickening of the musculoskeletal nerve <img src='img/arrows/WO.png' alt='white open arrow'/> indicative of severe traction injury.](images/app.statdx.com_image_thumbnail_c26b44a7-7280-40ed-bdd0-c7ea55dc6c31_annotated_true_size_900_quality_90_fe0acea63fc571fbf7c505c61454effe93b39588.jpg)
*Longitudinal US of the injured side in the same patient shows severe smooth thickening of the musculoskeletal nerve <img src='img/arrows/WO.png' alt='white open arrow'/> indicative of severe traction injury.*
![Transverse US in the same patient shows marked enlargement of the proximal right musculoskeletal nerve measuring 14.1 mm&sup2; <img src='img/arrows/WO.png' alt='white open arrow'/> as it courses between the biceps <img src='img/arrows/BC.png' alt='black curved arrow'/> and coracobrachialis <img src='img/arrows/WC.png' alt='white curved arrow'/> muscles. Surgery confirmed complete loss of musculocutaneous nerve function and severe injury to lateral and posterior cords.](images/app.statdx.com_image_thumbnail_e1de958d-b532-47a5-b8f3-d35ed90b6b14_annotated_true_size_900_quality_90_591097fae36fd936b802fdbcf6a6b66308a196ed.jpg)
*Transverse US in the same patient shows marked enlargement of the proximal right musculoskeletal nerve measuring 14.1 mm&sup2; <img src='img/arrows/WO.png' alt='white open arrow'/> as it courses between the biceps <img src='img/arrows/BC.png' alt='black curved arrow'/> and coracobrachialis <img src='img/arrows/WC.png' alt='white curved arrow'/> muscles. Surgery confirmed complete loss of musculocutaneous nerve function and severe injury to lateral and posterior cords.*
![Longitudinal US in the same patient shows a neuroma-in-continuity <img src='img/arrows/WS.png' alt='white solid arrow'/> of the posterior cord <img src='img/arrows/WO.png' alt='white open arrow'/> deep to the pectoralis minor muscle <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_c05a969c-2048-49d9-ad18-0f66dba28651_annotated_true_size_900_quality_90_59c4f211a234657d9fc204089f1f045bff873ea9.jpg)
*Longitudinal US in the same patient shows a neuroma-in-continuity <img src='img/arrows/WS.png' alt='white solid arrow'/> of the posterior cord <img src='img/arrows/WO.png' alt='white open arrow'/> deep to the pectoralis minor muscle <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
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---
## KEY FACTS
- ### Terminology
- Benign Schwann cell neoplasm that **arises from b****rachial plexus** (BP) in perivertebral space (PVS)
- ### Imaging
- Well-circumscribed, **fusiform mass** along course of BP
- Occurs along course of BP in any segment
- Intra- and extradural and neural foramen
- In PVS between anterior and middle scalene muscles
- 3D STIR to produce MR neurography increasing in utilization to depict BP normal anatomy and schwannomas
- ### Top Differential Diagnoses
- Nodal metastasis
- Neurofibroma
- Lateral meningocele
- Malignant peripheral nerve sheath tumor
- ### Pathology
- Cystic degeneration and hemorrhage common
- Firm, encapsulated, fusiform mass attaches to and displaces nerve
- Malignant peripheral nerve sheath tumors (MPNST) comprising 7% of all tumors of BP
- ### Clinical Issues
- 5% of benign soft tissue neoplasms
- Malignant degeneration rare, more common with multiple schwannoma syndromes
- Development of pain should raise suspicion for malignancy
- ### Diagnostic Checklist
- Determination that lesion is along course of BP is key
- Roots of BP (C5-T1) emerge into scalene triangle between anterior and middle scalene muscles
## TERMINOLOGY
- ### Abbreviations
- Brachial plexus (BP) schwannoma
- ### Synonyms
- Peripheral nerve sheath tumor
- Neurilemmoma, neurinoma, or neuroma
- ### Definitions
- Benign Schwann cell neoplasm that arises from BP in perivertebral space (PVS)
## IMAGING
- ### General Features
- #### Best diagnostic clue
- Well-circumscribed, fusiform mass along course of BP
- #### Location
- Occurs along course of BP in any segment
- Intra- and extradural and neural foramen
- In PVS between anterior and middle scalene muscles
- #### Size
- Variable
- #### Morphology
- Fusiform or dumbbell-shaped mass
- Cystic degeneration and hemorrhage common
- ### CT Findings
- #### NECT
- Typically isodense to muscle; calcification uncommon
- When paraspinal, bony neural foramen shows **smooth enlargement**
- #### CECT
- Mild to moderate enhancement
- ### MR Findings
- #### T1WI
- **Fusiform mass**, isointense to muscle
- #### T2WI
- Heterogeneously hyperintense
- **Target sign**: Central hypointense, peripheral hyperintense signal
- **Fascicular sign**: Multiple irregular, central hypointense foci
- #### STIR
- 3D STIR to produce MR neurography increasing in utilization to depict BP normal anatomy and schwannomas
- #### T1WI C+
- Moderate heterogeneous enhancement
- **Intramural cysts** common
- More uniform enhancement when small
- ### Ultrasonographic Findings
- Hypoechoic, well-defined mass
- May show distal acoustic enhancement
- ### Imaging Recommendations
- #### Best imaging tool
- MR best demonstrates normal BP segments and schwannoma
- #### Protocol advice
- T1WI with FS and STIR improve conspicuity
## DIFFERENTIAL DIAGNOSIS
- [Nodal Metastasis](/document/systemic-nodal-metastases-in-neck/7deeddbc-3b34-4361-af37-034a6a513de3)
- Supraclavicular nodes are metastatic site for chest and abdominal disease
- Lower cervical nodes medial to anterior scalene muscle, adjacent to internal jugular vein
- [Neurofibroma](/document/neurofibroma/2a6fc311-67d8-4789-9d68-b65d75552c06)
- May be indistinguishable from schwannoma on MR
- Typically lower density on NECT, approaching water density
- Cystic degeneration and hemorrhage uncommon
- ### Lateral Meningocele
- Fusiform cystic mass follows CSF density/intensity
- Contiguous with spinal canal
- [Malignant Peripheral Nerve Sheath Tumor](/document/malignant-peripheral-nerve-sheath--/27e44c24-a053-4db8-a50c-0411df7b1e79)
- Progressively enlarging, irregular, heterogeneous mass
- Typically associated with pain
## PATHOLOGY
- ### General Features
- #### Etiology
- Solitary schwannoma usually sporadic
- Multiple schwannomas occur with multiple inherited schwannomas, meningiomas, ependymomas, and schwannomatosis
- ### Gross Pathologic & Surgical Features
- Firm, encapsulated, well-circumscribed, gray-tan, fusiform mass attached to and displacing nerve
- Cystic degeneration and hemorrhage common
- ### Microscopic Features
- Tumor arises from Schwann cells of nerve sheath
- Alternating regions of high cellularity (Antoni A) and loose, myxoid component (Antoni B)
## CLINICAL ISSUES
- ### Presentation
- #### Most common signs/symptoms
- Painless, slow-growing mass in lateral neck ± radiculopathy
- Pain or dysesthesias on palpation said to be characteristic
- ### Demographics
- #### Age
- Peaks at 20-30 years
- #### Epidemiology
- 5% benign soft tissue neoplasms
- ### Natural History & Prognosis
- Slow-growing lesion
- Malignant degeneration rare, more common with multiple schwannoma syndromes
- Development of **pain** should raise suspicion for **malignancy**
- ### Treatment
- Surgical excision usually cures
- Tumors rarely recur
## DIAGNOSTIC CHECKLIST
- ### Image Interpretation Pearls
- Determination that lesion is along course of BP is key
- Roots of BP (C5-T1) emerge into scalene triangle between anterior and middle scalene muscles
- ### Reporting Tips
- When describing any low neck lesion, always describe relationship of lesion to BP course
88a4746c-7537-44aa-85ee-35e784abf174
## References
## Selected References
1. [Madhuranthakam AJ: Advanced techniques on horizon for MR imaging of brachial plexus. Eur Radiol. 34(2):885-6, 2024](http://www.ncbi.nlm.nih.gov/pubmed/?term=37624412%5Bpmid%5D)
1. [Davidson EJ et al: Brachial plexus magnetic resonance neurography: technical challenges and solutions. Invest Radiol. 58(1):14-27, 2023](http://www.ncbi.nlm.nih.gov/pubmed/?term=35926072%5Bpmid%5D)
1. [Lubelski D et al: Natural history of brachial plexus, peripheral nerve, and spinal schwannomas. Neurosurgery. 91(6):883-91, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=36069570%5Bpmid%5D)
1. [Gilcrease-Garcia BM et al: Anatomy, imaging, and pathologic conditions of the brachial plexus. Radiographics. 40(6):1686-714, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=33001787%5Bpmid%5D)
1. [Yonezawa H et al: Structural origin and surgical complications of peripheral schwannomas. Anticancer Res. 40(11):6563-70, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=33109598%5Bpmid%5D)
1. [Desai KI: The surgical management of symptomatic benign peripheral nerve sheath tumors of the neck and extremities: an experience of 442 cases. Neurosurgery. 81(4):568-80, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28475798%5Bpmid%5D)
1. [Jia X et al: Primary brachial plexus tumors: clinical experiences of 143 cases. Clin Neurol Neurosurg. 148:91-5, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27428490%5Bpmid%5D)
1. [Lutz AM et al: MR imaging of the brachial plexus. Neuroimaging Clin N Am. 24(1):91-108, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24210315%5Bpmid%5D)
1. [Siqueira MG et al: Management of brachial plexus region tumours and tumour-like conditions: relevant diagnostic and surgical features in a consecutive series of eighteen patients. Acta Neurochir (Wien). 151(9):1089-98, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=19448970%5Bpmid%5D)
1. [de Araujo CE et al: Neck nerve trunks schwannomas: clinical features and postoperative neurologic outcome. Laryngoscope. 118(9):1579-82, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18596560%5Bpmid%5D)
1. [Gupta G et al: Malignant peripheral nerve sheath tumors. Neurosurg Clin N Am. 19(4):533-43, v, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=19010279%5Bpmid%5D)
1. [Binder DK et al: Primary brachial plexus tumors: imaging, surgical, and pathological findings in 25 patients. Neurosurg Focus. 16(5):E11, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=15174831%5Bpmid%5D)
1. [Wittenberg KH et al: MR imaging of nontraumatic brachial plexopathies: frequency and spectrum of findings. Radiographics. 20(4):1023-32, 2000](http://www.ncbi.nlm.nih.gov/pubmed/?term=10903692%5Bpmid%5D)
1. [Murphey MD et al: From the archives of the AFIP. Imaging of musculoskeletal neurogenic tumors: radiologic-pathologic correlation. Radiographics. 19(5):1253-80, 1999](http://www.ncbi.nlm.nih.gov/pubmed/?term=10489179%5Bpmid%5D)
## Differential diagnosis
### Brachial Plexus Lesion
DDX:f15c5303-8598-421e-b978-fba4dea2b6a6
### Cervicothoracic Junction Lesion
DDX:0226620f-95d5-48cd-a7e5-c7662e898dc5
### Supraclavicular Mass
DDX:a6dff053-ced8-419f-9f7a-db4ba06b00f2
### Perivertebral Space Lesion
DDX:60caace9-af6d-42c6-ae93-b703e7bfb494
## Anatomy
### Accessory Nerve (CNXI)
Brain/ANATOMY:9d50453e-c26a-46a3-826e-265736e43174
### Suprahyoid and Infrahyoid Neck Overview
Head and Neck/ANATOMY:50ac1eaf-3866-4ebd-8f5c-437055a64ba4
### Perivertebral Space
Head and Neck/ANATOMY:ed29ca1b-3ac7-46be-8ea9-81e340d583b9
### Posterior Cervical Space
Head and Neck/ANATOMY:b274cd65-ed5c-43a0-b734-e61122b35ce3
### Cervical Lymph Nodes
Head and Neck/ANATOMY:c8f730fb-5aeb-40d8-9fbc-0c2320f12e63
### CNXI (Accessory Nerve)
Head and Neck/ANATOMY:18e60151-70bc-40a1-9b4f-4b86f8fd65c2
### Brachial Plexus
Head and Neck/ANATOMY:a702f5d9-f5dc-49b0-925b-20ebeecead44
### Brachial Plexus
Spine/ANATOMY:d40ec749-81b1-4900-b366-2921b7fcc467
## Images
### Selected Images
![Axial T1WI C+ FS MR demonstrates a large schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower right neck overlying the middle scalene muscle <img src='img/arrows/WC.png' alt='white curved arrow'/> with intense, irregular peripheral enhancement. Central nonenhancement represents cystic degeneration. The lesion is more lateral in location than expected for lower cervical nodes, which typically abut the internal jugular vein <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_4a58370e-d757-4805-b819-8e2ab9378032_annotated_true_size_900_quality_90_5ca293bf3babcd8d31c023fcb8126179c5fdde04.jpg)
*Axial T1WI C+ FS MR demonstrates a large schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower right neck overlying the middle scalene muscle <img src='img/arrows/WC.png' alt='white curved arrow'/> with intense, irregular peripheral enhancement. Central nonenhancement represents cystic degeneration. The lesion is more lateral in location than expected for lower cervical nodes, which typically abut the internal jugular vein <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Axial T1WI C+ FS MR demonstrates a large schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower right neck overlying the middle scalene muscle <img src='img/arrows/WC.png' alt='white curved arrow'/> with intense, irregular peripheral enhancement. Central nonenhancement represents cystic degeneration. The lesion is more lateral in location than expected for lower cervical nodes, which typically abut the internal jugular vein <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_4a58370e-d757-4805-b819-8e2ab9378032_size_174_quality_85_9928ab2c553598997ca168fc94c4e0bc19dbfa90.jpg)
*Axial T1WI C+ FS MR demonstrates a large schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower right neck overlying the middle scalene muscle <img src='img/arrows/WC.png' alt='white curved arrow'/> with intense, irregular peripheral enhancement. Central nonenhancement represents cystic degeneration. The lesion is more lateral in location than expected for lower cervical nodes, which typically abut the internal jugular vein <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Coronal CECT shows a fusiform mass with mild, patchy contrast enhancement <img src='img/arrows/WS.png' alt='white solid arrow'/>. Note relation to the C6 root of brachial plexus <img src='img/arrows/CO.png' alt='cyan open arrow'/>.](images/app.statdx.com_image_thumbnail_4b86814f-3459-405f-8e8c-56d7b3eebd85_annotated_true_size_900_quality_90_0e7d0ae5551304c9f3ae8a876fdc0c44fd99c1e2.jpg)
*Coronal CECT shows a fusiform mass with mild, patchy contrast enhancement <img src='img/arrows/WS.png' alt='white solid arrow'/>. Note relation to the C6 root of brachial plexus <img src='img/arrows/CO.png' alt='cyan open arrow'/>.*
![Coronal STIR MR (MR neurography technique) demonstrates an asymmetrically enlarged, lobulated right C8 nerve root <img src='img/arrows/WS.png' alt='white solid arrow'/> extending from the C8-T1 neural foramen.](images/app.statdx.com_image_thumbnail_ffd32d20-1752-48ba-912b-3779125bfb1f_annotated_true_size_900_quality_90_76af88c36c968523ea4d682bf9f075280389c1f8.jpg)
*Coronal STIR MR (MR neurography technique) demonstrates an asymmetrically enlarged, lobulated right C8 nerve root <img src='img/arrows/WS.png' alt='white solid arrow'/> extending from the C8-T1 neural foramen.*
![Coronal T2 FS MR demonstrates a well-circumscribed, lobulated, fusiform mass <img src='img/arrows/WS.png' alt='white solid arrow'/> oriented along the course of the C6 root of the brachial plexus. The mass is hyperintense on T2WI with areas of heterogeneity, signifying cystic degenerative change <img src='img/arrows/BC.png' alt='black curved arrow'/>.](images/app.statdx.com_image_thumbnail_e3d86399-3bc7-46b8-95fa-5f853964d78d_annotated_true_size_900_quality_90_dbf4b30fc8aa2e8cfa923c33a985caac963b10d0.jpg)
*Coronal T2 FS MR demonstrates a well-circumscribed, lobulated, fusiform mass <img src='img/arrows/WS.png' alt='white solid arrow'/> oriented along the course of the C6 root of the brachial plexus. The mass is hyperintense on T2WI with areas of heterogeneity, signifying cystic degenerative change <img src='img/arrows/BC.png' alt='black curved arrow'/>.*
### Additional Images
![Coronal T1WI C+ MR shows avidly enhancing fusiform mass <img src='img/arrows/WS.png' alt='white solid arrow'/> with multiple areas of intramural cystic change <img src='img/arrows/BO.png' alt='black open arrow'/>.](images/app.statdx.com_image_thumbnail_fe98cab5-234b-47a8-96a0-6f2a9dcf7eee_annotated_true_size_900_quality_90_5295c1bcbe826107f51820960a491e3304a09802.jpg)
*Coronal T1WI C+ MR shows avidly enhancing fusiform mass <img src='img/arrows/WS.png' alt='white solid arrow'/> with multiple areas of intramural cystic change <img src='img/arrows/BO.png' alt='black open arrow'/>.*
![Coronal T1WI MR of brachial plexus schwannoma reveals a well-circumscribed, fusiform, solid soft tissue mass <img src='img/arrows/WS.png' alt='white solid arrow'/> oriented along the brachial plexus, typical of a benign peripheral nerve sheath tumor.](images/app.statdx.com_image_thumbnail_f1bead4e-82c5-41d0-857b-c6f347e50d0c_annotated_true_size_900_quality_90_11829f518bef0065b060f18144a81f6a9acb981d.jpg)
*Coronal T1WI MR of brachial plexus schwannoma reveals a well-circumscribed, fusiform, solid soft tissue mass <img src='img/arrows/WS.png' alt='white solid arrow'/> oriented along the brachial plexus, typical of a benign peripheral nerve sheath tumor.*
![Axial CECT of brachial plexus schwannoma shows central cystic degeneration within a well-circumscribed soft tissue mass <img src='img/arrows/WS.png' alt='white solid arrow'/>. Cystic degeneration is uncommon with neurofibroma.](68234c2f-8fa7-454a-982d-400beceea922)
*Axial CECT of brachial plexus schwannoma shows central cystic degeneration within a well-circumscribed soft tissue mass <img src='img/arrows/WS.png' alt='white solid arrow'/>. Cystic degeneration is uncommon with neurofibroma.*
![Coronal T1WI C+ MR reveals an intensely enhancing mass <img src='img/arrows/WS.png' alt='white solid arrow'/> with central cystic degeneration, typical of schwannoma.](images/app.statdx.com_image_thumbnail_f0b9cbdc-397e-442b-b5f0-22acb127b712_annotated_true_size_900_quality_90_e54c88f6ef1882cadc2a234e90cc227843eb1834.jpg)
*Coronal T1WI C+ MR reveals an intensely enhancing mass <img src='img/arrows/WS.png' alt='white solid arrow'/> with central cystic degeneration, typical of schwannoma.*
![Sagittal T1WI MR demonstrates a well-defined, oval-shaped mass <img src='img/arrows/WS.png' alt='white solid arrow'/> in the posterior cervical space with slight mass effect on the adjacent paraspinous musculature <img src='img/arrows/WC.png' alt='white curved arrow'/>. The mass is isointense to the muscle.](images/app.statdx.com_image_thumbnail_8952f04c-3c78-4a8b-96e8-2c8dff2864e1_annotated_true_size_900_quality_90_ca34454e98c692cc4bc549d746eee692f7e7bab9.jpg)
*Sagittal T1WI MR demonstrates a well-defined, oval-shaped mass <img src='img/arrows/WS.png' alt='white solid arrow'/> in the posterior cervical space with slight mass effect on the adjacent paraspinous musculature <img src='img/arrows/WC.png' alt='white curved arrow'/>. The mass is isointense to the muscle.*
![Axial T1WI C+ FS MR following gadolinium administration demonstrates intense enhancement of solitary perivertebral space schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_7ea06e50-98fe-46c0-bf09-a50dab7ac341_annotated_true_size_900_quality_90_9aa38c9b9861eba541aeb0eb326b50b9059f3727.jpg)
*Axial T1WI C+ FS MR following gadolinium administration demonstrates intense enhancement of solitary perivertebral space schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Axial T2 MR in an older adult patient with a lower neck mass, right arm pain, and myelopathy shows a well-circumscribed, giant schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> effacing the lower brachial plexus and scalene muscles. The lesion is heterogeneously hyperintense on T2 MR.](images/app.statdx.com_image_thumbnail_a26e6684-d69a-4090-a2b1-4fdbd9998535_annotated_true_size_900_quality_90_d909fd337c8abe9924cb2e0ead48863735f8c6f4.jpg)
*Axial T2 MR in an older adult patient with a lower neck mass, right arm pain, and myelopathy shows a well-circumscribed, giant schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> effacing the lower brachial plexus and scalene muscles. The lesion is heterogeneously hyperintense on T2 MR.*
![Axial T2 MR at a higher level in the same patient shows a more dumbbell-shaped component of the biopsy- proven giant schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/>. Medially, the tumor extends through the C6-C7 neural foramen <img src='img/arrows/WO.png' alt='white open arrow'/> where the tumor compresses the spinal cord <img src='img/arrows/WC.png' alt='white curved arrow'/>. The spinal cord compression accounts for the patient's cervical myelopathy.](images/app.statdx.com_image_thumbnail_8588f2b7-17a9-4a01-9ac8-800310a4f01a_annotated_true_size_900_quality_90_97c04f281fbc3ac4054bdfc86d0a4b6a70f66e99.jpg)
*Axial T2 MR at a higher level in the same patient shows a more dumbbell-shaped component of the biopsy- proven giant schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/>. Medially, the tumor extends through the C6-C7 neural foramen <img src='img/arrows/WO.png' alt='white open arrow'/> where the tumor compresses the spinal cord <img src='img/arrows/WC.png' alt='white curved arrow'/>. The spinal cord compression accounts for the patient's cervical myelopathy.*
![Axial T1 C+ FS MR in the same patient shows that the giant schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> is solid and demonstrates heterogeneous enhancement. The vertebral artery <img src='img/arrows/WC.png' alt='white curved arrow'/> is displaced anteriorly by the mass.](images/app.statdx.com_image_thumbnail_b1224762-5f8b-4083-8e4a-a8d0ff7bb82f_annotated_true_size_900_quality_90_b41a6aabef25b9972cd139efe07c74088a13d7f7.jpg)
*Axial T1 C+ FS MR in the same patient shows that the giant schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> is solid and demonstrates heterogeneous enhancement. The vertebral artery <img src='img/arrows/WC.png' alt='white curved arrow'/> is displaced anteriorly by the mass.*
![Coronal T2 MR in this older adult patient with a giant schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> shows a heterogeneously T2 signal mass involving the scalene triangle. Extension into the neural foramen at C6-C7 <img src='img/arrows/WC.png' alt='white curved arrow'/> is a clue to the nerve sheath origin of the tumor. A normal contralateral C7 nerve <img src='img/arrows/WO.png' alt='white open arrow'/> is noted.](images/app.statdx.com_image_thumbnail_4f52c4a9-4d8e-430d-836c-79bd6eee501e_annotated_true_size_900_quality_90_8db471b005cb9be341d4483aa6211aeab01496db.jpg)
*Coronal T2 MR in this older adult patient with a giant schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> shows a heterogeneously T2 signal mass involving the scalene triangle. Extension into the neural foramen at C6-C7 <img src='img/arrows/WC.png' alt='white curved arrow'/> is a clue to the nerve sheath origin of the tumor. A normal contralateral C7 nerve <img src='img/arrows/WO.png' alt='white open arrow'/> is noted.*
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breadcrumbs:
- "Ultrasound"
- "Diagnosis"
- "Head and Neck"
- "Lumps and Bumps"
- "Solid"
- "Brachial Plexus Schwannoma"
---
## KEY FACTS
- ### Terminology
- Benign neoplasm of Schwann cells that wrap brachial plexus (BP) nerves in perivertebral space (PVS)
- ### Imaging
- Lesions within perivertebral spaces (PVS) are situated between anterior and middle scalene muscles
- US is best able to fully evaluate lesions in PVS/lateral neck
- Solid mass with well-defined margin, hypoechoic and heterogeneous echo pattern
- Fusiform/oval shape, ± tapering ends in continuity with brachial plexus (BP)
- ± sharply defined cystic/hemorrhagic areas within
- May have pseudocystic appearance with posterior enhancement (despite being solid)
- Color Doppler shows vascularity within, which may disappear upon excessive transducer pressure
- US identifies nature of lesion in lateral neck but may be unable to delineate proximal and distal extent of large lesions
- MR confirms extent, multiplicity (if any) of large lesions after US has made diagnosis
- Pressure/manipulating mass with transducer or needle biopsy may cause symptoms of radiculopathy
- Development of pain in BP schwannoma raises suspicion of malignancy
- ### Top Differential Diagnoses
- Neurofibroma
- Metastatic nodes
- Tuberculous nodes
- Lymphangioma
- ### Clinical Issues
- Painless, slow-growing mass in lateral neck ± radiculopathy
- Malignant degeneration rare
- Development of pain should raise suspicion for malignancy
## TERMINOLOGY
- ### Definitions
- Benign neoplasm of Schwann cells that wrap brachial plexus (BP) nerves in perivertebral space (PVS)
## IMAGING
- ### General Features
- #### Best diagnostic clue
- Well-circumscribed, fusiform, hypoechoic mass, ± intratumoral cystic spaces, vascularity, and in continuity with BP roots between anterior and middle scalene muscles
- #### Location
- May arise anywhere along course of BP roots, including intra- and extradural spaces, neural foramen, PVS
- Lesions within PVS are situated between anterior and middle scalene muscles
- US is best able to fully evaluate lesions in PVS/lateral neck
- ### Ultrasonographic Findings
- Solid mass with well-defined margins, hypoechoic and heterogeneous echo pattern
- Fusiform/oval shape, ± tapering ends in continuity with BP
- Often has sharply defined cystic/hemorrhagic areas within
- May have pseudocystic appearance with posterior enhancement (despite being solid)
- Color Doppler shows vascularity within, which may disappear upon excessive transducer pressure
- ± mass effect on adjacent vessels
- ### CT Findings
- #### NECT
- Typically isodense to muscle
- Calcification is uncommon
- #### CECT
- Moderate to strong enhancement
- ### MR Findings
- #### T1WI
- Isointense to muscle
- #### T2WI
- Hyperintense, approaching signal of regional vessels
- Target sign: Central hypo-, peripheral hyperintense signal commonly seen in benign peripheral nerve sheath tumor (PNST)
- Fascicular sign: Multiple, irregular, central hypointense foci typical of benign PNST
- #### T1WI C+
- Reverse target sign: Central enhancement > peripheral enhancement
- ### Imaging Recommendations
- #### Best imaging tool
- US identifies nature of lesion in lateral neck but may be unable to delineate proximal and distal extent of large lesions
- MR confirms extent, multiplicity (if any) of large lesions after US has made diagnosis
- #### Protocol advice
- Transverse scans identify normal BP roots/rami as round, hypoechoic structures between anterior and middle scalene
- Longitudinal scans identify roots/rami along their course
- Transverse scans help to quickly identify tumor, and longitudinal scans establish continuity with BP
- Intratumoral vascularity is sensitive to pressure; therefore, transducer must be held gently
- Pressure/manipulating mass with transducer or needle biopsy may cause symptoms of radiculopathy
## DIFFERENTIAL DIAGNOSIS
- [Neurofibroma](/document/nerve-sheath-tumors/f54585df-d9ce-4fec-a555-bd5b1b36a8e7)
- May be indistinguishable from schwannoma
- Cystic degeneration, hemorrhage uncommon
- Less vascular and shows no posterior enhancement
- [Metastatic Nodes](/document/systemic-metastases-in-neck-nodes/2bfe5a22-2a74-4d84-a488-b3f22163ecf0)
- Multiple, heterogeneous, hypoechoic, round nodes with necrosis, peripheral vascularity, known primary
- [Tuberculous Nodes](/document/tuberculous-adenopathy/0af17249-dfdf-4168-af92-61b2874ce27d)
- Multiple, matted, necrotic nodes with adjacent soft tissue edema; avascular/displaced vascularity within
- [Lymphangioma](/document/lymphatic-malformation/9db973b8-5ff0-4dca-b56b-c64734ac43ec)
- Transspatial, cystic, septate, avascular mass with negligible mass effect
## CLINICAL ISSUES
- ### Presentation
- #### Most common signs/symptoms
- Painless, slow-growing mass in lateral neck ± radiculopathy
- Malignant degeneration rare
- Development of pain should raise suspicion for malignancy
- ### Treatment
- Surgical excision
- Good prognosis with low risk of recurrence
## DIAGNOSTIC CHECKLIST
- ### Image Interpretation Pearls
- Fusiform solid mass, well-defined margin, ± intratumoral cystic spaces and vascularity in continuity with BP
- ### Reporting Tips
- When describing any low neck lesion, always indicate its relationship to BP
16dc2caa-468c-4217-97c1-32068a87fe8b
## References
## Selected References
1. [Lapegue F et al: Ultrasonography of the brachial plexus, normal appearance and practical applications. Diagn Interv Imaging. 95(3):259-75, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24603038%5Bpmid%5D)
1. Ahuja AT et al: Diagnostic Imaging: Ultrasound. 1st ed. Salt Lake City: Amirsys, Inc. 11-102-105, 2007
1. [Graif M et al: Sonographic evaluation of brachial plexus pathology. Eur Radiol. 14(2):193-200, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=12845468%5Bpmid%5D)
1. Harnsberger HR et al: Diagnostic Imaging: Head & Neck. 1st ed. Salt Lake City: Amirsys, Inc. III-10-14-15, 2004
1. Ahuja AT et al. Practical head and neck ultrasound. London: Greenwich Medical Media. 85-104, 2000
1. [King AD et al: Sonography of peripheral nerve tumors of the neck. AJR Am J Roentgenol. 169(6):1695-8, 1997](http://www.ncbi.nlm.nih.gov/pubmed/?term=9393192%5Bpmid%5D)
## Differential diagnosis
### Brachial Plexus Lesion
DDX:f15c5303-8598-421e-b978-fba4dea2b6a6
### Cervicothoracic Junction Lesion
DDX:0226620f-95d5-48cd-a7e5-c7662e898dc5
### Perivertebral Space Lesion
DDX:60caace9-af6d-42c6-ae93-b703e7bfb494
### Supraclavicular Mass
DDX:a6dff053-ced8-419f-9f7a-db4ba06b00f2
## Anatomy
### Accessory Nerve (CNXI)
Brain/ANATOMY:9d50453e-c26a-46a3-826e-265736e43174
### Suprahyoid and Infrahyoid Neck Overview
Head and Neck/ANATOMY:50ac1eaf-3866-4ebd-8f5c-437055a64ba4
### Cervical Lymph Nodes
Head and Neck/ANATOMY:c8f730fb-5aeb-40d8-9fbc-0c2320f12e63
### CNXI (Accessory Nerve)
Head and Neck/ANATOMY:18e60151-70bc-40a1-9b4f-4b86f8fd65c2
### Brachial Plexus
Head and Neck/ANATOMY:a702f5d9-f5dc-49b0-925b-20ebeecead44
### Brachial Plexus
Spine/ANATOMY:d40ec749-81b1-4900-b366-2921b7fcc467
### Posterior Cervical Space
Head and Neck/ANATOMY:b274cd65-ed5c-43a0-b734-e61122b35ce3
## Images
### Selected Images
![Transverse grayscale US in a patient with upper limb amputation for osteosarcoma shows a solid, hypoechoic, heterogeneous mass <img src='img/arrows/WC.png' alt='white curved arrow'/>, supraclavicular in location. Note the clavicle <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_32249425-243e-4ae1-8d36-152ff02f6dd9_annotated_true_size_900_quality_90_b19bc53df52f0cafc5ed16e83204a4c0877ed1c9.jpg)
*Transverse grayscale US in a patient with upper limb amputation for osteosarcoma shows a solid, hypoechoic, heterogeneous mass <img src='img/arrows/WC.png' alt='white curved arrow'/>, supraclavicular in location. Note the clavicle <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Transverse grayscale US in a patient with upper limb amputation for osteosarcoma shows a solid, hypoechoic, heterogeneous mass <img src='img/arrows/WC.png' alt='white curved arrow'/>, supraclavicular in location. Note the clavicle <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_32249425-243e-4ae1-8d36-152ff02f6dd9_size_174_quality_85_af7c90df3e1bf137dfd1aa8698a175ce60adc285.jpg)
*Transverse grayscale US in a patient with upper limb amputation for osteosarcoma shows a solid, hypoechoic, heterogeneous mass <img src='img/arrows/WC.png' alt='white curved arrow'/>, supraclavicular in location. Note the clavicle <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Transverse grayscale US (same patient) in a different plane shows continuation of the mass <img src='img/arrows/WC.png' alt='white curved arrow'/> with emerging brachial plexus (BP) roots/rami <img src='img/arrows/WO.png' alt='white open arrow'/>. Diagnosis of postoperative stump neuroma was made. US, with its high resolution, clearly identifies the mass and its continuation with the BP. Note the clavicle <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_84b14c22-bb03-49d5-b50d-6269833d405a_annotated_true_size_900_quality_90_a4940d8d7d0c7a6941b9c01eaae403fadbd3791d.jpg)
*Transverse grayscale US (same patient) in a different plane shows continuation of the mass <img src='img/arrows/WC.png' alt='white curved arrow'/> with emerging brachial plexus (BP) roots/rami <img src='img/arrows/WO.png' alt='white open arrow'/>. Diagnosis of postoperative stump neuroma was made. US, with its high resolution, clearly identifies the mass and its continuation with the BP. Note the clavicle <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Corresponding longitudinal power Doppler US (same patient) shows no significant vascularity in the neuroma <img src='img/arrows/WC.png' alt='white curved arrow'/>. Intratumoral vascularity is sensitive to pressure and the transducer must be held gently.](images/app.statdx.com_image_thumbnail_68ad214c-fac6-471a-8353-c6d59796dbac_annotated_true_size_900_quality_90_7d3db3c2f45602ab64462db4bd7cf266f1c6ed91.jpg)
*Corresponding longitudinal power Doppler US (same patient) shows no significant vascularity in the neuroma <img src='img/arrows/WC.png' alt='white curved arrow'/>. Intratumoral vascularity is sensitive to pressure and the transducer must be held gently.*
![Coronal T1WI MR defines the extent of the mass <img src='img/arrows/WC.png' alt='white curved arrow'/> and its continuity with BP roots/rami <img src='img/arrows/WS.png' alt='white solid arrow'/>. US is an ideal initial imaging modality as it quickly establishes thelocation and nature of such a lesion. However, MR better defines its entire extent and relationship to adjacent structures.](images/app.statdx.com_image_thumbnail_f98411f6-981f-487e-a7d0-5e5ccf7042c4_annotated_true_size_900_quality_90_53c76a696b382106c9f1faeb8f18b67ebf4a830a.jpg)
