407 lines
47 KiB
Markdown
407 lines
47 KiB
Markdown
---
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title: "Peripheral Facial Nerve Paralysis"
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docid: "4da52ac4-c03c-4711-ae7e-bb4f2f7c5ab8"
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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: "Temporal Bone"
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slug: "temporal-bone"
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treeNodeId: "2f7dc690-4970-486f-abb6-ed24d99b7a04"
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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: "a1829ef3-3870-48d4-81d6-2505fc8db7b8"
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-
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name: "Peripheral Facial Nerve Paralysis"
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slug: "peripheral-facial-nerve-paralysis"
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treeNodeId: null
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category: "Head and Neck"
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cmeTopicId: "e3a8ceca-c2c5-4be5-a423-e134a0965ae9"
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documentVersionId: "2701a4b6-e89a-41e8-a30f-d64d621b420f"
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imageCount: 48
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lastUpdated: "10/09/18"
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pageDescription: "Peripheral Facial Nerve Paralysis"
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pageKeywords: "Head and Neck, Differential Diagnosis, Temporal Bone, Clinically Based Differentials, Peripheral Facial Nerve Paralysis"
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pageTitle: "Peripheral Facial Nerve Paralysis | STATdx"
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enhancedTitle: "Peripheral Facial Nerve Paralysis"
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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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- "Temporal Bone"
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- "Clinically Based Differentials"
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- "Peripheral Facial Nerve Paralysis"
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---
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# ESSENTIAL INFORMATION
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- ## Key Differential Diagnosis Issues
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- Peripheral facial nerve paralysis
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- Definition: Unilateral facial nerve injury between pontine motor nucleus & proximal extracranial facial nerve trunk after it emerges from stylomastoid foramen
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- Clinical manifestation of peripheral facial nerve injury: All muscles of facial expression, including forehead muscles, are paralyzed
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- Motor: Facial expression muscles; stapedius muscles
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- Parasympathetic: Lacrimal, submandibular, & sublingual glands
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- Special sensory: Anterior 2/3 tongue taste
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- Imaging hints in searching for causes
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- **Typical** Bell palsy: Does not need imaged routinely
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- **Atypical** Bell palsy best examined by thin-section enhanced (C+) MR; increasing role of 3D-FLAIR C+
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- Subtle MR abnormalities: Imaged with T-bone CT to exclude facial nerve hemangioma
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- ## Helpful Clues for Common Diagnoses
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- **Bell Palsy**
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- Entire intratemporal facial nerve enhances on MR without mass effect
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- IAC fundal "tuft" often also present on T1 C+ MR
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- **Temporal Bone****Fractures**
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- Tympanic segment of facial nerve most vulnerable
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- **Metastases****in****CPA-IAC**
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- Poorly marginated enhancing mass in CPA-IAC ± dural enhancement
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- History of primary cancer usually known
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- Caveat: CPA-IAC mass with associated facial nerve paralysis is **not** vestibular schwannoma
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- **Pars Flaccida Acquired Cholesteatoma**
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- T-bone CT: Nondependent soft tissue in middle ear filling Prussak space with ossicle + bone erosion ± involving facial nerve canal
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- MR: Nonenhancing mass with reduced diffusivity
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- Reduced diffusivity better seen on nonecho-planar (e.g., HASTE) DWI than echo-planar DWI
