291 lines
24 KiB
Markdown
291 lines
24 KiB
Markdown
---
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title: "Intratemporal Facial Nerve Enhancement"
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docid: "a3569ec5-a566-411d-877f-41ad832e3fd2"
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authors:
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- key: "94f835c8-fa13-4e8a-995b-53048e6b0605"
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value: "Philip R. Chapman, MD"
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breadcrumbs:
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-
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name: "Head and Neck"
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slug: "head-and-neck"
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treeNodeId: "ed24ed8c-5d57-4629-879b-447b82d2973d"
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-
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name: "Diagnosis"
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slug: "diagnosis"
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treeNodeId: "19b6b986-97d0-40e7-b317-00f0c5cd8fa2"
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-
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name: "Temporal Bone"
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slug: "temporal-bone"
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treeNodeId: "9ad7d7b2-b2e4-4de2-be04-55ce607560c9"
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-
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name: "Intratemporal Facial Nerve"
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slug: "intratemporal-facial-nerve"
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treeNodeId: "35b77f60-796d-460f-8bac-4a187a150171"
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-
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name: "Pseudolesions"
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slug: "pseudolesions"
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treeNodeId: "eb1df224-339c-469f-857b-200d08f330df"
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-
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name: "Intratemporal Facial Nerve Enhancement"
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slug: "intratemporal-facial-nerve-enhance-"
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treeNodeId: null
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category: "Head and Neck"
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cmeTopicId: "2388da47-1d41-4309-8db6-b977b488180a"
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documentVersionId: "0fdb4514-1f1b-4100-a7fd-91cff6019fde"
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imageCount: 10
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lastUpdated: "09/24/21"
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pageDescription: "Intratemporal Facial Nerve Enhancement"
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pageKeywords: "Head and Neck, Diagnosis, Temporal Bone, Intratemporal Facial Nerve, Pseudolesions, Intratemporal Facial Nerve Enhancement"
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pageTitle: "Intratemporal Facial Nerve Enhancement | STATdx"
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enhancedTitle: "Intratemporal Facial Nerve Enhancement"
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type: "DX"
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references: true
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ddx: true
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anatomy:
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- "{'authors': 'Santhosh Gaddikeri, MD; Philip R. Chapman, MD', 'bookmarked': False, 'bookmarkUrl': '/document/bookmark/98cb2d45-e64c-4295-9662-3470cd46513a', 'category': 'Head and Neck', 'compareUrl': '/compare/document/98cb2d45-e64c-4295-9662-3470cd46513a/related-anatomy/treeNode?subContext=CNVII (Facial Nerve)', 'documentId': '98cb2d45-e64c-4295-9662-3470cd46513a', 'documentType': 'ANATOMY', 'documentUrl': '/document/cnvii-facial-nerve/98cb2d45-e64c-4295-9662-3470cd46513a', 'enhancedTitle': 'CNVII (Facial Nerve)', 'entryDate': '12/06/23', 'imageCount': 39, 'imageUrl': '/image/thumbnail/1f7e56c2-da7a-4445-ac01-44eee0776f17?size=174&quality=85', 'inCompareCart': False, 'rank': 2, 'referenceCount': 0, 'showCompareButton': False, 'title': 'CNVII (Facial Nerve)'}"
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cases: 1
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breadcrumbs:
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- "Head and Neck"
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- "Diagnosis"
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- "Temporal Bone"
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- "Intratemporal Facial Nerve"
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- "Pseudolesions"
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- "Intratemporal Facial Nerve Enhancement"
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---
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# KEY FACTS
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- ## Terminology
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- **Normal** contrast enhancement (CE) along course of intratemporal facial nerve (CNVII); typically subtle, symmetric with contralateral facial nerve and without bone changes or facial nerve symptoms
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- Prominent perineural arteriovenous plexus responsible for normal enhancement