*Coronal T1WI MR defines the extent of the mass <img src='img/arrows/WC.png' alt='white curved arrow'/> and its continuity with BP roots/rami <img src='img/arrows/WS.png' alt='white solid arrow'/>. US is an ideal initial imaging modality as it quickly establishes thelocation and nature of such a lesion. However, MR better defines its entire extent and relationship to adjacent structures.*
![Longitudinal grayscale US shows a posterior triangle mass <img src='img/arrows/WC.png' alt='white curved arrow'/> with intratumoral cystic degeneration/hemorrhage <img src='img/arrows/WS.png' alt='white solid arrow'/>. Note its proximal continuity with emerging BP root/rami <img src='img/arrows/WO.png' alt='white open arrow'/>, suggesting BP schwannoma.](images/app.statdx.com_image_thumbnail_7d2e05e0-e7a1-4915-af26-62e875f3b8dd_annotated_true_size_900_quality_90_f8dcd06c3a4a87a2d99c220e380076cfb965a5a5.jpg)
*Longitudinal grayscale US shows a posterior triangle mass <img src='img/arrows/WC.png' alt='white curved arrow'/> with intratumoral cystic degeneration/hemorrhage <img src='img/arrows/WS.png' alt='white solid arrow'/>. Note its proximal continuity with emerging BP root/rami <img src='img/arrows/WO.png' alt='white open arrow'/>, suggesting BP schwannoma.*
![Longitudinal grayscale US (same patient) shows cystic degeneration/hemorrhage <img src='img/arrows/WS.png' alt='white solid arrow'/> within a BP schwannoma <img src='img/arrows/WC.png' alt='white curved arrow'/>. Note the continuity with the BP distally <img src='img/arrows/WO.png' alt='white open arrow'/>. US readily establishes a diagnosis of BP schwannoma and obviates the need for confirmatory FNAC.](images/app.statdx.com_image_thumbnail_bdc50916-c7cc-4e42-a81f-a916e7f946d8_annotated_true_size_900_quality_90_e6bde5861e42821f690155c3d92132a226aed323.jpg)
*Longitudinal grayscale US (same patient) shows cystic degeneration/hemorrhage <img src='img/arrows/WS.png' alt='white solid arrow'/> within a BP schwannoma <img src='img/arrows/WC.png' alt='white curved arrow'/>. Note the continuity with the BP distally <img src='img/arrows/WO.png' alt='white open arrow'/>. US readily establishes a diagnosis of BP schwannoma and obviates the need for confirmatory FNAC.*
![Corresponding power Doppler US of cystic BP schwannoma shows no significant vascularity within the lesion <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_69e8cfe8-49d1-4ad4-be4e-7c2364aa5cb6_annotated_true_size_900_quality_90_64ea958a1bdc930672985c261e1c959784f70219.jpg)
*Corresponding power Doppler US of cystic BP schwannoma shows no significant vascularity within the lesion <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Coronal T1WI C+ MR clearly identifies BP schwannoma <img src='img/arrows/BS.png' alt='black solid arrow'/>, its location, and relationship to adjacent structures. Note its fusiform shape, moderate heterogeneous contrast enhancement, intratumoral cystic change, and continuity with brachial plexus. Cystic degeneration/hemorrhage is uncommon in neurofibroma vs. schwannoma.](images/app.statdx.com_image_thumbnail_d4811dda-37c3-49b2-a104-10672da40f1f_annotated_true_size_900_quality_90_68373d873a3c6db78a51bb1bd1848bfae4157a64.jpg)
*Coronal T1WI C+ MR clearly identifies BP schwannoma <img src='img/arrows/BS.png' alt='black solid arrow'/>, its location, and relationship to adjacent structures. Note its fusiform shape, moderate heterogeneous contrast enhancement, intratumoral cystic change, and continuity with brachial plexus. Cystic degeneration/hemorrhage is uncommon in neurofibroma vs. schwannoma.*
![Transverse grayscale US shows a well-defined, solid, hypoechoic mass <img src='img/arrows/WC.png' alt='white curved arrow'/> in the supraclavicular fossa. Note the proximal continuation with emerging BP root/rami <img src='img/arrows/WS.png' alt='white solid arrow'/>, suggesting BP schwannoma. Modern high-resolution transducers allow US to readily identify the lesion and illustrate its continuity with BP, making biopsy unnecessary. Note the clavicle <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_b8973e34-cc32-4702-bc24-3b790a25d357_annotated_true_size_900_quality_90_e1817dccb9b1ad6bee2d444f545ca0eb2bd102fc.jpg)
*Transverse grayscale US shows a well-defined, solid, hypoechoic mass <img src='img/arrows/WC.png' alt='white curved arrow'/> in the supraclavicular fossa. Note the proximal continuation with emerging BP root/rami <img src='img/arrows/WS.png' alt='white solid arrow'/>, suggesting BP schwannoma. Modern high-resolution transducers allow US to readily identify the lesion and illustrate its continuity with BP, making biopsy unnecessary. Note the clavicle <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Corresponding coronal T1WI MR shows the BP schwannoma <img src='img/arrows/BS.png' alt='black solid arrow'/>. Note its fusiform shape, isointensity to muscle, and continuity with BP.](images/app.statdx.com_image_thumbnail_cb27216b-f1cf-462e-8537-4e120907d39b_annotated_true_size_900_quality_90_979dc8179392b116b877e084cbc255d422121a5a.jpg)
*Corresponding coronal T1WI MR shows the BP schwannoma <img src='img/arrows/BS.png' alt='black solid arrow'/>. Note its fusiform shape, isointensity to muscle, and continuity with BP.*
![Transverse grayscale US shows a fusiform hypoechoic mass <img src='img/arrows/WS.png' alt='white solid arrow'/> low in the left neck in the known location of BP. Note its continuity with emerging BP root/rami <img src='img/arrows/WC.png' alt='white curved arrow'/>. Longitudinal scan (not shown) also demonstrated this continuity, and a diagnosis of BP schwannoma was suggested.](images/app.statdx.com_image_thumbnail_d605f8ea-3064-454e-a34e-40204ff0a34e_annotated_true_size_900_quality_90_a87c83432b7dc7aaafe09d7cd74f63a832053c10.jpg)
*Transverse grayscale US shows a fusiform hypoechoic mass <img src='img/arrows/WS.png' alt='white solid arrow'/> low in the left neck in the known location of BP. Note its continuity with emerging BP root/rami <img src='img/arrows/WC.png' alt='white curved arrow'/>. Longitudinal scan (not shown) also demonstrated this continuity, and a diagnosis of BP schwannoma was suggested.*
![Axial fat-suppressed T2WI MR demonstrates BP schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> and its continuity with an emerging root <img src='img/arrows/WC.png' alt='white curved arrow'/>. US quickly identifies the lesion and differentiates it from lymph nodes (which are more common) at the site.](images/app.statdx.com_image_thumbnail_36453ade-a1da-4716-aea6-636e7a1c93f3_annotated_true_size_900_quality_90_bd9f6e882949ebe58209e9eca8ded4695c05efeb.jpg)
*Axial fat-suppressed T2WI MR demonstrates BP schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> and its continuity with an emerging root <img src='img/arrows/WC.png' alt='white curved arrow'/>. US quickly identifies the lesion and differentiates it from lymph nodes (which are more common) at the site.*
![Transverse grayscale US shows a solid hypoechoic mass <img src='img/arrows/WS.png' alt='white solid arrow'/> with posterior enhancement <img src='img/arrows/BS.png' alt='black solid arrow'/> located between the anterior <img src='img/arrows/WO.png' alt='white open arrow'/> and middle <img src='img/arrows/WC.png' alt='white curved arrow'/> scalene muscles. The location in the perivertebral space and US features are diagnostic of BP schwannoma.](images/app.statdx.com_image_thumbnail_b1bfccba-72ab-4882-a4cb-76cc1375979e_annotated_true_size_900_quality_90_91de5e68a095c3cf0d32198ac17069f919130cec.jpg)
*Transverse grayscale US shows a solid hypoechoic mass <img src='img/arrows/WS.png' alt='white solid arrow'/> with posterior enhancement <img src='img/arrows/BS.png' alt='black solid arrow'/> located between the anterior <img src='img/arrows/WO.png' alt='white open arrow'/> and middle <img src='img/arrows/WC.png' alt='white curved arrow'/> scalene muscles. The location in the perivertebral space and US features are diagnostic of BP schwannoma.*
![Corresponding longitudinal grayscale US clearly shows continuity of the schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> with the brachial plexus root <img src='img/arrows/WO.png' alt='white open arrow'/>. Note the posterior enhancement <img src='img/arrows/WC.png' alt='white curved arrow'/> commonly seen in solid schwannomas in the head and neck.](images/app.statdx.com_image_thumbnail_a45ce079-e501-4a1a-9302-72dfad0cdcd1_annotated_true_size_900_quality_90_53f1ae88daa8d126dec9fed7e494eb5d619d78d3.jpg)
*Corresponding longitudinal grayscale US clearly shows continuity of the schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> with the brachial plexus root <img src='img/arrows/WO.png' alt='white open arrow'/>. Note the posterior enhancement <img src='img/arrows/WC.png' alt='white curved arrow'/> commonly seen in solid schwannomas in the head and neck.*
![Transverse grayscale US of right posterior triangle in patient with previous neck XRT shows prominent roots <img src='img/arrows/WS.png' alt='white solid arrow'/> of BP between scalene muscles, not to be mistaken for enlarged lymph nodes. Note carotid artery <img src='img/arrows/BO.png' alt='black open arrow'/> and jugular vein <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_c705113a-ea69-4523-86cc-a5c7c5fdfba0_annotated_true_size_900_quality_90_b5617a9bc15399dc8cd0a32cc633d0097559c9dc.jpg)
*Transverse grayscale US of right posterior triangle in patient with previous neck XRT shows prominent roots <img src='img/arrows/WS.png' alt='white solid arrow'/> of BP between scalene muscles, not to be mistaken for enlarged lymph nodes. Note carotid artery <img src='img/arrows/BO.png' alt='black open arrow'/> and jugular vein <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Longitudinal grayscale US and qualitative strain elastogram show a PNST from BP. Strain color scale ranges from purple (soft) to red (hard). The mass is heterogeneous on strain image with areas displaying red <img src='img/arrows/WS.png' alt='white solid arrow'/> and purple <img src='img/arrows/WO.png' alt='white open arrow'/>, suggesting intermediate or mixed stiffness.](images/app.statdx.com_image_thumbnail_473319b5-fbc8-4671-b8fc-42bf108f7fe0_annotated_true_size_900_quality_90_7cd389ea22a7bd147a1d2f1ee4d2b51442c49623.jpg)
*Longitudinal grayscale US and qualitative strain elastogram show a PNST from BP. Strain color scale ranges from purple (soft) to red (hard). The mass is heterogeneous on strain image with areas displaying red <img src='img/arrows/WS.png' alt='white solid arrow'/> and purple <img src='img/arrows/WO.png' alt='white open arrow'/>, suggesting intermediate or mixed stiffness.*
### Additional Images
![Sagittal T2WI FS MR shows a hyperintense BP schwannoma <img src='img/arrows/WO.png' alt='white open arrow'/> with an area of cystic necrosis <img src='img/arrows/BS.png' alt='black solid arrow'/>. MR is useful in evaluating the full extent of large lesions, which are not amenable to US.](images/app.statdx.com_image_thumbnail_e6152446-3c8b-4e13-9516-4c1cafcf9ac4_annotated_true_size_900_quality_90_151e946659d03a4f4afb5d0c60756f83daebc3ff.jpg)
*Sagittal T2WI FS MR shows a hyperintense BP schwannoma <img src='img/arrows/WO.png' alt='white open arrow'/> with an area of cystic necrosis <img src='img/arrows/BS.png' alt='black solid arrow'/>. MR is useful in evaluating the full extent of large lesions, which are not amenable to US.*
![US shows a well-defined, oval, hypoechoic BP schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> with focal areas of cystic/hemorrhagic change.](images/app.statdx.com_image_thumbnail_30edea7f-7569-4462-86db-a6c2652f2064_annotated_true_size_900_quality_90_06004e06d9f2cfeccdee664a0dd91ef21cb9fc39.jpg)
*US shows a well-defined, oval, hypoechoic BP schwannoma <img src='img/arrows/WS.png' alt='white solid arrow'/> with focal areas of cystic/hemorrhagic change.*
![Longitudinal grayscale US shows a BP schwannoma <img src='img/arrows/WO.png' alt='white open arrow'/>. Note its continuity with the BP trunk <img src='img/arrows/WS.png' alt='white solid arrow'/>. High-resolution US consistently demonstrates such continuity and internal echo pattern.](images/app.statdx.com_image_thumbnail_54cb03f9-77c0-4674-b639-8919576c4e7a_annotated_true_size_900_quality_90_00f845d178f2ced051f7fd930aeff40d128bd294.jpg)
*Longitudinal grayscale US shows a BP schwannoma <img src='img/arrows/WO.png' alt='white open arrow'/>. Note its continuity with the BP trunk <img src='img/arrows/WS.png' alt='white solid arrow'/>. High-resolution US consistently demonstrates such continuity and internal echo pattern.*
![Grayscale US demonstrates a well-defined, hypoechoic mass <img src='img/arrows/WC.png' alt='white curved arrow'/> with sharp cystic areas <img src='img/arrows/WS.png' alt='white solid arrow'/> and posterior enhancement <img src='img/arrows/WO.png' alt='white open arrow'/>, typical findings of nerve sheath tumor. Location suggested BP schwannoma.](images/app.statdx.com_image_thumbnail_a04da056-a359-40a3-8d90-6f3cd2680aea_annotated_true_size_900_quality_90_828a83c181e505b3f318907040451a5cf52aa05a.jpg)
*Grayscale US demonstrates a well-defined, hypoechoic mass <img src='img/arrows/WC.png' alt='white curved arrow'/> with sharp cystic areas <img src='img/arrows/WS.png' alt='white solid arrow'/> and posterior enhancement <img src='img/arrows/WO.png' alt='white open arrow'/>, typical findings of nerve sheath tumor. Location suggested BP schwannoma.*
![Corresponding color Doppler (CD) US shows prominent vascularity within the tumor. Grayscale/CD appearance and location between the anterior and middle scalene muscles is typical of a BP schwannoma.](images/app.statdx.com_image_thumbnail_25d364fe-0291-4b4c-a444-aaed5cabf63b_annotated_true_size_900_quality_90_5cc8964b002e0485cf73e5324785cc7b7e49de3a.jpg)
*Corresponding color Doppler (CD) US shows prominent vascularity within the tumor. Grayscale/CD appearance and location between the anterior and middle scalene muscles is typical of a BP schwannoma.*
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---
title: "Brachial Plexus Ultrasound"
docid: "76e1b01e-994d-4931-9196-109d17013f83"
authors:
- key: "ee435a54-df79-4d7a-b78c-b02157eac7f6"
value: "James F. Griffith, MBBCh BAO, MRCP, FRCR, FHKCR FHKAM, MD"
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name: "Ultrasound"
slug: "ultrasound"
treeNodeId: "517432cb-177e-4b78-bd9f-4c2e751d132e"
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name: "Technique"
slug: "technique"
treeNodeId: "7839c069-6ace-460f-9167-b47370188feb"
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name: "Musculoskeletal"
slug: "musculoskeletal"
treeNodeId: "c264894f-5d63-426a-aaca-c44cc70f6154"
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name: "Brachial Plexus Ultrasound"
slug: "brachial-plexus-ultrasound"
treeNodeId: null
category: "Ultrasound"
cmeTopicId: "104dc83d-6027-4775-8e7f-c56068347eab"
documentVersionId: "e2af4eb1-2d29-4d7d-a1cf-8c9b9e28d2b0"
imageCount: 16
lastUpdated: "11/11/24"
pageDescription: "Brachial Plexus Ultrasound"
pageKeywords: "Ultrasound, Technique, Musculoskeletal, Brachial Plexus Ultrasound"
pageTitle: "Brachial Plexus Ultrasound | STATdx"
enhancedTitle: "Brachial Plexus Ultrasound"
type: "DX"
breadcrumbs:
- "Ultrasound"
- "Technique"
- "Musculoskeletal"
- "Brachial Plexus Ultrasound"
---
## KEY FACTS
- ### Imaging Anatomy
- Brachial plexus (BP) is neural network to upper limb
- BP extends from ventral rami of C5-T1 roots to terminal branches in axilla
- Considerable variation in appearances of trunks, divisions, & cords of BP among individuals exists
- Contralateral normal or less-affected side axis is good internal reference as to expected brachial morphology on affected side
- 2/3 of BP US or MR examinations are normal
- US is as accurate as MR in detecting most BP pathologies
- Likelihood of finding abnormality on MR following negative US examination is extremely low
- BP US is standardized examination with all parts of BP examined in all patients
- Imperative to examine BP on both sides, starting with unaffected or least affected side
- ### Technique
- Best to start examination at intrascalene region
- Observe trunks & check for compression of lower trunk (wedge-sickle sign)
- Move transducer medially in same transverse plane to examine roots emerging from cervical spine
- Thumb-up sign & V-sign
- Return to intrascalene region & observe suprascapular nerve
- Scan in same transverse plane lateral to scalene muscles & observe divisions of BP
- Akin to bunch of grapes
- Ask patient to abduct arm to 90° & examine subpectoralis space
- Median, lateral, & posterior cords aligned around axillary artery
- Fully abduct arm to examine axillary region
- Median, ulnar, radial, & musculocutaneous nerve aligned in quite consistent position around axillary artery
## TERMINOLOGY
- ### Abbreviations
- Brachial plexus (BP)
## IMAGING ANATOMY
- ### General Anatomic Considerations
- BP is neural network to upper limb
- BP extends from ventral rami of C5-T1 roots to terminal branches in axilla
- Considerable variation in appearances of trunks, divisions, & cords of BP among individuals exists
- Fortunately, little intrinsic side-to-side variability exists
- Contralateral normal or less-affected side axis is good internal reference as to expected brachial morphology on affected side
- Clinical localization of symptoms to BP is difficult
- 2/3 of BP US or MR examinations are normal
- ### Limitations of Brachial Plexus US
- BP is accessible to US in vast majority of patients
- Intraforaminal or intraspinal portions of nerve roots are not accessible to US examination
- Not part of BP, which starts at ventral rami
- Small segment of BP deep to clavicle (costoclavicular gap) not accessible on US examination
- BP immediately proximal & distal to costoclavicular gap is consistently seen
- Dynamic spectral Doppler analysis enables assessment of vascular compression in this area
- Large open wound or severe soft tissue swelling may preclude US examination
- Inability to abduct arm limits examination of axilla
- BP US is also limited in young children with small necks
- ### Benefits of Brachial Plexus US
- US is as accurate as MR in detecting most BP pathologies
- Likelihood of finding abnormality on MR following negative US examination is extremely low
- US is very helpful at excluding BP pathology
- US is relatively quick & inexpensive compared to MR
- Allows ready examination of extraplexal nerves
- Facilitates US-guided biopsy of suspicious masses
- Facilitates US-guided therapeutic injection
- ### Technique
- BP US is usually performed with patient lying supine & head slightly elevated
- Gown should be tied below shoulders so that neck & shoulders fully exposed
- BP US is standardized examination with all parts of BP examined in all patients
- Imperative to examine BP on both sides, starting with unaffected or least affected side
- Contralateral normal side provides good internal reference as to expected BP morphology on affected side
- BP US is primarily performed in transverse plane
- Longitudinal plane is helpful when assessing
- Neural swelling following trauma to evaluate for transection or neuroma-in-continuity
- BP tumors to assess tumor eccentricity with respect to parent nerve
- Neural constriction in neuralgic amyotrophy
- Roots, trunks, & divisions are monofascicular & hypoechoic, while cords & terminal branches are polyfascicular
- **Best to start examination at interscalene region**
- Observe "traffic light sign" of upper, middle, & lower trunks
- Often, "traffic light sign" not seen with roots, trunks, & divisions variably present in interscalene region
- Check for compression of lower trunk (wedge-sickle sign)
- **Move transducer medially in same transverse plane to examine roots emerging from cervical spine**
- C7 root identified by recognizing thumbs up sign
- C6 & C5 roots more cephalad between tubercles of C6 & C5 transverse processes (V-sign)
- C8 & T1 caudad to C7 root
- Check for compression of lower trunk & roots (seen as wedge-sickle sign)
- Compression usually caused by fibromuscular band or medial edge of 1st rib
- **Return to interscalene region & observe suprascapular nerve**
- Trace this nerve laterally deep to omohyoid muscle
- Normal cross-sectional area < 2.8 ± 0.8 mm²
- **Scan in same transverse plane lateral to scalene muscles & observe divisions of BP**
- Follow divisions, aligned superolateral to subclavian artery & akin to bunch of grapes, in transverse plane to costoclavicular gap, angling transducer behind clavicle
- **Ask patient to abduct arm to 90° & examine subpectoralis space**
- Observe cords aligned lateral & inferior to axillary artery
- Subclavian termed axillary artery beyond 1st rib
- In patients with suspected vascular thoracic outlet syndrome, check for dynamic compression of axillary artery
- Undertake spectral Doppler analysis in subclavian & axillary arteries in neutral position & then of axillary artery with arm hyperabducted & externally rotated
- Significant hemodynamic disturbance indicated by 2-fold increase in peak systolic velocity (dynamic stenosis), cessation of arterial flow (dynamic occlusion), or poststenotic tardus-parvus spectral pattern
- **Fully abduct arm to examine axillary region**
- Identify brachial artery in proximal arm & follow it proximally to axilla where median, ulnar, & radial nerves lie in quite consistent position around axillary artery
- Likened to dog's paw
- Median nerve lies superolaterally closest to arm muscles
- Ulnar nerve lies superomedially
- Radial nerve lies inferomedially
- Musculocutaneous nerve lies between biceps & coracobrachialis muscles
## CLINICAL IMPLICATIONS
- ### Indications for US Examination
- BP US is helpful for assessing irradiation plexopathy, nerve sheath tumors, metastases, BP trauma, thoracic outlet syndrome, neuralgic amyotrophy, inflammatory polyneuropathies
c922e9e3-512f-4d28-8221-f29a732ef909
## Images
### Selected Images
![Clinical photograph shows the scan position for the supraclavicular portion of the brachial plexus, which includes the roots, trunks, divisions, and suprascapular nerve.](images/app.statdx.com_image_thumbnail_499bc147-1497-45db-8bb5-9fb127630d41_annotated_true_size_900_quality_90_5824c93157095d259969cc4478305db70a028874.jpg)
**Scan Position for Supraclavicular Region**
*Clinical photograph shows the scan position for the supraclavicular portion of the brachial plexus, which includes the roots, trunks, divisions, and suprascapular nerve.*
![Clinical photograph shows the scan position for the supraclavicular portion of the brachial plexus, which includes the roots, trunks, divisions, and suprascapular nerve.](images/app.statdx.com_image_thumbnail_499bc147-1497-45db-8bb5-9fb127630d41_size_174_quality_85_da9486c4eb85692c1d893856d45606f29b533848.jpg)
**Scan Position for Supraclavicular Region**
*Clinical photograph shows the scan position for the supraclavicular portion of the brachial plexus, which includes the roots, trunks, divisions, and suprascapular nerve.*
![Transverse US of supraclavicular region shows the classic &quot;traffic light sign&quot; with the upper <img src='img/arrows/WS.png' alt='white solid arrow'/>, middle <img src='img/arrows/BS.png' alt='black solid arrow'/>, and lower <img src='img/arrows/CS.png' alt='cyan solid arrow'/> trunks of the brachial plexus lined up between the scalenus anterior <img src='img/arrows/BC.png' alt='black curved arrow'/> and medius <img src='img/arrows/WC.png' alt='white curved arrow'/> muscles. The suprascapular nerve <img src='img/arrows/WO.png' alt='white open arrow'/> arising from the upper trunk is also shown.](images/app.statdx.com_image_thumbnail_d8163e0d-32e2-4838-9282-57569622097f_annotated_true_size_900_quality_90_75ab237d5bd27206c6643c90d40d7336b4535741.jpg)
**"Traffic Light Sign"**
*Transverse US of supraclavicular region shows the classic &quot;traffic light sign&quot; with the upper <img src='img/arrows/WS.png' alt='white solid arrow'/>, middle <img src='img/arrows/BS.png' alt='black solid arrow'/>, and lower <img src='img/arrows/CS.png' alt='cyan solid arrow'/> trunks of the brachial plexus lined up between the scalenus anterior <img src='img/arrows/BC.png' alt='black curved arrow'/> and medius <img src='img/arrows/WC.png' alt='white curved arrow'/> muscles. The suprascapular nerve <img src='img/arrows/WO.png' alt='white open arrow'/> arising from the upper trunk is also shown.*
![Transverse US shows a more typical appearance of the interscalene triangle in another patient. Rather than the classic &quot;traffic light sign,&quot; a mixture of roots, trunks, and divisions is seen between the scalenus anterior <img src='img/arrows/WC.png' alt='white curved arrow'/> and medius <img src='img/arrows/BC.png' alt='black curved arrow'/> muscles. The phrenic nerve <img src='img/arrows/WO.png' alt='white open arrow'/>, passing over the scalenus anterior muscle, is also shown.](images/app.statdx.com_image_thumbnail_04a3f48e-67b3-46b6-9161-f12855dae30a_annotated_true_size_900_quality_90_069ff3d653dc196b0ca9fc2d5910e8ad32b92bfa.jpg)
**Interscalene Triangle**
*Transverse US shows a more typical appearance of the interscalene triangle in another patient. Rather than the classic &quot;traffic light sign,&quot; a mixture of roots, trunks, and divisions is seen between the scalenus anterior <img src='img/arrows/WC.png' alt='white curved arrow'/> and medius <img src='img/arrows/BC.png' alt='black curved arrow'/> muscles. The phrenic nerve <img src='img/arrows/WO.png' alt='white open arrow'/>, passing over the scalenus anterior muscle, is also shown.*
![Graphic shows the 5 roots <img src='img/arrows/WS.png' alt='white solid arrow'/>, 3 trunks <img src='img/arrows/WO.png' alt='white open arrow'/>, 6 divisions <img src='img/arrows/WC.png' alt='white curved arrow'/>, 3 cords <img src='img/arrows/BS.png' alt='black solid arrow'/>, and 5 terminal branches <img src='img/arrows/BO.png' alt='black open arrow'/> of the brachial plexus. The brachial plexus is the neural highway to the upper limb.](images/app.statdx.com_image_thumbnail_807db977-d295-4853-bd7b-4b42ea65462e_annotated_true_size_900_quality_90_83e02025c42dfe1abdb8e6d20631e9d1aca9c599.jpg)
**Brachial Plexus Components**
*Graphic shows the 5 roots <img src='img/arrows/WS.png' alt='white solid arrow'/>, 3 trunks <img src='img/arrows/WO.png' alt='white open arrow'/>, 6 divisions <img src='img/arrows/WC.png' alt='white curved arrow'/>, 3 cords <img src='img/arrows/BS.png' alt='black solid arrow'/>, and 5 terminal branches <img src='img/arrows/BO.png' alt='black open arrow'/> of the brachial plexus. The brachial plexus is the neural highway to the upper limb.*
![Transverse US shows the prominent posterior tubercle <img src='img/arrows/WS.png' alt='white solid arrow'/> of C7 transverse process (outlined). This is known as the thumbs-up sign and is a good marker for the C7 root <img src='img/arrows/WC.png' alt='white curved arrow'/>, located anterior to the tubercle. The C7 vertebral body has either no anterior tubercle or a small rudimentary one.](images/app.statdx.com_image_thumbnail_8f08337c-d2f5-41b3-a1af-b0b73124124b_annotated_true_size_900_quality_90_91b91182e7b3e38e2168bcaf249177314d34416b.jpg)
**C7 Transverse Process and Nerve Root**
*Transverse US shows the prominent posterior tubercle <img src='img/arrows/WS.png' alt='white solid arrow'/> of C7 transverse process (outlined). This is known as the thumbs-up sign and is a good marker for the C7 root <img src='img/arrows/WC.png' alt='white curved arrow'/>, located anterior to the tubercle. The C7 vertebral body has either no anterior tubercle or a small rudimentary one.*
![Transverse US shows typical V-shaped appearance (V-sign) of the anterior <img src='img/arrows/WS.png' alt='white solid arrow'/> and posterior <img src='img/arrows/BS.png' alt='black solid arrow'/> tubercles of the C6 transverse process. Between the tubercles is the C6 root <img src='img/arrows/WC.png' alt='white curved arrow'/>, which exits the C5/C6 exit foramen cephalad to this level.](images/app.statdx.com_image_thumbnail_e9499f4b-336d-40dd-b306-d724bd557d29_annotated_true_size_900_quality_90_90cf5224458423e94c011e6b856c5656f090ee01.jpg)
**C6 Transverse Process and Nerve Root**
*Transverse US shows typical V-shaped appearance (V-sign) of the anterior <img src='img/arrows/WS.png' alt='white solid arrow'/> and posterior <img src='img/arrows/BS.png' alt='black solid arrow'/> tubercles of the C6 transverse process. Between the tubercles is the C6 root <img src='img/arrows/WC.png' alt='white curved arrow'/>, which exits the C5/C6 exit foramen cephalad to this level.*
![Transverse US shows the suprascapular nerve <img src='img/arrows/WS.png' alt='white solid arrow'/> lying more lateral to the scalene muscles and deep to the omohyoid muscle <img src='img/arrows/WC.png' alt='white curved arrow'/>. The suprascapular nerve has a similar course to the omohyoid muscle, which inserts on the scapula just lateral to the suprascapular notch.](images/app.statdx.com_image_thumbnail_8f91dbf5-9507-4831-8886-309aa76ba677_annotated_true_size_900_quality_90_700d385f025d3230ee84bdcc83f5c9dc045b5ed8.jpg)
**Suprascapular Nerve**
*Transverse US shows the suprascapular nerve <img src='img/arrows/WS.png' alt='white solid arrow'/> lying more lateral to the scalene muscles and deep to the omohyoid muscle <img src='img/arrows/WC.png' alt='white curved arrow'/>. The suprascapular nerve has a similar course to the omohyoid muscle, which inserts on the scapula just lateral to the suprascapular notch.*
![Transverse US shows the divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus, akin to a bunch of grapes, located superior to the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_fdb16571-d330-4c43-9dc0-4273da799de7_annotated_true_size_900_quality_90_fe275bf1e3d533876eac1190c5b8094717cc7fdc.jpg)
**Divisions of Brachial Plexus**
*Transverse US shows the divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus, akin to a bunch of grapes, located superior to the subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Transverse color Doppler US shows the transverse cervical artery, which frequently passes over the divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus. This proximity to the brachial plexus is not of any known clinical significance. The subclavian artery <img src='img/arrows/WO.png' alt='white open arrow'/> is located more deeply.](images/app.statdx.com_image_thumbnail_dd610490-b852-4648-ac4d-f19ba1350e83_annotated_true_size_900_quality_90_9ef1bd530e6a2179d114ff616ff7524ca4a15a9d.jpg)
**Divisions of Brachial Plexus**
*Transverse color Doppler US shows the transverse cervical artery, which frequently passes over the divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus. This proximity to the brachial plexus is not of any known clinical significance. The subclavian artery <img src='img/arrows/WO.png' alt='white open arrow'/> is located more deeply.*
![Transverse US shows the divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus lined up lateral to the subclavian artery <img src='img/arrows/WO.png' alt='white open arrow'/> just proximal to the costoclavicular gap. The lateral end of the clavicle <img src='img/arrows/BS.png' alt='black solid arrow'/> and pleura <img src='img/arrows/BC.png' alt='black curved arrow'/> are shown.](images/app.statdx.com_image_thumbnail_76622a1f-a919-4ba0-be90-cde516b2ff7f_annotated_true_size_900_quality_90_db7ec2fe52739d0a19eae86ebb6e3389e8a10d1b.jpg)
**Divisions of Brachial Plexus**
*Transverse US shows the divisions <img src='img/arrows/WS.png' alt='white solid arrow'/> of the brachial plexus lined up lateral to the subclavian artery <img src='img/arrows/WO.png' alt='white open arrow'/> just proximal to the costoclavicular gap. The lateral end of the clavicle <img src='img/arrows/BS.png' alt='black solid arrow'/> and pleura <img src='img/arrows/BC.png' alt='black curved arrow'/> are shown.*
![The costoclavicular gap is the narrowest portion of the brachial plexus passageway from the spine to the axilla. It is the most common site of vascular compression and also a common site of neural compression in patients with thoracic outlet syndrome. Most compression is due to anomalies within the costoclavicular region rather than previous fractures of the clavicle or 1st rib.](images/app.statdx.com_image_thumbnail_990f5db3-ec4c-4c51-9e5a-50a5d761f717_annotated_true_size_900_quality_90_239f4403dc2673be977e18e75c852d0383280404.jpg)
**Costoclavicular Gap**
*The costoclavicular gap is the narrowest portion of the brachial plexus passageway from the spine to the axilla. It is the most common site of vascular compression and also a common site of neural compression in patients with thoracic outlet syndrome. Most compression is due to anomalies within the costoclavicular region rather than previous fractures of the clavicle or 1st rib.*
![Clinical photograph shows the transducer position for the subpectoralis space. The arm is abducted to 90&deg;.](images/app.statdx.com_image_thumbnail_ff5aeb15-a246-485b-80ce-7d7dddfc9fd9_annotated_true_size_900_quality_90_91d5031911227392550d3869b6307059f3337c40.jpg)
**Scan Position for Subpectoralis Space**
*Clinical photograph shows the transducer position for the subpectoralis space. The arm is abducted to 90&deg;.*
![Transverse US shows the medial <img src='img/arrows/WS.png' alt='white solid arrow'/>, lateral <img src='img/arrows/WO.png' alt='white open arrow'/>, and posterior <img src='img/arrows/WC.png' alt='white curved arrow'/> cords of the brachial plexus lying alongside the axillary artery <img src='img/arrows/BS.png' alt='black solid arrow'/> deep to the pectoralis minor muscle <img src='img/arrows/BC.png' alt='black curved arrow'/>. The subclavian artery becomes the axillary artery on crossing over the 1st rib. The subclavian vein <img src='img/arrows/BO.png' alt='black open arrow'/> lies medially.](images/app.statdx.com_image_thumbnail_691295d7-a921-4130-aaf9-6228db486b7f_annotated_true_size_900_quality_90_37b6ce8c5d0fece6d11ee534a16f4c34aab9b3b3.jpg)