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- **Acute Cerebral Ischemia-Infarction in Pons**
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- MR: Reduced diffusivity (~ 30 minutes) + increased T2/FLAIR signal (~ 6 hours)
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- ## Helpful Clues for Less Common Diagnoses
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- **Facial Nerve Perineural Tumor**
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- Parotid space malignancy ascends through stylomastoid foramen to mastoid facial nerve (CNVII)
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- **Facial Nerve Schwannoma in T-Bone**
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- Fusiform enhancing mass along CNVII canal with expansile bone margins
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- Geniculate fossa most common location
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- **Glomus Jugulare****Paraganglioma**
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- Bone CT: Permeative destructive bone changes along jugular foramen (JF) margins
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- T1 C+ MR: Enhancing JF mass with high-velocity flow voids projects superolateral through middle ear floor
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- Clinical clues: Vascular retrotympanic mass, pulsatile tinnitus
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- **Meningioma in CPA-IAC**
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- Bone CT: Underlying bone ± hyperostosis or permeative sclerosis
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- T1 C+ MR: Lobulated, enhancing CPA mass with dural base ± dural tails
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- **Congenital Cholesteatoma in Middle Ear**
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- Otoscopy: White mass behind **intact** tympanic membrane in child
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- Bone CT: Nondependent soft tissue mass often medial to ossicles
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- MR: Nonenhancing mass with reduced diffusivity
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- Reduced diffusivity better seen on nonecho-planar (e.g., HASTE) DWI than echo-planar DWI
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- **Meningioma****in****T-Bone**
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- Bone CT: Hyperostosis or permeative sclerosis of tegmen, JF margins
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- T1 C+ MR: Middle ear enhancing tumor comes from tegmen tympani, JF, or inner ear
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- **Metastasis in T-Bone**
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- Destructive T-bone mass in patient with known cancer
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- **Multiple Sclerosi****s****in Brainstem**
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- Young adult with predominantly supratentorial white matter disease
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- Pontine plaques may or may not be visible in setting of facial nerve paralysis
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- ## Helpful Clues for Rare Diagnoses
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- **Adenoid Cystic Carcinoma****in****Parotid**
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- Flame-shaped enhancing parotid space invasive mass
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- Tumor replaces normal fat in stylomastoid foramen
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- **Mucoepidermoid Carcinoma in****Parotid**
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- Ovoid invasive parotid space mass usually with complex matrix
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- **Facial Nerve Venous Malformation ("Hemangioma")**
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- Bone CT: Poorly marginated mass in geniculate fossa with “honeycomb” matrix (50%)
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- T1 C+ MR: Lesion enhances avidly
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- Geniculate fossa most common location
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- **Cavernous Malformation in Pons**
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- CT: Pontine lesion with "popcorn" calcifications
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- MR: Pontine lesion with complex signal from blood products & calcifications ± nearby DVA
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- **Ramsay Hunt Syndrome**
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- Herpes zoster oticus affects facial nerve ± vestibulocochlear nerve ± inner ear
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- External auditory canal vesicles usually precede facial nerve symptoms
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- T1 C+ MR: Enhancing facial nerve in IAC & temporal bone
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- Other MR findings: Enhancement of inner ear structures & vestibulocochlear nerve variable; increasing role of 3D-FLAIR C+ to differentiate from Bell palsy