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- ## Imaging
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- T1 C+ MR enhancement along CNVII
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- Mastoid, tympanic, and geniculate ganglion segments generally show CE
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- CE variable, dependent on technique and field strength but normally symmetric bilaterally
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- Facial nerve within internal auditory canal should not enhance normally
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- ## Top Differential Diagnoses
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- Bell palsy
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- Ramsay Hunt syndrome
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- Perineural parotid tumor of intratemporal CNVII
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- Facial nerve schwannoma within temporal bone
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- Facial nerve venous malformation
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- ## Clinical Issues
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- Normal nerve enhancement **a****symptomatic** by definition
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- ## Diagnostic Checklist
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- **Asymmetric** intratemporal facial nerve CE should be viewed with suspicion
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- Correlation with facial nerve paralysis or hemifacial spasm important if abnormal CE suspected
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- Any previous history of H&N cancer should alert to possibility of perineural tumor spread
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- High-resolution T1 C+ FS MR through temporal bone should cover from brainstem through parotid glands to evaluate for facial nerve pathology
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- Bone CT complementary in evaluation to exclude underlying bony changes
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# TERMINOLOGY
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- ## Definitions
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- **Normal** contrast enhancement (CE) along course of intratemporal facial nerve (CNVII); typically mild to moderate, **symmetric** with contralateral facial nerve and without bone changes or facial nerve symptoms
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- Prominent perineural arteriovenous plexus responsible for normal enhancement
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# IMAGING
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- ## General Features
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- ### Best diagnostic clue
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- T1 C+ MR CE along CNVII geniculate ganglion, tympanic and mastoid segments without bony CNVII canal changes
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- CE variable, dependent on technique and field strength but **normally symmetric** bilaterally
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- Facial nerve within internal auditory canal (IAC) should not enhance normally
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- ## CT Findings
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- ### Bone CT
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- Normal bony intratemporal CNVII canal
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- ## MR Findings
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- ### T1WI
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- Normal CNVII can be seen as isointense signal that can appear prominent compared with surrounding low signal of adjacent osseous or pneumatized structures
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- ### T1WI C+
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- Normal CE along portions of CNVII (1.5T spin-echo CE T1)
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- Mastoid > geniculate ganglion > tympanic segments
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- Usually symmetrical side-to-side
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- MR field strength and sequence summary
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- 1.5T MR: CE of CNVII canalicular and labyrinthine segments not seen
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- 3T MR: CE of CNVII
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- Mastoid (100%), geniculate (75%), tympanic (40%)
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- Subtle enhancement can even be seen****in****canalicular (15%) and labyrinthine (5%) segments
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- Comparing CE spin-echo to CE inversion recovery-prepared fast spoiled gradient-echo (IR-FSPGR)
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- IR-FSPGR: Greater CNVII signal intensity in all segments
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- ## Imaging Recommendations
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- ### Best imaging tool
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- Normal CE seen best on 3-mm axial and coronal spin-echo T1 C+ MR at 3T
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# DIFFERENTIAL DIAGNOSIS
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- [Bell Palsy](/document/bell-palsy/0958e575-8f76-4d70-b806-0dbed9c62a67)
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- Clinical: Acute onset of unilateral peripheral CNVII paralysis