**Cords of Brachial Plexus**
*Transverse US shows the medial <img src='img/arrows/WS.png' alt='white solid arrow'/>, lateral <img src='img/arrows/WO.png' alt='white open arrow'/>, and posterior <img src='img/arrows/WC.png' alt='white curved arrow'/> cords of the brachial plexus lying alongside the axillary artery <img src='img/arrows/BS.png' alt='black solid arrow'/> deep to the pectoralis minor muscle <img src='img/arrows/BC.png' alt='black curved arrow'/>. The subclavian artery becomes the axillary artery on crossing over the 1st rib. The subclavian vein <img src='img/arrows/BO.png' alt='black open arrow'/> lies medially.*
![Clinical photograph shows the scan position for the axilla. The arm is fully abducted.](images/app.statdx.com_image_thumbnail_ae78b3aa-cca8-4b11-b8fe-41446da8658d_annotated_true_size_900_quality_90_730487ed7e6f2faba4c719ddbbe9bdab5bd29f3a.jpg)
**Scan Position for Axilla**
*Clinical photograph shows the scan position for the axilla. The arm is fully abducted.*
![Graphic shows neural arrangement around the axillary artery as a clock face. Median nerve <img src='img/arrows/WS.png' alt='white solid arrow'/> lies superolaterally, ulnar nerve <img src='img/arrows/WO.png' alt='white open arrow'/> lies superomedially, and radial nerve <img src='img/arrows/WC.png' alt='white curved arrow'/> lies inferomedially. Musculocutaneous nerve <img src='img/arrows/CS.png' alt='cyan solid arrow'/> lies inferomedially between the biceps and coracobrachialis muscles.](images/app.statdx.com_image_thumbnail_67ccdbbc-618f-4530-94ea-a54eba467df6_annotated_true_size_900_quality_90_e39cc75d19a3b29a4756ad5267eac5ee8e964d30.jpg)
**Neural Arrangement Around Axillary Artery**
*Graphic shows neural arrangement around the axillary artery as a clock face. Median nerve <img src='img/arrows/WS.png' alt='white solid arrow'/> lies superolaterally, ulnar nerve <img src='img/arrows/WO.png' alt='white open arrow'/> lies superomedially, and radial nerve <img src='img/arrows/WC.png' alt='white curved arrow'/> lies inferomedially. Musculocutaneous nerve <img src='img/arrows/CS.png' alt='cyan solid arrow'/> lies inferomedially between the biceps and coracobrachialis muscles.*
![Transverse US shows median <img src='img/arrows/WS.png' alt='white solid arrow'/>, ulnar <img src='img/arrows/WO.png' alt='white open arrow'/>, and radial <img src='img/arrows/WC.png' alt='white curved arrow'/> nerves aligned alongside the axillary artery <img src='img/arrows/BO.png' alt='black open arrow'/>. Musculocutaneous nerve <img src='img/arrows/CS.png' alt='cyan solid arrow'/> lies between the biceps and coracobrachialis muscles.](images/app.statdx.com_image_thumbnail_23716fc7-dece-46a0-9cbd-54200d855586_annotated_true_size_900_quality_90_18b14a071058c91fd77f42c22cbdfc14197e8688.jpg)
**Neural Arrangement at Axilla**
*Transverse US shows median <img src='img/arrows/WS.png' alt='white solid arrow'/>, ulnar <img src='img/arrows/WO.png' alt='white open arrow'/>, and radial <img src='img/arrows/WC.png' alt='white curved arrow'/> nerves aligned alongside the axillary artery <img src='img/arrows/BO.png' alt='black open arrow'/>. Musculocutaneous nerve <img src='img/arrows/CS.png' alt='cyan solid arrow'/> lies between the biceps and coracobrachialis muscles.*
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title: "Brachial Plexus"
docid: "a702f5d9-f5dc-49b0-925b-20ebeecead44"
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pageTitle: "Brachial Plexus | STATdx"
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---
## TERMINOLOGY
- ### Abbreviations
- Brachial plexus (BP)
- ### Definitions
- Collection of interconnecting nerves of lower cervical spine (C5-C8) and 1st thoracic nerve (T1) that provides cutaneous and motor innervation of upper extremity
## GROSS ANATOMY
- ### Overview
- **Cervical cord**
- Internally, cervical spinal cord arranged so that white matter tracts are positioned in periphery of cord
- Gray matter formed by neuronal cell bodies arranged in vertical columns located centrally within cord
- Gray matter columns form H-shaped arrangement in axial plane (in cross section)
- Lateral sagittally oriented components referred to as horns
- Transverse coronal components referred to as gray commissures
- Ventral (anterior) horns: Thicker, shorter, and contain multipolar motor neurons
- Dorsal (posterior) horns: Thinner, longer, and contain cell bodies that receive sensory axons from dorsal root ganglions (DRGs)
- **Cervical nerve rootlets,** **nerve roots, and proximal nerves**
- At each cervical level, ventral horns give rise to motor axons that exit ipsilateral ventrolateral sulci of cervical cord as several tiny (< 1-mm) **nerve rootlets**
- Ventral nerve rootlets at each level coalesce within few millimeters of cord to form ipsilateral **ventral root**(~ 1 mm)
- Similarly, dorsal horns receive multiple tiny nerve rootlets at posterolateral sulcus of cord
- Dorsal nerve rootlets also coalesce within few millimeters of cord to form **dorsal root**
- Dorsal root extends laterally from cord, passes and merges with**DRG** within **lower aspect of neural foramen (NF)**
- Within lateral aspect of cervical NF, DRG fuses with ventral root to become **spinal nerve proper**
- Immediately after proper spinal nerve formation, small, posteriorly oriented **dorsal ramus** emerges
- Dorsal ramus supplies motor and sensory innervation to posterior paraspinous muscles and cervical soft tissues
- Larger remaining segment of spinal nerve represents **ventral ramus**
- Ventral ramus typically main part of spinal nerve in cervical region; often referred to as simply **spinal nerve** itself
- Large ventral rami of nerves C5-T1 also referred to as **roots of BP**
- On sagittal MR and CT, spinal DRG and contiguous cervical spinal nerve/BP root seen along lower aspect of NF
- Bird's dropping-appearing filling defect of DRG in bright NF fat on sagittal T1WI MR
- In contrast, thoracic and lumbar DRG and contiguous spinal nerves seen along upper aspect of NF
- Bird's eye-appearing filling defect of DRG in bright NF fat on sagittal T1WI MR
- **1st cervical nerve (C1)** exits spinal canal between occiput and C1
- C1 nerve exits above C1 vertebra (atlas)
- C2 nerve exits between C1 and C2 vertebrae, and so forth
- C8 nerve exits between C7 and T1 vertebrae
- Arrangement of **cervical nerve roots** passing laterally to DRG in lower aspect of NF just **above pedicle**, and **thoracic (and lumbar) nerve roots** just **below pedicle** to DRG in upper aspect of NF
- Allows for 8 cervical nerves with only 7 cervical vertebrae
- C8 nerve exits above T1 pedicle to lower C7-T1 NF
- T1 nerve exits below T1 pedicle to upper T1-T2 NF
- T2 nerve exits below T2 pedicle to upper T2-T3 NF
- **Cervical plexus**
- Formed from ventral rami of C1-C4 ± minor branch of C5
- Has ascending superficial, descending superficial, deep branches
- Supplies nuchal muscles, diaphragm, cutaneous head/neck tissues
- **BP**
- Formed from **ventral rami of C5-T1** ± minor branches from C4 and T2
- BP divided into anatomic segments moving from medial to lateral: Rami/roots, trunks, divisions, cords, terminal branches
- Relationships of these segments with adjacent anatomic structures variable
- **Ventral rami/roots of BP**
- Originate from spinal cord levels C5-T1
- Roots of BP represent ventral rami of nerves C5-T1
- Term BP "root" in this context is not to be confused with ventral and dorsal nerve roots in spinal canal discussed previously
- Latter roots represent small nerves within spinal canal and within proximal NF before joining DRG
- Some nerves arise directly from roots
- **Dorsal scapular nerve** (C5)
- **Long thoracic nerve** (C5, C6, C7)
- **Phrenic nerve** (C3, C4, C5; mainly C4)
- On coronal MR, **T1 root** easily seen as horizontal linear structure surrounded by **fat** close to **lung apex**
- **Good starting point** to identify BP roots; then count C8, C7, C6, C5 upwards
- Stellate ganglion can also be seen at this level
- **Trunks**
- Within interscalene triangle, upper roots of BP (C5-C6) fuse to form **superior (upper) trunk**
- Only **upper trunk**gives off branches
- **Suprascapular nerve**(C5, C6)
- **Nerve to subclavius muscle**(C5, C6)
- C7 root continues laterally as **middle trunk**
- Lower roots (C8-T1) fuse to form **inferior (lower) trunk**
- **Divisions**
- As BP passes laterally beyond interscalene triangle over lateral margin of 1st rib in **retroclavicular** location, and begins to descend toward axilla
- Each trunk divides into 2 main nerve branches: **A****nterior and posterior divisions**
- Subsequently, each BP contains total of 6 divisions: 3 anterior and 3 posterior
- Anterior divisions innervate anterior (flexor) muscles
- Posterior divisions innervate posterior (extensor) muscles
- **No named branches** arising directly from divisions
- Divisions located at level of clavicle and above junction of subclavian and axillary arteries
- **Cords**
- As BP passes into axilla, divisions fuse again to form **cords**
- Cords intimately associated with **axillary artery**; named by their relationship to artery itself
- **Lateral cord** (anterior divisions of superior, middle trunks) innervates anterior (flexor) muscles
- **Medial cord** (anterior division of inferior trunk) innervates anterior (flexor) muscles
- **Posterior cord** (posterior divisions of all 3 trunks) innervates posterior (extensor) muscles
- **Branches (terminal)**
- Cords form terminal **branches** of BP at approximately level of **lateral margin of pectoralis minor** muscle
- **Lateral cord branches**
- **Musculocutaneous nerve** (C5, C6, C7)
- **Lateral pectoral nerve** (C5, C6, C7)
- **Lateral root of median nerve** (C5, C6, C7)
- **Medial cord branches**
- **Ulnar nerve**(C7, C8,T1)
- **Medial pectoral nerve**(C8, T1)
- **Medial cutaneous nerve of arm**(C8, T1)
- **Medial cutaneous nerve of forearm**(C8, T1)
- **Medial root of median nerve**(C8, T1)
- Note: **Median nerve**(C5-T1) formed by confluence of contributions from both medial and lateral cords
- **Posterior cord branches**
- **Radial nerve** (C5, C6, C7, C8, T1)
- **Axillary nerve** (C5, C6)
- **Thoracodorsal nerve (nerve to latissimus dorsi)** (C6, C7, C8)
- Upper and lower **subscapular nerves**(C5, C6)
- ### Anatomy Relationships
- **NF**
- C5 nerve passes through NF at C4-C5
- C6 nerve passes through NF at C5-C6
- C7 nerve passes through C6-C7 NF
- C8 nerve passes through NF at C7-T1
- T1 nerve passes through NF at T1-T2
- Within NF, DRG most conspicuous neural structure: Bulbous enlargement of dorsal root
- Within NF, nerves of **C5, C6, and C7** positioned immediately posterior to vertebral artery
- **Lateral neural sulcus**
- Transverse processes of C3-C6 have similar anatomic appearance with transverse foramen that transmits vertebral artery and lateral neural sulcus (superolateral groove of transverse process), where corresponding cervical nerve is positioned
- e.g., after exiting NF at C4-C5, C5 nerve descends and passes laterally to lateral neural sulcus of transverse process of C5 vertebra
- When vertebrae of C3-C6 are viewed in axial plane through transverse process, vertebral artery separated from proximal ventral ramus by small bony bar that separates transverse foramen from lateral neural sulcus
- **Interscalene triangle**
- Anterior scalene muscle arises from anterior tubercles of transverse processes of C3-C6 cervical vertebrae and inserts on superior surface of 1st rib anteriorly
- Middle scalene muscle arises from posterior tubercles of transverse processes of C2-C7 vertebrae and attaches to 1st rib laterally
- Borders of interscalene triangle
- Anterior border: Posterior margin of anterior scalene muscle
- Posterior border: Anterior edge of middle scalene muscle
- Inferior border (base): Superior margin of 1st rib, between separate attachments for 2 muscles
- Interscalene triangle can also be considered 3D space with both lateral and medial borders as well
- Medial border represented by plane extending from medial margins of anterior and middle scalene muscles, and lateral border as plane between lateral margins of both muscles
- Widest portion of triangle at base, along 1st rib
- Distance between attachments of anterior and middle scalene muscles to ribs is ~ 1 cm (range: 1.0-2.5 cm)
- Interscalene triangle contains variable amounts of fat
- Interscalene fat most conspicuous in lower aspect of triangle
- More superiorly, anterior and middle scalene muscles closely approximated, and distinct fat separating muscles may be minimal or absent
- Presence of fat, particularly perineural fat, useful for identifying proximal components of BP within interscalene triangle on MR and CT scans
- BP **roots of C5-C7** located **within** upper aspect of interscalene triangle
- Begin to form upper and middle trunks as they pass through triangle itself
- BP **r****oots of C8-T1**are actually **medial to triangle initially**
- Begin to form lower trunk as they enter medial margin of interscalene triangle
- Interscalene triangle considered to contain upper, middle, and lower trunks of BP
- **Subclavian artery**
- Gives off vertebral artery and internal thoracic artery before entering interscalene triangle
- Passes through **base of interscalene triangle**, passing just over superior margin of 1st rib
- Within triangle, subclavian artery intimately associated with proximal BP
- **C5-C7 roots** located **superior** to artery; **C8 and T1 roots** often more **posterior** to artery
- Subclavian artery and BP **separated from subclavian vein** by **anterior scalene muscle** itself
- Subclavian artery transitions to axillary artery at lateral margin of 1st rib
- **Axillary artery**
- As subclavian artery passes 1st rib, it becomes axillary artery
- Components of BP **above proximal axillary artery** generally consist of anterior and posterior **divisions**
- Divisions then form cords intimately associated with axillary artery; named by their relationship to artery itself
- **Cords** generally formed **prior to reaching sagittal plane** that passes through **coracoid process** of scapula
- **Phrenic nerve**
- Arises primarily as branch from C4 ventral ramus with variable contributions from C5 and, occasionally, C3
- Passes around lateral margin of anterior scalene muscle and descends in neck along**anterior surface of anterior scalene**
- Near base of anterior scalene muscle, phrenic nerve passes **between subclavian vein and subclavian artery** before passing **anterior to internal thoracic artery** and entering mediastinum
- Supplies motor and sensory innervation to diaphragm
## IMAGING ANATOMY
- ### Overview
- Knowledge of normal BP anatomy and relationship of BP components to surrounding structures critical for evaluating BP
- Components of BP complex difficult to identify and fully evaluate with single MR sequence or in single plane
- Surrounding perineural fat often provides excellent visualization of nerves on T1WI and allows them to be distinguished from adjacent soft tissues
- Corresponding T2WI, STIR sequences best for evaluating intrinsic signal and architecture of nerves
- Characteristics of normal nerve on MR
- In cross section, nerve appears as well-defined oval structure
- Discrete fascicles identified with high-resolution imaging
- Fascicles uniform in size, shape
- Isointense to adjacent muscle tissue on T1WI
- Slightly hyperintense to adjacent muscle on fat-saturated T2WI, STIR
- Normal nerves should be similar in signal intensity compared to adjacent normal nerves and contralateral normal nerves
- While DRG enhances with IV gadolinium, major components of BP should not enhance normally
## ANATOMY IMAGING ISSUES
- ### Imaging Recommendations
- **3D STIR (fat suppression) with gadolinium contrast (better water suppression, nerve visualization, and lesion enhancement)**
- Reformatted in multiplanar maximum-intensity projections **(****MIP****)** and volumetric **3D**reconstructions
- Diffusion-weighted imaging with background signal suppression **(****DWIBS****)**-based MR neurography
- Diffusion tensor imaging **(****DTI****)** tractography
- MR of cervical spine can be useful primary examination to evaluate for spinal cord pathology as well as common degenerative findings, including spinal stenosis and NF stenosis, that create BP symptoms
- CECT of neck/chest for evaluation of neck/apical pulmonary masses (Pancoast tumor) that involve BP
- CT myelography can be effective tool to evaluate for traumatic nerve root avulsion and associated traumatic pseudomeningoceles
- CT of cervical spine with bone windows preferred for cervical spine fracture
- CTA of neck can demonstrate relationship of proximal BP masses with vertebral arteries
- High-frequency transducer US provides excellent spatial resolution to visualize small components of BP
- Seen as long, tubular, hypoechoic structures against background of echogenic fat on longitudinal scan
- Several small ovoid/round hypoechoic nodules in lower posterior triangle between scalenus anterior and scalenus medius muscles on transverse scan
- Lack of flow distinguishes them from vascular structures
- ### Imaging Approaches
- Best imaging sequences: 3D STIR with contrast and reconstructions, coronal T1, oblique sagittal T1
- Best imaging reconstruction planes: Coronal and oblique sagittal planes from C3 (rostral) through T2 (caudal), nerve roots (medial) through axilla (lateral)
- Optional sequences
- Oblique sagittal and coronal contrast-enhanced fat-saturated T1 (for cases of known or suspected neoplasm, scar, or infection)
- Coronal technique with larger field of view (FOV) can include contralateral BP for comparison
- ### Imaging Pitfalls
- Too-large FOV reduces spatial resolution, compromises visualization of internal BP architecture
- Technically simpler to evaluate supraclavicular plexus than infraclavicular plexus
- STIR provides more reliable fat suppression than chemical fat-saturated T2WI
- Motion artifact (especially respiratory motion of chest) degrades image quality
- Subclavian/axillary vessels (especially veins) can show linear high signal on fast spin-echo or inversion recovery sequences and can be difficult to separate from BP
- Saturation bands can help decrease vascular signal
- **3D STIR SPACE/3D STIR VISTA with contrast**: Normal BP signal not affected, while high signals from vessels completely suppressed
- Enhancing vascular structures and normal perineural venous plexus mimic pathologically enhancing BP
## CLINICAL IMPLICATIONS
- ### Clinical Importance
- Variety of pathologies affect BP, including idiopathic inflammation, traumatic injuries, neoplasm, and compression syndromes
- Due to complex anatomy of BP and variable pathologies, clinical symptoms may range from focal neurologic symptoms involving distal branch to more extensive brachial plexopathy involving multiple nerves
- Combination of neurologic evaluation and MR key to identify and localize lesion as well as plan treatment
038bdcc2-41d5-4cd4-bce1-bcd1322cad9b
## Images
### Graphics: Overview
![Coronal graphic demonstrates an overview of the cervical spine and supraclavicular brachial plexus. This shows the basic arrangement of the cervical ventral primary rami combining to form the brachial plexus. The C1-C7 cervical nerves exit above the same numbered pedicle, C8 nerve exits above the T1 pedicle, and more caudal roots exit below their numbered pedicle.](images/app.statdx.com_image_thumbnail_050b6784-47e7-4214-b766-449b264c85a8_annotated_false_size_900_quality_90_cd8af780624dd4caf6c22e3d1833eeb1ea74cc1d.jpg)
*Coronal graphic demonstrates an overview of the cervical spine and supraclavicular brachial plexus. This shows the basic arrangement of the cervical ventral primary rami combining to form the brachial plexus. The C1-C7 cervical nerves exit above the same numbered pedicle, C8 nerve exits above the T1 pedicle, and more caudal roots exit below their numbered pedicle.*
![Coronal graphic of the brachial plexus demonstrates an overview of the more distal plexus elements extending into the axilla. The trunks recombine into posterior and anterior divisions that form the cords. The posterior cord forms the radial, axillary, thoracodorsal, and upper and lower subscapular nerves. The medial cord forms the ulnar nerve, medial pectoral nerve, medial cutaneous nerve of arm and medial cutaneous nerve of forearm, and also gives off the medial root of median nerve. The lateral cord forms the musculocutaneous nerve and lateral pectoral nerve and also gives off the lateral root of median nerve. Note that the median nerve is formed from branches of both the lateral and medial cords.](images/app.statdx.com_image_thumbnail_4fcdb950-e1aa-4b8e-bc7e-2c3184db66eb_annotated_false_size_900_quality_90_c38b7106b010de4d4e7894feb8f122f77c345051.jpg)
*Coronal graphic of the brachial plexus demonstrates an overview of the more distal plexus elements extending into the axilla. The trunks recombine into posterior and anterior divisions that form the cords. The posterior cord forms the radial, axillary, thoracodorsal, and upper and lower subscapular nerves. The medial cord forms the ulnar nerve, medial pectoral nerve, medial cutaneous nerve of arm and medial cutaneous nerve of forearm, and also gives off the medial root of median nerve. The lateral cord forms the musculocutaneous nerve and lateral pectoral nerve and also gives off the lateral root of median nerve. Note that the median nerve is formed from branches of both the lateral and medial cords.*
### Graphic: Brachial Plexus
![Graphic shows the components of the brachial plexus. The exiting nerves quickly divide into small dorsal rami and larger ventral rami. The ventral rami (roots) of C5-T1 pass into the scalene triangle and merge into trunks. Branches arising directly from the brachial plexus roots are the dorsal scapular nerve (C5), long thoracic nerve (C5, C6, C7) and phrenic nerve (C3, C4, C5; mainly C4). The upper trunk is formed by C5 and C6 ventral rami or roots. Only the upper trunk gives off branches, namely suprascapular nerve and nerve to subclavius muscle. The middle trunk is formed by continuation of the C7 root. The lower trunk is formed by the coalescence of C8 and T1 roots. Each trunk divides into a ventral and dorsal division. Divisions do not have any named branches. The 3 dorsal divisions merge into the posterior cord. Ventral divisions of the upper and middle trunks unite to form the lateral cord. The ventral division of the lower trunk merges and forms the medial cord. The cords ultimately give rise to the terminal branches of the upper extremity.](images/app.statdx.com_image_thumbnail_98349cc1-1bd6-4fb9-8654-230085b7e9bd_annotated_false_size_900_quality_90_617aa5341c73ff6d7a9b9edfea2642316a2cacd7.jpg)
*Graphic shows the components of the brachial plexus. The exiting nerves quickly divide into small dorsal rami and larger ventral rami. The ventral rami (roots) of C5-T1 pass into the scalene triangle and merge into trunks. Branches arising directly from the brachial plexus roots are the dorsal scapular nerve (C5), long thoracic nerve (C5, C6, C7) and phrenic nerve (C3, C4, C5; mainly C4). The upper trunk is formed by C5 and C6 ventral rami or roots. Only the upper trunk gives off branches, namely suprascapular nerve and nerve to subclavius muscle. The middle trunk is formed by continuation of the C7 root. The lower trunk is formed by the coalescence of C8 and T1 roots. Each trunk divides into a ventral and dorsal division. Divisions do not have any named branches. The 3 dorsal divisions merge into the posterior cord. Ventral divisions of the upper and middle trunks unite to form the lateral cord. The ventral division of the lower trunk merges and forms the medial cord. The cords ultimately give rise to the terminal branches of the upper extremity.*
### Coronal Relationships of Brachial Plexus
![Graphic demonstrates the relationship of the proximal brachial plexus to the vertebral bodies, middle scalene muscle, subclavian artery, and pulmonary apex. Anterior scalene has been removed to expose the scalene triangle, the region between scalene muscles. Note subclavian vein passes anterior to the inferior attachment of anterior scalene muscle, and the subclavian artery passes posterior to this attachment. The subclavian artery can serve as a marker to find brachial plexus elements on imaging. Note that if an apical lung tumor invades superiorly, it often involves the subclavian artery before it involves the brachial plexus.](images/app.statdx.com_image_thumbnail_d746a097-1b83-48e2-b502-38e56a49e4a1_annotated_false_size_900_quality_90_cea1f35925a4dcee36deb897436ed084e9831e11.jpg)
*Graphic demonstrates the relationship of the proximal brachial plexus to the vertebral bodies, middle scalene muscle, subclavian artery, and pulmonary apex. Anterior scalene has been removed to expose the scalene triangle, the region between scalene muscles. Note subclavian vein passes anterior to the inferior attachment of anterior scalene muscle, and the subclavian artery passes posterior to this attachment. The subclavian artery can serve as a marker to find brachial plexus elements on imaging. Note that if an apical lung tumor invades superiorly, it often involves the subclavian artery before it involves the brachial plexus.*
![Thin source image (right) of postcontrast 3D STIR MR shows the hyperintense distal aspects of the roots of the right brachial plexus. 3D STIR (fat suppression) with gadolinium contrast (better water/vessel signal suppression, nerve visualization and lesion enhancement) is a very efficient way of doing high-resolution brachial plexus MR. 15-mm maximum-intensity projection (MIP) image (left) shows roots joining to form trunks.](images/app.statdx.com_image_thumbnail_e3539f6e-1124-43a6-be17-02bd9630eb42_annotated_false_size_900_quality_90_d6d89f6ba66ecd3af25c40ae2c86cb0d8814b5fd.jpg)
*Thin source image (right) of postcontrast 3D STIR MR shows the hyperintense distal aspects of the roots of the right brachial plexus. 3D STIR (fat suppression) with gadolinium contrast (better water/vessel signal suppression, nerve visualization and lesion enhancement) is a very efficient way of doing high-resolution brachial plexus MR. 15-mm maximum-intensity projection (MIP) image (left) shows roots joining to form trunks.*
![3D volumetric grayscale (right) and colored (left) images from same 3D STIR MR with contrast show the brachial plexus.](images/app.statdx.com_image_thumbnail_30db4b11-6acc-44ad-a284-a98626ffbf11_annotated_false_size_900_quality_90_c02f185c9955cd362b775064e64cef09caa5ae14.jpg)
*3D volumetric grayscale (right) and colored (left) images from same 3D STIR MR with contrast show the brachial plexus.*
### Axial Anatomy: Proximal Cervical Nerves
![Graphic demonstrates ventral and dorsal roots of C6 nerve merging in upper medial neural foramen (NF). Localized expansion of the dorsal nerve is the dorsal root ganglion (DRG). Note the intimate relationship of the DRG to the vertebral artery as it passes through NF. The extraforaminal nerve descends slightly toward the lateral neural sulcus that cradles the nerve before it extends into the scalene triangle. When the nerve is within lateral neural sulcus, it is separated from the vertebral artery within transverse foramen by thin bony bridge of the lateral process.](images/app.statdx.com_image_thumbnail_56c32276-2114-4572-b41e-80ac64e9f9b6_annotated_false_size_900_quality_90_8badc09f7ea48718e2984bcf377abcdb3b9c7d2b.jpg)
*Graphic demonstrates ventral and dorsal roots of C6 nerve merging in upper medial neural foramen (NF). Localized expansion of the dorsal nerve is the dorsal root ganglion (DRG). Note the intimate relationship of the DRG to the vertebral artery as it passes through NF. The extraforaminal nerve descends slightly toward the lateral neural sulcus that cradles the nerve before it extends into the scalene triangle. When the nerve is within lateral neural sulcus, it is separated from the vertebral artery within transverse foramen by thin bony bridge of the lateral process.*
![Axial CTA images descending through C5-C6 disc space show there is prominent enhancement of epidural and perineural venous plexus that surround exiting nerves.](images/app.statdx.com_image_thumbnail_8ef4036c-3cd0-4bc5-894e-2dd6c3d72989_annotated_false_size_900_quality_90_3e0935d51333d8354555a25a4b75bacde90c5d4e.jpg)
*Axial CTA images descending through C5-C6 disc space show there is prominent enhancement of epidural and perineural venous plexus that surround exiting nerves.*
![Axial images continue to descend from disc space at C5-C6 into C6 vertebrae. As the nerve begins to exit NF, it moves inferiorly and laterally and begins to separate from vertebral artery. The extraforaminal nerve will pass lateral to the transverse process within a shallow groove known as lateral neural sulcus, which is a reliable landmark for cervical nerves C3-C6. In many patients, it is difficult to fully distinguish separate scalene muscles on imaging.](images/app.statdx.com_image_thumbnail_cc71c1e4-75a2-4ecf-a73e-902b3bef203a_annotated_false_size_900_quality_90_a88f348aa2aa7dd3460bb10f2d1154b7aebee1dd.jpg)
*Axial images continue to descend from disc space at C5-C6 into C6 vertebrae. As the nerve begins to exit NF, it moves inferiorly and laterally and begins to separate from vertebral artery. The extraforaminal nerve will pass lateral to the transverse process within a shallow groove known as lateral neural sulcus, which is a reliable landmark for cervical nerves C3-C6. In many patients, it is difficult to fully distinguish separate scalene muscles on imaging.*
### Coronal STIR MR
![Coronal T1 MR shows vertebral bodies (upper) and anterior scalene muscles (lower). Anterior scalene muscles arise from transverse processes of cervical vertebrae and attach to 1st rib laterally. Subclavian vein passes anteriorly to attachment of anterior scalene.](images/app.statdx.com_image_thumbnail_93be7fd4-07be-4288-b960-6e2e0da2243c_annotated_false_size_900_quality_90_1e7024f828ff0dbd4f829ca7f117611a27a18063.jpg)
*Coronal T1 MR shows vertebral bodies (upper) and anterior scalene muscles (lower). Anterior scalene muscles arise from transverse processes of cervical vertebrae and attach to 1st rib laterally. Subclavian vein passes anteriorly to attachment of anterior scalene.*
![Coronal T1 MR reveals the difficulty in distinguishing normal nerve tissue from adjacent muscle. Oblique bands of hypointense tissue traverse the ventral face of middle scalene muscle, but the nerves are difficult to separate from oblique tendinous attachments of the muscle itself. There is minimal interscalene fat to provide satisfactory contrast. Subclavian artery is a useful landmark for determining best plane for proximal components of brachial plexus, particularly the trunks. The trunks will pass above the subclavian artery as it passes over the 1st rib.](images/app.statdx.com_image_thumbnail_5deb7f33-7f19-4987-9139-d5423900fd49_annotated_false_size_900_quality_90_b2260b4763ae29f1df6b1a74b5aa2bc06a409ddd.jpg)
*Coronal T1 MR reveals the difficulty in distinguishing normal nerve tissue from adjacent muscle. Oblique bands of hypointense tissue traverse the ventral face of middle scalene muscle, but the nerves are difficult to separate from oblique tendinous attachments of the muscle itself. There is minimal interscalene fat to provide satisfactory contrast. Subclavian artery is a useful landmark for determining best plane for proximal components of brachial plexus, particularly the trunks. The trunks will pass above the subclavian artery as it passes over the 1st rib.*
![Coronal STIR MR shows relative hyperintensity of normal nerves to muscle. Fat has been suppressed to enhance contrast resolution of nerves. Note DRGs are easily identified as focal enlargements of proximal nerves within NF. Given complex curvature of components, it is difficult to obtain a full view of the brachial plexus in a single slice on 2D MR.](images/app.statdx.com_image_thumbnail_a7677c07-5e05-4ad5-9a6d-f60ce3b21484_annotated_false_size_900_quality_90_b5cf7d66e893fc58081d23178edebae210b6c7e3.jpg)
*Coronal STIR MR shows relative hyperintensity of normal nerves to muscle. Fat has been suppressed to enhance contrast resolution of nerves. Note DRGs are easily identified as focal enlargements of proximal nerves within NF. Given complex curvature of components, it is difficult to obtain a full view of the brachial plexus in a single slice on 2D MR.*
### Axial STIR MR
![First of 3 axial STIR MR images presented from rostral to caudal shows the upper brachial plexus elements [C5-C7 ventral primary rami (VPR)] traveling between the anterior and middle scalene muscles in preparation to form the brachial plexus.](images/app.statdx.com_image_thumbnail_86c98541-7ebd-49b1-93a9-94ebe00a9c08_annotated_false_size_900_quality_90_6baf0cc7b2dafc8b22efdd31c914fcb12ffbcc3c.jpg)
*First of 3 axial STIR MR images presented from rostral to caudal shows the upper brachial plexus elements [C5-C7 ventral primary rami (VPR)] traveling between the anterior and middle scalene muscles in preparation to form the brachial plexus.*
![Image at the C7/T1 level depicts the linear alignment of the C5-C8 VPR. C5 and C6 are closely approximated and form the left upper trunk.](images/app.statdx.com_image_thumbnail_2808498e-8b15-45ad-b275-43e118264f38_annotated_false_size_900_quality_90_dc7b3945dcbfb7b739d156547efd95a890bc9888.jpg)
*Image at the C7/T1 level depicts the linear alignment of the C5-C8 VPR. C5 and C6 are closely approximated and form the left upper trunk.*