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- 3D-FLAIR C+ enhancement of CNVIII, IAC wall, & inner ear more typical of Ramsay Hunt than Bell palsy
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- **Sarcoidosis****in****CPA-IAC**
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- MR: Dural-based enhancing "meningioma mimic" that may track along cistern-IAC CNVII
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- **Langerhans Histiocytosis****in****T-Bone**
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- Expansile punched-out T-bone lytic lesion in child
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- **Rhabdomyosarcoma in T-bone**
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- Destructive lesion of T-bone in child
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- Often centered in middle ear
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- **F****acial Nerve****Schwannoma in CPA-IAC**
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- CPA-IAC enhancing "vestibular schwannoma mimic"
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- Diagnosis can be made if schwannoma projects into labyrinthine segment of CNVII
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- Looks like "labyrinthine tail" projecting off IAC fundus
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- ## Alternative Differential Approaches
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- Organize by **anatomic segment of CNVII**
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- Divide facial nerve into its discrete segments
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- **Intramedullary**: 3 nuclei (1 motor & 2 sensory) tracts; motor fibers circle CNVI nucleus to create facial colliculus in floor of 4th ventricle
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- **CPA-IAC cistern**: Root exit zone of lateral brainstem to fundus of IAC
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- **Intratemporal**: Labyrinthine, tympanic, & mastoid intratemporal CNVII
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- **Extracranial**: Stylomastoid foramen to functional terminal segment of CNVII
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- By looking at CNVII injury from this vantage point, you create method for designing your imaging protocol
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- Scanning protocol must include pons, CPA-IAC cistern, T-bone, & parotid space
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- Segmental anatomic approach to CNVII paralysis DDx
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- **Intramedullary lesions**
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- [Cavernous malformation in pons](/document/cavernous-malformation/d6c0dfc6-25d3-4713-941f-373c68ca8f0d)
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- [Multiple sclerosis in brainstem](/document/multiple-sclerosis/7892b2a2-f52a-4d7f-9858-a326f2b7ab04)
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- [Acute cerebral ischemia-infarction in pons](/document/acute-cerebral-ischemiainfarction/a405285f-aaea-43ca-8dc4-6f8120eaabc1)
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- **CPA-IAC lesions**
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- [Metastases in CPA-IAC](/document/cpa-iac-metastases/451451c8-7b49-4ce9-bf22-7c02b4652f23)
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- [Meningioma in CPA-IAC](/document/cpa-iac-meningioma/88301b77-f1c8-4efc-acf7-405999b42c3d)
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- [Sarcoidosis in CPA-IAC](/document/cpa-iac-neurosarcoid/2fdac517-7385-4bfd-92fc-a3445502675b)
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- [Ramsay Hunt syndrome](/document/ramsay-hunt-syndrome/94fd9d75-cbe7-4f01-9d36-7c54d629f5c6)
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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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- **T-bone lesions**
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- [Bell palsy](/document/bell-palsy/0958e575-8f76-4d70-b806-0dbed9c62a67)
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- [Temporal bone fractures](/document/temporal-bone-fractures/12b6bafb-6bd8-498b-87b9-f4bb8222da57)
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- [Pars flaccida acquired cholesteatoma](/document/pars-flaccida-cholesteatoma/cf2c20e7-2417-4373-b771-ed3f65a793b4)
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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 venous malformation in T-bone](/document/temporal-bone-facial-nerve-venous--/dcd6a44e-cbe6-457c-9b03-598a2b874ece)
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- Glomus jugulare paraganglioma
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- [Congenital cholesteatoma in middle ear](/document/congenital-middle-ear-cholesteatoma/5990c663-ca85-4177-9109-aed6949fc115)
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- [Meningioma in T-bone](/document/temporal-bone-meningioma/959c8ccf-fe4f-405a-97fd-ba9fe822c8c7)
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- Metastasis in T-bone
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- [Langerhans histiocytosis in T-bone](/document/temporal-bone-langerhans-cell-hist-/e8ad8ade-9299-471b-9ef1-d381c1ed20c4)