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- T1 C+ MR: Intense enhancement of intratemporal CNVII
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- "Tuft" of IAC fundal enhancement highly suggestive
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- Bone CT: CNVII bony canal normal
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- [Ramsay Hunt Syndrome](/document/ramsay-hunt-syndrome/94fd9d75-cbe7-4f01-9d36-7c54d629f5c6)
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- Reactivation of herpes zoster from geniculate ganglion
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- Typically robust enhancement of intratemporal facial nerve with typical vesicular rash of ear or soft palate
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- ## Perineural Parotid Tumor of Intratemporal CNVII
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- T1 C+ MR: Nodular, asymmetric enhancement of facial nerve usually extending from intraparotid segment into mastoid segment and beyond
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- May occur from primary parotid neoplasm or local spread of cutaneous malignancy
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- [Facial Nerve Schwannoma of Intratemporal CNVII](/document/temporal-bone-facial-nerve-schwann-/cf2bcc82-4a1b-4989-adeb-f4e82116111b)
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- Most frequently found in geniculate fossa
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- T1 C+ MR: Focal, enhancing mass along CNVII course
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- Bone CT: Enlargement of intratemporal CNVII canal
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- [Facial Nerve Venous Malformation (Hemangioma) Within Temporal Bone](/document/temporal-bone-facial-nerve-venous--/dcd6a44e-cbe6-457c-9b03-598a2b874ece)
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- Clinical: Early, unilateral CNVII paralysis
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- Most frequent location = geniculate fossa
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- T1 C+ MR: Enhancing mass enlarges geniculate fossa
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- Bone CT: Honeycomb bony changes ~ 50%
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- Irregular margins common
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# PATHOLOGY
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- ## General Features
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- Embryology/anatomy
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- CNVII plexus has 3 components
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- Anterior: From anterior tympanic branch of internal maxillary artery or middle meningeal artery
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- Middle: Tympanic plexus on medial wall of mesotympanum supplied from ascending pharyngeal artery
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- Posterior: From stylomastoid artery (from occipital artery)
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- Lush**arteriovenous plexus** surrounds CNVII within temporal bone
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- Labyrinthine segment is least well vascularized
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- ## Gross Pathologic & Surgical Features
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- Arteriovenous plexus consists of combination of relatively large arteries and veins in capillary plexus
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- ## Microscopic Features
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- Dense CNVII circumneutral arteriovenous plexus predominantly located in geniculate ganglion, tympanic and mastoid segments ± greater superficial petrosal nerve
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# CLINICAL ISSUES
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- ## Presentation
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- ### Most common signs/symptoms
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- **Asymptomatic** by definition
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- CNVII normal enhancement seen incidentally during T1 C+ MR work-up for unrelated clinical findings
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# DIAGNOSTIC CHECKLIST
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- ## Consider
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- If facial nerve is normal in size and enhancement is symmetric to corresponding contralateral facial nerve segment, probably normal
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- **Asymmetric** intratemporal facial nerve CE should be viewed with suspicion
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- Correlation with facial nerve paralysis or hemifacial spasm important if abnormal CE suspected
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- Any previous history of H&N cancer should alert to possibility of perineural tumor spread
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- Higher field strength (3T) and IR-FSPGR MR sequences make normal CNVII CE more conspicuous
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- If fundal vestibular schwannoma present, labyrinthine segment of CNVII may enhance normally
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- Arteriovenous plexus congestion is likely cause
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- Evaluation of tympanic or mastoid segments difficult if opacification, inflammation, or infection of middle ear and mastoid air cells
