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30 KiB
Markdown
305 lines
30 KiB
Markdown
---
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title: "Hemifacial Spasm"
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docid: "1b390143-1212-4447-beb3-ed9e85ef34e4"
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authors:
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- key: "eef2f839-5706-47b9-89c3-60d8315b2b3a"
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value: "Nicholas A. Koontz, 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: "Differential Diagnosis"
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slug: "differential-diagnosis"
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treeNodeId: "40d68862-8975-4dde-ac2b-ebc43ab0fb5c"
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-
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name: "CPA-IAC and Posterior Fossa"
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slug: "cpa-iac-and-posterior-fossa"
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treeNodeId: "c590eedb-4a3b-4158-a04f-ad880564c992"
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-
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name: "Clinically Based Differentials"
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slug: "clinically-based-differentials"
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treeNodeId: "55dd15ac-e67d-48dd-8134-f52884dab28b"
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-
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name: "Hemifacial Spasm"
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slug: "hemifacial-spasm"
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treeNodeId: null
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category: "Head and Neck"
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documentVersionId: "959076b8-9c94-4244-89b0-0721f3a2387b"
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imageCount: 23
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lastUpdated: "08/15/18"
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pageDescription: "Hemifacial Spasm"
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pageKeywords: "Head and Neck, Differential Diagnosis, CPA-IAC and Posterior Fossa, Clinically Based Differentials, Hemifacial Spasm"
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pageTitle: "Hemifacial Spasm | STATdx"
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enhancedTitle: "Hemifacial Spasm"
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type: "DDX"
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references: true
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breadcrumbs:
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- "Head and Neck"
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- "Differential Diagnosis"
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- "CPA-IAC and Posterior Fossa"
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- "Clinically Based Differentials"
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- "Hemifacial Spasm"
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---
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# ESSENTIAL INFORMATION
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- ## Key Differential Diagnosis Issues
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- Overall statistics
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- In > 95% of cases, **arterial vascular loop** is cause of hemifacial spasm (HFS)
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- All other causes listed account for < 5% of cases
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- HFS
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- Definition: Segmental myoclonus of muscles of face innervated by facial nerve
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- Presentation: Patients 50-80 years old, unilateral
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- Begins around eye, spreads gradually to other facial muscles
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- Principal symptom: Rhythmic, involuntary, myoclonic facial muscle contractions
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- Pathophysiology: Irritation of facial nerve or facial nucleus
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- Vascular loop syndrome affecting CNVII (aka pimary HFS)
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- By far most common cause of HFS
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- Aberrant or ectatic vessels in cistern
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- Anterior inferior cerebellar artery (AICA) most common offending artery (40-50%)
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- Other less common causal vessels include posterior inferior cerebellar artery (PICA) (~ 30%), vertebral artery (VA) (~ 20%), or large vein (< 5%)
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- Multivessel impingement is frequent (~ 40%)
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- High-resolution MR-MRA routinely identifies compressive aberrant or ectatic arteries
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- T2 SPACE, CISS, or FIESTA sequences most commonly employed
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- Critical to recognize that vascular contact of facial nerve is very common (~ 50% of population) with only tiny minority (< 0.01 %) manifesting HFS
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- **In absence of HFS symptoms, this is incidental finding that should be ignored**
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- ## Helpful Clues for Common Diagnoses
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- **Vascular Loop Syndrome Affecting CNVII**
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- Negative high-resolution MR exam does not preclude surgery for smaller vascular loop causing HFS
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- High-resolution MR makes this situation far less common
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- Imaging findings
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- MR-MRA: Asymmetric looping artery impinges on CNVII in CPA