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- [Rhabdomyosarcoma in T-bone](/document/temporal-bone-rhabdomyosarcoma/f1f41d58-2289-4d55-b398-95fd00f7babe)
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- **Parotid lesions**
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- Facial nerve perineural tumor
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- [Adenoid cystic carcinoma](/document/parotid-adenoid-cystic-carcinoma/8571ae8a-0aae-432d-977c-1bab4f8888e9)
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- [Mucoepidermoid carcinoma](/document/parotid-mucoepidermoid-carcinoma/74ed7ee4-5869-49f5-a28e-638a04849ce8)
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## References
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# Selected References
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1. [Jindal G et al: Imaging evaluation and treatment of vascular lesions at the skull base. Radiol Clin North Am. 55(1):151-166, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=27890183%5Bpmid%5D)
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1. [Kuya J et al: Usefulness of high-resolution 3D multi-sequences for peripheral facial palsy: differentiation between Bell's palsy and Ramsay Hunt syndrome. Otol Neurotol. 38(10):1523-1527, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=29135869%5Bpmid%5D)
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1. [Lingam RK et al: A meta-analysis on the diagnostic performance of non-echoplanar diffusion-weighted imaging in detecting middle ear cholesteatoma: 10 years on. Otol Neurotol. 38(4):521-528, 2017](http://www.ncbi.nlm.nih.gov/pubmed/?term=28195998%5Bpmid%5D)
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1. [Chevallier KM et al: Differentiating pediatric rhabdomyosarcoma and Langerhans cell histiocytosis of the temporal bone by imaging appearance. AJNR Am J Neuroradiol. 37(6):1185-9, 2016](http://www.ncbi.nlm.nih.gov/pubmed/?term=26869468%5Bpmid%5D)
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1. [Chung MS et al: The clinical significance of findings obtained on 3D-FLAIR MR imaging in patients with Ramsay-Hunt syndrome. Laryngoscope. 125(4):950-5, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25346250%5Bpmid%5D)
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1. [Gamss C et al: Imaging evaluation of the suprahyoid neck. Radiol Clin North Am. 53(1):133-44, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=25476177%5Bpmid%5D)
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1. [Ho ML et al: Anatomy and pathology of the facial nerve. AJR Am J Roentgenol. 204(6):W612-9, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=26001250%5Bpmid%5D)
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1. [Singh AK et al: Imaging spectrum of facial nerve lesions. Curr Probl Diagn Radiol. 44(1):60-75, 2015](http://www.ncbi.nlm.nih.gov/pubmed/?term=24975082%5Bpmid%5D)
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1. [McRackan TR et al: Facial nerve outcomes in facial nerve schwannomas. Otol Neurotol. 2012 Jan;33(1):78-82. Erratum in: Otol Neurotol. 33(3):472, 2012](http://www.ncbi.nlm.nih.gov/pubmed/?term=22143290%5Bpmid%5D)
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1. [Magliulo G et al: Facial nerve dehiscence and cholesteatoma. Ann Otol Rhinol Laryngol. 120(4):261-7, 2011](http://www.ncbi.nlm.nih.gov/pubmed/?term=21585157%5Bpmid%5D)
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1. [Benoit MM et al: Facial nerve hemangiomas: vascular tumors or malformations? Otolaryngol Head Neck Surg. 142(1):108-14, 2010](http://www.ncbi.nlm.nih.gov/pubmed/?term=20096233%5Bpmid%5D)
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1. [Nakata S et al: 3D-FLAIR MRI in facial nerve paralysis with and without audio-vestibular disorder. Acta Otolaryngol. 130(5):632-6, 2010](http://www.ncbi.nlm.nih.gov/pubmed/?term=19916898%5Bpmid%5D)
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1. [Finsterer J: Management of peripheral facial nerve palsy. Eur Arch Otorhinolaryngol. 265(7):743-52, 2008](http://www.ncbi.nlm.nih.gov/pubmed/?term=18368417%5Bpmid%5D)
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1. [Moody MW et al: Incidence of dehiscence of the facial nerve in 416 cases of cholesteatoma. Otol Neurotol. 28(3):400-4, 2007](http://www.ncbi.nlm.nih.gov/pubmed/?term=17159491%5Bpmid%5D)
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1. [Quaranta N et al: Facial paralysis associated with cholesteatoma: a review of 13 cases. Otol Neurotol. 28(3):405-7, 2007](http://www.ncbi.nlm.nih.gov/pubmed/?term=17414046%5Bpmid%5D)
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1. [Critchley EP: Multiple sclerosis initially presenting as facial palsy. Aviat Space Environ Med. 75(11):1001-4, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=15559004%5Bpmid%5D)
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1. [Park SU et al: The usefulness of MR imaging of the temporal bone in the evaluation of patients with facial and audiovestibular dysfunction. Korean J Radiol. 3(1):16-23, 2002](http://www.ncbi.nlm.nih.gov/pubmed/?term=11919474%5Bpmid%5D)
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1. [Martin N et al: Haemangioma of the petrous bone: MRI. Neuroradiology. 34(5):420-2, 1992](http://www.ncbi.nlm.nih.gov/pubmed/?term=1407526%5Bpmid%5D)