![Imaging more caudal at C7/T1 level depicts the upper trunk on the left. Note that the brachial plexus elements exit the neck between the anterior and middle scalene muscles.](images/app.statdx.com_image_thumbnail_c6cc8ceb-3919-4d11-aaeb-b3321f36492c_annotated_false_size_900_quality_90_4835dea70bd43d74cf8504c681eefbc95123bdc4.jpg)
*Imaging more caudal at C7/T1 level depicts the upper trunk on the left. Note that the brachial plexus elements exit the neck between the anterior and middle scalene muscles.*
### Oblique Sagittal STIR MR
![First of 4 oblique sagittal STIR MR images presented from medial to lateral demonstrates the ventral primary rami of C5-T1 proximal to the trunks. C8 exits above the 1st rib while T1 exits below. The brachial plexus is normally sandwiched between the anterior and middle scalene muscles.](images/app.statdx.com_image_thumbnail_93af6df7-9ef3-47c4-9370-62c01626a8dd_annotated_false_size_900_quality_90_cef8fcc804dea00b450cd318647ea576fa9d8ef5.jpg)
*First of 4 oblique sagittal STIR MR images presented from medial to lateral demonstrates the ventral primary rami of C5-T1 proximal to the trunks. C8 exits above the 1st rib while T1 exits below. The brachial plexus is normally sandwiched between the anterior and middle scalene muscles.*
![A slightly more lateral slice demonstrates the formation of the upper, middle, and lower trunks arranged in a vertical line between the scalene muscles. The C5 and C6 VPR can be still resolved as distinct elements within the upper trunk at this level.](images/app.statdx.com_image_thumbnail_bce53611-bcdd-4a49-9aaf-a569c6d9b0c6_annotated_false_size_900_quality_90_a955ccca52c09901b77d54e39cc6feb310042396.jpg)
*A slightly more lateral slice demonstrates the formation of the upper, middle, and lower trunks arranged in a vertical line between the scalene muscles. The C5 and C6 VPR can be still resolved as distinct elements within the upper trunk at this level.*
![Image at the division level shows mixing and matching of the trunks into anterior and posterior divisions. Note that the divisions are retroclavicular. The posterior divisions will form the posterior cord, and the anterior divisions will form the lateral and medial cords. It is generally not possible to follow individual branches of the divisions from trunk to cord.](images/app.statdx.com_image_thumbnail_cb366834-6667-4e1f-b2dd-e9271841b0d9_annotated_false_size_900_quality_90_641b70a85ffb7ce365ebf4711a765e6a92700431.jpg)
*Image at the division level shows mixing and matching of the trunks into anterior and posterior divisions. Note that the divisions are retroclavicular. The posterior divisions will form the posterior cord, and the anterior divisions will form the lateral and medial cords. It is generally not possible to follow individual branches of the divisions from trunk to cord.*
![Image demonstrates the formation of the 3 cords (lateral, medial, and posterior). The most important terminal branch of the lateral cord is the musculocutaneous nerve. The posterior cord forms the axillary and radial nerve terminal branches. The medial cord terminates as the ulnar nerve.](images/app.statdx.com_image_thumbnail_db503bae-7485-4616-9eab-877825c46b9c_annotated_false_size_900_quality_90_8d8cdffa763ebe589ecbe039d3e5bde4c606563b.jpg)
*Image demonstrates the formation of the 3 cords (lateral, medial, and posterior). The most important terminal branch of the lateral cord is the musculocutaneous nerve. The posterior cord forms the axillary and radial nerve terminal branches. The medial cord terminates as the ulnar nerve.*
### Anatomic-Pathologic Correlation
![Coronal T2 FS MR demonstrates mild relative hyperintensity in the brachial plexus diffusely in the right side of this patient with idiopathic plexitis. On coronal MR, T1 root is easily seen as a horizontal linear structure surrounded by fat close to lung apex. This is a good starting point to identify brachial plexus roots and then count C8, C7, C6, C5 upward. Stellate ganglion can also be seen at this level.](images/app.statdx.com_image_thumbnail_6ec596cd-bda2-4a5e-a1b6-e4ead8f309c7_annotated_false_size_900_quality_90_f8d4c8c05ddc6acd17d4dca20d86e34ee1689e97.jpg)
*Coronal T2 FS MR demonstrates mild relative hyperintensity in the brachial plexus diffusely in the right side of this patient with idiopathic plexitis. On coronal MR, T1 root is easily seen as a horizontal linear structure surrounded by fat close to lung apex. This is a good starting point to identify brachial plexus roots and then count C8, C7, C6, C5 upward. Stellate ganglion can also be seen at this level.*
![Coronal STIR MR depicts massive enlargement of all of the proximal cervical nerves and supraclavicular components of the brachial plexus in this patient with neurofibromatosis type 1. In this case, essentially all the nerves have given rise to neurofibromas.](images/app.statdx.com_image_thumbnail_c62f3d86-3fe8-4bc6-9980-c709cb233846_annotated_false_size_900_quality_90_241f40b4ef616a726444bc6162805dc3d5249749.jpg)
*Coronal STIR MR depicts massive enlargement of all of the proximal cervical nerves and supraclavicular components of the brachial plexus in this patient with neurofibromatosis type 1. In this case, essentially all the nerves have given rise to neurofibromas.*
![Axial T2 and contrast-enhanced T1 FS MR images through the C4-C5 NF demonstrate a solitary, enlarged, fusiform enhancing mass along the proximal C5 nerve on the patient's left. Notice the lesion's relationship to the left vertebral artery; the lesion pushes the vertebral artery anteriorly. Notice the DRG on the unaffected side enhances normally.](images/app.statdx.com_image_thumbnail_511a2b05-5dfa-42b8-9e45-cafff278a8f7_annotated_false_size_900_quality_90_6982e30c627c6b4f59ef0cd8980cc09b4d423e4f.jpg)
*Axial T2 and contrast-enhanced T1 FS MR images through the C4-C5 NF demonstrate a solitary, enlarged, fusiform enhancing mass along the proximal C5 nerve on the patient's left. Notice the lesion's relationship to the left vertebral artery; the lesion pushes the vertebral artery anteriorly. Notice the DRG on the unaffected side enhances normally.*
### Transverse and Longitudinal Ultrasound
![Longitudinal grayscale ultrasound of the posterior triangle of the neck shows the root and trunk of the brachial plexus, which appears as a thin, tubular, hypoechoic structure related superficially to the scalenus anterior muscle and deeply to the cervical vertebrae.](images/app.statdx.com_image_thumbnail_fdc4a500-5e6a-489e-a7a3-ebf6684e6201_annotated_false_size_900_quality_90_ade33eaea08a3e9af6c65b12daa82d5736d4636f.jpg)
*Longitudinal grayscale ultrasound of the posterior triangle of the neck shows the root and trunk of the brachial plexus, which appears as a thin, tubular, hypoechoic structure related superficially to the scalenus anterior muscle and deeply to the cervical vertebrae.*
![Longitudinal grayscale ultrasound of the right posterior triangle/supraclavicular fossa confirms the elongated linear, hypoechoic, thickened elements of the brachial plexus. The patient had past history of neck irradiation for metastatic neck nodes, and the nerve thickening is likely secondary to postradiation change.](images/app.statdx.com_image_thumbnail_f6c17b1d-81da-4f81-829d-82d9aa00166d_annotated_false_size_900_quality_90_f28a4faeb5b8a830209b33b9528e9b9622275f0a.jpg)
*Longitudinal grayscale ultrasound of the right posterior triangle/supraclavicular fossa confirms the elongated linear, hypoechoic, thickened elements of the brachial plexus. The patient had past history of neck irradiation for metastatic neck nodes, and the nerve thickening is likely secondary to postradiation change.*
![Transverse grayscale ultrasound of the right lower posterior triangle/supraclavicular fossa shows round smooth hypoechoic &quot;nodules&quot; between the scalenus anterior and medius muscles, representing thickened brachial plexus elements viewed in cross section. If there is a question, rotate the transducer to elongate the nerve.](images/app.statdx.com_image_thumbnail_4b95185c-44ad-499d-8103-3bc4428a7911_annotated_false_size_900_quality_90_9ff1242eb8c635dfaa20c8cd03e39e5b0da1e5af.jpg)
*Transverse grayscale ultrasound of the right lower posterior triangle/supraclavicular fossa shows round smooth hypoechoic &quot;nodules&quot; between the scalenus anterior and medius muscles, representing thickened brachial plexus elements viewed in cross section. If there is a question, rotate the transducer to elongate the nerve.*
![Transverse ultrasound of the anterolateral lower neck shows the hypoechoic roots of the brachial plexus as they exit the NF and move to the scalene triangle.](images/app.statdx.com_image_thumbnail_4acc1acc-282e-4718-ac13-54d91229dd75_annotated_false_size_900_quality_90_984f24cb2dd2664c0d81c90248223db94019739e.jpg)
*Transverse ultrasound of the anterolateral lower neck shows the hypoechoic roots of the brachial plexus as they exit the NF and move to the scalene triangle.*
![Longitudinal ultrasound shows the longitudinal section of the hypoechoic C5 nerve root as it exits from the foramen and descends to the intrascalene area.](images/app.statdx.com_image_thumbnail_437794a5-9127-42b3-85b9-d48b00b96330_annotated_false_size_900_quality_90_5a3172830263aef7562da6716fe5e038039221af.jpg)
*Longitudinal ultrasound shows the longitudinal section of the hypoechoic C5 nerve root as it exits from the foramen and descends to the intrascalene area.*
![Transverse ultrasound at the entry into the interscalene triangle shows 5 hypoechoic roots of the brachial plexus between the scalenus anterior and medius muscles. The hypoechoic roots are clearly seen against the adjacent hyperechoic intermuscular fat.](images/app.statdx.com_image_thumbnail_54327b7f-f1be-4884-a20d-906efd14c426_annotated_false_size_900_quality_90_54fcf161be7b7f07f85ba3117e9b5ebf5053c1d0.jpg)
*Transverse ultrasound at the entry into the interscalene triangle shows 5 hypoechoic roots of the brachial plexus between the scalenus anterior and medius muscles. The hypoechoic roots are clearly seen against the adjacent hyperechoic intermuscular fat.*
docs_md/articles/brachial-plexus_d29276cd-f7fc-4944-9594-33172fe697ab.md
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---
title: "Brachial Plexus"
docid: "d29276cd-f7fc-4944-9594-33172fe697ab"
authors:
- key: "ee435a54-df79-4d7a-b78c-b02157eac7f6"
value: "James F. Griffith, MBBCh BAO, MRCP, FRCR, FHKCR FHKAM, MD"
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slug: "anatomy"
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name: "Upper Limb"
slug: "upper-limb"
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name: "Brachial Plexus"
slug: "brachial-plexus"
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lastUpdated: "12/12/24"
pageDescription: "Brachial Plexus"
pageKeywords: "Ultrasound, Anatomy, Upper Limb, Brachial Plexus"
pageTitle: "Brachial Plexus | STATdx"
enhancedTitle: "Brachial Plexus"
type: "ANATOMY"
breadcrumbs:
- "Ultrasound"
- "Anatomy"
- "Upper Limb"
- "Brachial Plexus"
---
## TERMINOLOGY
- ### Abbreviations
- Artery (a.)
- Ligament (l.)
- Muscle (m.)
- Tendon (t.)
- Vein (v.)
## GROSS ANATOMY
- ### Overview
- Brachial plexus is neural highway to upper limbs
- Formed from C5-T1 ventral rami combining to form 3 trunks, 6 divisions, 3 cords, & 5 terminal branches (classic pattern)
- 5 terminal branches are ulnar, median, musculocutaneous, axillary, & radial nerves
- Many variations in this classic anatomy exist
- Cannot rely on having definite number of trunks, divisions, or cords at any particular location
- Roots, trunks, & divisions are monofascicular & hypoechoic, while cords & terminal branches are polyfascicular & hyperechoic
- ### US Anatomy
- 5 specific areas should be assessed to ensure complete evaluation
- Extraforaminal, interscalene, supraclavicular, infraclavicular, & axillary areas
- **Extraforaminal area (5 roots)**
- Single large anterior ramus emerging from spinal root levels C5-T1
- C5 & C5 roots seen between anterior & posterior tubercles of C5 & C6 vertebrae
- Anterior tubercle of C7 transverse process is small; so C7 root is seen lying anterior to large posterior tubercle
- C8 & T1 roots are more difficult to see due to their deep location
- Cross-sectional area (CSA) of C7 & C8 roots (~ 11 mm²) > C6 (~ 9 mm²) > C5 root (~ 6 mm²)
- **Interscalene area****(****5****roots form 3 trunks)**
- Between scalenus anterior muscle anteromedially & scalenus medius muscle posterolaterally
- Roots unite to form trunks in more distal interscalene area
- **Upper (C5-C6), middle (C7), lower (C8, T1) trunks**
- CSA of upper trunk (~ 17 mm²) > middle & lower trunks (~ 14 mm²)
- Upper trunk or C5, C6 roots may pass through or anterior to anterior scalene muscle
- Dorsal scapular artery frequently runs posteriorly between upper & middle trunks
- Upper trunk gives rise to suprascapular nerve
- Normal suprascapular nerve CSA is 2.8 ± 0.8 mm²
- Interscalene triangle is common site for nerve block
- **Supraclavicular area****(6 divisions)**
- Trunks divide into anterior & posterior divisions in supraclavicular fossa; 3 trunks form 6 divisions
- Lie posterior & superoposterior to subclavian artery
- Anterior divisions innervate anterior (flexor) muscles
- Posterior divisions innervate posterior (extensor) muscles
- Transverse cervical artery often loops over divisions
- Costoclavicular gap is between clavicle & 1st rib
- Narrowest passageway for brachial plexus
- Can be narrowed with fracture of clavicle or 1st rib
- Not possible to see costoclavicular gap with US
- **Infraclavicular area****(3****cords)**
- Passageway between supraclavicular fossa & apex of axilla
- Also called retropectoralis minor space or subcoracoid space
- 6 divisions form 3 cords, located lateral, medial, & posterior to axillary artery
- Lateral & medial cords innervate flexor muscles
- Posterior cord innervates extensor muscles
- Cords tend to be more hyperechoic than hypoechoic trunks or divisions
- Brachial plexus components become more fascicular & contain more connective tissue distally
- Roots are monofascicular & hypoechoic, while terminal branches are polyfascicular & hyperechoic
- Pectoralis major muscle overlies cords medially, pectoralis minor muscle overlies cords laterally
- **Axillary area****(5 terminal branches)**
- Pyramidal space with apex superomedially
- **Lateral cord**gives rise to median nerve & musculocutaneous nerve (C5-C6)
- **Medial cord** gives rise to median nerve & ulnar nerve (C8-T1)
- **Posterior cord** gives rise to axillary nerve (C5-C6), radial nerve (C5-T1), thoracodorsal nerve (C6-C8) as well as upper (C6-C7) & lower (C5-C6) subscapular nerves
- Both lateral & medial cords contribute to median nerve
- **Nerves are arranged around axillary artery** with median nerve at 10-11 o'clock, ulnar nerve at 1-2 o'clock, & radial nerve at 4-6 o'clock
- Median nerve lies closest to biceps & coracobrachialis muscles
- This neural arrangement is quite constant, seen in ~ 80% of patients
- In most cases, musculocutaneous nerve branches early from lateral cord
- Continues distally with median nerve in 30% of patients
- Musculocutaneous nerve runs between coracobrachialis & biceps muscles before piercing coracobrachialis muscle
## ANATOMY IMAGING ISSUES
- ### Imaging Approaches
- US is efficient way of assessing brachial plexus
- Excellent 1st-line investigation for most pathologies
- Always start with examining contralateral asymptomatic or less symptomatic side
- Good side-to-side symmetry of brachial plexus appearances in normal subjects
- Familiarity with normal anatomy helps assessment of pathology
- Routinely evaluate extraforaminal (roots), interscalene (trunks), supraclavicular (divisions), infraclavicular (cords), & axillary (terminal branches) areas
- Understand that considerable variation exists in normal neural anatomy of brachial plexus
- Remember that brachial plexus is not isolated group of nerves
- Many neural pathologies (inflammatory polyneuropathy, neuralgic amyotrophy) may also affect nerves beyond brachial plexus (extraplexal nerves)
77b8eb8e-1d7b-475a-88a8-ec6310fac645
## Images
### Brachial Plexus
![Graphic of cervical spine and supraclavicular brachial plexus shows the C5-T1 ventral rami combining to form the brachial plexus. C5 nerve root exits out through the C4/5 neural foramen. C5-C6 ventral rami form the upper trunk, C7 the middle trunk, and C8-T1 the lower trunk.](images/app.statdx.com_image_thumbnail_dd095f36-10f9-482f-bbd5-0947acab33d9_annotated_true_size_900_quality_90_560193f6fd2d847b757b8bf2a08ea7a32d1c3056.jpg)
*Graphic of cervical spine and supraclavicular brachial plexus shows the C5-T1 ventral rami combining to form the brachial plexus. C5 nerve root exits out through the C4/5 neural foramen. C5-C6 ventral rami form the upper trunk, C7 the middle trunk, and C8-T1 the lower trunk.*
![Graphic of cervical spine and supraclavicular brachial plexus shows the C5-T1 ventral rami combining to form the brachial plexus. C5 nerve root exits out through the C4/5 neural foramen. C5-C6 ventral rami form the upper trunk, C7 the middle trunk, and C8-T1 the lower trunk.](images/app.statdx.com_image_thumbnail_dd095f36-10f9-482f-bbd5-0947acab33d9_size_174_quality_85_ff6b5f985471784888b90cfb8d91ace5194b0bb2.jpg)
*Graphic of cervical spine and supraclavicular brachial plexus shows the C5-T1 ventral rami combining to form the brachial plexus. C5 nerve root exits out through the C4/5 neural foramen. C5-C6 ventral rami form the upper trunk, C7 the middle trunk, and C8-T1 the lower trunk.*
![Graphic of the brachial plexus demonstrates the more distal plexus elements extending to the axilla. The trunks divide into posterior and anterior divisions. The divisions combine to form the cords. The posterior cord forms the radial and axillary nerves. The medial cord forms the ulnar nerve, and the lateral cord forms the musculocutaneous nerve. The median nerve is formed from contributions of both the medial and lateral cords.](images/app.statdx.com_image_thumbnail_965ae1a8-5cb5-4608-bbb7-823da065f13e_annotated_false_size_900_quality_90_69ec7a9858a912fcf7ef49bb59d9ef3e69e005ea.jpg)
*Graphic of the brachial plexus demonstrates the more distal plexus elements extending to the axilla. The trunks divide into posterior and anterior divisions. The divisions combine to form the cords. The posterior cord forms the radial and axillary nerves. The medial cord forms the ulnar nerve, and the lateral cord forms the musculocutaneous nerve. The median nerve is formed from contributions of both the medial and lateral cords.*
### Brachial Plexus and Terminal Branches
![Graphic shows 3 of the 5 terminal branches of the brachial plexus (median, radial, and ulnar nerves) as they course down the arm. The other 2 terminal branches are the musculocutaneous and axillary nerves. The axillary nerve innervates the teres minor and deltoid muscles, while the musculocutaneous nerve innervates the 3 muscles of the anterior compartment of the arm, namely the coracobrachialis, biceps, and brachialis muscles.](images/app.statdx.com_image_thumbnail_2091b92b-aaf9-46a5-b3b1-9a922ee0e135_annotated_false_size_900_quality_90_089ba03fcf76555a133410a7d3f01a6a9b444db1.jpg)
*Graphic shows 3 of the 5 terminal branches of the brachial plexus (median, radial, and ulnar nerves) as they course down the arm. The other 2 terminal branches are the musculocutaneous and axillary nerves. The axillary nerve innervates the teres minor and deltoid muscles, while the musculocutaneous nerve innervates the 3 muscles of the anterior compartment of the arm, namely the coracobrachialis, biceps, and brachialis muscles.*
### Brachial Plexus Overview
![Graphic shows the anterior and posterior rootlets emerging from the spinal cord. The roots unite within the spinal ganglia from which emerge the larger ventral and smaller dorsal rami. The brachial plexus is formed from the ventral rami of the C5-T1 roots. The ganglia and nerve rootlets are not part of the brachial plexus. The vertebral arteries within the transverse foramina of the transverse processes are also depicted.](images/app.statdx.com_image_thumbnail_4ccce873-e03d-4cf5-b02e-e365e479a17e_annotated_false_size_900_quality_90_86c395865eba5258d6ffc9c2f2b47fc0c3c3573a.jpg)
*Graphic shows the anterior and posterior rootlets emerging from the spinal cord. The roots unite within the spinal ganglia from which emerge the larger ventral and smaller dorsal rami. The brachial plexus is formed from the ventral rami of the C5-T1 roots. The ganglia and nerve rootlets are not part of the brachial plexus. The vertebral arteries within the transverse foramina of the transverse processes are also depicted.*
![Graphic shows the relationship of the brachial plexus to the arteries, veins, muscles, skeleton of the thoracic outlet, supraclavicular fossa, and axillary regions.](images/app.statdx.com_image_thumbnail_4af5f2bb-37aa-4c38-bf4d-33c4c89e6cb3_annotated_false_size_900_quality_90_2964891c80e0bccc914fcdb9798ef33e214676c1.jpg)
*Graphic shows the relationship of the brachial plexus to the arteries, veins, muscles, skeleton of the thoracic outlet, supraclavicular fossa, and axillary regions.*
![Longitudinal US shows the C5, C6, and C7 roots arising from the neural foramina. The brachial plexus extends from beyond the spinal ganglia where the ventral rami become known as the roots. The brachial plexus is generally scanned in a transverse rather than a longitudinal section. Longitudinal scanning of the roots is most helpful when looking for a root avulsion or assessing the location of nerve sheath tumors.](images/app.statdx.com_image_thumbnail_e32cb812-b129-4466-a1cf-d3486444b349_annotated_false_size_900_quality_90_177c47c8d346bf9e91642afd510bb84b8ec4d369.jpg)
*Longitudinal US shows the C5, C6, and C7 roots arising from the neural foramina. The brachial plexus extends from beyond the spinal ganglia where the ventral rami become known as the roots. The brachial plexus is generally scanned in a transverse rather than a longitudinal section. Longitudinal scanning of the roots is most helpful when looking for a root avulsion or assessing the location of nerve sheath tumors.*
### Transverse US Roots
![Transverse US of the C7 root is shown. The C7 root passes anterior to the large posterior tubercle (outlined) of the C7 transverse process (thumbs-up sign). The C7 anterior tubercle is absent or rudimentary. The vertebral artery is located anterior to the C7 root. At C6 and C5, the vertebral artery is within the foramen transversarium of the transverse process.](images/app.statdx.com_image_thumbnail_b3f05d0a-0e31-492c-b683-0cba02bcc8cc_annotated_false_size_900_quality_90_ec55fa00bb1439d10517f71b7bc385210a2d7add.jpg)
*Transverse US of the C7 root is shown. The C7 root passes anterior to the large posterior tubercle (outlined) of the C7 transverse process (thumbs-up sign). The C7 anterior tubercle is absent or rudimentary. The vertebral artery is located anterior to the C7 root. At C6 and C5, the vertebral artery is within the foramen transversarium of the transverse process.*
![Transverse US shows the C6 root passing between the anterior and posterior tubercles of the C6 transverse process (V-sign, outlined).](images/app.statdx.com_image_thumbnail_f06d9682-a2ea-46fa-beab-96cb7e42e918_annotated_false_size_900_quality_90_6c05d383dd0ce8ea482a9aacddd9fe893a204d83.jpg)
*Transverse US shows the C6 root passing between the anterior and posterior tubercles of the C6 transverse process (V-sign, outlined).*
![Transverse US shows the C5 root passing between the anterior and posterior tubercles of the C5 transverse process (outlined). The tubercles of the transverse processes become smaller and more closely aligned from C6 to C5 to C4.](images/app.statdx.com_image_thumbnail_4c82f633-50e5-4b84-907e-10a3d2e89f8a_annotated_false_size_900_quality_90_c20861e1713e372e1a5cdbe9292aa30339979bb1.jpg)
*Transverse US shows the C5 root passing between the anterior and posterior tubercles of the C5 transverse process (outlined). The tubercles of the transverse processes become smaller and more closely aligned from C6 to C5 to C4.*
### Transverse US Trunks
![Transverse US at interscalene level shows the upper, middle, and lower trunks (&quot;traffic light sign&quot;) of the brachial plexus between the anterior and middle scalene muscles. Note the hypoechoic appearance of the monofascicular trunks. The suprascapular nerve, which arises from either the C5 root or the upper trunk, is also shown.](images/app.statdx.com_image_thumbnail_7235e0d3-8b52-4daf-96c0-ffe9fcf96ad4_annotated_false_size_900_quality_90_93c6d3459fa4707c828cf7e6c0db1fd155f0f0eb.jpg)
*Transverse US at interscalene level shows the upper, middle, and lower trunks (&quot;traffic light sign&quot;) of the brachial plexus between the anterior and middle scalene muscles. Note the hypoechoic appearance of the monofascicular trunks. The suprascapular nerve, which arises from either the C5 root or the upper trunk, is also shown.*
![Transverse US shows roots and trunks of the brachial plexus between the scalenus medius and anterior muscles. Often, 3 distinct trunks are not visible with the trunks being rudimentary and the roots passing almost directly to divisions. Such variability in the brachial plexus morphology limits the use of objective size measurements to define normality. It is best to compare with the contralateral normal or less symptomatic side, as good side-to-side symmetry in brachial plexus morphology normally exists.](images/app.statdx.com_image_thumbnail_af7d5ef7-a97f-4a63-aa9a-5a4c57a4929f_annotated_false_size_900_quality_90_6725607845ad2b3cf27897b247880437e2437c34.jpg)
*Transverse US shows roots and trunks of the brachial plexus between the scalenus medius and anterior muscles. Often, 3 distinct trunks are not visible with the trunks being rudimentary and the roots passing almost directly to divisions. Such variability in the brachial plexus morphology limits the use of objective size measurements to define normality. It is best to compare with the contralateral normal or less symptomatic side, as good side-to-side symmetry in brachial plexus morphology normally exists.*
![Transverse US of the interscalene triangle outlet shows the dorsal scapular artery running between the upper and middle trunks. This is a fairly common finding. The suprascapular nerve is also shown. This nerve is the 1st branch of either the upper trunk or C5 root.](images/app.statdx.com_image_thumbnail_c16d21e6-0090-4708-bb03-81ad46590a6f_annotated_false_size_900_quality_90_4dbd58ae0288f29ad742bc546793098864c52f77.jpg)
*Transverse US of the interscalene triangle outlet shows the dorsal scapular artery running between the upper and middle trunks. This is a fairly common finding. The suprascapular nerve is also shown. This nerve is the 1st branch of either the upper trunk or C5 root.*
### Transverse US Divisions
![Transverse US of the extrascalenus supraclavicular portion of the brachial plexus shows the divisions of the brachial plexus. These resemble a bunch of grapes and line up lateral or superolateral to the subclavian artery. The upper, middle, and lower trunks divide into 6 divisions. Note the normal hyperechoic fat between the divisions.](images/app.statdx.com_image_thumbnail_48adfe10-b548-44bf-8164-b71fb514c0d1_annotated_false_size_900_quality_90_2b86dd6c1eff1009c0360b276ef05cf31b1bcc78.jpg)
*Transverse US of the extrascalenus supraclavicular portion of the brachial plexus shows the divisions of the brachial plexus. These resemble a bunch of grapes and line up lateral or superolateral to the subclavian artery. The upper, middle, and lower trunks divide into 6 divisions. Note the normal hyperechoic fat between the divisions.*
![Transverse US just slightly more distal to the previous image in the immediate retroclavicular area shows the divisions arranged lateral and superolateral to the subclavian artery. The divisions, similar to the other components of the brachial plexus, are variable in size across the population, though good individual side-to-side symmetry exists in normal subjects.](images/app.statdx.com_image_thumbnail_cc2891a9-8217-4f35-b801-4bfe7eabd5c3_annotated_false_size_900_quality_90_0c08996cce544020f71c670cd2b63e0de45ab722.jpg)
*Transverse US just slightly more distal to the previous image in the immediate retroclavicular area shows the divisions arranged lateral and superolateral to the subclavian artery. The divisions, similar to the other components of the brachial plexus, are variable in size across the population, though good individual side-to-side symmetry exists in normal subjects.*
![Graphic shows the costoclavicular gap, which is the narrowest area through which the brachial plexus passes. This gap can be compressed by deformity of the 1st rib or the clavicle. This small segment of the brachial plexus is not visible on US, though one can still appreciate the brachial plexus immediately proximal and distal to the costoclavicular gap. The subclavian artery becomes the axillary artery after it passes over the 1st rib.](images/app.statdx.com_image_thumbnail_410a7de7-f4b4-4858-bc27-81cdff404388_annotated_false_size_900_quality_90_e02aba6cd446e72a3f3ec84f436dd15ceea5f8c3.jpg)
*Graphic shows the costoclavicular gap, which is the narrowest area through which the brachial plexus passes. This gap can be compressed by deformity of the 1st rib or the clavicle. This small segment of the brachial plexus is not visible on US, though one can still appreciate the brachial plexus immediately proximal and distal to the costoclavicular gap. The subclavian artery becomes the axillary artery after it passes over the 1st rib.*
### Transverse US Cords and Terminal Branches
![Transverse US of the infraclavicular area, also known as the subpectoralis minor space or the subcoracoid space, shows the 3 cords of the brachial plexus positioned alongside the axillary artery. This area is examined with the arm abducted to 90&deg;. The cords are not always readily clearly visible on US, though one can still appreciate normality of the tissues around the axillary artery.](images/app.statdx.com_image_thumbnail_a7daec20-1af9-440c-ac7e-e7b86a3bfc7c_annotated_false_size_900_quality_90_7767b02c587929c72f70108b32d3f8f56670887a.jpg)
*Transverse US of the infraclavicular area, also known as the subpectoralis minor space or the subcoracoid space, shows the 3 cords of the brachial plexus positioned alongside the axillary artery. This area is examined with the arm abducted to 90&deg;. The cords are not always readily clearly visible on US, though one can still appreciate normality of the tissues around the axillary artery.*
![Graphic shows clock face relationship of the nerves around the axillary artery in the axilla with the arm fully abducted. The median nerve lies superolateral, the ulnar nerve lies superomedial, and the radial nerve lies posteromedial or posterior to the axillary artery. The musculocutaneous nerve lies posterolateral to the axillary artery between the coracobrachialis and biceps muscles.](images/app.statdx.com_image_thumbnail_ecc6cc60-9d33-4dec-87f9-03912cf7db59_annotated_false_size_900_quality_90_5fbf4c1d0da89b303060e352a1de02bcb66523eb.jpg)
*Graphic shows clock face relationship of the nerves around the axillary artery in the axilla with the arm fully abducted. The median nerve lies superolateral, the ulnar nerve lies superomedial, and the radial nerve lies posteromedial or posterior to the axillary artery. The musculocutaneous nerve lies posterolateral to the axillary artery between the coracobrachialis and biceps muscles.*
![Transverse US of the axilla with the arm fully abducted shows nerves surrounding the axillary artery. The 2-3 axillary veins have been effaced by transducer pressure. The musculocutaneous nerve lies between the coracobrachialis and biceps brachii muscles. The terminal branches in the axilla can be traced distally to the arm region to confirm their identify.](images/app.statdx.com_image_thumbnail_b4968011-4f82-430d-ba3d-129a4a47b446_annotated_false_size_900_quality_90_5d869b211e072572ec0f9b56f79f63a7424c9376.jpg)
*Transverse US of the axilla with the arm fully abducted shows nerves surrounding the axillary artery. The 2-3 axillary veins have been effaced by transducer pressure. The musculocutaneous nerve lies between the coracobrachialis and biceps brachii muscles. The terminal branches in the axilla can be traced distally to the arm region to confirm their identify.*
docs_md/articles/brachial-plexus_d40ec749-81b1-4900-b366-2921b7fcc467.md
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---
title: "Brachial Plexus"
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value: "Philip R. Chapman, MD"
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pageDescription: "Brachial Plexus"
pageKeywords: "Spine, Anatomy, Plexus, Brachial Plexus"
pageTitle: "Brachial Plexus | STATdx"
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---
## TERMINOLOGY
- ### Abbreviations
- Brachial plexus (BP)
- ### Definitions
- Collection of interconnecting nerves of lower cervical spine (C5-8) and 1st thoracic nerve (T1) that provide cutaneous and motor innervation of upper extremity
## GROSS ANATOMY
- ### Overview
- **Cervical cord**
- Internally, cervical spinal cord is arranged so that white matter tracts are positioned in periphery of cord
- Gray matter is formed by neuronal cell bodies arranged in vertical columns that are centrally located within cord
- Gray matter columns form H-shaped arrangement in axial plane (in cross section) where lateral, sagittally oriented components are referred to as horns and transverse coronal components are referred to as gray commissures