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- Root exit zone and attached segment (where CNVII is adherent to pons) are most sensitive to neurovascular compression
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- AICA > PICA > VA > venous, though all are possible culprits
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- ## Helpful Clues for Less Common Diagnoses
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- **Epidermoid Cyst in CPA**
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- Morphology: Assumes shape of cistern it occupies
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- Insinuating margins, encasing cranial nerves and vessels
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- Imaging findings
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- Near CSF signal intensity of epidermoid cyst makes it difficult to see on T1, T2, and FLAIR sequences
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- DWI shows reduced diffusivity
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- **Meningioma in CPA**
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- Morphology: Dural-based sessile mass
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- Imaging findings
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- Bone CT: Bony hyperostosis possible
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- MR: Enhancing mass with dural tail(s)
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- **Aneurysm in CPA****-IAC**
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- Morphology: Ovoid or fusiform shape
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- Imaging findings
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- MR: Complex lesion signal from wall calcification, clot, and flow
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- **Facial Nerve Schwannoma in CPA-IAC**
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- Morphology: CPA-IAC "ice cream on cone" mass and labyrinthine segment tail
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- Imaging findings
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- Bone CT: Labyrinthine segment CNVII enlarged
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- MR: Enhancing tubular mass with tail; may have intramural cysts
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- **Facial Nerve Schwannoma in T-Bone**
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- Morphology: Tubular mass within enlarged facial nerve canal may pedunculate into middle ear cavity (tympanic segment CNVII) or mastoid air cells (mastoid segment CNVII)
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- Imaging findings
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- Bone CT: Obvious enlargement of CNVII canal; geniculate ganglion most commonly affected
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- MR: Enhancing mass enlarges bony facial nerve canal
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- **Facial Nerve Perineural Tumor**
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- Morphology: Enlargement of intratemporal CNVII connected through stylomastoid foramen (usually from invasive parotid malignancy)
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- Imaging findings
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- Mastoid segment most common
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- CT: Soft tissue replacement of fat at stylomastoid foramen ± enlargement of bony CNVII canal
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- MR: Enhancing minimally enlarged intratemporal CNVII
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- **Facial Nerve Venous Malformation ("Hemangioma") in T-Bone**
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- Lesion of abnormal vascular morphogenesis; thus "hemangioma" is misnomer
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- Morphology: Amorphous geniculate ganglion area mass
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- Imaging findings
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- Bone CT: "Honeycomb" bone matrix (50%)
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- MR: Avidly enhancing mass with foci of low signal intensity and gradient susceptibility (calcifications)
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- ## Helpful Clues for Rare Diagnoses
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- **A****cute****Cerebral Ischemia-Infarction**
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- Acute onset of brainstem-related symptoms
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- Pontine CVA secondary to basilar artery perforator injury
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- Imaging findings
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- MR: DWI shows reduced diffusivity in pons
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- **Multiple Sclerosis**
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- HFS is rare presentation of multiple sclerosis
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- Imaging findings
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- Plaques in vicinity of facial nerve nucleus in floor of 4th ventricle may or may not be seen
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- MR: T2/FLAIR show ↑ signal intensity of supratentorial white matter plaques
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- **Arteriovenous Malformation**
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- More commonly supratentorial
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- Imaging findings
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- MR: Large ectatic arterial flow voids
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- Enhancing nidus on T1 C+ fat-saturated sequence
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- Large draining veins
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- **Arachnoid Cyst in CPA**
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- More common than epidermoid cyst in CPA, but epidermoid cyst in CPA more often associated with HFS
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- Morphology