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1. [Curtin HD et al: "Ossifying" hemangiomas of the temporal bone: evaluation with CT. Radiology. 164(3):831-5, 1987](http://www.ncbi.nlm.nih.gov/pubmed/?term=3112865%5Bpmid%5D)
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## Images
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### Selected Images
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**Bell Palsy**
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*Axial T1 C+ FS MR in a patient with Bell palsy shows the classic faint, tuft-like enhancement at the fundus of the IAC <img src='img/arrows/WS.png'/>, which extends as a linear enhancement along the labyrinthine segment <img src='img/arrows/WO.png'/>, anterior genu <img src='img/arrows/WC.png'/>, and anterior tympanic <img src='img/arrows/BS.png'/> segments of the facial nerve.*
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**Bell Palsy**
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*Axial T1 C+ FS MR in a patient with Bell palsy shows the classic faint, tuft-like enhancement at the fundus of the IAC <img src='img/arrows/WS.png'/>, which extends as a linear enhancement along the labyrinthine segment <img src='img/arrows/WO.png'/>, anterior genu <img src='img/arrows/WC.png'/>, and anterior tympanic <img src='img/arrows/BS.png'/> segments of the facial nerve.*
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**Bell Palsy**
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*Coronal T1 C+ FS MR shows a classic "tuft" of enhancement at the superior fundus of the IAC <img src='img/arrows/WS.png'/> as well as along the tympanic segment <img src='img/arrows/WO.png'/> of the facial nerve in a patient with Bell palsy.*
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**Temporal Bone Fractures**
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*Axial NECT shows a complex temporal bone fracture with a longitudinal component <img src='img/arrows/WS.png'/> traversing the anterior genu <img src='img/arrows/WO.png'/> of the facial nerve canal and resulting in facial nerve injury. Note a large distracted fragment of the anterior petrous ridge <img src='img/arrows/WC.png'/> and temporal squamosal fracture component <img src='img/arrows/BS.png'/>.*
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**Temporal Bone Fractures**
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*Axial NECT shows a complex T-bone fracture with transverse component <img src='img/arrows/WS.png'/> violating the anterior genu <img src='img/arrows/WO.png'/> and anterior tympanic <img src='img/arrows/WC.png'/> segments of the CNVII canal.*
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**Metastases in CPA-IAC**
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*Axial T1 C+ MR in a patient with breast cancer & progressive facial weakness shows enhancement along CNVII & CNVIII within the right IAC <img src='img/arrows/WS.png'/> due to leptomeningeal metastatic disease. Additional enhancing focus is present at the left IAC fundus <img src='img/arrows/WO.png'/>.*
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**Metastases in CPA-IAC**
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*Axial FLAIR C+ MR in a melanoma patient presenting with progressive facial weakness, vestibular symptoms, & hearing loss shows avid enhancement in IAC <img src='img/arrows/WS.png'/> & cochlea bilaterally <img src='img/arrows/WO.png'/> at left trigeminal cave <img src='img/arrows/WC.png'/> due to florid leptomeningeal metastatic disease.*
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**Pars Flaccida Acquired Cholesteatoma**
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*Axial NECT in a patient with cholesteatoma post mastoidectomy and new facial weakness shows a large soft tissue mass <img src='img/arrows/WS.png'/> within the mastoidectomy bowl corresponding to recurrent cholesteatoma, which has eroded into the descending mastoid segment <img src='img/arrows/WO.png'/> of the CNVII canal.*
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**Pars Flaccida Acquired Cholesteatoma**
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*Coronal nonecho-planar (HASTE) DWI in a patient with pars flaccida cholesteatoma shows a markedly hyperintense mass <img src='img/arrows/WS.png'/> in the right middle ear. Cholesteatomas characteristically show reduced diffusivity on DWI.*
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**Acute Cerebral Ischemia-Infarction in Pons**
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*Axial T2 MR demonstrates a subacute lateral pontine infarction <img src='img/arrows/WS.png'/> on the right. This patient presented with acute onset of right facial nerve paralysis and facial numbness.*
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**Facial Nerve Perineural Tumor**
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*Axial T1 C+ FS MR demonstrates adenoid cystic carcinoma spreading along a branch of the extracranial facial nerve <img src='img/arrows/WS.png'/>. In cases where antegrade perineural tumor spreads from the parotid distally along CNVII, peripheral facial nerve paralysis may be only partial.*
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**Facial Nerve Schwannoma in T-Bone**