- Ventral (anterior) horns of H are thicker, shorter, and contain multipolar motor neurons
- Dorsal (posterior) horns are thinner, longer, and contain cell bodies that receive sensory axons from dorsal root ganglions (DRGs)
- **Cervical nerve rootlets,** **nerve roots, and proximal nerves**
- At each cervical level, ventral horns give rise to motor axons that exit ipsilateral ventrolateral sulci of cervical cord as several tiny (< 1-mm) **nerve rootlets**
- Ventral nerve rootlets at each level coalesce within few millimeters of cord to form as ipsilateral **ventral root**(~ 1 mm)
- Similarly, dorsal horns receive multiple tiny nerve rootlets at posterolateral sulcus of cord
- Dorsal nerve rootlets also coalesce within few millimeters of cord to form **dorsal root**
- Dorsal root extends laterally from cord and merges with**DRG** within neural foramen (NF)
- Within lateral aspect of cervical NF, DRG fuses with ventral root to become **spinal nerve proper**
- Immediately after proper spinal nerve is formed, small, posteriorly oriented **dorsal ramus** is given off, supplying motor and sensory innervation to posterior paraspinous muscles and cervical soft tissues
- Larger remaining segment of spinal nerve represents **ventral ramus**
- Since ventral ramus is typically main part of spinal nerve in cervical region, it is often referred to as simply spinal nerve itself
- These large ventral rami of nerves C5-T1 are also referred to as roots of BP
- **1st cervical nerve** exits spinal canal between occiput and C1; that is, C1 nerve exits above C1 vertebra (atlas)
- C2 nerve exits between C1 and C2 vertebrae and so forth
- C8 nerve exits between C7 and T1 vertebrae
- **Cervical plexus**
- Formed from ventral rami of C1-4 ± minor branch of C5
- Has ascending superficial, descending superficial, deep branches
- Supplies nuchal muscles, diaphragm, cutaneous head/neck tissues
- **BP**
- Formed from **ventral rami of C5-T1** ± minor branches from C4, T2
- Has some proximal branches originating above BP proper
- Dorsal scapular nerve
- Long thoracic nerve
- Nerves to scalene/longus colli muscles
- Branch to phrenic nerve
- Remaining minor, all major peripheral branches arise from BP proper
- BP divided into anatomic segments moving from medial to lateral: Rami/roots, trunks, divisions, cords, terminal branches
- Relationships of these segments with adjacent anatomic structures is variable
- **Ventral rami/roots of BP**
- Originate from spinal cord levels C5 to T1
- Roots of BP represent ventral rami of nerves C5-T1
- Term "root" in this context is not to be confused with nerve roots discussed previously, which represent small nerves within spinal canal and within proximal NF
- Some nerves arise directly from roots: Dorsal scapular nerve (C5), phrenic (mainly C5), long thoracic nerve (C5, 6, and 7)
- **Trunks**
- Within interscalene triangle, upper roots of BP (C5-6) fuse to form **superior (upper) trunk**
- Lower roots (C8-T1) fuse to form **inferior (lower) trunk**
- C7 root continues laterally as **middle trunk**
- Minor nerves arising directly from upper trunk: Suprascapular nerve, nerve to subclavius muscle
- **Divisions**
- As BP passes laterally beyond interscalene triangle over lateral margin of 1st rib and begins to descend toward axilla, each trunk divides into 2 main nerve branches: **A****nterior and posterior divisions**
- Subsequently, each BP contains total of 6 divisions: 3 anterior and 3 posterior
- Anterior divisions innervate anterior (flexor) muscles
- Posterior divisions innervate posterior (extensor) muscles
- No named minor nerves arising directly from divisions
- Divisions are located at level of clavicle and above junction of subclavian and axillary arteries
- **Cords**
- As BP passes into axilla, divisions fuse again to form **cords**
- Cords are intimately associated with axillary artery and are named by their relationship to artery itself
- **Lateral cord** (anterior divisions of superior, middle trunks) innervates anterior (flexor) muscles
- **Medial cord** (anterior division of inferior trunk) innervates anterior (flexor) muscles
- **Posterior cord** (posterior divisions of all 3 trunks) innervates posterior (extensor) muscles
- **Branches (terminal)**
- Cords form terminal **branches** of BP at approximately level of lateral margin of pectoralis minor muscle
- **Musculocutaneous nerve** (C5-6) arises from lateral cord
- Medial cord gives rise to **ulnar nerve**(C8-T1)
- Medial cord also gives rise to medial pectoral nerve, medial cutaneous nerve of arm, medial cutaneous nerve of forearm
- Axillary nerve (C5-6), radial nerve (C5-T1), thoracodorsal nerve (C6-8), upper (C6-7) and lower (C5-6) subscapular nerves all arise from posterior cord
- **Median nerve**(C5-T1) formed by confluence of contributions from both medial and lateral cords
- ### Anatomy Relationships
- **NF**
- C5 nerve passes through NF at C4-5
- C6 nerve passes through NF at C5-6
- C7 nerve through C6-7 NF
- C8 nerve passes through NF at C7-T1
- T1 nerve passes through NF at T1-2
- Within NF, most conspicuous neural structure is DRG, bulbous enlargement of dorsal root
- Within NF, nerves of C5, 6, and 7 are positioned immediately posterior to vertebral artery
- **Lateral neural sulcus**
- Transverse processes of C3-6 have similar anatomic appearance with transverse foramen that transmits vertebral artery and lateral neural sulcus (superolateral groove of transverse process), where corresponding cervical nerve is positioned
- e.g., after exiting NF at C4-5, C5 nerve descends and passes laterally to lateral neural sulcus of transverse process of C5 vertebra
- When vertebrae of C3-6 are viewed in axial plane through transverse process, vertebral artery is separated from proximal ventral ramus by small bony bar that separates transverse foramen from lateral neural sulcus
- **Interscalene triangle**
- Anterior scalene muscle arises from anterior tubercles of transverse processes of 3rd through 6th cervical vertebrae and inserts on superior surface of 1st rib anteriorly
- Middle scalene muscle arises from posterior tubercles of transverse processes of 2nd through 7th vertebrae and attaches to 1st rib laterally
- Borders of interscalene triangle
- Anterior border: Posterior margin of anterior scalene muscle
- Posterior border: Anterior edge of middle scalene muscle
- Inferior border (base): Superior margin of 1st rib, between separate attachments for 2 muscles
- Interscalene triangle can also be considered 3-dimensional space with both lateral and medial borders as well
- Medial border is represented by plane extending from medial margins of anterior and middle scalene muscles and lateral border as plane between lateral margins of both muscles
- Widest portion of triangle is at base, along 1st rib
- Distance between attachments of anterior and middle scalene muscles to ribs is ~ 1 cm (range: 1.0-2.5 cm)
- Interscalene triangle contains variable amounts of fat
- Interscalene fat is most conspicuous in lower aspect of triangle
- More superiorly, anterior and middle scalene muscles are closely approximated, and distinct fat separating muscles may be minimal or absent
- Presence of fat, particularly perineural fat, is useful for identifying proximal components of BP within interscalene triangle on MR and CT scans
- BP roots of C5-7 are located within upper aspect of interscalene triangle and begin to form upper and middle trunks as they pass through triangle itself
- BP roots of C8-T1 are actually medial to triangle initially and begin to form lower trunk as they enter medial margin of interscalene triangle
- Interscalene triangle is considered to contain upper, middle, and lower trunks of BP
- **Subclavian artery**
- Subclavian artery gives off vertebral artery and internal thoracic artery before entering interscalene triangle
- Subclavian artery passes through base of interscalene triangle, passing just over superior margin of 1st rib
- Within triangle, subclavian artery is intimately associated with proximal BP
- C5-7 roots are located superior to artery; C8 and T1 roots are often more posterior to artery
- Subclavian artery and BP are separated from subclavian vein by anterior scalene muscle itself
- Subclavian artery transitions to axillary artery at lateral margin of 1st rib
- **Axillary artery**
- As subclavian artery passes 1st rib, it becomes axillary artery
- Components of BP above proximal axillary artery generally consists of anterior and posterior divisions
- Divisions then form cords that are intimately associated with axillary artery and are named by their relationship to artery itself
- Cords are generally formed prior to reaching sagittal plane that passes through coracoid process of scapula
- **Phrenic nerve**
- Arises primarily as branch from C4 ventral ramus with variable contributions from C5 and occasionally C3
- Passes around lateral margin of anterior scalene muscle and descends in neck along anterior surface of anterior scalene
- Near base of anterior scalene muscle, phrenic nerve passes between subclavian vein and subclavian artery before passing anterior to internal thoracic artery and entering mediastinum
- Supplies motor and sensory innervation to diaphragm
## IMAGING ANATOMY
- ### Overview
- Knowledge of normal BP anatomy and relationship of BP components to surrounding structures critical for evaluating BP
- Multiplanar high-resolution MR using surface coil is single best method for imaging BP
- Components of BP are complex and difficult to identify and fully evaluate with single MR sequence or in single plane
- Surrounding perineural fat often provides excellent visualization of nerves on T1WI and allows them to be distinguished from adjacent soft tissues
- Corresponding T2WI, STIR sequences are best for evaluating intrinsic signal and architecture of nerves
- Characteristics of normal nerve on MR
- In cross section, nerve appears as well-defined oval structure
- Discrete fascicles can be identified with high-resolution imaging
- Fascicles are uniform in size, shape
- Isointense to adjacent muscle tissue on T1WI
- Slightly hyperintense to adjacent muscle on fat-saturated T2WI, STIR
- Normal nerves should be similar in signal intensity compared to adjacent normal nerves and contralateral normal nerves
- While DRG enhances with intravenous gadolinium, major components of BP should not enhance normally
## ANATOMY IMAGING ISSUES
- ### Imaging Recommendations
- Multiplanar high-resolution MR peripheral nerve imaging using surface coil is **single best** method for imaging BP
- MR of cervical spine can be useful primary examination to evaluate for spinal cord pathology as well as common degenerative findings, including spinal stenosis and NF stenosis, that create BP symptoms
- CECT of neck or chest may be useful for evaluation of neck masses or apical pulmonary masses (Pancoast tumor) that involve BP
- CT myelography can be effective tool at evaluating for traumatic nerve root avulsion and associated traumatic pseudomeningoceles
- CT of cervical spine with bone windows preferred for cervical spine fracture
- CTA neck can demonstrate relationship of proximal BP masses with vertebral arteries
- Ultrasonography is alternative imaging technique to visualize small component of BP
- Excellent spatial resolution provided by high-frequency transducer
- Seen as long, tubular, hypoechoic structures against background of echogenic fat on longitudinal scan
- Several small ovoid/round hypoechoic nodules in lower posterior triangle between scalenus anterior and scalenus medius muscles on transverse scan
- Lack of flow distinguishes them from vascular structures
- ### Imaging Approaches
- Preferred coil: Multipurpose flexible phase array surface coil
- Alternative coil: Neurovascular phase array coil
- Best imaging planes: Coronal and oblique sagittal planes from C3 (rostral) through T2 (caudal), nerve roots (medial) through axilla (lateral)
- Best imaging sequences: Coronal T1, coronal STIR, oblique sagittal T1, and oblique sagittal STIR
- Optional sequences
- Oblique sagittal and coronal contrast-enhanced fat-saturated T1WI (for cases of known or suspected neoplasm, scar, or infection)
- Coronal technique with larger field of view (FOV) can include contralateral BP for comparison
- ### Imaging Pitfalls
- Too-large FOV reduces spatial resolution, compromises visualization of internal BP architecture
- Technically simpler to evaluate supraclavicular plexus than infraclavicular plexus
- STIR provides more reliable fat suppression than chemical fat-saturated T2WI
- Motion artifact (especially respiratory motion of chest) can degrade image quality
- Subclavian and axillary vessels (especially venous structures) can demonstrate linear high signal on fast spin-echo or inversion recovery sequences and can be difficult to separate from BP
- Saturation bands can help decrease vascular signal
- Enhancing vascular structures and normal perineural venous plexus can mimic pathologically enhancing BP components
## CLINICAL IMPLICATIONS
- ### Clinical Importance
- Variety of pathologies can affect BP, including idiopathic inflammation, traumatic injuries, neoplasm, and compression syndromes
- Due to complex anatomy of BP and variable pathologies, clinical symptoms may range from focal neurologic symptoms involving distal branch to more extensive brachial plexopathy involving multiple nerves
- Combination of neurologic evaluation and MR is key to identifying and localizing lesion as well as treatment planning
6ade3c25-700e-41b2-9444-e7caeadc75bd
## Images
### Graphic: Overview
![Coronal graphic demonstrates an overview of the cervical spine and supraclavicular brachial plexus. This shows the basic arrangement of the cervical ventral primary rami combining to form the brachial plexus. The C1-7 cervical nerves exit above the same numbered pedicle, C8 nerve exits above the T1 pedicle, and more caudal roots exit below their numbered pedicle.](dc2fb0f9-27cb-4c9f-861b-5f83a346fabe)
*Coronal graphic demonstrates an overview of the cervical spine and supraclavicular brachial plexus. This shows the basic arrangement of the cervical ventral primary rami combining to form the brachial plexus. The C1-7 cervical nerves exit above the same numbered pedicle, C8 nerve exits above the T1 pedicle, and more caudal roots exit below their numbered pedicle.*
![Coronal graphic of the brachial plexus demonstrates an overview of the more distal plexus elements extending into the axilla. The trunks recombine into posterior and anterior divisions that form the cords. The posterior cord forms the radial and axillary nerves. The medial cord forms the ulnar nerve, while the lateral cord forms the musculocutaneous nerve. The median nerve is formed from branches of both the lateral and medial cords.](da5bb161-9cfc-4d95-9297-82ea27d67bd1)
*Coronal graphic of the brachial plexus demonstrates an overview of the more distal plexus elements extending into the axilla. The trunks recombine into posterior and anterior divisions that form the cords. The posterior cord forms the radial and axillary nerves. The medial cord forms the ulnar nerve, while the lateral cord forms the musculocutaneous nerve. The median nerve is formed from branches of both the lateral and medial cords.*
### Graphic: Brachial Plexus
![Graphic schematically demonstrates the components of the brachial plexus. The exiting nerves quickly divide into small dorsal rami and larger ventral rami. The ventral rami (roots) of C5-T1 pass into the scalene triangle and merge into trunks. The upper trunk is formed by C5 and C6 ventral rami or roots. The middle trunk is formed by continuation of the C7 root. The lower trunk is formed by the coalescence of C8 and T1 roots. Each trunk divides into a ventral and dorsal division. The 3 dorsal divisions merge into the posterior cord. Ventral divisions of the upper and middle trunks unite to form the lateral cord. The ventral division of the lower trunk merges and forms the medial cord. The cords ultimately give rise to the terminal branches of the upper extremity.](7b617571-b645-4042-98b0-193e29a99472)
*Graphic schematically demonstrates the components of the brachial plexus. The exiting nerves quickly divide into small dorsal rami and larger ventral rami. The ventral rami (roots) of C5-T1 pass into the scalene triangle and merge into trunks. The upper trunk is formed by C5 and C6 ventral rami or roots. The middle trunk is formed by continuation of the C7 root. The lower trunk is formed by the coalescence of C8 and T1 roots. Each trunk divides into a ventral and dorsal division. The 3 dorsal divisions merge into the posterior cord. Ventral divisions of the upper and middle trunks unite to form the lateral cord. The ventral division of the lower trunk merges and forms the medial cord. The cords ultimately give rise to the terminal branches of the upper extremity.*
### Coronal Relationships of Brachial Plexus
![Graphic demonstrates the relationship of the proximal brachial plexus to the vertebral bodies, middle scalene muscle, subclavian artery, and pulmonary apex. The anterior scalene has been removed to expose the scalene triangle, the region between the scalene muscles. Note the subclavian vein passes anterior to the inferior attachment of the anterior scalene muscle and the subclavian artery passes posterior to this attachment. The subclavian artery can serve as a marker to find the brachial plexus elements on imaging. Note that if an apical lung tumor invades superiorly, it often involves the subclavian artery before it involves the brachial plexus.](49fd1199-141a-4ad6-bb96-4c4d28c50252)
*Graphic demonstrates the relationship of the proximal brachial plexus to the vertebral bodies, middle scalene muscle, subclavian artery, and pulmonary apex. The anterior scalene has been removed to expose the scalene triangle, the region between the scalene muscles. Note the subclavian vein passes anterior to the inferior attachment of the anterior scalene muscle and the subclavian artery passes posterior to this attachment. The subclavian artery can serve as a marker to find the brachial plexus elements on imaging. Note that if an apical lung tumor invades superiorly, it often involves the subclavian artery before it involves the brachial plexus.*
![Slightly more anterior image demonstrates the proximal cervical roots/ventral primary ramus (VPR) combining to form the upper and middle trunks of the brachial plexus. Normal nerve is slightly isointense to muscle on T1 MR imaging. Note the close anatomic proximity of the brachial plexus elements to the subclavian artery.](images/app.statdx.com_image_thumbnail_0912f53a-7c9e-4582-8153-f068994ee5d0_annotated_false_size_900_quality_90_0e84d4ea907c3f917670018749b68507c627b23d.jpg)
*Slightly more anterior image demonstrates the proximal cervical roots/ventral primary ramus (VPR) combining to form the upper and middle trunks of the brachial plexus. Normal nerve is slightly isointense to muscle on T1 MR imaging. Note the close anatomic proximity of the brachial plexus elements to the subclavian artery.*
![Image shows the proximal cervical ventral rami &quot;roots&quot; combining to form the upper and middle trunks of the brachial plexus. Normal nerve is slightly hyperintense to muscle on STIR and FS T2 MR imaging.](images/app.statdx.com_image_thumbnail_5f0616d3-7284-4096-bd46-7b05d9aa162e_annotated_false_size_900_quality_90_cc177418ea9167a54cec8db7dfea60eac173b31c.jpg)
*Image shows the proximal cervical ventral rami &quot;roots&quot; combining to form the upper and middle trunks of the brachial plexus. Normal nerve is slightly hyperintense to muscle on STIR and FS T2 MR imaging.*
### Axial Anatomy: Proximal Cervical Nerves
![Graphic demonstrates ventral &amp; dorsal roots of C6 nerve merging in upper medial neural foramen (NF). Localized expansion of the dorsal nerve is the dorsal root ganglion (DRG). Note the intimate relationship of the DRG to the vertebral artery as it passes through NF. The extraforaminal nerve descends slightly toward the lateral neural sulcus that cradles the nerve before it extends into the scalene triangle. When the nerve is within lateral neural sulcus, it is separated from the vertebral artery within transverse foramen by thin bony bridge of the lateral process.](5a034949-38aa-46dc-bb08-517ab31f71f5)
*Graphic demonstrates ventral &amp; dorsal roots of C6 nerve merging in upper medial neural foramen (NF). Localized expansion of the dorsal nerve is the dorsal root ganglion (DRG). Note the intimate relationship of the DRG to the vertebral artery as it passes through NF. The extraforaminal nerve descends slightly toward the lateral neural sulcus that cradles the nerve before it extends into the scalene triangle. When the nerve is within lateral neural sulcus, it is separated from the vertebral artery within transverse foramen by thin bony bridge of the lateral process.*
![Axial CTA images descending through C5-6 disc space shows there is prominent enhancement of epidural &amp; perineural venous plexus that surround exiting nerves.](images/app.statdx.com_image_thumbnail_a34c1447-b281-4c5b-ba1f-ee768cad1c32_annotated_false_size_900_quality_90_2a60f6fe671e6b1c37c68e22e30a654125d9c0c7.jpg)
*Axial CTA images descending through C5-6 disc space shows there is prominent enhancement of epidural &amp; perineural venous plexus that surround exiting nerves.*
![Axial images continue to descend from disc space at C5-6 into C6 vertebrae. As the nerve begins to exit NF, it moves inferiorly &amp; laterally &amp; begins to separate from vertebral artery. The extraforaminal nerve will pass lateral to the transverse process within a shallow groove known as lateral neural sulcus, which is a reliable landmark for cervical nerves C3-6. In many patients, it is difficult to fully distinguish separate scalene muscles on imaging.](images/app.statdx.com_image_thumbnail_61cdc6a4-22c1-4de5-b4a3-e9bff64ea274_annotated_false_size_900_quality_90_95983154f9f841eecf939df17600d802ca07c0f0.jpg)
*Axial images continue to descend from disc space at C5-6 into C6 vertebrae. As the nerve begins to exit NF, it moves inferiorly &amp; laterally &amp; begins to separate from vertebral artery. The extraforaminal nerve will pass lateral to the transverse process within a shallow groove known as lateral neural sulcus, which is a reliable landmark for cervical nerves C3-6. In many patients, it is difficult to fully distinguish separate scalene muscles on imaging.*
### Coronal STIR MR
![Coronal T1 MR shows vertebral bodies (upper) &amp; anterior scalene muscles (lower). Anterior scalene muscles arise from transverse processes of the cervical vertebrae &amp; attach to the 1st rib laterally. Subclavian vein passes anteriorly to attachment of anterior scalene.](images/app.statdx.com_image_thumbnail_0ff63f38-60ba-43fe-bb88-7be37358bbb3_annotated_false_size_900_quality_90_67818a4e70b55a02c212d7f592a9f32facd8bea2.jpg)
*Coronal T1 MR shows vertebral bodies (upper) &amp; anterior scalene muscles (lower). Anterior scalene muscles arise from transverse processes of the cervical vertebrae &amp; attach to the 1st rib laterally. Subclavian vein passes anteriorly to attachment of anterior scalene.*
![Coronal T1 MR reveals the difficulty in distinguishing normal nerve tissue from adjacent muscle. Oblique bands of hypointense tissue traverse the ventral face of middle scalene muscle, but the nerves are difficult to separate from oblique tendinous attachments of the muscle itself. There is minimal interscalene fat to provide satisfactory contrast. Subclavian artery is a useful landmark for determining the best plane for proximal components of the brachial plexus, particularly the trunks. The trunks will pass above the subclavian artery as it passes over the 1st rib.](images/app.statdx.com_image_thumbnail_2fa1bda5-6de8-4420-a70e-e58a529435be_annotated_false_size_900_quality_90_4b413ea0e3955d79b12951c6bc49bd5d45cacc17.jpg)
*Coronal T1 MR reveals the difficulty in distinguishing normal nerve tissue from adjacent muscle. Oblique bands of hypointense tissue traverse the ventral face of middle scalene muscle, but the nerves are difficult to separate from oblique tendinous attachments of the muscle itself. There is minimal interscalene fat to provide satisfactory contrast. Subclavian artery is a useful landmark for determining the best plane for proximal components of the brachial plexus, particularly the trunks. The trunks will pass above the subclavian artery as it passes over the 1st rib.*
![Coronal STIR MR shows relative hyperintensity of normal nerves to muscle. Fat has been suppressed to enhance contrast resolution of nerves. Note DRGs are easily identified as focal enlargements of proximal nerves within NF. Given complex curvature of components, it is difficult to obtain a full view of the brachial plexus in a single slice.](images/app.statdx.com_image_thumbnail_d1f4f4d3-ebd2-4a76-8ad5-784ca9e89257_annotated_false_size_900_quality_90_012bcd280541bfaad13893101a6fa532cda6d41f.jpg)
*Coronal STIR MR shows relative hyperintensity of normal nerves to muscle. Fat has been suppressed to enhance contrast resolution of nerves. Note DRGs are easily identified as focal enlargements of proximal nerves within NF. Given complex curvature of components, it is difficult to obtain a full view of the brachial plexus in a single slice.*
### Axial STIR MR
![First of 4 axial STIR MR images presented from rostral to caudal shows the upper brachial plexus elements (C5-7 VPR) traveling between the anterior and middle scalene muscles in preparation to form the brachial plexus.](images/app.statdx.com_image_thumbnail_f13df97c-88d7-45a0-b4cb-f0958d4e4591_annotated_false_size_900_quality_90_ed7af0e2075292a85fc02610f707c1551a5984cd.jpg)
*First of 4 axial STIR MR images presented from rostral to caudal shows the upper brachial plexus elements (C5-7 VPR) traveling between the anterior and middle scalene muscles in preparation to form the brachial plexus.*
![Image at the C7/T1 level depicts the linear alignment of the C5 through C8 VPR. C5 and C6 are closely approximated and form the left upper trunk.](images/app.statdx.com_image_thumbnail_3051f034-fe6a-485c-8f10-6a095e2d92a1_annotated_false_size_900_quality_90_767d2d9fc19f0c1ff35c1c5de3ce02890e638424.jpg)
*Image at the C7/T1 level depicts the linear alignment of the C5 through C8 VPR. C5 and C6 are closely approximated and form the left upper trunk.*
![Imaging more caudal at C7/T1 level depicts the upper trunk on the left. Note that the brachial plexus elements exit the neck between the anterior and middle scalene muscles.](images/app.statdx.com_image_thumbnail_21b11483-4d5a-4887-ba18-e4ec93ca4209_annotated_false_size_900_quality_90_43f330285834d29c2dab437e34d1e048bc0cb6cf.jpg)
*Imaging more caudal at C7/T1 level depicts the upper trunk on the left. Note that the brachial plexus elements exit the neck between the anterior and middle scalene muscles.*
### Sagittal Oblique STIR MR
![First of 4 sagittal oblique STIR MR images presented from medial to lateral demonstrates the ventral primary rami of C5 through T1 proximal to the trunks. C8 exits above the 1st rib while T1 exits below. The brachial plexus is normally sandwiched between the anterior and middle scalene muscles.](images/app.statdx.com_image_thumbnail_39a56d11-9fb0-432c-8b5d-3d6bac842637_annotated_false_size_900_quality_90_1959187124424d9c45b2fe76ce577c3d377c3bd9.jpg)
*First of 4 sagittal oblique STIR MR images presented from medial to lateral demonstrates the ventral primary rami of C5 through T1 proximal to the trunks. C8 exits above the 1st rib while T1 exits below. The brachial plexus is normally sandwiched between the anterior and middle scalene muscles.*
![A slightly more lateral slice demonstrates the formation of the upper, middle, and lower trunks arranged in a vertical line between the scalene muscles. The C5 and C6 VPR can still be resolved as distinct elements within the upper trunk at this level.](images/app.statdx.com_image_thumbnail_6f0afa0a-d62f-41e7-803f-865e5dfe33ab_annotated_false_size_900_quality_90_1618a6f514503bcb713f729e31786f03c3cc2c5c.jpg)
*A slightly more lateral slice demonstrates the formation of the upper, middle, and lower trunks arranged in a vertical line between the scalene muscles. The C5 and C6 VPR can still be resolved as distinct elements within the upper trunk at this level.*
![Image at the division level shows mixing and matching of the trunks into anterior and posterior divisions. Note that the divisions are retroclavicular. The posterior divisions will form the posterior cord, and the anterior divisions will form the lateral and medial cords. It is generally not possible to follow individual branches of the divisions from trunk to cord.](images/app.statdx.com_image_thumbnail_b7dcfa6a-6519-4d68-92c8-ae2e2b948be5_annotated_false_size_900_quality_90_2459673780d615147cae8ec6f5f1fe1557cb5e07.jpg)
*Image at the division level shows mixing and matching of the trunks into anterior and posterior divisions. Note that the divisions are retroclavicular. The posterior divisions will form the posterior cord, and the anterior divisions will form the lateral and medial cords. It is generally not possible to follow individual branches of the divisions from trunk to cord.*
![Image demonstrates the formation of the 3 cords (lateral, medial, and posterior). The most important terminal branch of the lateral cord is the musculocutaneous nerve. The posterior cord forms the axillary and radial nerve terminal branches. The medial cord terminates as the ulnar nerve.](images/app.statdx.com_image_thumbnail_76e87cc0-4fa1-4079-98aa-e801b252d599_annotated_false_size_900_quality_90_9561f64be79ea15a9a39c43c7c139bef0b6a2cc6.jpg)
*Image demonstrates the formation of the 3 cords (lateral, medial, and posterior). The most important terminal branch of the lateral cord is the musculocutaneous nerve. The posterior cord forms the axillary and radial nerve terminal branches. The medial cord terminates as the ulnar nerve.*
### Anatomic-Pathologic Correlation
![Coronal FS T2 MR demonstrates mild relative hyperintensity in the brachial plexus diffusely in the right side of this patient with idiopathic plexitis.](images/app.statdx.com_image_thumbnail_424608e6-4a1e-42c1-bbaa-a238d8bf27b7_annotated_false_size_900_quality_90_ff98e285671ff8a662e06f2b4480d7f7ecd17823.jpg)
*Coronal FS T2 MR demonstrates mild relative hyperintensity in the brachial plexus diffusely in the right side of this patient with idiopathic plexitis.*
![Coronal STIR MR depicts massive enlargement of all proximal cervical nerves and supraclavicular components of the brachial plexus in this patient with neurofibromatosis type 1. In this case, essentially all the nerves have given rise to neurofibromas.](images/app.statdx.com_image_thumbnail_ce30fc1e-ae96-4876-8182-247eee344e32_annotated_false_size_900_quality_90_441a2df198ff0555e3e6f71dfb01d85a882879aa.jpg)
*Coronal STIR MR depicts massive enlargement of all proximal cervical nerves and supraclavicular components of the brachial plexus in this patient with neurofibromatosis type 1. In this case, essentially all the nerves have given rise to neurofibromas.*
![Axial T2 and FS contrast-enhanced T1 MR images through the C4-5 NF demonstrate a solitary enlarged, fusiform enhancing mass along the proximal C5 nerve on the patient's left. Notice the lesion's relationship to the left vertebral artery; the lesion pushes the vertebral artery anteriorly. Notice the DRG on the unaffected side enhances normally.](images/app.statdx.com_image_thumbnail_8a0f7b91-93a9-419a-ba48-ef82b9590036_annotated_false_size_900_quality_90_bac5039743fe7b6b347ba7be756abf6d9e4fbec1.jpg)
*Axial T2 and FS contrast-enhanced T1 MR images through the C4-5 NF demonstrate a solitary enlarged, fusiform enhancing mass along the proximal C5 nerve on the patient's left. Notice the lesion's relationship to the left vertebral artery; the lesion pushes the vertebral artery anteriorly. Notice the DRG on the unaffected side enhances normally.*
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---
title: "Cervicothoracic Junction Lesion"
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pageDescription: "Cervicothoracic Junction Lesion"
pageKeywords: "Head and Neck, Differential Diagnosis, Suprahyoid and Infrahyoid Neck, Anatomically Based Differentials, Cervicothoracic Junction Lesion"
pageTitle: "Cervicothoracic Junction Lesion | STATdx"
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---
## ESSENTIAL INFORMATION
- ### Helpful Clues for Common Diagnoses
- **Multinodular Goiter**
- Key facts: Common neck mass
- Imaging: Heterogeneous, multilobulated, 90% calcification
- Must image inferior extent
- **Diverticulum, Esophagopharyngeal (Zenker)**
- Key facts: Zenker diverticulum
- Herniation between fibers of inferior constrictor muscle at C5-C6
- Imaging: Heterogeneous mass posterior to & left of esophagus
- **Squamous Cell Carcinoma****, Nodes**
- Key facts: Supraclavicular nodes drain from upper neck nodes
- If no other nodes, think primary lung squamous cell carcinoma (SCCa)
- Imaging: Rounded supraclavicular mass
- May be necrotic
- **Differentiated Carcinoma, Thyroid**
- Key facts: 90% of thyroid malignancies
- Presents as mass or nodal disease
- Imaging: Well-defined, ill-defined, or invasive mass ± calcification
- **Differentiated Thyroid Carcinoma, Nodal**
- Key facts: Level IV & VI common sites for thyroid lymph node metastases
- Includes papillary (80%) & follicular (10%) carcinomas
- Papillary tends to have nodal metastases
- Follicular tends to have hematogenous metastases
- Imaging: Solid, cystic, ± calcified
- Calcified neck node, consider thyroid 1st
- MR signal variable, including bright T1
- **Metastases, Systemic, Nodal**