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- Fills cistern with rounded or flat margins
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- Imaging findings
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- T1 C+: No enhancement
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- FLAIR: Follows dark CSF signal intensity
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- DWI: No reduced diffusivity
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- **Venous Malformation ("Hemangioma") in IAC**
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- Lesion of abnormal vascular morphogenesis; thus "hemangioma" is misnomer
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- Morphology: Distal intracanalicular (IAC) ovoid to round cystic mass
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- Imaging findings
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- Bone CT: Lesion with punctate calcifications
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- MR: Avidly enhancing IAC lesion with foci of low signal intensity and gradient susceptibility (calcifications)
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- ## Alternative Differential Approaches
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- Radiologist generally searches for cause of cranial neuropathy by following cranial nerve from origin to functional endplate
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- Such anatomic approach permits segmentation of potential causes into anatomic groups
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- Anatomic delineation of HFS causes
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- 3 general anatomic sites where facial nerve may be injured causing HFS
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- Intraaxial (nuclear)
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- Cisternal (CPA or IAC cistern)
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- Intratemporal (intratemporal facial nerve canal)
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- Intraaxial (nuclear)
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- [Acute cerebral ischemia-infarction](/document/acute-cerebral-ischemiainfarction/a405285f-aaea-43ca-8dc4-6f8120eaabc1)
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- [Multiple sclerosis](/document/multiple-sclerosis/7892b2a2-f52a-4d7f-9858-a326f2b7ab04)
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- [Arteriovenous malformation](/document/arteriovenous-malformation/55b35b26-df2e-4baf-8860-8073297cb738)
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- Cisternal (CPA or IAC cistern)
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- [Vascular loop syndrome affecting CNVII](/document/hemifacial-spasm/00871c72-c6c8-4913-b993-ebdb3da21947)
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- [Epidermoid cyst in CPA](/document/cpa-iac-epidermoid-cyst/5e83f596-1ca4-41cb-95aa-469147ca5f8f)
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- [Meningioma in CPA](/document/cpa-iac-meningioma/88301b77-f1c8-4efc-acf7-405999b42c3d)
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- [Aneurysm in CPA-IAC](/document/cpa-iac-aneurysm/548f4994-c72a-40b8-a94c-d96fd6c39a21)
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- [Facial nerve schwannoma in CPA-IAC](/document/cpa-iac-facial-nerve-schwannoma/9db01630-23a4-4f42-ad83-0ec399503495)
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- [Arachnoid cyst in CPA](/document/cpa-iac-arachnoid-cyst/f1af2d0f-adfd-49c7-a3b9-8a1c66dce2be)
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- [Venous malformation ("hemangioma") in IAC](/document/iac-venous-malformation/3a3d68e3-a087-4749-b13d-758c9ae8b9eb)
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- Intratemporal (intratemporal CNVII canal)
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- [Facial nerve schwannoma in T-bone](/document/temporal-bone-facial-nerve-schwann-/cf2bcc82-4a1b-4989-adeb-f4e82116111b)
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- Facial nerve perineural tumor
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- [Facial nerve venous malformation ("hemangioma") in T-bone](/document/temporal-bone-facial-nerve-venous--/dcd6a44e-cbe6-457c-9b03-598a2b874ece)
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## References
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# Selected References
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1. [Donahue JH et al: Imaging of vascular compression syndromes. Radiol Clin North Am. 55(1):123-138, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=27890181%5Bpmid%5D)
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1. [Deep NL et al: Magnetic resonance imaging assessment of vascular contact of the facial nerve in the asymptomatic patient. J Neurol Surg B Skull Base. 77(6):503-509, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=27857878%5Bpmid%5D)
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1. [Haller S et al: Imaging of neurovascular compression syndromes: trigeminal neuralgia, hemifacial spasm, vestibular paroxysmia, and glossopharyngeal neuralgia. AJNR Am J Neuroradiol. 37(8):1384-92, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26892985%5Bpmid%5D)
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1. [Öcal R et al: Comparison of brain MRI angiography and brain MRI cisternography in patients with hemifacial spasm. Acta Neurol Belg. 116(4):593-598, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26908032%5Bpmid%5D)
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1. [Ray DK et al: Surgical outcome and improvement in quality of life after microvascular decompression for hemifacial spasms: a case series assessment using a validated disease-specific scale. Stereotact Funct Neurosurg. 88(6):383-9, 2010](http://www.ncbi.nlm.nih.gov/pubmed/?term=20948243%5Bpmid%5D)
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1. [Pyen JS et al: Tic convulsif caused by cerebellopontine angle schwannoma. Yonsei Med J. 2001 Apr;42(2):255-7. Retraction in: Yonsei Med J. 49(6):1060, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=19108035%5Bpmid%5D)