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*Axial NECT in a patient with CNVII schwannoma shows a soft tissue middle ear mass <img src='img/arrows/WS.png'/> extending eccentrically from tympanic segment <img src='img/arrows/WO.png'/> of CNVII. Widening of the CNVII canal at the posterior genu <img src='img/arrows/WC.png'/> was a helpful feature in recognizing the CNVII origin of this lesion.*
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**Glomus Jugulare Paraganglioma**
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*Axial NECT shows a permeative-destructive lesion of the left jugular foramen <img src='img/arrows/WS.png'/>, typical of a glomus jugulare. Facial weakness was due to invasion of the descending mastoid segment of CNVII <img src='img/arrows/WO.png'/>. Note normal appearance of right jugular foramen <img src='img/arrows/WC.png'/>.*
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**Meningioma in CPA-IAC**
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*Axial T1 C+ FS MR shows an avidly enhancing extraaxial mass <img src='img/arrows/WS.png'/> centered in the CPA but extending into the IAC <img src='img/arrows/WO.png'/>. Note the prominent dural tails <img src='img/arrows/WC.png'/> of enhancement, characteristic of meningioma.*
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**Congenital Cholesteatoma in Middle Ear**
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*Coronal bone CT shows a large congenital cholesteatoma of the middle ear that has eroded the lateral bony wall of the anterior tympanic segment of the facial nerve canal <img src='img/arrows/WS.png'/> as well as the ossicles. This child presented with a middle ear mass behind the intact tympanic membrane and CNVII paresis.*
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**Meningioma in T-Bone**
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*Axial T1 C+ FS MR shows an enhancing extraaxial mass <img src='img/arrows/WS.png'/> with dural tail <img src='img/arrows/WO.png'/>, intraosseous extension, and hyperostosis <img src='img/arrows/WC.png'/> consistent with aggressive meningioma that obliterates the CPA. Note schwannomas of left CNV <img src='img/arrows/BS.png'/> and right IAC <img src='img/arrows/BO.png'/> in this NF2 patient.*
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**Metastasis in T-Bone**
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*Axial T1 C+ MR shows a large left T-bone mass <img src='img/arrows/WS.png'/> obliterating the middle ear, including the expected course of CNVII <img src='img/arrows/WO.png'/>. Note a similar-appearing but smaller mass in the right occipital bone <img src='img/arrows/WC.png'/>. Multiplicity is a helpful clue to metastatic disease, in this case, from neuroblastoma.*
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**Multiple Sclerosis in Brainstem**
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*Axial FLAIR MR demonstrates a large pontine multiple sclerosis plaque <img src='img/arrows/WS.png'/> in this patient with florid supratentorial white matter disease (not shown).*
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**Adenoid Cystic Carcinoma in Parotid**
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*Axial T1 MR in a patient with adenoid cystic carcinoma of the parotid shows an irregular-shaped, infiltrative mass replacing the deep lobe of the parotid <img src='img/arrows/WS.png'/> and extending through the stylomandibular tunnel into the superficial parotid <img src='img/arrows/WO.png'/>, obliterating the plane of the facial nerve.*
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**Mucoepidermoid Carcinoma in Parotid**
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*Axial T2 FS MR shows an infiltrating, ill-defined mass spanning deep & superficial lobes of parotid gland, obliterating plane of CNVII. Note T2-bright mucous cystic regions <img src='img/arrows/WS.png'/> as well as areas of dark T2 signal intensity <img src='img/arrows/WO.png'/> from high cellularity portions of the tumor.*
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**Facial Nerve Venous Malformation (Hemangioma)**
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*Axial NECT in a patient with CNVII venous malformation shows a permeative expansile lesion centered at geniculate fossa <img src='img/arrows/WS.png'/> that widens labyrinthine segment <img src='img/arrows/WO.png'/> of CNVII canal. Note the characteristic "honeycomb" matrix within the lesion.*
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**Cavernous Malformation in Pons**
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*Coronal T2* GRE MR reveals a "blooming" cavernous malformation in the left pons <img src='img/arrows/WS.png'/>. T1 images (not shown) showed hyperintense foci of methemoglobin, consistent with prior hemorrhage.*
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**Ramsay Hunt Syndrome**
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*Axial T1 C+ MR in Ramsay Hunt syndrome shows enhancement along the IAC <img src='img/arrows/WS.png'/> and intratemporal facial nerve <img src='img/arrows/WO.png'/>. A compelling clinical history is helpful, as distinguishing from Bell palsy on imaging alone is challenging. 3D-FLAIR C+ has shown promise in this regard.*
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**Sarcoidosis in CPA-IAC**