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- Significant CE along cisternal, labyrinthine segment or extracranial mastoid CNVII segments **not** normal
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44fba962-014f-4057-a9c3-52a2c22841ca
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## References
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# Selected References
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1. [George E et al: Facial nerve palsy: clinical practice and cognitive errors. Am J Med. 133(9):1039-44, 2020](http://www.ncbi.nlm.nih.gov/pubmed/?term=32445717%5Bpmid%5D)
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1. [Radhakrishnan R et al: Comparison of normal facial nerve enhancement at 3T MRI using gadobutrol and gadopentetate dimeglumine. Neuroradiol J. 30(6):554-60, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28696161%5Bpmid%5D)
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1. [Dehkharghani S et al: Redefining normal facial nerve enhancement: healthy subject comparison of typical enhancement patterns--unenhanced and contrast-enhanced spin-echo versus 3D inversion recovery-prepared fast spoiled gradient-echo imaging. AJR Am J Roentgenol. 202(5):1108-13, 2014](http://www.ncbi.nlm.nih.gov/pubmed/?term=24758667%5Bpmid%5D)
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1. [Hong HS et al: Enhancement pattern of the normal facial nerve at 3.0 T temporal MRI. Br J Radiol. 83(986):118-21, 2010](http://www.ncbi.nlm.nih.gov/pubmed/?term=19546177%5Bpmid%5D)
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1. [Tabuchi T et al: Vascular permeability to fluorescent substance in human cranial nerves. Ann Otol Rhinol Laryngol. 111(8):736-7, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=12184597%5Bpmid%5D)
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1. [Martin-Duverneuil N et al: Contrast enhancement of the facial nerve on MRI: normal or pathological? Neuroradiology. 39(3):207-12, 1997](http://www.ncbi.nlm.nih.gov/pubmed/?term=9106296%5Bpmid%5D)
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1. [Gebarski SS et al: Enhancement along the normal facial nerve in the facial canal: MR imaging and anatomic correlation. Radiology. 183(2):391-4, 1992](http://www.ncbi.nlm.nih.gov/pubmed/?term=1561339%5Bpmid%5D)
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## Differential diagnosis
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### Facial Nerve Lesion, Temporal Bone
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DDX:1428754b-a8ee-48a0-98f8-4faeebf8dbab
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## Anatomy
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### Facial Nerve (CNVII)
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Brain/ANATOMY:2f4818dd-6438-405b-8561-5cbbb9c91562
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### CNVII (Facial Nerve)
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Head and Neck/ANATOMY:98cb2d45-e64c-4295-9662-3470cd46513a
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## Cases
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- {'cases': [{'authors': [{'key': '624acd80-0502-4325-be71-e68fec740eb3', 'value': 'Richard H. Wiggins, III, MD, CIIP, FSIIM, FAHSE, FACR'}], 'caseVersionId': '1e34cd15-48c8-4451-b42b-14d967d90b75', 'description': 'This is a classic case of normal enhancement of the intra-temporal bone facial nerve on MR.\n\nThe right axial T1 weighted post-contrasted image (#1) shows normal enhancement at the geniculate ganglion (open arrow) and proximal tympanic segment (arrow). The coronal post-contrasted T1 weighted image (#2) also demonstrates the normal enhancement at the right geniculate ganglion (open arrow), superior to the normal cochlea (curved arrow).', 'history': None, 'imagePoolId': 'ad489f2a-935a-42a8-9c38-0fd41bfbc40a', 'name': 'Classic', 'teachingPoint': None, 'demographics': '35 Years old male'}, {'authors': [{'key': '624acd80-0502-4325-be71-e68fec740eb3', 'value': 'Richard H. Wiggins, III, MD, CIIP, FSIIM, FAHSE, FACR'}], 'caseVersionId': '32a339bf-b7cc-49ec-ae61-8c92fb74a06a', 'description': 'This is a classic case of normal enhancement along the facial nerve on MR.\n\nThe axial post-contrasted T1 weighted MRI with fat-saturation (#1) shows normal enhancement at the right geniculate ganglion (arrow).\n\nThe coronal images (#2-3) show the normal enhancement along the proximal tympanic segment (arrow, #2), superior to the cochlea (curved arrow, #2). A more posterior coronal image also show the normal tympanic segment enhancement (arrow, #3), below the lateral semicircular canal (open arrow, #3).', 'history': None, 'imagePoolId': 'be5d1b24-1eab-41b1-9c48-497b9c4667a8', 'name': 'Classic', 'teachingPoint': None, 'demographics': '44 Years old female'}, {'authors': [{'key': '624acd80-0502-4325-be71-e68fec740eb3', 'value': 'Richard H. Wiggins, III, MD, CIIP, FSIIM, FAHSE, FACR'}], 'caseVersionId': '53a809ba-0d87-4e1c-8e0a-91f32d64b307', 'description': 'This is a typical case of normal enhancement along the intratemporal facial nerve on MR.\n\nThe axial, whole brain, post-contrasted T1 weighted MR fat-saturated images (#1-5) shows normal enhancement at the geniculate ganglion on the left (arrow, #1), and the right (arrow, #2), and the proximal left tympanic segment (open arrow, #2). The magnified axial images confirm this enhancement at the right geniculate ganglion (arrow, #3), and on the left (arrow, #4), and at the left proximal tympanic segment (open arrow, #5).