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1. [Desai K et al: Cerebellopontine angle epidermoid tumor presenting with hemifacial spasms. Neurol India. 51(2):288-9, 2003](http://www.ncbi.nlm.nih.gov/pubmed/?term=14571040%5Bpmid%5D)
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1. [Iwai Y et al: Hemifacial spasm due to cerebellopontine angle meningiomas--two case reports. Neurol Med Chir (Tokyo). 41(2):87-9, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11255633%5Bpmid%5D)
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1. [Takano S et al: Facial spasm and paroxysmal tinnitus associated with an arachnoid cyst of the cerebellopontine angle--case report. Neurol Med Chir (Tokyo). 38(2):100-3, 1998](http://www.ncbi.nlm.nih.gov/pubmed/?term=9557537%5Bpmid%5D)
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1. [Illingworth RD et al: Hemifacial spasm: a prospective long-term follow up of 83 cases treated by microvascular decompression at two neurosurgical centres in the United Kingdom. J Neurol Neurosurg Psychiatry. 60(1):72-7, 1996](http://www.ncbi.nlm.nih.gov/pubmed/?term=8558156%5Bpmid%5D)
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1. [Moriuchi S et al: Hemifacial spasm due to compression of the facial nerve by vertebral artery-posterior inferior cerebellar artery aneurysm and elongated vertebral artery--case report. Neurol Med Chir (Tokyo). 36(12):884-7, 1996](http://www.ncbi.nlm.nih.gov/pubmed/?term=9002718%5Bpmid%5D)
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1. [Nagata S et al: Hemifacial spasm caused by CP angle AVM associated with ruptured aneurysm in the feeding artery--case report. Neurol Med Chir (Tokyo). 31(7):406-9, 1991](http://www.ncbi.nlm.nih.gov/pubmed/?term=1720219%5Bpmid%5D)
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## Images
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### Selected Images
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**Vascular Loop Syndrome Affecting CNVII**
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*Axial T2 FS MR in a patient with left hemifacial spasm (HFS) shows neurovascular compression of the left facial nerve <img src='img/arrows/WS.png'/> by an ectatic vertebral artery <img src='img/arrows/WO.png'/>. Note the point of neurovascular impingement <img src='img/arrows/WC.png'/> against the adjacent cerebellar flocculus <img src='img/arrows/BO.png'/>.*
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**Vascular Loop Syndrome Affecting CNVII**
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*Axial T2 FS MR in a patient with left hemifacial spasm (HFS) shows neurovascular compression of the left facial nerve <img src='img/arrows/WS.png'/> by an ectatic vertebral artery <img src='img/arrows/WO.png'/>. Note the point of neurovascular impingement <img src='img/arrows/WC.png'/> against the adjacent cerebellar flocculus <img src='img/arrows/BO.png'/>.*
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**Vascular Loop Syndrome Affecting CNVII**
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*Axial T2 FS MR in a patient with left hemifacial spasm (HFS) shows neurovascular compression of the left facial nerve <img src='img/arrows/WS.png'/> by an ectatic vertebral artery <img src='img/arrows/WO.png'/>. Note the point of neurovascular impingement <img src='img/arrows/WC.png'/> against the adjacent cerebellar flocculus <img src='img/arrows/BO.png'/>.*
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**Vascular Loop Syndrome Affecting CNVII**
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*Coronal T2 MR shows an ectatic vertebral artery <img src='img/arrows/WO.png'/> "lifting" the posterior inferior cerebellar artery into the root exit zone of the facial nerve <img src='img/arrows/WS.png'/>. Note compression of the lateral pons.*
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**Epidermoid Cyst in CPA**
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*Axial DWI MR in a patient with chronic left HFS shows a left CPA mass <img src='img/arrows/WS.png'/> with reduced diffusivity and scalloped, insinuating margins, typical of an epidermoid cyst.*
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**Meningioma in CPA**
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*Axial T1 C+ FS MR in a patient with right HFS shows an avidly enhancing mass with the configuration of "ice cream" (CPA component) <img src='img/arrows/WS.png'/> "on cone" (IAC component) <img src='img/arrows/WO.png'/>. Note enhancing dural tails <img src='img/arrows/WC.png'/>, which help differentiate this histologically-proven CPA-IAC meningioma from a schwannoma.*
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**Aneurysm in CPA-IAC**
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*Axial T2 FS MR shows a giant right vetebral artery aneurysm <img src='img/arrows/WS.png'/> with complex signal intensity. The aneurysm obliterates the pontomedullary junction at the region of the right CNVII root exit zone <img src='img/arrows/WO.png'/>. The same tortuous right vertebral artery <img src='img/arrows/WC.png'/> also effaces the left CNVII root exit zone region.*
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**Facial Nerve Schwannoma in CPA-IAC**
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*Axial SPGR C+ MR of left facial nerve schwannoma <img src='img/arrows/WS.png'/> shows an avidly enhancing CPA-IAC mass with a labyrinthine tail of enhancement <img src='img/arrows/WO.png'/> extending to the geniculate ganglion <img src='img/arrows/WC.png'/>, which differentiates it from a vestibular schwannoma.*
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**Facial Nerve Schwannoma in T-Bone**
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*Axial T1 C+ MR shows an aggressive schwannoma involving the tympanic segment <img src='img/arrows/WS.png'/>, posterior genu <img src='img/arrows/WO.png'/>, and descending mastoid segment of the right facial nerve. Note several nonenhancing intramural cysts <img src='img/arrows/WC.png'/>.*
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**Facial Nerve Perineural Tumor**