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*Axial T1 C+ FS MR reveals sarcoid affecting the 7th and 8th CNs in the IAC <img src='img/arrows/WS.png'/>. Notice that the tympanic segment of the facial nerve is also avidly enhancing <img src='img/arrows/WO.png'/>.*
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**Langerhans Histiocytosis in T-Bone**
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*Axial T1 C+ FS MR in a child with Langerhans histiocytosis shows a destructive middle ear/mastoid mass <img src='img/arrows/WS.png'/> with ossicular encasement <img src='img/arrows/WO.png'/> and encroachment of the CNVII tympanic segment <img src='img/arrows/WC.png'/>. Note aggressive periosteal reaction <img src='img/arrows/BS.png'/> not commonly seen with Langerhans calvarial lesions.*
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**Rhabdomyosarcoma in T-Bone**
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*Coronal T1 C+ FS MR shows transspatial mass of middle ear <img src='img/arrows/WS.png'/>, external auditory canal <img src='img/arrows/WO.png'/>, & infratemporal fossa <img src='img/arrows/WC.png'/>. Note obliteration of the tympanic segment of CNVII <img src='img/arrows/BS.png'/>. Histology revealed rhabdomyosarcoma.*
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**Facial Nerve Schwannoma in CPA-IAC**
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*Axial T2 MR shows a CPA mass <img src='img/arrows/WS.png'/> extending along posterior IAC <img src='img/arrows/WO.png'/> into CNVII labyrinthine segment <img src='img/arrows/WC.png'/>. While CNVII lives anteriorly in IAC, close attention shows a near-CSF signal-associated arachnoid cyst <img src='img/arrows/BS.png'/> displacing CNVII schwannoma posteriorly. Note CSF <img src='img/arrows/BO.png'/> is slightly brighter.*
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### Additional Images
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**Bell Palsy**
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*Axial T1 C+ FS MR shows a "tuft" sign <img src='img/arrows/WS.png'/> in this patient with acute onset of left peripheral CNVII paralysis. The enhancing fundal portion of the IAC CNVII often has this diffuse, less linear appearance.*
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**Bell Palsy**
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*Axial T1 C+ FS MR demonstrates enhancement of the labyrinthine <img src='img/arrows/WO.png'/> and tympanic <img src='img/arrows/WS.png'/> segments of the intratemporal facial nerve. Mastoid segment enhancement was also present (not shown).*
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**Bell Palsy**
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*Coronal T1 C+ FS MR demonstrates avid enhancement of the mastoid segment of the facial nerve <img src='img/arrows/WS.png'/> and the proximal extracranial segment in the stylomastoid foramen <img src='img/arrows/WO.png'/> in this patient with typical acute onset Bell palsy.*
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**Temporal Bone Fractures**
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*Axial bone CT shows healing bone fragments in the lateral geniculate fossa <img src='img/arrows/WS.png'/>. This patient suffered temporal bone fracture with persistent facial nerve paralysis 6 weeks before this CT.*
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**Temporal Bone Fractures**
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*Sagittal bone CT demonstrates disrupted ossicles in the attic <img src='img/arrows/WO.png'/> and healing bone in the lateral roof of the geniculate fossa <img src='img/arrows/WS.png'/>. Six weeks after temporal bone fracture, persistent conductive hearing loss and facial nerve paralysis were still present.*
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**Metastases in CPA-IAC**
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*Axial T1 C+ MR shows breast carcinoma metastases in both IACs <img src='img/arrows/WS.png'/>. This type of linear enhancement is seen when the metastasis is in the pia-arachnoid of CNVII and CNVIII.*
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**Metastases in CPA-IAC**
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*Axial T2WI MR reveals bilateral IAC breast carcinoma metastases <img src='img/arrows/WS.png'/> thickening the facial and vestibulocochlear nerve bundles. Pia-arachnoid metastasis has a floating in CSF appearance.*
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**Pars Flaccida Acquired Cholesteatoma**
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*Axial bone CT demonstrates an epitympanic cholesteatoma that has eroded the anterior superior wall of the attic, shaved off the anterior head of the malleus <img src='img/arrows/WO.png'/>, and dehisced the lateral bony wall of the anterior tympanic segment of the facial nerve canal <img src='img/arrows/WS.png'/>.*
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**Pars Flaccida Acquired Cholesteatoma**
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*Sagittal bone CT shows an anterior middle ear cholesteatoma that has both eroded the tegmen tympani <img src='img/arrows/WO.png'/> and dehisced the lateral bony wall of the geniculate fossa <img src='img/arrows/WS.png'/>.*