\n\nThe coronal post-contrasted images (#6-7) also show the normal enhancement at the left geniculate ganglion (arrow), and the proximal tympanic segment (open arrow).', 'history': None, 'imagePoolId': '07ca0ec3-ae96-4902-b30e-b3c5de01328b', 'name': 'Classic', 'teachingPoint': None, 'demographics': '68 Years old male'}, {'authors': [{'key': '624acd80-0502-4325-be71-e68fec740eb3', 'value': 'Richard H. Wiggins, III, MD, CIIP, FSIIM, FAHSE, FACR'}], 'caseVersionId': '8346972f-258e-4307-a8e2-c75c98682cbb', 'description': 'This is a classic case of normal facial nerve enhancement on MR.\n\nThis axial post-contrasted T1 weighted MRI with fat-saturation show the normal enhancement along the proximal tympanic segment (arrow). There is no enhancement seen within the internal auditory canal (open arrow).', 'history': None, 'imagePoolId': '6573d494-b008-42da-b7b7-91aa1ebb4142', 'name': 'Classic', 'teachingPoint': None, 'demographics': '74 Years old female'}, {'authors': [{'key': '624acd80-0502-4325-be71-e68fec740eb3', 'value': 'Richard H. Wiggins, III, MD, CIIP, FSIIM, FAHSE, FACR'}], 'caseVersionId': 'b5352292-4ccc-473b-892e-1c190d205953', 'description': 'This is a typical case of normal enhancement of the intratemporal facial nerve.\n\nThese axial T1 weighted post-contrasted images (#1, 2) with fat-saturation show subtle normal enhancement along the proximal tympanic segment of the left facial nerve (arrow) and the geniculate ganglion (open arrow, #1). There is no enhancement seen in the cisternal or canalicular segments of the facial nerve.', 'history': None, 'imagePoolId': '1afc0120-5710-4f04-b641-4ad3ebd006bd', 'name': 'Classic', 'teachingPoint': None, 'demographics': '59 Years old female'}], 'caseType': 'typical', 'name': 'TYPICAL'}
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## Images
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### Selected Images
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*Typical normal enhancement pattern of facial intratemporal facial nerves in a patient with vestibular schwannoma is shown. On this axial MR, the geniculate ganglia (triangular structures superolateral to the IAC) <img src='img/arrows/WS.png'/> demonstrate moderate symmetric enhancement. Right vestibular schwannoma is noted <img src='img/arrows/WC.png'/>.*
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*Typical normal enhancement pattern of facial intratemporal facial nerves in a patient with vestibular schwannoma is shown. On this axial MR, the geniculate ganglia (triangular structures superolateral to the IAC) <img src='img/arrows/WS.png'/> demonstrate moderate symmetric enhancement. Right vestibular schwannoma is noted <img src='img/arrows/WC.png'/>.*
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*Axial MR slightly lower shows mild to moderate symmetric enhancement of the tympanic portions of the facial nerves <img src='img/arrows/WS.png'/>. Aside from the vestibular schwannoma <img src='img/arrows/WC.png'/>, no IAC enhancement is identified.*
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*Axial (slightly oblique) MR in the same patient demonstrates little or no enhancement of the posterior genu <img src='img/arrows/WS.png'/> of the left facial nerve and subtle normal enhancement of the proximal mastoid segment <img src='img/arrows/WO.png'/> of the right facial nerve. The lower vestibular schwannoma <img src='img/arrows/WC.png'/> is noted.*
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*Axial MR in the same patient shows moderate, normal linear enhancement of the lower mastoid segments <img src='img/arrows/WS.png'/> of the facial nerves. Contrast enhancement of mastoid segment CNVII is usually more robust distally.*
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### Additional Images
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*Axial T1 C+ FS MR through the internal auditory canals reveals a normal geniculate ganglion <img src='img/arrows/WS.png'/> and anterior tympanic segment CNVII <img src='img/arrows/WO.png'/> enhancement on the left. On the right, normal anterior tympanic segment enhancement <img src='img/arrows/WC.png'/> is visible.*
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*Axial T1 C+ FS MR in a patient with right vestibular schwannoma demonstrates increased enhancement of the labyrinthine <img src='img/arrows/WS.png'/> CNVII, geniculate ganglion <img src='img/arrows/WO.png'/>, and anterior tympanic segment <img src='img/arrows/WC.png'/> CNVII.*
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*Coronal T1 C+ FS MR at the level of the vestibules <img src='img/arrows/WO.png'/> reveals normal enhancement of the midtympanic segment of the facial nerves <img src='img/arrows/WS.png'/>.*
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*Coronal T1 C+ FS MR in the same patient shows the normal geniculate ganglion enhancement <img src='img/arrows/WS.png'/> just superior to the cochleas <img src='img/arrows/WC.png'/>. Note that the tensor tympani muscles <img src='img/arrows/WO.png'/> both also enhance. With 3T imaging, more normal enhancement of structures within the temporal bone is seen.*
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*Axial T1 C+ MR at 3T shows prominent but normal enhancement of geniculate ganglion <img src='img/arrows/WS.png'/> as well as the anterior tympanic segment <img src='img/arrows/WO.png'/> of intratemporal CNVII.*
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*Coronal T1 C+ MR at 3T demonstrates conspicuous enhancement of the geniculate ganglion <img src='img/arrows/WS.png'/>; compare the degree of enhancement to the nonenhancing cochlea <img src='img/arrows/WO.png'/> that is seen inferiorly.*
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