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*Coronal T1 MR shows invasive parotid space malignancy <img src='img/arrows/WS.png'/> with perineural tumor spread cephalad through the stylomastoid foramen to involve the mastoid segment of the facial nerve <img src='img/arrows/WO.png'/>.*
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**Facial Nerve Venous Malformation ("Hemangioma") in T-Bone**
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*Axial T1 C+ FS MR shows an enhancing lesion <img src='img/arrows/WS.png'/> within enlarged geniculate fossa. Note the black central dot of low signal intensity <img src='img/arrows/WO.png'/> corresponding with punctate calcification and suggesting the diagnosis of facial nerve venous malformation.*
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**Acute Cerebral Ischemia-Infarction**
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*Axial DWI MR shows an acute left pontine infarction <img src='img/arrows/WS.png'/> with reduced diffusivity. Corresponding hypointensity was present on the ADC map (not shown). Patients with brainstem infarctions may develop hemifacial spasm in the subacute to chronic phase.*
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**Multiple Sclerosis**
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*Axial T2 FS MR in patient with multiple sclerosis shows a subtle demyelinating plaque <img src='img/arrows/WS.png'/> in the left lateral pons near the root exit zone of the facial nerve <img src='img/arrows/WO.png'/>. Demyelinating lesions accounting for HFS are often subtle and may not always be seen.*
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**Arteriovenous Malformation**
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*Axial T2 MR shows a left cerebellopontine cistern arteriovenous malformation nidus <img src='img/arrows/WO.png'/> with a large posterior draining vein <img src='img/arrows/WC.png'/>.*
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**Arachnoid Cyst in CPA**
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*Axial T2 FS MR shows a right CPA arachnoid cyst <img src='img/arrows/WS.png'/>, which exerts mild mass effect upon the cisternal segments of the vestibulocochlear and facial nerves <img src='img/arrows/WO.png'/>. The cyst also flattens the lateral cerebellum. This cyst follows CSF signal intensity on all sequences.*
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**Venous Malformation ("Hemangioma") in IAC**
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*Coronal T1 C+ MR of an lAC venous malformation shows a lateral IAC enhancing mass <img src='img/arrows/WS.png'/> with focus of internal low signal intensity from punctate intralesional calcification <img src='img/arrows/WO.png'/>.*
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### Additional Images
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**Vascular Loop Syndrome Affecting CNVII**
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*Axial T2 MR shows a markedly asymmetric left vertebral artery <img src='img/arrows/WO.png'/> lifting the posterior inferior cerebellar artery <img src='img/arrows/WS.png'/> into the medial aspect of the CPA cistern in the CNVII root exit zone vicinity.*
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**Epidermoid Cyst in CPA**
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*Axial T2 MR demonstrates a right CPA cistern epidermoid cyst with penetration of the porus acusticus <img src='img/arrows/WS.png'/> and lobulated mass effect on the lateral margin of the brachium pontis <img src='img/arrows/WO.png'/>.*
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**Arachnoid Cyst in CPA**
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*Axial T2 MR through the CPA cistern reveals a CSF intensity arachnoid cyst on the left <img src='img/arrows/WS.png'/>. The arachnoid cyst flattens the cerebellar hemisphere and bows the facial and vestibulocochlear nerves <img src='img/arrows/BO.png'/> anteromedially.*
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**Epidermoid Cyst in CPA**
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*Axial T2 MR shows a right CPA cistern epidermoid cyst <img src='img/arrows/WS.png'/> scalloping the cerebellar contour and bowing the cisternal facial nerve anteriorly <img src='img/arrows/WO.png'/>. The root exit zone is also affected <img src='img/arrows/WC.png'/>.*
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**Meningioma in CPA**
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*Axial T2 MR reveals a dural-based CPA mass with IAC penetration <img src='img/arrows/WO.png'/> with a "CSF-vascular cleft" <img src='img/arrows/WS.png'/> between it and the adjacent brachium pontis-pons. Note the normal root exit zone of the contralateral left CNVII <img src='img/arrows/WC.png'/>.*
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**Aneurysm in CPA-IAC**
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*Axial T1 MR shows complex signal associated with a vertebral artery aneurysm <img src='img/arrows/WS.png'/>. The aneurysm is wedged into the medial CPA cistern in the immediate vicinity of the CNVII root exit zone.*
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**Facial Nerve Schwannoma in CPA-IAC**
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*Axial T1 C+ MR shows a small facial nerve schwannoma of the lateral IAC <img src='img/arrows/WS.png'/>, labyrinthine segment <img src='img/arrows/WO.png'/>, and geniculate ganglion <img src='img/arrows/WC.png'/> portions of the facial nerve.*
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**Facial Nerve Schwannoma in T-Bone**
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*Axial T1 C+ MR demonstrates a mastoid segment facial nerve schwannoma <img src='img/arrows/WS.png'/>. Notice that the enhancing tumor has dehisced the posterior wall of the external auditory canal <img src='img/arrows/WO.png'/>.*
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**Multiple Sclerosis**
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*Axial T2 MR shows a multiple sclerosis plaque <img src='img/arrows/WS.png'/> situated in the lateral right pons near the root exit zone of the facial nerve. Note a 2nd more subtle plaque in the left cerebellum <img src='img/arrows/WO.png'/>.*
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