- Key facts: Supraclavicular = Virchow or "signal" node
- Left-sided adenopathy from chest, breast, & abdominal primaries
- Abdominal primaries, melanoma, esophagus, breast, lung
- Right-sided adenopathy from chest & breast primaries
- Imaging: Frequently large when present
- **Adenoma, Thyroid**
- Key facts: Common, often incidental
- Imaging: Circumscribed, usually < 4 cm
- Heterogeneous enhancement if degenerated
- **Non-Hodgkin Lymphoma, Lymph Nodes**
- Key facts: Supraclavicular nodes & levels IV, VB common sites
- Imaging: Multiple nodes, may be large, often homogeneous without necrosis
- **Hodgkin Lymphoma, Lymph Nodes**
- Key facts: Unilateral supraclavicular & level IV common
- Imaging: Homogeneous bulky nodes
- **Pancoast Tumor**
- Key facts: Lung SCCa or adenocarcinoma
- Frequently present with lower trunk (C8, T1) brachial plexopathy
- Imaging: Soft tissue mass invading lower neck from lung apex
- ### Helpful Clues for Less Common Diagnoses
- **Esophageal Carcinoma, Cervical**
- Key facts: Most often SCCa
- Imaging: Ill-defined, circumferential esophageal thickening
- Often extends into tracheoesophageal groove & may result in vocal cord paralysis
- **Anaplastic Carcinoma, Thyroid**
- Key facts: Undifferentiated carcinoma = rapidly growing, aggressive mass
- Typically in older adult women
- Imaging: Heterogeneous, necrotic thyroid mass invading adjacent structures
- **Non-Hodgkin Lymphoma, Thyroid**
- Key facts: Primary to thyroid gland
- Presents as rapidly growing mass
- Older adult woman with history of chronic lymphocytic thyroiditis
- Imaging: Large, homogeneous, noncalcified thyroid mass
- Compression more typical than invasion
- 80% solitary homogeneous thyroid mass; 20% multiple masses or diffuse infiltration
- Nodes typically multiple, solid, hypodense
- **Adenoma, Parathyroid, Visceral Space**
- Key facts: Presents with hypercalcemia
- Imaging: Ultrasound & nuclear medicine usual 1st-line imaging modality for localization
- 20% ectopic glands, especially inferior pair
- Increasing use of multiphase CT as 2nd-line imaging modality
- Multiphase CT with at least arterial- & delayed (venous)-phase optimize detection
- Noncontrast shows hypodense mass compared to normally dense thyroid and is helpful for adenomas contacting thyroid
- Most adenomas show marked enhancement on arterial-phase imaging
- Washout of enhancement on venous-phase imaging
- Allows differentiation from lymph nodes
- **Medullary Carcinoma, Thyroid**
- Key facts: Thyroid neuroendocrine carcinoma
- Most are sporadic; 15-25% are inherited
- Imaging: CT low-density mass ± fine calcification
- Intravenous iodine not contraindicated
- **Colloid Cyst, Thyroid**
- Key facts: Palpable mass or incidental imaging finding
- Imaging: Cystic, well-circumscribed mass
- Variable CT density & MR intensity
- **Thyroiditis, Chronic Lymphocytic**
- Key facts: Also called Hashimoto thyroiditis
- Imaging
- CT: Diffusely enlarged, low-density gland without calcification
- US useful for surveillance
- Early: Enlarged lobulated thyroid ↓ echogenicity, ↑ vascularity
- Late: Small, echogenic, fibrosed gland; no flow
- **Schwannoma, Brachial Plexus,****Perivertebral Space**
- Key facts: Painless low lateral neck mass
- Imaging: Well-circumscribed, fusiform mass between anterior & middle scalene muscles
- Intratumoral cysts more common in larger masses
- **Metastasis, Vertebral Body,****Perivertebral Space**
- Key facts: May present with pain, cord compression
- Imaging: Destructive solid vertebral mass
- Look for epidural soft tissue extension
- **Air Cyst, Paratracheal**
- Key facts: Asymptomatic outpouching of trachea
- Relatively common in adults (3-8%); right > left sided
- Uncommon in children (prevalence ~ 1%)
- Imaging: Posterior & right of trachea
- Look for tracheal communication
- ### Helpful Clues for Rare Diagnoses
- **Aneurysm, Subclavian Artery**
- Key facts: Pulsatile low neck mass
- Imaging: CTA arterial-enhancing outpouching
- MR complex signal from flow
- **Thymic Remnant, Adult**
- Key facts: Residual thymic tissue
- Imaging: Solid masses in superior mediastinum
- CT soft tissue density (slightly less than muscle), but with progressive fatty replacement & lower attenuation with increasing age
- May be visible on CT into 7th decade
- **Thymic Cyst**
- Key facts: Congenital remnant, most commonly in **left** neck
- Imaging: Uni- or multilocular lateral mass
- Unilocular thymic cysts lack irregular wall thickening, nodularity, or septations
- Normal temporal changes include mural calcification, changes in size, CT density, &/or MR signal over time
- **Parathyroid Cyst, Visceral Space**
- Key facts: Rare cause of hyperparathyroidism
- < 1% of all parathyroid lesions
- Functional (20%) or nonfunctional (80%)
- Functional cysts may develop within parathyroid adenoma, hyperplasia, or carcinoma
- Imaging: Homogeneous, unilocular
- Located posterior to thyroid; rarely ectopic
- **Parathyroid Carcinoma, Visceral Space**
- Key facts: Present with bone pain & ↑↑ serum calcium, parathyroid hormone
- Imaging: Larger, less enhancing, & more invasive mass than parathyroid adenomas or cysts
- **Diverticulum, Lateral Cervical Esophageal**
- Key facts: Less common than thoracic lesions
- Imaging: Lateral outpouching of esophageal wall
- ### Alternative Differential Approaches
- Extensive DDx list for lesions at cervicothoracic junction
- Consider lesions by anatomic sites of origin
- Arising from lower neck: Thyroid, lymph nodes, parathyroid, esophagus, trachea, brachial plexus
- Arising from chest: Lung apices, great vessels, thymus
## References
## Selected References
1. [Taka M et al: Diagnostic approach for mediastinal masses with radiopathological correlation. Eur J Radiol. ePub, 2023](http://www.ncbi.nlm.nih.gov/pubmed/?term=36921376%5Bpmid%5D)
1. [Szaro P et al: Magnetic resonance imaging of the brachial plexus. Part 1: anatomical considerations, magnetic resonance techniques, and non-traumatic lesions. Eur J Radiol Open. 9:100392, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=34988263%5Bpmid%5D)
1. [Zarei A et al: Multimodality imaging in primary hyperparathyroidism. Clin Radiol. 77(6):e401-16, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=35393101%5Bpmid%5D)
1. [Ackman JB et al: Longitudinal CT and MRI characteristics of unilocular thymic cysts. Radiology. 301(2):443-54, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=34427460%5Bpmid%5D)
1. [Garrana SH et al: Imaging of the anterior/prevascular mediastinum. Radiol Clin North Am. 59(2):155-68, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=33551078%5Bpmid%5D)
1. [Heeger AP et al: Added value of magnetic resonance imaging for the evaluation of mediastinal lesions. Radiol Clin North Am. 59(2):251-77, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=33551086%5Bpmid%5D)
1. [Lichtenberger JP 3rd et al: Thymic epithelial neoplasms: radiologic-pathologic correlation. Radiol Clin North Am. 59(2):169-82, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=33551079%5Bpmid%5D)
1. [Patnaik S et al: Rare mediastinal masses - imaging review. J Cancer Res Ther. 17(1):13-21, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=33723126%5Bpmid%5D)
1. [Varma V et al: Thymic masses and mimics in adults: review of common and uncommon pathologies. Clin Imaging. 77:98-110, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=33662714%5Bpmid%5D)
1. [Azour L et al: Radiologic and pathologic correlation of anterior mediastinal lesions. Mediastinum. 4:5, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=35118273%5Bpmid%5D)
1. [Itani M et al: Parathyroid imaging. Radiol Clin North Am. 58(6):1071-83, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=33040849%5Bpmid%5D)
1. [Li B et al: Does [18F] fluorodeoxyglucose-positron emission tomography/computed tomography have a role in cervical nodal staging for esophageal squamous cell carcinoma? J Thorac Cardiovasc Surg. 160(2):544-50, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=31932053%5Bpmid%5D)
1. [Sims JR et al: A rare invasion route for differentiated thyroid carcinoma: the tracheoesophageal common party wall. Laryngoscope. 129(12):E455-9, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=30860597%5Bpmid%5D)
1. [Drabkin MJ et al: Age-stratified patterns of thymic involution on multidetector CT. J Thorac Imaging. 33(6):409-16, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=30067569%5Bpmid%5D)
1. [Fustar Preradovic L et al: Small nonfunctional parathyroid cysts: single institution experience. Endocr J. 64(2):151-6, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=27760899%5Bpmid%5D)
1. [Lee MK et al: Paratracheal air cysts are uncommon findings in the pediatric population. Jpn J Radiol. 34(8):579-84, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27314683%5Bpmid%5D)
1. [Kim JS et al: Paratracheal air cysts using low-dose screening chest computed tomography: clinical significance and imaging findings. Jpn J Radiol. 29(9):644-8, 2011](http://www.ncbi.nlm.nih.gov/pubmed/?term=21956370%5Bpmid%5D)
1. [Parker EE et al: MR imaging of the thoracic inlet. Magn Reson Imaging Clin N Am. 16(2):341-53, x, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18474336%5Bpmid%5D)
1. [Núñez DB Jr et al: Vascular injuries of the neck and thoracic inlet: helical CT-angiographic correlation. Radiographics. 24(4):1087-98; discussion 1099-100, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=15256630%5Bpmid%5D)
1. [Obuchowski AM et al: MR imaging of the thoracic inlet. Magn Reson Imaging Clin N Am. 8(1):183-203, ix-x, 2000](http://www.ncbi.nlm.nih.gov/pubmed/?term=10730242%5Bpmid%5D)
1. [Dalley RW: Lesions and nodes of the thoracic inlet. Semin Ultrasound CT MR. 17(6):576-604, 1996](http://www.ncbi.nlm.nih.gov/pubmed/?term=9023869%5Bpmid%5D)
1. [Reede DL: The thoracic inlet: normal anatomy. Semin Ultrasound CT MR. 17(6):509-18, 1996](http://www.ncbi.nlm.nih.gov/pubmed/?term=9023865%5Bpmid%5D)
## Images
### Selected Images
![Axial CECT demonstrates a heterogeneously enhancing thyroid goiter <img src='img/arrows/WS.png' alt='white solid arrow'/>. No calcifications are seen. There is inferior extension into the superior mediastinum. Note that the thyroid has sharp contours and displaces the trachea <img src='img/arrows/WC.png' alt='white curved arrow'/> to the right.](images/app.statdx.com_image_thumbnail_b9874941-2c8c-4598-b2cf-90b55f074921_annotated_true_size_900_quality_90_2f56c69c588f47b42ba9082f88c8b0c3327a7865.jpg)
**Multinodular Goiter**
*Axial CECT demonstrates a heterogeneously enhancing thyroid goiter <img src='img/arrows/WS.png' alt='white solid arrow'/>. No calcifications are seen. There is inferior extension into the superior mediastinum. Note that the thyroid has sharp contours and displaces the trachea <img src='img/arrows/WC.png' alt='white curved arrow'/> to the right.*
![Axial CECT demonstrates a heterogeneously enhancing thyroid goiter <img src='img/arrows/WS.png' alt='white solid arrow'/>. No calcifications are seen. There is inferior extension into the superior mediastinum. Note that the thyroid has sharp contours and displaces the trachea <img src='img/arrows/WC.png' alt='white curved arrow'/> to the right.](images/app.statdx.com_image_thumbnail_b9874941-2c8c-4598-b2cf-90b55f074921_size_174_quality_85_0b90876e0304fb312a5cca37f364f591180b8e95.jpg)
**Multinodular Goiter**
*Axial CECT demonstrates a heterogeneously enhancing thyroid goiter <img src='img/arrows/WS.png' alt='white solid arrow'/>. No calcifications are seen. There is inferior extension into the superior mediastinum. Note that the thyroid has sharp contours and displaces the trachea <img src='img/arrows/WC.png' alt='white curved arrow'/> to the right.*
![Axial CECT shows an enlarged thyroid gland with multiple heterogeneous nodules <img src='img/arrows/WS.png' alt='white solid arrow'/>. There are no invasive features, and normal tissue planes are preserved in this benign goiter.](images/app.statdx.com_image_thumbnail_f362cb1e-ec81-4bc6-92f9-0ae153e6d6e7_annotated_true_size_900_quality_90_b10f4665bfb8908fd4b572593a51a83bbc98d4c5.jpg)
**Multinodular Goiter**
*Axial CECT shows an enlarged thyroid gland with multiple heterogeneous nodules <img src='img/arrows/WS.png' alt='white solid arrow'/>. There are no invasive features, and normal tissue planes are preserved in this benign goiter.*
![Axial CECT through the lower neck shows midline air-fluid level <img src='img/arrows/WS.png' alt='white solid arrow'/> immediately posterior to the lowest aspect of the hypopharynx <img src='img/arrows/WC.png' alt='white curved arrow'/> and anterior to vertebral bodies. This is the cranial aspect of the diverticulum, not to be mistaken for abscess.](images/app.statdx.com_image_thumbnail_c04254a7-fc5d-40a8-8c1c-2d3188447fc4_annotated_true_size_900_quality_90_ccfdbb1e5c216a7a8f092065f30382651d37a143.jpg)
**Diverticulum, Esophagopharyngeal (Zenker)**
*Axial CECT through the lower neck shows midline air-fluid level <img src='img/arrows/WS.png' alt='white solid arrow'/> immediately posterior to the lowest aspect of the hypopharynx <img src='img/arrows/WC.png' alt='white curved arrow'/> and anterior to vertebral bodies. This is the cranial aspect of the diverticulum, not to be mistaken for abscess.*
![Axial T1 C+ MR through the lower neck in a patient with prior left neck dissection for squamous cell carcinoma (SCCa) of unknown primary shows 2 palpable, heterogeneous recurrent SCCa nodes <img src='img/arrows/WS.png' alt='white solid arrow'/> compressing the right jugular vein <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_26660734-18f1-4ccd-8c92-f2a1edf6505a_annotated_true_size_900_quality_90_aaad6943ea63dc99d12735e44ece17b33833cc05.jpg)
**Squamous Cell Carcinoma, Nodes**
*Axial T1 C+ MR through the lower neck in a patient with prior left neck dissection for squamous cell carcinoma (SCCa) of unknown primary shows 2 palpable, heterogeneous recurrent SCCa nodes <img src='img/arrows/WS.png' alt='white solid arrow'/> compressing the right jugular vein <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Axial CECT shows an enlarged heterogeneous right neck node <img src='img/arrows/WS.png' alt='white solid arrow'/> abutting the internal jugular vein. A primary tumor was found in the right thyroid lobe <img src='img/arrows/WC.png' alt='white curved arrow'/>, which is heterogeneous and enlarged with several small, ill-defined areas of calcification.](images/app.statdx.com_image_thumbnail_0456b581-a437-4453-80d8-61123563cbfa_annotated_true_size_900_quality_90_d6ec16e02cfcf5a34dc3b5a5342a98e24ad32d48.jpg)
**Differentiated Carcinoma, Thyroid**
*Axial CECT shows an enlarged heterogeneous right neck node <img src='img/arrows/WS.png' alt='white solid arrow'/> abutting the internal jugular vein. A primary tumor was found in the right thyroid lobe <img src='img/arrows/WC.png' alt='white curved arrow'/>, which is heterogeneous and enlarged with several small, ill-defined areas of calcification.*
![Axial T2 FS MR demonstrates heterogeneous and cystic, enlarged lymph nodes <img src='img/arrows/WS.png' alt='white solid arrow'/> from metastatic thyroid carcinoma in the low neck. Note the heterogeneous appearance to the thyroid gland, which contains multiple nodules <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_44e9ff7a-db0f-4bee-b4f4-8d3d0d645513_annotated_true_size_900_quality_90_9f127fdc6549f158d428d1eb9ce81337d682d5f2.jpg)
**Differentiated Thyroid Carcinoma, Nodal**
*Axial T2 FS MR demonstrates heterogeneous and cystic, enlarged lymph nodes <img src='img/arrows/WS.png' alt='white solid arrow'/> from metastatic thyroid carcinoma in the low neck. Note the heterogeneous appearance to the thyroid gland, which contains multiple nodules <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Axial CECT through the lower neck shows a large, heterogeneous supraclavicular mass <img src='img/arrows/WS.png' alt='white solid arrow'/> displacing and deforming the patent left internal jugular vein <img src='img/arrows/WC.png' alt='white curved arrow'/>. This is a metastatic malignant testicular germ cell tumor.](images/app.statdx.com_image_thumbnail_67685c0e-161c-4790-bd1b-c63f7aa61237_annotated_true_size_900_quality_90_33f8b821f93eb29bc400f2af75b8b558a634acaf.jpg)
**Metastases, Systemic, Nodal**
*Axial CECT through the lower neck shows a large, heterogeneous supraclavicular mass <img src='img/arrows/WS.png' alt='white solid arrow'/> displacing and deforming the patent left internal jugular vein <img src='img/arrows/WC.png' alt='white curved arrow'/>. This is a metastatic malignant testicular germ cell tumor.*
![Axial CECT shows a heterogeneous, centrally low-density mass <img src='img/arrows/WS.png' alt='white solid arrow'/> arising from the left thyroid lobe and extending into the superior mediastinum. This degenerated adenoma appears necrotic but is well demarcated from adjacent tissues.](images/app.statdx.com_image_thumbnail_1c9c88be-e85a-46de-a504-a0df7702432d_annotated_true_size_900_quality_90_77d1201147fc80e0ffb3a85fb0d7c22f731c99f6.jpg)
**Adenoma, Thyroid**
*Axial CECT shows a heterogeneous, centrally low-density mass <img src='img/arrows/WS.png' alt='white solid arrow'/> arising from the left thyroid lobe and extending into the superior mediastinum. This degenerated adenoma appears necrotic but is well demarcated from adjacent tissues.*
![Axial T1 MR shows conglomerate lymph node masses in the left supraclavicular fossa <img src='img/arrows/WO.png' alt='white open arrow'/> and multiple additional lower right neck lymph nodes <img src='img/arrows/WS.png' alt='white solid arrow'/>. Non-Hodgkin lymphoma may present as homogeneous solitary &amp;/or conglomerate nodal masses.](images/app.statdx.com_image_thumbnail_941d5622-eee5-4f3c-bf90-be2ebf1d69ee_annotated_true_size_900_quality_90_6eeebf8bdd1cf647e8934624bca815161fc98845.jpg)
**Non-Hodgkin Lymphoma, Lymph Nodes**
*Axial T1 MR shows conglomerate lymph node masses in the left supraclavicular fossa <img src='img/arrows/WO.png' alt='white open arrow'/> and multiple additional lower right neck lymph nodes <img src='img/arrows/WS.png' alt='white solid arrow'/>. Non-Hodgkin lymphoma may present as homogeneous solitary &amp;/or conglomerate nodal masses.*
![Axial CECT in a patient with Hodgkin lymphoma shows unilateral, bulky, homogeneous nodes <img src='img/arrows/WS.png' alt='white solid arrow'/> in the supraclavicular fossa and lower jugular chain. There was no right-sided adenopathy.](images/app.statdx.com_image_thumbnail_d72582d8-171d-4621-ac30-e03f353d097b_annotated_true_size_900_quality_90_9ad90606b06adbe91561578319bef71204da3b54.jpg)
**Hodgkin Lymphoma, Lymph Nodes**
*Axial CECT in a patient with Hodgkin lymphoma shows unilateral, bulky, homogeneous nodes <img src='img/arrows/WS.png' alt='white solid arrow'/> in the supraclavicular fossa and lower jugular chain. There was no right-sided adenopathy.*
![Axial CECT through the cervicothoracic junction reveals an apical lung mass <img src='img/arrows/WO.png' alt='white open arrow'/> destroying the 1st and 2nd ribs and infiltrating the soft tissues posterior to the right subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/> where the brachial plexus is located.](images/app.statdx.com_image_thumbnail_26f24026-9b9e-47ca-aa7c-a62783882dc4_annotated_true_size_900_quality_90_f48d615a9f76bfcbcdfebbeec48b2ac96dbb962a.jpg)
**Pancoast Tumor**
*Axial CECT through the cervicothoracic junction reveals an apical lung mass <img src='img/arrows/WO.png' alt='white open arrow'/> destroying the 1st and 2nd ribs and infiltrating the soft tissues posterior to the right subclavian artery <img src='img/arrows/WC.png' alt='white curved arrow'/> where the brachial plexus is located.*
![Axial CECT at the thoracic inlet in a patient with right vocal cord paralysis reveals an eccentric necrotic esophageal carcinoma <img src='img/arrows/BO.png' alt='black open arrow'/>. Marked dilatation of the cervical esophagus was noted above this level (not shown). A small level VI node <img src='img/arrows/BC.png' alt='black curved arrow'/> is also noted.](images/app.statdx.com_image_thumbnail_0ca344e5-4e96-4c15-8dbf-f6cb84dd325c_annotated_true_size_900_quality_90_5048f3c653d66fdedc1b2681c5d6f8d5a24d7236.jpg)
**Esophageal Carcinoma, Cervical**
*Axial CECT at the thoracic inlet in a patient with right vocal cord paralysis reveals an eccentric necrotic esophageal carcinoma <img src='img/arrows/BO.png' alt='black open arrow'/>. Marked dilatation of the cervical esophagus was noted above this level (not shown). A small level VI node <img src='img/arrows/BC.png' alt='black curved arrow'/> is also noted.*
![Axial CECT through the lower neck shows a heterogeneous mass arising from the right thyroid lobe, infiltrating soft tissues of the neck and encircling the right common carotid artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. The mass cannot be separated from the esophagus <img src='img/arrows/WS.png' alt='white solid arrow'/> or trachea <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_92f48695-c819-4d62-b576-2f1f3b93e6b7_annotated_true_size_900_quality_90_8141e37860dbdf4601824a155a9b8b800f7d6f89.jpg)
**Anaplastic Carcinoma, Thyroid**
*Axial CECT through the lower neck shows a heterogeneous mass arising from the right thyroid lobe, infiltrating soft tissues of the neck and encircling the right common carotid artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. The mass cannot be separated from the esophagus <img src='img/arrows/WS.png' alt='white solid arrow'/> or trachea <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Axial CECT reveals a mass <img src='img/arrows/WS.png' alt='white solid arrow'/> infiltrating the lower neck symmetrically and enveloping adjacent tissues. There is compression of the trachea <img src='img/arrows/WC.png' alt='white curved arrow'/> and bilateral carotid sheath involvement with encasement and displacement of vessels.](images/app.statdx.com_image_thumbnail_218f8bd7-37b1-426b-851f-ad55d39b3c3c_annotated_true_size_900_quality_90_bb45a129cc7b8f80bf858b28bea93882ca13b1a8.jpg)
**Non-Hodgkin Lymphoma, Thyroid**
*Axial CECT reveals a mass <img src='img/arrows/WS.png' alt='white solid arrow'/> infiltrating the lower neck symmetrically and enveloping adjacent tissues. There is compression of the trachea <img src='img/arrows/WC.png' alt='white curved arrow'/> and bilateral carotid sheath involvement with encasement and displacement of vessels.*
![Axial arterial-phase CECT demonstrates a heterogeneously enhancing ectopic parathyroid nodule <img src='img/arrows/WS.png' alt='white solid arrow'/> in the right tracheoesophageal groove. Cystic change, as seen here, is an uncommon feature that may be seen in parathyroid adenomas.](images/app.statdx.com_image_thumbnail_6fc81b66-8372-4ffb-b729-65d249b8b7d4_annotated_true_size_900_quality_90_997ec2e739f03882df86beff1dc91d38ec966fa4.jpg)
**Adenoma, Parathyroid, Visceral Space**
*Axial arterial-phase CECT demonstrates a heterogeneously enhancing ectopic parathyroid nodule <img src='img/arrows/WS.png' alt='white solid arrow'/> in the right tracheoesophageal groove. Cystic change, as seen here, is an uncommon feature that may be seen in parathyroid adenomas.*
![Axial CECT through the lower neck reveals a heterogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> arising from the left thyroid. While not clearly infiltrating the adjacent tissues, the presence of ipsilateral heterogeneous adenopathy <img src='img/arrows/WC.png' alt='white curved arrow'/> suggests malignancy.](images/app.statdx.com_image_thumbnail_69cde72c-b0ce-4878-b610-3696676a8938_annotated_true_size_900_quality_90_039f5514bbe21df500e6fe9e527006a748797f2d.jpg)
**Medullary Carcinoma, Thyroid**
*Axial CECT through the lower neck reveals a heterogeneous mass <img src='img/arrows/WS.png' alt='white solid arrow'/> arising from the left thyroid. While not clearly infiltrating the adjacent tissues, the presence of ipsilateral heterogeneous adenopathy <img src='img/arrows/WC.png' alt='white curved arrow'/> suggests malignancy.*
![Axial CECT through the neck shows a well-defined round mass displacing and distorting the larynx. Higher density in the dependent portion <img src='img/arrows/WC.png' alt='white curved arrow'/> suggests recent hemorrhage. No aggressive features or neck adenopathy is seen.](images/app.statdx.com_image_thumbnail_b76f6e81-b263-440e-b920-34d0a64956b8_annotated_true_size_900_quality_90_e60ab0582f851bd69365ed788732a443b38bc7e2.jpg)
**Colloid Cyst, Thyroid**
*Axial CECT through the neck shows a well-defined round mass displacing and distorting the larynx. Higher density in the dependent portion <img src='img/arrows/WC.png' alt='white curved arrow'/> suggests recent hemorrhage. No aggressive features or neck adenopathy is seen.*
![Axial CECT shows diffuse enlargement of both thyroid lobes <img src='img/arrows/WC.png' alt='white curved arrow'/> and the pyramidal <img src='img/arrows/WS.png' alt='white solid arrow'/> lobe. The thyroid gland is diffusely decreased in density and has an almost infiltrated appearance. There are no calcifications or associated neck adenopathy.](images/app.statdx.com_image_thumbnail_6be26d82-0ffb-4ede-8156-bd0cdc21a8c8_annotated_true_size_900_quality_90_e5484bf36a4b5f3e7fe99e65ed99c6eb1bd71562.jpg)
**Thyroiditis, Chronic Lymphocytic**
*Axial CECT shows diffuse enlargement of both thyroid lobes <img src='img/arrows/WC.png' alt='white curved arrow'/> and the pyramidal <img src='img/arrows/WS.png' alt='white solid arrow'/> lobe. The thyroid gland is diffusely decreased in density and has an almost infiltrated appearance. There are no calcifications or associated neck adenopathy.*
![Axial T2 MR through the lower neck demonstrates a well-defined, hyperintense and heterogeneous round mass adjacent to the anterior <img src='img/arrows/WS.png' alt='white solid arrow'/> and middle/posterior <img src='img/arrows/WO.png' alt='white open arrow'/> scalene muscles.](images/app.statdx.com_image_thumbnail_d4d26104-74ee-45d8-b962-8d8d9efecf6e_annotated_true_size_900_quality_90_58f981da8e11fea9529cf5c785da57dc26a28049.jpg)
**Schwannoma, Brachial Plexus, Perivertebral Space**
*Axial T2 MR through the lower neck demonstrates a well-defined, hyperintense and heterogeneous round mass adjacent to the anterior <img src='img/arrows/WS.png' alt='white solid arrow'/> and middle/posterior <img src='img/arrows/WO.png' alt='white open arrow'/> scalene muscles.*
![Axial T1 C+ MR reveals a destructive mass centered on the 1st thoracic vertebral body with extensive paravertebral <img src='img/arrows/WC.png' alt='white curved arrow'/> and epidural <img src='img/arrows/WO.png' alt='white open arrow'/> tumor as well as involvement of the adjacent rib <img src='img/arrows/WS.png' alt='white solid arrow'/>. This was the initial presentation of renal cell carcinoma.](images/app.statdx.com_image_thumbnail_0713b36b-a319-41b4-b921-9bce29b90302_annotated_true_size_900_quality_90_b7c28a35ec45486f4b603abf4f369d1a47e88c42.jpg)
**Metastasis, Vertebral Body, Perivertebral Space**
*Axial T1 C+ MR reveals a destructive mass centered on the 1st thoracic vertebral body with extensive paravertebral <img src='img/arrows/WC.png' alt='white curved arrow'/> and epidural <img src='img/arrows/WO.png' alt='white open arrow'/> tumor as well as involvement of the adjacent rib <img src='img/arrows/WS.png' alt='white solid arrow'/>. This was the initial presentation of renal cell carcinoma.*
![Coronal NECT through the neck was performed following trauma and revealed an incidental small, air-filled lesion <img src='img/arrows/WO.png' alt='white open arrow'/> to the right of the cervical trachea <img src='img/arrows/WC.png' alt='white curved arrow'/> with a small tract <img src='img/arrows/WS.png' alt='white solid arrow'/> connecting the 2 structures.](images/app.statdx.com_image_thumbnail_261e0898-0181-40ef-b9ed-7a2ef19d22a8_annotated_true_size_900_quality_90_26ac94b3aab586e29828a6f2fa9a17aa66f37419.jpg)
**Air Cyst, Paratracheal**
*Coronal NECT through the neck was performed following trauma and revealed an incidental small, air-filled lesion <img src='img/arrows/WO.png' alt='white open arrow'/> to the right of the cervical trachea <img src='img/arrows/WC.png' alt='white curved arrow'/> with a small tract <img src='img/arrows/WS.png' alt='white solid arrow'/> connecting the 2 structures.*
![Axial CECT shows arterial enhancement of the central aspect of a left lower neck mass <img src='img/arrows/WC.png' alt='white curved arrow'/> arising from the subclavian artery <img src='img/arrows/WS.png' alt='white solid arrow'/> distal to origin of left vertebral artery <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_29234cc5-baec-45a4-bece-b064141b1251_annotated_true_size_900_quality_90_b28d65cba90daa30285d1abc1dca582a0980be10.jpg)
**Aneurysm, Subclavian Artery**
*Axial CECT shows arterial enhancement of the central aspect of a left lower neck mass <img src='img/arrows/WC.png' alt='white curved arrow'/> arising from the subclavian artery <img src='img/arrows/WS.png' alt='white solid arrow'/> distal to origin of left vertebral artery <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Axial CECT demonstrates 2 well-circumscribed lower neck masses <img src='img/arrows/WS.png' alt='white solid arrow'/> immediately posterior to the strap muscles and anterior to the common carotid arteries <img src='img/arrows/WC.png' alt='white curved arrow'/>. Both are slightly less dense than muscle. Both conform to adjacent tissues.](images/app.statdx.com_image_thumbnail_7c7a3a00-7b00-4732-9333-d407ccc4a446_annotated_true_size_900_quality_90_67e8b5b69f25a445a01be98ca3442e98cab72b3c.jpg)
**Thymic Remnant, Adult**
*Axial CECT demonstrates 2 well-circumscribed lower neck masses <img src='img/arrows/WS.png' alt='white solid arrow'/> immediately posterior to the strap muscles and anterior to the common carotid arteries <img src='img/arrows/WC.png' alt='white curved arrow'/>. Both are slightly less dense than muscle. Both conform to adjacent tissues.*
![Axial CECT in a toddler shows a large, low-density, nonenhancing mass <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower neck, displacing the left carotid artery <img src='img/arrows/WC.png' alt='white curved arrow'/> laterally and the visceral space structures to the right of midline. The cyst is most intimately related to the left thyroid lobe <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_62537f76-c358-4390-b0e4-5ad3c12ad6bb_annotated_true_size_900_quality_90_cb881e3ce3c01b2a8f2b1b460d01794995306497.jpg)
**Thymic Cyst**
*Axial CECT in a toddler shows a large, low-density, nonenhancing mass <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower neck, displacing the left carotid artery <img src='img/arrows/WC.png' alt='white curved arrow'/> laterally and the visceral space structures to the right of midline. The cyst is most intimately related to the left thyroid lobe <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Axial CECT reveals a well-defined small , cystic lesion <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower right neck immediately posterior to the internal carotid artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. This incidentally found parathyroid cyst was discovered during imaging for trauma.](images/app.statdx.com_image_thumbnail_4d38db57-0742-4a7f-a0cc-3dca0962f143_annotated_true_size_900_quality_90_fb1dade1fb2ad77658a8ef9b15de5b04cb1e5b30.jpg)
**Parathyroid Cyst, Visceral Space**
*Axial CECT reveals a well-defined small , cystic lesion <img src='img/arrows/WS.png' alt='white solid arrow'/> in the lower right neck immediately posterior to the internal carotid artery <img src='img/arrows/WC.png' alt='white curved arrow'/>. This incidentally found parathyroid cyst was discovered during imaging for trauma.*
![Axial CECT through the lower neck demonstrates an air-filled structure <img src='img/arrows/WS.png' alt='white solid arrow'/> immediately lateral to the cervical esophagus in the left tracheoesophageal groove. The medial aspect of the lesion &quot;points&quot; toward the esophagus rather than the trachea.](images/app.statdx.com_image_thumbnail_837f35ca-9f7f-4517-89c8-5a6c1183e1d4_annotated_true_size_900_quality_90_15d5a98308b19ac73ebd5ecb95477f79ad126404.jpg)
**Diverticulum, Lateral Cervical Esophageal**
*Axial CECT through the lower neck demonstrates an air-filled structure <img src='img/arrows/WS.png' alt='white solid arrow'/> immediately lateral to the cervical esophagus in the left tracheoesophageal groove. The medial aspect of the lesion &quot;points&quot; toward the esophagus rather than the trachea.*
### Additional Images
![Axial CECT shows a poorly enhancing mass invading the left tracheoesophageal groove <img src='img/arrows/WS.png' alt='white solid arrow'/>. The lack of a fat plane between the mass and the esophagus is concerning for malignancy. A primary esophageal malignancy could appear similar, but a history of hypercalcemia supports the correct diagnosis.](images/app.statdx.com_image_thumbnail_7fa32eaa-6851-4413-829d-5f03db9a645b_annotated_true_size_900_quality_90_9043c452e3bec7e7d060c5e3615912d5e7cd22a0.jpg)
**Parathyroid Carcinoma, Visceral Space**
*Axial CECT shows a poorly enhancing mass invading the left tracheoesophageal groove <img src='img/arrows/WS.png' alt='white solid arrow'/>. The lack of a fat plane between the mass and the esophagus is concerning for malignancy. A primary esophageal malignancy could appear similar, but a history of hypercalcemia supports the correct diagnosis.*