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**Facial Nerve Schwannoma in T-Bone**
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*Axial T1 C+ FS MR in a patient with facial nerve schwannoma shows an avidly enhancing middle ear mass <img src='img/arrows/WS.png'/> growing along the expected course of the tympanic segment <img src='img/arrows/WO.png'/> of the facial nerve.*
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**Facial Nerve Schwannoma in T-Bone**
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*Coronal T1 C+ FS MR in a patient with facial nerve schwannoma shows an avidly enhancing middle ear mass <img src='img/arrows/WS.png'/> growing below the level of the lateral semicircular canal, which is the typical course of the tympanic segment of the facial nerve <img src='img/arrows/WO.png'/>. Note the eccentric growth pattern relative to the nerve of origin, typical of schwannomas.*
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**Facial Nerve Schwannoma in T-Bone**
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*Axial bone CT shows smooth enlargement of the geniculate fossa <img src='img/arrows/WO.png'/> by a facial nerve schwannoma. T1-enhanced MR (not shown) revealed enhancing tissue within the enlarged geniculate fossa.*
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**Glomus Jugulare Paraganglioma**
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*Coronal T1 C+ FS MR shows a glomus jugulare paraganglioma filling the jugular foramen <img src='img/arrows/WO.png'/> and spreading superolaterally through the middle ear floor to involve the tympanic segment of CNVII <img src='img/arrows/WS.png'/>.*
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**Meningioma in CPA-IAC**
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*Axial T2 FS MR reveals a lobulated dural-based meningioma with a CSF vascular cleft <img src='img/arrows/WS.png'/> and asymmetric relationship to the porus acusticus <img src='img/arrows/WO.png'/>.*
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**Meningioma in T-Bone**
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*Axial bone CT reveals the permeative-sclerotic bone changes of an anterior tegmen tympani meningioma <img src='img/arrows/WS.png'/>. Notice that the lateral wall of the anterior tympanic segment of the facial nerve canal is affected by the meningioma <img src='img/arrows/WO.png'/>.*
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**Metastasis in T-Bone**
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*Axial bone CT shows a large floor of middle cranial fossa destructive metastasis eroding the anterior wall of the middle ear cavity <img src='img/arrows/WO.png'/> and invading the geniculate fossa <img src='img/arrows/BS.png'/>. This patient with known colon cancer presented with acute onset of facial nerve paralysis.*
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**Adenoid Cystic Carcinoma in Parotid**
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*Axial CECT shows a poorly marginated adenoid cystic carcinoma <img src='img/arrows/WS.png'/> of the parotid gland with deep invasion toward the stylomastoid foramen and proximal extracranial facial nerve <img src='img/arrows/WO.png'/>.*
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**Mucoepidermoid Carcinoma in Parotid**
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*Axial T1 C+ FS MR shows an aggressive-appearing enhancing left parotid mucoepidermoid carcinoma that involves both the superficial <img src='img/arrows/WS.png'/> and the deep <img src='img/arrows/WO.png'/> lobes. Note the spread into the lower portion of the stylomastoid foramen <img src='img/arrows/WC.png'/>.*
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**Facial Nerve Venous Malformation (Hemangioma)**
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*Axial bone CT reveals a venous malformation enlarging the geniculate fossa <img src='img/arrows/WS.png'/>. Note the central tumor matrix calcifications.*
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**Langerhans Histiocytosis in T-Bone**
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*Axial bone CT demonstrates a lesion of the right temporal bone eroding the bones of the petrous apex <img src='img/arrows/WS.png'/> and middle ear <img src='img/arrows/WO.png'/>. The lateral wall of the middle ear/mastoid is absent <img src='img/arrows/WC.png'/> with periauricular soft tissue mass visible.*
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**Rhabdomyosarcoma in T-Bone**
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*Axial T1 C+ FS MR shows a very large skull base <img src='img/arrows/WS.png'/> and temporal bone <img src='img/arrows/WO.png'/> rhabdomyosarcoma. The inner ear bony otic capsule appears to be "floating" in the tumor <img src='img/arrows/WC.png'/>.*
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**Facial Nerve Schwannoma in CPA-IAC**
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*Axial T1 C+ MR shows an enhancing tumor of the CPA <img src='img/arrows/WS.png'/> and IAC <img src='img/arrows/WO.png'/>. This tumor can be correctly identified as a facial nerve schwannoma because of the "labyrinthine tail" of enhancement of the facial nerve <img src='img/arrows/WC.png'/>.*
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