![Sagittal T1 MR shows a large lower neck mass <img src='img/arrows/WS.png' alt='white solid arrow'/> distorting and compressing the trachea <img src='img/arrows/WO.png' alt='white open arrow'/> and extending into the superior mediastinum. Focal T1 shortening <img src='img/arrows/WC.png' alt='white curved arrow'/> may be due to calcification, hemorrhage, or colloid.](images/app.statdx.com_image_thumbnail_02e36a29-0dd6-4a43-ae00-76a030e35531_annotated_true_size_900_quality_90_529842460549f2bf0a785eb2059c091edfe05342.jpg)
**Multinodular Goiter**
*Sagittal T1 MR shows a large lower neck mass <img src='img/arrows/WS.png' alt='white solid arrow'/> distorting and compressing the trachea <img src='img/arrows/WO.png' alt='white open arrow'/> and extending into the superior mediastinum. Focal T1 shortening <img src='img/arrows/WC.png' alt='white curved arrow'/> may be due to calcification, hemorrhage, or colloid.*
![Axial CECT through the cervicothoracic junction demonstrates asymmetrically enlarged, heterogeneous thyroid lobes <img src='img/arrows/WS.png' alt='white solid arrow'/> that displace and distort the trachea as they extend into the superior mediastinum.](images/app.statdx.com_image_thumbnail_016d0213-e1a6-42ab-a406-bf023d831eef_annotated_true_size_900_quality_90_eef45fa8619233ff0e8a0bd8f592c398d03b1809.jpg)
**Multinodular Goiter**
*Axial CECT through the cervicothoracic junction demonstrates asymmetrically enlarged, heterogeneous thyroid lobes <img src='img/arrows/WS.png' alt='white solid arrow'/> that displace and distort the trachea as they extend into the superior mediastinum.*
![Axial T2 MR through the lower neck shows a large midline mass <img src='img/arrows/WC.png' alt='white curved arrow'/> anterior to the thoracic vertebra containing an air-fluid level. The esophagus <img src='img/arrows/WS.png' alt='white solid arrow'/> is just visible between the mass and more anterior trachea.](images/app.statdx.com_image_thumbnail_f10baa53-ab18-484a-9aa1-9748516fda60_annotated_true_size_900_quality_90_8e7f22ba4be39b65ff831eb160c91becacdb56a2.jpg)
**Diverticulum, Esophagopharyngeal (Zenker)**
*Axial T2 MR through the lower neck shows a large midline mass <img src='img/arrows/WC.png' alt='white curved arrow'/> anterior to the thoracic vertebra containing an air-fluid level. The esophagus <img src='img/arrows/WS.png' alt='white solid arrow'/> is just visible between the mass and more anterior trachea.*
![Axial T2 MR shows heterogeneous nodal metastases <img src='img/arrows/WS.png' alt='white solid arrow'/> and a heterogeneous thyroid gland <img src='img/arrows/WC.png' alt='white curved arrow'/> primary tumor.](images/app.statdx.com_image_thumbnail_ab1e5151-58ea-415d-8b3e-b43752d063eb_annotated_true_size_900_quality_90_d3d694911de588ecce54eb4d29e37278b205ccf3.jpg)
**Differentiated Thyroid Carcinoma, Nodal**
*Axial T2 MR shows heterogeneous nodal metastases <img src='img/arrows/WS.png' alt='white solid arrow'/> and a heterogeneous thyroid gland <img src='img/arrows/WC.png' alt='white curved arrow'/> primary tumor.*
![Axial CECT reveals multiple nodes extending into the superior mediastinum with a curvilinear rim of calcification seen in one <img src='img/arrows/WO.png' alt='white open arrow'/> and focal dense calcification in another <img src='img/arrows/WS.png' alt='white solid arrow'/>.](images/app.statdx.com_image_thumbnail_e67e3e7a-be29-478a-bba4-03a2f6f56f08_annotated_true_size_900_quality_90_080c784a15c4e1be2e93676663054cea18e5727a.jpg)
**Differentiated Thyroid Carcinoma, Nodal**
*Axial CECT reveals multiple nodes extending into the superior mediastinum with a curvilinear rim of calcification seen in one <img src='img/arrows/WO.png' alt='white open arrow'/> and focal dense calcification in another <img src='img/arrows/WS.png' alt='white solid arrow'/>.*
![Axial CECT demonstrates a well-defined nodule <img src='img/arrows/WS.png' alt='white solid arrow'/> arising from the thyroid isthmus and almost isodense to the normal thyroid. Cross-sectional imaging is nonspecific, although absence of infiltration of the adjacent tissues or nodes favors a benign etiology.](images/app.statdx.com_image_thumbnail_4682e38a-d078-415d-a23f-c3d3dd76f88b_annotated_true_size_900_quality_90_091c4ae60d05791c447e849c614e11145f933201.jpg)
**Adenoma, Thyroid**
*Axial CECT demonstrates a well-defined nodule <img src='img/arrows/WS.png' alt='white solid arrow'/> arising from the thyroid isthmus and almost isodense to the normal thyroid. Cross-sectional imaging is nonspecific, although absence of infiltration of the adjacent tissues or nodes favors a benign etiology.*
![Coronal T1 MR shows multiple masses bilaterally in the lower neck <img src='img/arrows/WS.png' alt='white solid arrow'/> and superior mediastinum <img src='img/arrows/WC.png' alt='white curved arrow'/> forming nodal conglomerates. The masses appear slightly hyperintense to muscle and displace vascular structures without compressing them.](images/app.statdx.com_image_thumbnail_b47fd609-9c24-4ceb-80c6-6f95e38d6d26_annotated_true_size_900_quality_90_12edc7aa6a4426d011ebd4eaf27ac52f93b4bb5a.jpg)
**Non-Hodgkin Lymphoma, Lymph Nodes**
*Coronal T1 MR shows multiple masses bilaterally in the lower neck <img src='img/arrows/WS.png' alt='white solid arrow'/> and superior mediastinum <img src='img/arrows/WC.png' alt='white curved arrow'/> forming nodal conglomerates. The masses appear slightly hyperintense to muscle and displace vascular structures without compressing them.*
![Axial arterial-phase CECT demonstrates a partially cystic, peripherally enhancing nodule posterior to the right thyroid lobe in the tracheoesophageal groove <img src='img/arrows/WS.png' alt='white solid arrow'/>. Cystic change is an uncommon finding in parathyroid adenomas.](images/app.statdx.com_image_thumbnail_23f5f427-48e5-437c-938e-7b6a2bd5d991_annotated_true_size_900_quality_90_25233542032e69cee3a9f4a61ebd024ad61e2274.jpg)
**Adenoma, Parathyroid, Visceral Space**
*Axial arterial-phase CECT demonstrates a partially cystic, peripherally enhancing nodule posterior to the right thyroid lobe in the tracheoesophageal groove <img src='img/arrows/WS.png' alt='white solid arrow'/>. Cystic change is an uncommon finding in parathyroid adenomas.*
![Axial CECT through the neck shows a well-circumscribed but irregularly contoured mass <img src='img/arrows/WC.png' alt='white curved arrow'/> immediately posterior to the left thyroid lobe. The mass has heterogeneous enhancement and is hypodense, as compared to the thyroid tissue.](images/app.statdx.com_image_thumbnail_4a28b3e4-89ca-4626-be40-0d3416fa0067_annotated_true_size_900_quality_90_3e8f6188d1e15ca871951a2617997482c453dc3b.jpg)
**Adenoma, Parathyroid, Visceral Space**
*Axial CECT through the neck shows a well-circumscribed but irregularly contoured mass <img src='img/arrows/WC.png' alt='white curved arrow'/> immediately posterior to the left thyroid lobe. The mass has heterogeneous enhancement and is hypodense, as compared to the thyroid tissue.*
![Axial CECT shows a bulky, homogeneous mass arising from the proximal cervical esophagus and infiltrating the right thyroid <img src='img/arrows/WS.png' alt='white solid arrow'/>. The mass surrounds the right common carotid artery <img src='img/arrows/WC.png' alt='white curved arrow'/> and invades the trachea.](images/app.statdx.com_image_thumbnail_998b7379-93bd-473b-bdd7-87a2026f0459_annotated_true_size_900_quality_90_2066f52dbcf5255c38310d2dfde3575e0f745b35.jpg)
**Esophageal Carcinoma, Cervical**
*Axial CECT shows a bulky, homogeneous mass arising from the proximal cervical esophagus and infiltrating the right thyroid <img src='img/arrows/WS.png' alt='white solid arrow'/>. The mass surrounds the right common carotid artery <img src='img/arrows/WC.png' alt='white curved arrow'/> and invades the trachea.*
![Axial CECT in an adult shows a low-density mass <img src='img/arrows/WS.png' alt='white solid arrow'/> at the cervicothoracic junction that appears inseparable from the esophagus <img src='img/arrows/WO.png' alt='white open arrow'/> and trachea <img src='img/arrows/WC.png' alt='white curved arrow'/>, both of which are displaced to the right side.](images/app.statdx.com_image_thumbnail_089a6ecb-acb8-472d-bd91-3dda109efd1b_annotated_true_size_900_quality_90_504ba98ddfe5dfa01ad83448046ceef3f2760329.jpg)
**Parathyroid Cyst, Visceral Space**
*Axial CECT in an adult shows a low-density mass <img src='img/arrows/WS.png' alt='white solid arrow'/> at the cervicothoracic junction that appears inseparable from the esophagus <img src='img/arrows/WO.png' alt='white open arrow'/> and trachea <img src='img/arrows/WC.png' alt='white curved arrow'/>, both of which are displaced to the right side.*
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---
title: "Common Peroneal/Tibial Nerves"
docid: "62c7711e-263f-4d56-94a3-bd7f5fc1ea20"
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---
## TERMINOLOGY
- ### Abbreviations
- Sciatic nerve (SN)
- Common peroneal nerve (CPN)
- Tibial nerve (TN)
## GROSS ANATOMY
- ### Overview
- **SN**
- Major continuation of sacral plexus
- Passes behind, below piriformis muscle
- Common variation: Passes through piriformis
- Exits pelvis through greater sciatic foramen
- Passes between greater trochanter, ischial tuberosity
- Descends along posterior thigh
- Proximal to knee, divides into 2 major terminal branches
- Common peroneal (fibular) nerve
- TN
- CPN, TN divisions discrete entities within SN prior to division
- TN usually larger, more medially located than CPN
- Supplies knee flexors + all muscles below knee
- **TN**
- Larger terminal branch of SN
- Ventral primary rami of L4-L5, S1-S3
- Descends along back of thigh, popliteal fossa
- Sends articular branches to knee
- Branches to posterior leg muscles
- Gastrocnemius
- Plantaris
- Soleus
- Popliteus
- Tibialis posterior
- Flexor digitorum longus
- Flexor hallucis longus
- Sural nerve (posterior/lateral skin of distal 1/3 of leg, lateral foot)
- Medial calcaneal branches (skin of heel, medial plantar surface)
- Medial plantar nerve (main termination of TN to medial sole of foot, plantar muscles)
- Lateral plantar nerve
- Lateral sole of foot
- Most deep muscles of foot
- **CPN**
- Smaller terminal branch of SN
- Descends obliquely along lateral popliteal fossa to fibula
- Traverses lateral aspect of head of fibula
- Especially vulnerable to injury at this point
- 2 major terminal branches
- Superficial peroneal nerve (SPN)
- Deep peroneal nerve (DPN)
- DPN supplies anterior compartment leg muscles
- Tibialis anterior
- Peroneus tertius
- Extensor hallucis longus, brevis
- Skin on lateral aspect of ankle, dorsal foot
- SPN supplies
- Peroneus longus, brevis
- Skin of lower leg
## ANATOMY IMAGING ISSUES
- ### Imaging Recommendations
- **TN**
- MR coils
- Preferred: Torso wraparound phased-array coil
- Alternative: Flexible extremity surface coil
- Best plane: Direct axial
- Best sequences
- T1, STIR/fat-suppressed T2
- Optional: Fat-suppressed T1 C+
- **CPN**
- MR coils
- Preferred: Torso wraparound phased-array coil
- Alternative: Knee coil (excellent images but limited coverage) or flexible extremity surface coil
- Best plane: Direct axial
- Best sequences
- T1, STIR/fat-saturated T2
- Optional: Fat-suppressed T1 C+
- Sonography
- Uniform thickness, internal striations with echogenicity lower than tendon, greater than skeletal muscle
- ### Imaging Approaches
- Torso coil preferred for most suspected TN, CPN lesions
- Excellent signal-to-noise ratio (SNR)
- Large coverage distance
- Wrap coil around both legs
- Image 1 leg at a time → maximizes spatial resolution
- Imaging both legs simultaneously → ↑ FOV, ↓ SNR
- Knee coil
- Optimal if specifically imaging CPN at fibular head
## CLINICAL IMPLICATIONS
- ### Clinical Importance
- Lesions of SN, branches (CPN, TN) can occur at numerous locations
- SN
- Compression as components leave lumbosacral spine
- Compression as SN leaves pelvis
- Piriformis syndrome (common anatomic variant but entrapment rare)
- Deep gluteal syndrome (entrapment of nerve in deep gluteal space)
- CPN neuropathy
- Paresis/weakness of ankle/toe dorsiflexion (foot drop)
- Most common cause: CPN compression at fibular head
- Less common: After total knee arthroplasty, proximal tibial osteotomy
- TN neuropathy
- Pain, paresthesias, paresis of plantar flexion at ankle
- TN can be entrapped as traverses tarsal tunnel
a3b0518a-cbbf-4699-992f-f3f9bdc270a1
## References
## Selected References
1. [Daniels SP et al: Intravenous contrast does not improve detection of nerve lesions or active muscle denervation changes in MR neurography of the common peroneal nerve. Skeletal Radiol. 50(12):2483-94, 2021](http://www.ncbi.nlm.nih.gov/pubmed/?term=34021773%5Bpmid%5D)
1. [Grant TH et al: Sonographic evaluation of common peroneal neuropathy in patients with foot drop. J Ultrasound Med. 34(4):705-11, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25792587%5Bpmid%5D)
1. [Martin HD et al: Deep gluteal syndrome. J Hip Preserv Surg. 2(2):99-107, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=27011826%5Bpmid%5D)
1. [Van den Bergh FR et al: Peroneal nerve: normal anatomy and pathologic findings on routine MRI of the knee. Insights Imaging. 4(3):287-99, 2013](http://www.ncbi.nlm.nih.gov/pubmed/?term=23709403%5Bpmid%5D)
1. [Chhabra A et al: High-resolution 3-T MR neurography of peroneal neuropathy. Skeletal Radiol. 41(3):257-71, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=21416383%5Bpmid%5D)
## Images
### Graphic
![Anterior graphic of the right leg demonstrates the normal course of the sciatic nerve and its terminal tibial nerve and common peroneal nerve branches. The tibial nerve remains in the posterior compartment where it supplies the muscles of the posterior leg, while the common peroneal nerve moves laterally around the fibular head (where it is vulnerable to injury) and descends in the anterolateral leg to supply the anterior leg muscles. Common peroneal nerve divides into superficial and deep terminal branches. The superficial peroneal nerve supplies the peroneus muscles and extensor digitorum brevis muscle, while the deep peroneal nerve supplies the tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles.](images/app.statdx.com_image_thumbnail_46eda35e-76d4-4ed3-b0c0-87f84fc243b4_annotated_false_size_900_quality_90_1f4182b47b6589d6645757d28730166747d46984.jpg)
*Anterior graphic of the right leg demonstrates the normal course of the sciatic nerve and its terminal tibial nerve and common peroneal nerve branches. The tibial nerve remains in the posterior compartment where it supplies the muscles of the posterior leg, while the common peroneal nerve moves laterally around the fibular head (where it is vulnerable to injury) and descends in the anterolateral leg to supply the anterior leg muscles. Common peroneal nerve divides into superficial and deep terminal branches. The superficial peroneal nerve supplies the peroneus muscles and extensor digitorum brevis muscle, while the deep peroneal nerve supplies the tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles.*
![Anterior graphic of the right leg demonstrates the normal course of the sciatic nerve and its terminal tibial nerve and common peroneal nerve branches. The tibial nerve remains in the posterior compartment where it supplies the muscles of the posterior leg, while the common peroneal nerve moves laterally around the fibular head (where it is vulnerable to injury) and descends in the anterolateral leg to supply the anterior leg muscles. Common peroneal nerve divides into superficial and deep terminal branches. The superficial peroneal nerve supplies the peroneus muscles and extensor digitorum brevis muscle, while the deep peroneal nerve supplies the tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles.](images/app.statdx.com_image_thumbnail_46eda35e-76d4-4ed3-b0c0-87f84fc243b4_size_174_quality_85_5e8bdf68df01ba8d7563187ec2aef9146d261fb6.jpg)
*Anterior graphic of the right leg demonstrates the normal course of the sciatic nerve and its terminal tibial nerve and common peroneal nerve branches. The tibial nerve remains in the posterior compartment where it supplies the muscles of the posterior leg, while the common peroneal nerve moves laterally around the fibular head (where it is vulnerable to injury) and descends in the anterolateral leg to supply the anterior leg muscles. Common peroneal nerve divides into superficial and deep terminal branches. The superficial peroneal nerve supplies the peroneus muscles and extensor digitorum brevis muscle, while the deep peroneal nerve supplies the tibialis anterior, extensor digitorum longus, and extensor hallucis longus muscles.*
### Axial T1 MR
![First of 2 axial T1 MR images through the left thigh, presented from superior to inferior, demonstrates the left sciatic nerve residing between the obturator internus and gluteus maximus muscles. Even at this level, the common peroneal division and tibial division fibers are anatomically distinguishable even though the sciatic nerve proper contains both divisions within a single epineurium layer.](images/app.statdx.com_image_thumbnail_c9cdb5de-1498-4cc0-b88d-c991201f9396_annotated_false_size_900_quality_90_eaa76beaeed82d8eff834a3b4e5701d8c76bbf79.jpg)
*First of 2 axial T1 MR images through the left thigh, presented from superior to inferior, demonstrates the left sciatic nerve residing between the obturator internus and gluteus maximus muscles. Even at this level, the common peroneal division and tibial division fibers are anatomically distinguishable even though the sciatic nerve proper contains both divisions within a single epineurium layer.*
![Image obtained more distally through the left thigh shows clear separation of the common peroneal nerve and tibial nerve fibers within the sciatic nerve. This somatotopic distribution of nerve fibers explains why some patients with sciatic nerve lesions may clinically demonstrate either a common peroneal or tibial neuropathy only.](images/app.statdx.com_image_thumbnail_a4643880-3b9f-4bcf-8b3a-5f3c1cbe8fc1_annotated_false_size_900_quality_90_c4cba609d9a1f77cbb8af45dae1f69a3e4850bf4.jpg)
*Image obtained more distally through the left thigh shows clear separation of the common peroneal nerve and tibial nerve fibers within the sciatic nerve. This somatotopic distribution of nerve fibers explains why some patients with sciatic nerve lesions may clinically demonstrate either a common peroneal or tibial neuropathy only.*
![First of 2 axial T1 MR images through the left midthigh depicts the proximal bifurcation of the sciatic nerve into common peroneal and tibial nerve branches. The tibial nerve is normally larger than the common peroneal nerve.](images/app.statdx.com_image_thumbnail_124baa24-66ab-4c86-8644-3e40e550b39b_annotated_false_size_900_quality_90_58279aff41d9daa3b98b8714faa2085eaa6da8fb.jpg)
*First of 2 axial T1 MR images through the left midthigh depicts the proximal bifurcation of the sciatic nerve into common peroneal and tibial nerve branches. The tibial nerve is normally larger than the common peroneal nerve.*
![Image more distal in the left thigh depicts the common peroneal and tibial nerves as separate nerves with separate epineurium but traveling adjacent to each other in the posterior thigh.](images/app.statdx.com_image_thumbnail_327d4413-d7c7-40ec-aaba-7d8846d6fd3b_annotated_false_size_900_quality_90_6722d92704c7fa8b11e013f261b4aff1f7b35229.jpg)
*Image more distal in the left thigh depicts the common peroneal and tibial nerves as separate nerves with separate epineurium but traveling adjacent to each other in the posterior thigh.*
![First of 2 axial T1 MR images through the distal thigh, presented from superior to inferior, depicts the larger tibial nerve continuing straight distally, and the smaller common peroneal nerve moving laterally in preparation to transit around the fibular head.](images/app.statdx.com_image_thumbnail_7c48cd17-28a9-4003-bd6e-298de0aad618_annotated_false_size_900_quality_90_7fa8cc9b9c252183f7c74c61bf9cd81ddf05fc64.jpg)
*First of 2 axial T1 MR images through the distal thigh, presented from superior to inferior, depicts the larger tibial nerve continuing straight distally, and the smaller common peroneal nerve moving laterally in preparation to transit around the fibular head.*
![Image obtained more distally in the left thigh at the level of the supracondylar femur clearly depicts the isointense (to muscle) tibial nerve fascicles separated by bright fibrofatty connective tissue. The smaller common peroneal nerve is laterally positioned.](images/app.statdx.com_image_thumbnail_1fd6243b-fcf2-4794-ba96-59ef9309aff3_annotated_false_size_900_quality_90_9dfb2e2710b9a5fab1292f52578cd6c7ae58dd95.jpg)
*Image obtained more distally in the left thigh at the level of the supracondylar femur clearly depicts the isointense (to muscle) tibial nerve fascicles separated by bright fibrofatty connective tissue. The smaller common peroneal nerve is laterally positioned.*
![Axial T1 MR obtained at the femoral condyle level confirms little change in location of the tibial nerve as it moves distally towards the knee joint. Conversely, the common peroneal nerve is moving progressively laterally.](images/app.statdx.com_image_thumbnail_a38fcdb1-d59c-4cdd-a444-717a1b43555b_annotated_false_size_900_quality_90_b1a1d1846654de1916cf0d1200073211b4b1d00c.jpg)
*Axial T1 MR obtained at the femoral condyle level confirms little change in location of the tibial nerve as it moves distally towards the knee joint. Conversely, the common peroneal nerve is moving progressively laterally.*
![Axial T1 MR obtained below the knee joint at the level of the proximal tibia and fibula reveals the lateral superficial position of the common peroneal nerve at the fibular head. Because of this superficial anatomic position adjacent to the hard fibular head, the common peroneal nerve is commonly injured in this location.](images/app.statdx.com_image_thumbnail_3439d46b-6ccf-4dab-9ebe-57c7a8f54e21_annotated_false_size_900_quality_90_095b8079b31c17de428a828488fa5a169aeec293.jpg)
*Axial T1 MR obtained below the knee joint at the level of the proximal tibia and fibula reveals the lateral superficial position of the common peroneal nerve at the fibular head. Because of this superficial anatomic position adjacent to the hard fibular head, the common peroneal nerve is commonly injured in this location.*
docs_md/articles/femoral-nerve_02197ef4-b297-4172-9728-7d07a91562c9.md
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---
title: "Femoral Nerve"
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---
## TERMINOLOGY
- ### Abbreviations
- Femoral nerve (FN)
- Lumbar plexus (LP)
- Ventral primary ramus (VPR)
## GROSS ANATOMY
- ### Overview
- **Lumbar plexus**
- Paraspinal nerve plexus
- Lies in posterior part of psoas major
- Formed by L2-L4 VPRs
- Branches
- Ventral branches of L2-L4 VPRs form **obturator nerve**
- Smaller dorsal branches of L2, L3 VPRs unite to form **lateral femoral cutaneous nerve**
- Larger dorsal branches of L2-L4 VPRs form **FN**
- **Femoral nerve**
- Largest branch of LP
- Composed of
- Dorsal branches of L2-L4 VPRs
- Abdominal branches supply iliacus, pectineus muscles
- In thigh, FN splits into anterior, posterior divisions
- Anterior division branches
- **Intermediate femoral cutaneous nerve**
- **Medial femoral cutaneous nerve**
- Branches to sartorius muscle
- Posterior division
- **Saphenous nerve** (largest femoral cutaneous branch)
- **Muscular branches** to quadriceps, rectus femoris, vastus muscles
- ### Anatomy Relationships
- FN descends through psoas major
- Runs caudally in iliopsoas groove, deep to iliac fascia
- Exits pelvis by passing behind inguinal ligament
- Runs inferiorly in close proximity to femoral artery/vein
- Courses lateral to femoral artery/vein within femoral canal
- Acronym for femoral canal contents from lateral to medial = NAVL (nerve, artery, vein, lymphatics)
- FN splits into anterior, posterior divisions
- Anterior division branches
- **Intermediate femoral cutaneous nerve**
- Pierces fascia lata
- Descends on front of thigh
- Supplies skin to knee
- **Medial femoral cutaneous nerve**
- Lateral, then anterior to femoral artery at apex of femoral triangle
- Anterior branch descends on sartorius, supplies skin as low as medial aspect of knee
- Posterior branch anastomoses with saphenous, obturator nerve branches; supplies medial leg
- Posterior division branches
- **Saphenous nerve**
- Descends in adductor canal
- First lateral, then medial to femoral artery
- Descends on medial side of leg
- Supplies skin of medial thigh, knee, leg
## IMAGING ANATOMY
- ### Overview
- MR of normal FN
- T1WI: Round/ovoid shape
- STIR/fat-suppressed T2WI
- Well-defined internal fascicular architecture
- Uniformly mildly hyperintense fascicles + interspersed hypointense fibrofatty connective tissue
## ANATOMY IMAGING ISSUES
- ### Imaging Recommendations
- MR/MR neurography (MRN)
- High resolution
- 3T
- Best coils
- Preferred: Torso wrap-around multichannel phase-array coil
- Alternative: Flexible extremity surface coil
- Best planes
- Direct coronal, axial
- Best sequences
- Coronal T1WI, STIR, or fat-suppressed T2WI
- Axial T1WI, STIR, or fat-suppressed T2WI
- Optional: Coronal, axial fat-suppressed T1 C+
- 3D sequences: Combination of fast imaging techniques (parallel acquisition or compressed sensing) → reduce acquisition time
- Area to cover: Similar to sciatic nerve imaging in thigh
- Extend scan from sacrum (posterior) to skin of groin (anterior)
- Visualizes FN under inguinal ligament
## CLINICAL IMPLICATIONS
- ### Clinical Importance
- FN neuropathy characterized by
- Quadriceps wasting/weakness
- Pain/paresthesias anteromedial thigh, medial leg
- FN especially vulnerable to injuries at 2 points
- Within iliopsoas groove
- At groin
- FN generally not subject to entrapment but may be compressed
- Compressive FN neuropathy
- Secondary to pelvis tumor, such as
- Lymphoma
- Sarcoma
- Secondary to psoas hematoma
- Trauma
- Coagulopathy
- Hemophilia
- Noncompressive FN neuropathy
- Diabetes
- Surgery (e.g., inadvertent ligation during herniorrhaphy)
- Infectious plexopathy
2fb233c2-b21f-486d-8366-5a1e9cdb41ea
## References
## Selected References
1. [Kim SG et al: Role of MR neurography for evaluation of the lumbosacral plexus: a scoping review. J Korean Soc Radiol. 83(6):1273-85, 2022](http://www.ncbi.nlm.nih.gov/pubmed/?term=36545407%5Bpmid%5D)
1. [Robbins NM et al: Magnetic resonance neurography in the diagnosis of neuropathies of the lumbosacral plexus: a pictorial review. Clin Imaging. 40(6):1118-30, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27454861%5Bpmid%5D)
## Images
### Graphic
![Graphic shows the femoral nerve (FN) arising from L2, L3, and L4 nerve roots (ventral primary rami) and traveling in groove created by iliacus and psoas muscles (iliopsoas groove). FN travels with the femoral artery and vein under the inguinal ligament to provide innervation to quadriceps muscles in thigh. The well-known acronym &quot;NAVL&quot; (nerve, artery, vein, lymphatics) describes the order of femoral canal contents from lateral to medial.](images/app.statdx.com_image_thumbnail_320c2916-be82-41a7-98a0-160ac98b3262_annotated_false_size_900_quality_90_b798839acbbc339d92aaca8e543685375af0e950.jpg)
*Graphic shows the femoral nerve (FN) arising from L2, L3, and L4 nerve roots (ventral primary rami) and traveling in groove created by iliacus and psoas muscles (iliopsoas groove). FN travels with the femoral artery and vein under the inguinal ligament to provide innervation to quadriceps muscles in thigh. The well-known acronym &quot;NAVL&quot; (nerve, artery, vein, lymphatics) describes the order of femoral canal contents from lateral to medial.*
![Graphic shows the femoral nerve (FN) arising from L2, L3, and L4 nerve roots (ventral primary rami) and traveling in groove created by iliacus and psoas muscles (iliopsoas groove). FN travels with the femoral artery and vein under the inguinal ligament to provide innervation to quadriceps muscles in thigh. The well-known acronym &quot;NAVL&quot; (nerve, artery, vein, lymphatics) describes the order of femoral canal contents from lateral to medial.](images/app.statdx.com_image_thumbnail_320c2916-be82-41a7-98a0-160ac98b3262_size_174_quality_85_2994975728bde8d91ea9f8029883e7da8443bf70.jpg)
*Graphic shows the femoral nerve (FN) arising from L2, L3, and L4 nerve roots (ventral primary rami) and traveling in groove created by iliacus and psoas muscles (iliopsoas groove). FN travels with the femoral artery and vein under the inguinal ligament to provide innervation to quadriceps muscles in thigh. The well-known acronym &quot;NAVL&quot; (nerve, artery, vein, lymphatics) describes the order of femoral canal contents from lateral to medial.*
### Coronal T1 MR
![First of 2 coronal T1 MR images presented from posterior to anterior demonstrates the ventral primary rami (L2-L4), which will form the lumbar plexus. L5 will combine with a minor branch of L4 to form the lumbosacral trunk.](images/app.statdx.com_image_thumbnail_0b12e3df-0c52-460a-b29c-2690239418f3_annotated_false_size_900_quality_90_7124482117724f69132d3d5c045f4bc7338013e6.jpg)
*First of 2 coronal T1 MR images presented from posterior to anterior demonstrates the ventral primary rami (L2-L4), which will form the lumbar plexus. L5 will combine with a minor branch of L4 to form the lumbosacral trunk.*
![Image more anteriorly after formation of the lumbar plexus shows the FN in the iliopsoas groove. The lumbar plexus is isointense to muscle signal and often difficult to identify on coronal T1 MR images.](images/app.statdx.com_image_thumbnail_435aca6d-7ada-4ed0-a91c-e5bd76f4eb93_annotated_false_size_900_quality_90_baab47d667743c007d3884911359c2651d388592.jpg)
*Image more anteriorly after formation of the lumbar plexus shows the FN in the iliopsoas groove. The lumbar plexus is isointense to muscle signal and often difficult to identify on coronal T1 MR images.*
### Coronal STIR MR
![First of 2 coronal STIR MR images depicts the proximal rami contributions to the lumbar plexus. The proximal FN travels in the iliopsoas groove and is easily identifiable by its fascicular nature and mild hyperintensity (to adjacent muscle).](images/app.statdx.com_image_thumbnail_4fda8e44-2a47-4936-b5fb-db11220e77da_annotated_false_size_900_quality_90_47f980cb8fb24794e3ce72a7cb12a26a339af8a3.jpg)
*First of 2 coronal STIR MR images depicts the proximal rami contributions to the lumbar plexus. The proximal FN travels in the iliopsoas groove and is easily identifiable by its fascicular nature and mild hyperintensity (to adjacent muscle).*
![Image more anteriorly located shows the bilateral FNs traveling in the iliopsoas grooves. The distinct fascicular pattern is unique to normal nerves and readily permits their distinction from vessels.](images/app.statdx.com_image_thumbnail_5b4f2946-8b3b-46de-b991-98b8c48873af_annotated_false_size_900_quality_90_3750257d0a765ca2f1bc05c1e67c3bf3e0e28cb7.jpg)
*Image more anteriorly located shows the bilateral FNs traveling in the iliopsoas grooves. The distinct fascicular pattern is unique to normal nerves and readily permits their distinction from vessels.*
### Coronal & Axial STIR MR
![Coronal STIR MR shows the FNs as they descend out of the pelvis into the femoral canal. The normal left FN is mildly hyperintense to muscle. The right FN is swollen and abnormally hyperintense to the level of a suture inadvertently ligating the FN during a herniorrhaphy. This image reinforces the importance of continuing coronal slices anteriorly to groin skin to avoid missing lesions within the femoral canal.](images/app.statdx.com_image_thumbnail_062c16ad-f37e-4ce5-930f-adc6433e020d_annotated_false_size_900_quality_90_bc18dbf5f657bfff48c4f365d8e3ab22c6771d45.jpg)
*Coronal STIR MR shows the FNs as they descend out of the pelvis into the femoral canal. The normal left FN is mildly hyperintense to muscle. The right FN is swollen and abnormally hyperintense to the level of a suture inadvertently ligating the FN during a herniorrhaphy. This image reinforces the importance of continuing coronal slices anteriorly to groin skin to avoid missing lesions within the femoral canal.*
![Axial STIR MR obtained in the pelvis of the same patient contrasts the normal left FN within the iliopsoas groove to the abnormally swollen hyperintense right FN proximal to an inadvertent surgical ligature during herniorrhaphy. Note that both nerves clearly demonstrate the distinctive fascicular architecture of nerves. At this level, the iliacus and psoas muscles functionally form the iliopsoas muscle.](images/app.statdx.com_image_thumbnail_8fae0983-41ed-492b-baa8-f1ca4ffb238a_annotated_false_size_900_quality_90_23032377ed5238a07646302616cd25ec2d8785ef.jpg)
*Axial STIR MR obtained in the pelvis of the same patient contrasts the normal left FN within the iliopsoas groove to the abnormally swollen hyperintense right FN proximal to an inadvertent surgical ligature during herniorrhaphy. Note that both nerves clearly demonstrate the distinctive fascicular architecture of nerves. At this level, the iliacus and psoas muscles functionally form the iliopsoas muscle.*
### Axial T1 MR
![Axial T1 MR obtained at the level of the femoral canal demonstrates the right FN lateral to the femoral artery, veins, and lymphatics (not seen). The acronym &quot;NAVL&quot; helps to recall the order of structures within the femoral canal from lateral to medial. The left FN is not well shown. The FN is small at this level and often difficult to identify as a discrete structure unless abnormally swollen.](images/app.statdx.com_image_thumbnail_4f68f355-1c52-4435-90f0-b842454e992a_annotated_false_size_900_quality_90_bde962716b1c7eaabaf92f58995016f8d7957004.jpg)
*Axial T1 MR obtained at the level of the femoral canal demonstrates the right FN lateral to the femoral artery, veins, and lymphatics (not seen). The acronym &quot;NAVL&quot; helps to recall the order of structures within the femoral canal from lateral to medial. The left FN is not well shown. The FN is small at this level and often difficult to identify as a discrete structure unless abnormally swollen.*
![Axial T1 MR through the proximal thigh shows the FN branching into muscular branches that will supply the anterior thigh quadriceps muscles. It is difficult to image FNs distal to these proximal branches because of their small size and similar signal intensity to muscles.](images/app.statdx.com_image_thumbnail_0c7c15f8-d55f-4e72-925e-0a3d34baae46_annotated_false_size_900_quality_90_c30a4536f276440558df0a411290522d8643a3cf.jpg)
*Axial T1 MR through the proximal thigh shows the FN branching into muscular branches that will supply the anterior thigh quadriceps muscles. It is difficult to image FNs distal to these proximal branches because of their small size and similar signal intensity to muscles.*
docs_md/articles/idiopathic-brachial-plexus-neuritis_b7bded5d-050c-47a9-affe-4028085b3398.md
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---
## KEY FACTS
- ### Terminology
- Parsonage-Turner syndrome
- ### Imaging
- Can affect any muscle innervated by brachial plexus
- Most common: Rotator cuff, deltoid, biceps, triceps
- Denervation edema is earliest finding
- Diffuse, homogeneous high signal on T2, STIR MR throughout affected muscle
- Fatty atrophy occurs in chronic denervation
- Uncommonly seen
- Often, muscles innervated by ≥ 2 different peripheral nerves are affected
- ### Top Differential Diagnoses
- Cervical radiculopathy
- Suprascapular nerve entrapment
- Brachial plexus neoplasm
- Brachial plexus or cervical nerve root avulsion
- Radiation neuritis/myositis
- Quadrilateral space syndrome
- Pancoast tumor
- Muscle injury
- ### Pathology
- Often associated with viral or bacterial infection
- Can also be post traumatic or post surgery
- ### Clinical Issues
- Sudden onset of pain, followed by weakness, paresthesias
- M > F
- Most cases resolve in 3 months to 2 years
- Physical therapy to preserve range of motion
- ### Diagnostic Checklist
- Often unexpected finding on shoulder MR performed to evaluate weakness, pain
- Abnormal muscle signal often involves > 1 peripheral nerve distribution
## TERMINOLOGY
- ### Synonyms
- Neuralgic amyotrophy idiopathic neuritis involving upper brachial plexus (idiopathic brachial plexus neuritis), cervical plexus, lumbosacral plexus ± cranial nerves
- Synonym: Parsonage-Turner syndrome
- Subset of neuralgic amyotrophy
- Acute brachial neuritis
- ### Definitions
- Immune-mediated neuropathy of brachial plexus
## IMAGING
- ### General Features
- #### Best diagnostic clue
- Homogeneously increased signal on T2 MR in 1 or more muscles of shoulder
- #### Location
- Any muscle innervated by brachial plexus
- Most common: Rotator cuff, deltoid, biceps, triceps
- Uncommon: Brachialis, forearm muscles, diaphragm, serratus anterior (long thoracic nerve)
- Sometimes bilateral
- May cause pure sensory nerve deficit
- #### Size
- Mild, uniform enlargement of affected muscles
- Muscle atrophy seen in chronic cases
- #### Morphology
- Diffuse involvement of muscle without focal mass
- ### CT Findings
- Used to exclude mass involving brachial plexus or peripheral nerves
- Muscle atrophy, fatty infiltration evident in chronic cases
- ### MR Findings
- **Brachial plexus**
- Affected nerves high signal intensity on T2, STIR MR
- Nerves show mild enhancement with gadolinium
- No mass along course of nerves
- **Affected muscles**
- Denervation edema is earliest finding
- Muscle normal on T1 MR
- Diffuse, homogeneous, high signal on T2, STIR MR throughout affected muscle
- No disruption of muscle fibers
- Diffuse, homogeneous enhancement with gadolinium
- Fatty atrophy occurs in chronic denervation
- Fatty streaking greater than in unaffected muscles
- Decreased size of muscle
- Uncommonly seen; most cases spontaneously resolve
- Often, muscles innervated by ≥ 2 different peripheral nerves are affected
- e.g., infraspinatus (suprascapular nerve) + teres minor (axillary nerve)
- ### Imaging Recommendations
- #### Best imaging tool
- MR
- #### Protocol advice
- T1, T2, or STIR MR along long and short axes of symptomatic muscles
- MR of shoulder should have 16- to 18-cm FOV on coronal images
- Include spinoglenoid notch to rule out impingement on suprascapular nerve
- Include quadrilateral space to rule out impingement on axillary nerve
- Imaging of brachial plexus excludes brachial plexus mass
- If patient gives characteristic history, not needed unless symptoms do not resolve
## DIFFERENTIAL DIAGNOSIS
- [Cervical Radiculopathy](/document/cervical-intervertebral-disc-herni-/4d314bb5-dec5-49b4-a420-8381c9b69215)
- Evaluate with cervical spine MR
- Most commonly see involvement of single nerve root
- Brachial neuritis involves multiple nerve roots
- Severe cases may have denervation changes in affected muscles
- ### Suprascapular Nerve Entrapment
- Causes denervation edema
- Mass in suprascapular notch: Affects supraspinatus + infraspinatus
- Mass in spinoglenoid notch: Affects infraspinatus
- [Brachial Plexus Neoplasm](/document/peripheral-nerve-sheath-tumor/6999556f-4f8b-4c3f-8e5b-52f6a384d3a5)
- Presents with pain, muscle weakness
- Causes denervation edema
- Mass seen on MR of brachial plexus
- Usually metastasis; primary tumor uncommon
- [Brachial Plexus or Cervical Nerve Root Avulsion](/document/brachial-plexus-traction-injury/f65e1a98-e048-482b-8a0f-754adc9bce08)
- Severe, high-velocity injury
- Loss of nerve continuity, fluid around nerve course seen on MR
- ### Radiation Neuritis/Myositis
- Diffusely enlarged nerves and muscles showing increased T2 signal
- Geographic distribution
- History of radiation therapy
- [Quadrilateral Space Syndrome](/document/rotator-cuff-impingement/09c7dc6b-e29b-4e0f-8ccc-a9270e73fbc4)
- Mass between teres minor and teres major muscles
- Compresses axillary nerve, affects deltoid, teres minor muscles
- ### Diabetic Neuropathy
- Usually distal, symmetric
- Sometimes involves 1 or more proximal muscles
- [Pancoast Tumor](/document/superior-sulcus-tumor/d171bbc1-8a78-4d8e-a0fe-26ca500a0ba8)
- Bronchogenic carcinoma at lung apex ("superior sulcus")
- May directly extend to involve brachial plexus
- ### Myositis
- Diffuse T2 signal abnormalities in muscle
- Edema in surrounding fat
- Usually bilaterally symmetric, multiple muscles
- ### Muscle Injury
- High T2 signal intensity is heterogeneous, focal
- Disruption of muscle fibers usually visible
- Blood products often evident
- Surrounding soft tissues usually show edema/hematoma
- [Rotator Cuff Tear](/document/rotator-cuff-full-thickness-tear/5c85c554-cdc4-4680-bf85-e75335438508)
- Chronic, large tears show muscle atrophy
- Fluid in tendon defect on MR
- ### Burner/Stinger Syndrome
- Common athletic injury in contact sports
- Pain, paresthesias, muscle weakness
- Direct blow to brachial plexus in supraclavicular region
- Alternatively caused by traction to brachial plexus or cervical nerve root
- Usually transient but may persist for weeks
- MR may be performed to exclude nerve avulsion
## PATHOLOGY
- ### General Features
- #### Etiology
- Often associated with viral or bacterial infection
- EBV, CMV, HIV among viral infections
- Can occur post vaccination
- Can also be posttraumatic or post surgery
- Surgery may not be in same region
- e.g., hip arthroplasty has been reported as cause
- ### Gross Pathologic & Surgical Features
- Perineural edema, edema in affected muscles
- ### Microscopic Features
- Perineural inflammatory infiltrate
- Thinning of myelin sheath
- Axonal degeneration
## CLINICAL ISSUES
- ### Presentation
- #### Most common signs/symptoms
- Sudden onset of pain followed by weakness, paresthesias
- May have sensory abnormalities only
- Long thoracic nerve involvement: Winging of scapula
- Phrenic nerve involvement: Shortness of breath, diaphragm dysfunction
- ### Demographics
- #### Age
- May occur at any age
- #### Epidemiology
- 1.6 cases per 100,000 people
- #### Sex
- M > F
- ### Natural History & Prognosis
- Most cases resolve in 3 months to 2 years
- ### Treatment
- #### Options, risks, complications
- Physical therapy to preserve range of motion
## DIAGNOSTIC CHECKLIST
- ### Consider
- Often unexpected finding on shoulder MR performed to evaluate weakness, pain
- Brachial plexus MR performed to exclude other causes in atypical cases
- Muscles outside of shoulder girdle
- Respiratory compromise
- Pure sensory loss
- ### Image Interpretation Pearls
- Abnormal muscle signal often involves > 1 peripheral nerve distribution
- Distribution of signal abnormalities helps to distinguish from nerve entrapment syndromes
be0368a8-16ad-4e1c-8236-14d64e6f79a8
## References
## Selected References
1. [Seror P: Neuralgic amyotrophy of Parsonage and Turner. Which nerves are most frequently involved in daily practice? Data from 355 patients. Joint Bone Spine. 105777, 2024](http://www.ncbi.nlm.nih.gov/pubmed/?term=39303939%5Bpmid%5D)
1. [Sparasci D et al: Immune triggers preceding neuralgic amyotrophy. Eur J Neurol. e16462, 2024](http://www.ncbi.nlm.nih.gov/pubmed/?term=39364568%5Bpmid%5D)
1. [Patel RH et al: Post-operative emergence of acute brachial neuritis following posterior cervical laminectomy with fusion: a case report and review of the literature. Int J Surg Case Rep. 65:197-200, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=31726257%5Bpmid%5D)
1. [Su PH et al: A CARE-compliant article: a case report of idiopathic brachial neuritis treated with ultrasound-guided electroacupuncture. Medicine (Baltimore). 98(19):e15325, 2019](http://www.ncbi.nlm.nih.gov/pubmed/?term=31083162%5Bpmid%5D)
1. [van Alfen N et al: Phrenic neuropathy and diaphragm dysfunction in neuralgic amyotrophy. Neurology. 91(9):e843-9, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=30054437%5Bpmid%5D)
1. [McEnery T et al: Phrenic nerve palsy secondary to Parsonage-Turner syndrome: a diagnosis commonly overlooked. Lung. 195(2):173-7, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28138789%5Bpmid%5D)
1. [Seror P: Neuralgic amyotrophy. An update. Joint Bone Spine. 84(2):153-8, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=27263426%5Bpmid%5D)
1. [Yuh EL et al: Diffusivity measurements differentiate benign from malignant lesions in patients with peripheral neuropathy or plexopathy. AJNR Am J Neuroradiol. 36(1):202-9, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25300985%5Bpmid%5D)
1. [Fransz DP et al: Parsonage-Turner syndrome following post-exposure prophylaxis. BMC Musculoskelet Disord. 15:265, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=25098693%5Bpmid%5D)
1. [Gupta A et al: Neuralgic amyotrophy (Parsonage Turner syndrome). Orthopedics. 37(2):75, 130-33, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24495384%5Bpmid%5D)
1. [Nociti V et al: Case of postpartum Parsonage-Turner syndrome. Muscle Nerve. 49(2):294-5, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24037750%5Bpmid%5D)
1. [Park MS et al: Magnetic resonance neurographic findings in classic idiopathic neuralgic amyotrophy in subacute stage: a report of four cases. Ann Rehabil Med. 38(2):286-91, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24855627%5Bpmid%5D)
1. [Smith CC et al: Challenging pain syndromes: Parsonage-Turner syndrome. Phys Med Rehabil Clin N Am. 25(2):265-77, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24787332%5Bpmid%5D)
1. [Smith DP et al: Intravenous corticosteroid therapy for bilateral parsonage-turner syndrome: a case report and review of the literature. Reg Anesth Pain Med. 39(3):243-7, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24694999%5Bpmid%5D)
1. [Kumar I et al: Utility of magnetic resonance imaging in the diagnosis of unsuspected cases of Parsonage-Turner syndrome: two case reports. J Med Case Rep. 7:255, 2013](http://www.ncbi.nlm.nih.gov/pubmed/?term=24199631%5Bpmid%5D)
1. [Gazioglu S et al: Magnetic resonance imaging in bilateral brachial neuritis with pure sensory involvement. Neurol Sci. 33(4):927-30, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22113229%5Bpmid%5D)
1. [Tjoumakaris FP et al: Neuralgic amyotrophy (Parsonage-Turner syndrome). J Am Acad Orthop Surg. 20(7):443-9, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22751163%5Bpmid%5D)
1. [Zara G et al: MR imaging of peripheral nervous system involvement: Parsonage-Turner syndrome. J Neurol Sci. 315(1-2):170-1, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22115632%5Bpmid%5D)
1. [Yamada K et al: MRI findings and steroid therapy for neuralgic amyotrophy in children. Pediatr Neurol. 45(3):200-2, 2011](http://www.ncbi.nlm.nih.gov/pubmed/?term=21824572%5Bpmid%5D)
1. [Sureka J et al: MRI of brachial plexopathies. Clin Radiol. 64(2):208-18, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=19103352%5Bpmid%5D)
1. [Safran MR: Nerve injury about the shoulder in athletes, part 1: suprascapular nerve and axillary nerve. Am J Sports Med. 32(3):803-19, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=15090401%5Bpmid%5D)
1. [Safran MR: Nerve injury about the shoulder in athletes, part 2: long thoracic nerve, spinal accessory nerve, burners/stingers, thoracic outlet syndrome. Am J Sports Med. 32(4):1063-76, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=15150060%5Bpmid%5D)
1. [Gourie-Devi M et al: Long-term follow-up of 44 patients with brachial monomelic amyotrophy. Acta Neurol Scand. 107(3):215-20, 2003](http://www.ncbi.nlm.nih.gov/pubmed/?term=12614316%5Bpmid%5D)
1. [Janes SE et al: Brachial neuritis following infection with Epstein-Barr virus. Eur J Paediatr Neurol. 7(6):413-5, 2003](http://www.ncbi.nlm.nih.gov/pubmed/?term=14623221%5Bpmid%5D)
1. [Carroll KW et al: Magnetic resonance imaging of the shoulder: a review of potential sources of diagnostic errors. Skeletal Radiol. 31(7):373-83, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12107570%5Bpmid%5D)
1. [Cruz-Martinez A et al: Neuralgic amyotrophy: variable expression in 40 patients. J Peripher Nerv Syst. 7(3):198-204, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12365568%5Bpmid%5D)
1. [Gonzalez-Alegre P et al: Idiopathic brachial neuritis. Iowa Orthop J. 22:81-5, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12180618%5Bpmid%5D)
1. [Antoniou J et al: Suprascapular neuropathy. Variability in the diagnosis, treatment, and outcome. Clin Orthop. (386):131-8, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11347826%5Bpmid%5D)
1. [Simon JP et al: Parsonage-Turner syndrome after total-hip arthroplasty. J Arthroplasty. 16(4):518-20, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11402420%5Bpmid%5D)
1. [Watson BV et al: Isolated brachialis wasting: an unusual presentation of neuralgic amyotrophy. Muscle Nerve. 24(12):1699-702, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11745981%5Bpmid%5D)
1. [Miller JD et al: Acute brachial plexus neuritis: an uncommon cause of shoulder pain. Am Fam Physician. 62(9):2067-72, 2000](http://www.ncbi.nlm.nih.gov/pubmed/?term=11087188%5Bpmid%5D)
1. [Bredella MA et al: Denervation syndromes of the shoulder girdle: MR imaging with electrophysiologic correlation. Skeletal Radiol. 28(10):567-72, 1999](http://www.ncbi.nlm.nih.gov/pubmed/?term=10550533%5Bpmid%5D)
1. [Helms CA et al: Acute brachial neuritis (Parsonage-Turner syndrome): MR imaging appearance--report of three cases. Radiology. 207(1):255-9, 1998](http://www.ncbi.nlm.nih.gov/pubmed/?term=9530324%5Bpmid%5D)
## Anatomy
### Brachial Plexus
Head and Neck/ANATOMY:a702f5d9-f5dc-49b0-925b-20ebeecead44
### Brachial Plexus
Spine/ANATOMY:d40ec749-81b1-4900-b366-2921b7fcc467
### Brachial Plexus
Ultrasound/ANATOMY:d29276cd-f7fc-4944-9594-33172fe697ab
## Cases
- {'cases': [{'authors': [{'key': '86b8c311-8667-4afd-9b2b-0c2036a02b8a', 'value': 'Julia Crim, MD'}], 'caseVersionId': '0f9a2d4c-0fcb-4682-9e7f-0adc88c9113a', 'description': 'Typical MRI appearance of denervation edema involving multiple muscles innervated by different nerves arising from the brachial plexus.\n\nOblique coronal T1WI MR (#1) is unremarkable except for mild fatty streaking in the deltoid (arrow). Oblique coronal T2WI fat-saturated MR images (#2-3) show mild edema limited to the periphery of the supraspinatus muscle (arrows), and more extensive edema in the deltoid (open arrow) and teres minor (curved arrow) muscles. Sagittal oblique T2WI fat-saturated MR (#4) shows involvement of supraspinatus (black arrow), deltoid (white arrow), teres minor (curved arrow) and subscapularis (black open arrow). Infraspinatus (white open arrow) is spared.', 'history': 'Severe shoulder pain and weakness.', 'imagePoolId': '21499cdc-f23e-4906-9aa7-8fb8036e2be3', 'name': 'Multiple muscle involvement', 'teachingPoint': None, 'demographics': '30 Years old female'}, {'authors': [{'key': '86b8c311-8667-4afd-9b2b-0c2036a02b8a', 'value': 'Julia Crim, MD'}], 'caseVersionId': '94499573-9b94-4ed4-aef6-3c0fb0937c32', 'description': 'MRI appearance of denervation edema without muscle atrophy.\n\nCoronal (#1) and Sagittal (#2) T2WI FS MR both show abnormal increased signal throughout the teres minor muscle (arrows). Other rotator cuff muscles are spared. On Coronal MR (#3) no atrophy is evident in the teres minor (arrow). Abnormal signal in the muscles on T2WI MR and STIR MR precedes evidence of fatty atrophy on T1WI MR.\n\nComment: Isolated denervation of the teres minor muscles can also be due to mass in the quadrilateral space impinging on the axillary nerve.', 'history': 'Shoulder pain and equivocal weakness. MRI performed for suspected rotator cuff tear.', 'imagePoolId': '4a33e830-04eb-4a63-9ab0-e2007f19aa98', 'name': 'Isolated involvement of teres minor', 'teachingPoint': None, 'demographics': '27 Years old female'}, {'authors': [{'key': '86b8c311-8667-4afd-9b2b-0c2036a02b8a', 'value': 'Julia Crim, MD'}], 'caseVersionId': 'b4d11426-cfd9-4e97-8fde-5c0e99790978', 'description': 'Muscle atrophy and denervation edema.\n\nCoronal T1WI MR (#1) shows fatty atrophy in the infraspinatus muscle (arrows). Coronal T2WI MR (#2) at the same level shows diffuse muscle edema (arrows). Sagittal T2WI MR (#3) shows denervation changes involve the supraspinatus (arrow), infraspinatus (open arrow) and deltoid (curved arrow) muscles.', 'history': None, 'imagePoolId': 'a116cd2d-0beb-40d6-a2ed-98f5bd87b486', 'name': 'Muscle edema and atrophy', 'teachingPoint': None, 'demographics': '25 Years old male'}, {'authors': [{'key': '86b8c311-8667-4afd-9b2b-0c2036a02b8a', 'value': 'Julia Crim, MD'}, {'key': '99e1aff7-f42c-43a0-95ae-d89c8551aa01', 'value': 'Kevin R. Moore, MD'}], 'caseVersionId': 'c44f28f6-5f37-4136-a1f2-9956cec53b05', 'description': 'MRI through the brachial plexus shows diffuse nerve inflammation.\n\nCoronal oblique T1WI (#1) shows diffuse enlargement (arrow) of visualized portions of brachial plexus. Coronal oblique STIR (#2, 3) show increased signal intensity as well as enlargement of the nerves (arrows).', 'history': 'Severe shoulder pain and weakness.', 'imagePoolId': '52ae6a45-fc3c-48ce-8ca4-3b05e2d17373', 'name': 'Brachial plexus abnormalities', 'teachingPoint': None, 'demographics': '30 Years old male'}, {'authors': [{'key': '86b8c311-8667-4afd-9b2b-0c2036a02b8a', 'value': 'Julia Crim, MD'}], 'caseVersionId': 'da899b3a-50b7-439f-a65f-cc40499f1d35', 'description': 'MRI findings before and after gadolinium administration.\n\nAxial PD FS MR (#1) shows increased homogeneously signal intensity (arrow) throughout the visualized portions of the infraspinatus. This represents denervation edema. Oblique sagittal T2WI FS MR (#2) shows increased signal intensity involves the supraspinatus (arrow) as well as infraspinatus (open arrow) muscles. Oblique sagittal T1 C+ FS MR shows both muscle enhance diffusely (arrow shows supraspinatus, open arrow shows infraspinatus), and there is also mild enhancement of the teres minor (curved arrow).', 'history': 'Shoulder pain and weakness.', 'imagePoolId': '8c1a6fa0-e5bb-4269-8caa-d1bc7b9bc663', 'name': 'Denervation changes in muscle', 'teachingPoint': None, 'demographics': '30 Years old male'}], 'caseType': 'typical', 'name': 'TYPICAL'}
## Images
### Selected Images
![Coronal STIR MR shows diffusely increased signal intensity in brachial plexus <img src='img/arrows/WO.png' alt='white open arrow'/> due to idiopathic brachial neuritis.](images/app.statdx.com_image_thumbnail_9d9d1ea2-db09-4dba-8630-3a45d6864186_annotated_true_size_900_quality_90_af902652734052a94bb2f1889ee480ba53a596c6.jpg)
*Coronal STIR MR shows diffusely increased signal intensity in brachial plexus <img src='img/arrows/WO.png' alt='white open arrow'/> due to idiopathic brachial neuritis.*
![Coronal STIR MR shows diffusely increased signal intensity in brachial plexus <img src='img/arrows/WO.png' alt='white open arrow'/> due to idiopathic brachial neuritis.](images/app.statdx.com_image_thumbnail_9d9d1ea2-db09-4dba-8630-3a45d6864186_size_174_quality_85_32fac9376fcd113ff63fadf43e59a9148aa12bd1.jpg)
*Coronal STIR MR shows diffusely increased signal intensity in brachial plexus <img src='img/arrows/WO.png' alt='white open arrow'/> due to idiopathic brachial neuritis.*
![Coronal oblique T2 MR shows denervation edema of the teres minor <img src='img/arrows/WS.png' alt='white solid arrow'/> due to brachial neuritis. Edema is homogeneous and uniform, and there is no disruption of muscle fibers. Quadrilateral space <img src='img/arrows/WO.png' alt='white open arrow'/> shows no evidence of mass involving axillary nerve. Whenever denervation edema is seen, a search should be made for nerve mass or extrinsic compression.](images/app.statdx.com_image_thumbnail_f398a0f0-8875-400d-8cf5-cf1038ec58d7_annotated_true_size_900_quality_90_b853643266870c900c69e47856ac0af914150bb7.jpg)
*Coronal oblique T2 MR shows denervation edema of the teres minor <img src='img/arrows/WS.png' alt='white solid arrow'/> due to brachial neuritis. Edema is homogeneous and uniform, and there is no disruption of muscle fibers. Quadrilateral space <img src='img/arrows/WO.png' alt='white open arrow'/> shows no evidence of mass involving axillary nerve. Whenever denervation edema is seen, a search should be made for nerve mass or extrinsic compression.*
![Coronal oblique T2 MR shows diffuse increase in signal intensity throughout superior fibers of infraspinatus muscle <img src='img/arrows/WC.png' alt='white curved arrow'/>. Interestingly, the inferior portion of the muscle <img src='img/arrows/WO.png' alt='white open arrow'/> is spared. Unusual distributions of denervation edema are common in brachial neuritis.](images/app.statdx.com_image_thumbnail_bd7dfef8-4a12-488e-9dda-c9708a3e0ba7_annotated_true_size_900_quality_90_ce1958a77b3c6572df9912439d9ca2446bd89369.jpg)
*Coronal oblique T2 MR shows diffuse increase in signal intensity throughout superior fibers of infraspinatus muscle <img src='img/arrows/WC.png' alt='white curved arrow'/>. Interestingly, the inferior portion of the muscle <img src='img/arrows/WO.png' alt='white open arrow'/> is spared. Unusual distributions of denervation edema are common in brachial neuritis.*
![Sagittal T2 MR shows diffusely abnormal signal intensity in the infraspinatus <img src='img/arrows/WO.png' alt='white open arrow'/> and supraspinatus muscles <img src='img/arrows/WC.png' alt='white curved arrow'/>. Differential diagnosis, in this case, includes suprascapular nerve entrapment.](images/app.statdx.com_image_thumbnail_4999d6bb-779a-4447-a6c7-01ee94e0bcb0_annotated_true_size_900_quality_90_c6897e537a88b949e48c27df531dd71abd8fea45.jpg)
*Sagittal T2 MR shows diffusely abnormal signal intensity in the infraspinatus <img src='img/arrows/WO.png' alt='white open arrow'/> and supraspinatus muscles <img src='img/arrows/WC.png' alt='white curved arrow'/>. Differential diagnosis, in this case, includes suprascapular nerve entrapment.*
![Coronal STIR MR in an older adult patient with idiopathic right arm pain and weakness demonstrates abnormal enlargement and T2 hyperintensity of the right brachial plexus elements <img src='img/arrows/WS.png' alt='white solid arrow'/>, approaching signal intensity of the subclavian vein <img src='img/arrows/WC.png' alt='white curved arrow'/>.](images/app.statdx.com_image_thumbnail_c9af0b6d-d836-45b0-afa3-9980ed283edc_annotated_true_size_900_quality_90_6eb58f0c5269f310805fefab6b793a65f1ce50d5.jpg)
*Coronal STIR MR in an older adult patient with idiopathic right arm pain and weakness demonstrates abnormal enlargement and T2 hyperintensity of the right brachial plexus elements <img src='img/arrows/WS.png' alt='white solid arrow'/>, approaching signal intensity of the subclavian vein <img src='img/arrows/WC.png' alt='white curved arrow'/>.*
![Oblique sagittal T2 FS MR in the same patient reveals abnormal enlargement of all of the plexus elements <img src='img/arrows/WS.png' alt='white solid arrow'/> (shown at the level of the cords) with preservation of the internal fascicular architecture.](images/app.statdx.com_image_thumbnail_f07cc010-31a4-42db-8232-58e48db3f423_annotated_true_size_900_quality_90_471f62c40e1886e066395f3328bde700afb6755e.jpg)
*Oblique sagittal T2 FS MR in the same patient reveals abnormal enlargement of all of the plexus elements <img src='img/arrows/WS.png' alt='white solid arrow'/> (shown at the level of the cords) with preservation of the internal fascicular architecture.*
![Coronal STIR MR in an older adult patient with bilateral idiopathic brachial plexus neuritis shows abnormal increased signal in the bilateral plexus elements <img src='img/arrows/WS.png' alt='white solid arrow'/> approaching signal of dorsal root ganglion (DRG) in addition to acute/ongoing muscle denervation <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_626b2bff-987c-4012-8d1d-c3c3c2c15a2a_annotated_true_size_900_quality_90_18fedfa2776681a2accb23a2e41690b15e508623.jpg)
*Coronal STIR MR in an older adult patient with bilateral idiopathic brachial plexus neuritis shows abnormal increased signal in the bilateral plexus elements <img src='img/arrows/WS.png' alt='white solid arrow'/> approaching signal of dorsal root ganglion (DRG) in addition to acute/ongoing muscle denervation <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Axial T2 FS MR in the same patient shows extensive muscle denervation changes <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_567f3fa8-b354-4e17-a04f-974cce871cfb_annotated_true_size_900_quality_90_4a08b31c65517491afe8ff750d4a22974c0e4e88.jpg)
*Axial T2 FS MR in the same patient shows extensive muscle denervation changes <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Sagittal T2 MR shows severe fatty atrophy of the teres minor muscle <img src='img/arrows/WS.png' alt='white solid arrow'/> manifested in volume loss and increased signal intensity. Most cases of idiopathic brachial plexus neuritis resolve without developing such severe atrophy.](images/app.statdx.com_image_thumbnail_1ba6baaf-7131-4f06-8eac-c137148e389d_annotated_true_size_900_quality_90_50056b8eac5368b5dad4ba8c314cd865e190708c.jpg)
*Sagittal T2 MR shows severe fatty atrophy of the teres minor muscle <img src='img/arrows/WS.png' alt='white solid arrow'/> manifested in volume loss and increased signal intensity. Most cases of idiopathic brachial plexus neuritis resolve without developing such severe atrophy.*
![Coronal T1 MR in the same patient again shows marked fatty atrophy <img src='img/arrows/WS.png' alt='white solid arrow'/> limited to the teres minor. Quadrilateral space <img src='img/arrows/WO.png' alt='white open arrow'/> is normal, indicating that the atrophy is not due to compression of the axillary nerve.](images/app.statdx.com_image_thumbnail_d813d6ed-996a-46c9-8adb-7b5dd184a38d_annotated_true_size_900_quality_90_d50a0c6fa6451d927dd07ec6e9b01f37d842c498.jpg)
*Coronal T1 MR in the same patient again shows marked fatty atrophy <img src='img/arrows/WS.png' alt='white solid arrow'/> limited to the teres minor. Quadrilateral space <img src='img/arrows/WO.png' alt='white open arrow'/> is normal, indicating that the atrophy is not due to compression of the axillary nerve.*
### Additional Images
![Sagittal T2 FS MR demonstrates denervation edema of the supraspinatus <img src='img/arrows/WS.png' alt='white solid arrow'/> and infraspinatus <img src='img/arrows/WC.png' alt='white curved arrow'/> muscles. This pattern may also occur from impingement of the suprascapular nerve at the suprascapular notch.](images/app.statdx.com_image_thumbnail_3944a3c6-98a2-4e38-8c4c-84f8000f9032_annotated_true_size_900_quality_90_4935622a73961d96a4eb5a4a23955590596c40ef.jpg)
*Sagittal T2 FS MR demonstrates denervation edema of the supraspinatus <img src='img/arrows/WS.png' alt='white solid arrow'/> and infraspinatus <img src='img/arrows/WC.png' alt='white curved arrow'/> muscles. This pattern may also occur from impingement of the suprascapular nerve at the suprascapular notch.*
![Coronal T2 FS MR in the same patient confirms that the edema <img src='img/arrows/WC.png' alt='white curved arrow'/> spares a portion of the infraspinatus muscle <img src='img/arrows/WS.png' alt='white solid arrow'/>. This pattern is not seen in nerve entrapment at the spinoglenoid or suprascapular notch, which affects all of the muscles innervated distal to the entrapment.](images/app.statdx.com_image_thumbnail_3f45c617-2c6c-4b42-a5d6-2d2b398eb351_annotated_true_size_900_quality_90_28a455803d9455a6925e466b9e386a237b0dd98e.jpg)
*Coronal T2 FS MR in the same patient confirms that the edema <img src='img/arrows/WC.png' alt='white curved arrow'/> spares a portion of the infraspinatus muscle <img src='img/arrows/WS.png' alt='white solid arrow'/>. This pattern is not seen in nerve entrapment at the spinoglenoid or suprascapular notch, which affects all of the muscles innervated distal to the entrapment.*
![Sagittal T2 FS MR demonstrates increased signal intensity representing a mild case of denervation edema involving the supraspinatus <img src='img/arrows/WS.png' alt='white solid arrow'/>, infraspinatus <img src='img/arrows/WC.png' alt='white curved arrow'/>, and trapezius <img src='img/arrows/WO.png' alt='white open arrow'/> muscles.](images/app.statdx.com_image_thumbnail_c3989dab-b6a6-4295-8549-eae2c894282e_annotated_true_size_900_quality_90_107ef6cd0457f48874e30e747354ce4c65239599.jpg)
*Sagittal T2 FS MR demonstrates increased signal intensity representing a mild case of denervation edema involving the supraspinatus <img src='img/arrows/WS.png' alt='white solid arrow'/>, infraspinatus <img src='img/arrows/WC.png' alt='white curved arrow'/>, and trapezius <img src='img/arrows/WO.png' alt='white open arrow'/> muscles.*
![Axial T2 FS MR confirms hyperintense denervation edema of the supraspinatus <img src='img/arrows/WS.png' alt='white solid arrow'/> and infraspinatus <img src='img/arrows/WC.png' alt='white curved arrow'/> muscles.](images/app.statdx.com_image_thumbnail_38231fdc-e6bf-423d-a557-a0f00c279268_annotated_true_size_900_quality_90_0419bd09cfbf215ada3ab09508d853e1dda9bd62.jpg)
*Axial T2 FS MR confirms hyperintense denervation edema of the supraspinatus <img src='img/arrows/WS.png' alt='white solid arrow'/> and infraspinatus <img src='img/arrows/WC.png' alt='white curved arrow'/> muscles.*
![Coronal STIR MR shows uniform, tubular nerve enlargement <img src='img/arrows/WS.png' alt='white solid arrow'/> and increased signal intensity, which is primarily at the periphery of the nerves.](images/app.statdx.com_image_thumbnail_1f757730-4838-472f-a665-b48f17f6c66f_annotated_true_size_900_quality_90_77d66b78b421de3ae937b6836d1e28334ec0ca6b.jpg)
*Coronal STIR MR shows uniform, tubular nerve enlargement <img src='img/arrows/WS.png' alt='white solid arrow'/> and increased signal intensity, which is primarily at the periphery of the nerves.*
![Coronal T1 MR in this patient with brachial neuritis shows uniform, smooth enlargement of visualized portions of the right brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/> compared to the normal left side <img src='img/arrows/WO.png' alt='white open arrow'/>.](images/app.statdx.com_image_thumbnail_02a02636-b8cc-41b2-b031-776a0031fb4f_annotated_true_size_900_quality_90_fbbc06b39335618d1aba24c6db0a943829b58701.jpg)
*Coronal T1 MR in this patient with brachial neuritis shows uniform, smooth enlargement of visualized portions of the right brachial plexus <img src='img/arrows/WS.png' alt='white solid arrow'/> compared to the normal left side <img src='img/arrows/WO.png' alt='white open arrow'/>.*
![Axial PD/intermediate MR shows mild increase in signal intensity throughout the infraspinatus muscle <img src='img/arrows/WO.png' alt='white open arrow'/>. Deltoid is slightly higher signal than subscapularis muscle due to signal drop-off from surface coil.](images/app.statdx.com_image_thumbnail_4fc9d735-fd75-4c8e-aafc-6379eb0b7f63_annotated_true_size_900_quality_90_cbf3d996a5634c5bf3ffc67c3fc43f1a2fde5acf.jpg)
*Axial PD/intermediate MR shows mild increase in signal intensity throughout the infraspinatus muscle <img src='img/arrows/WO.png' alt='white open arrow'/>. Deltoid is slightly higher signal than subscapularis muscle due to signal drop-off from surface coil.*
![Sagittal oblique STIR MR shows abnormal signal intensity in brachial plexus <img src='img/arrows/WO.png' alt='white open arrow'/> due to idiopathic brachial neuritis.](images/app.statdx.com_image_thumbnail_53572aba-15c7-491d-8832-d6169d2bf48d_annotated_true_size_900_quality_90_bb3cf81afdfa6b84bf4acd93b8457471901fe401.jpg)
*Sagittal oblique STIR MR shows abnormal signal intensity in brachial plexus <img src='img/arrows/WO.png' alt='white open arrow'/> due to idiopathic brachial neuritis.*
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