308 lines
30 KiB
Markdown
308 lines
30 KiB
Markdown
---
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title: "Facial Nerve Lesion, Temporal Bone"
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docid: "1428754b-a8ee-48a0-98f8-4faeebf8dbab"
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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: "Anatomically Based Differentials"
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slug: "anatomically-based-differentials"
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treeNodeId: "115faedf-cc6e-41cd-a155-665ce5b062ee"
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-
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name: "Facial Nerve Lesion, Temporal Bone"
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slug: "facial-nerve-lesion-temporal-bone"
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treeNodeId: null
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category: "Head and Neck"
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cmeTopicId: "5d11bc10-dd61-4bcd-8c3b-ac0d32054bb1"
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documentVersionId: "61084d95-357b-49d1-8ce1-5fc8c8732500"
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imageCount: 23
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lastUpdated: "08/13/18"
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pageDescription: "Facial Nerve Lesion, Temporal Bone"
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pageKeywords: "Head and Neck, Differential Diagnosis, Temporal Bone, Anatomically Based Differentials, Facial Nerve Lesion, Temporal Bone"
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pageTitle: "Facial Nerve Lesion, Temporal Bone | STATdx"
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enhancedTitle: "Facial Nerve Lesion, Temporal Bone"
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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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- "Anatomically Based Differentials"
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- "Facial Nerve Lesion, Temporal Bone"
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---
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# ESSENTIAL INFORMATION
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- ## Key Differential Diagnosis Issues
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- Differential diagnosis considerations
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- Differential diagnosis built on lesions primary to intratemporal facial nerve
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- Other lesions included because part of lesion complex is abnormal facial nerve canal
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- Imaging recommendations for Bell palsy
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- Routine acute-onset Bell palsy **not** imaged
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- Image only "atypical" Bell palsy
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- Imaging recommendations for facial nerve lesion group
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- Temporal bone (T-bone) CT & high-resolution MR are often complementary
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- Particularly true when larger lesions are discovered with either modality
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- ## Helpful Clues for Common Diagnoses
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- **Normal Facial Nerve Enhancement**
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- Key facts
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- Asymptomatic patient
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- Normal imaging finding
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- More prominent on 3T MR
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- Imaging findings
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- Bone CT: Normal facial nerve canal
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- T1 C+ MR: Area of geniculate ganglion, anterior tympanic segment, & posterior genu of facial nerve may normally enhance
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- Symmetric enhancement typical of normal variation
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- **Bell Palsy**
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- Key facts
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- Acute onset of unilateral peripheral facial nerve paralysis
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- > 90% recover & do not need imaging
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- MR imaging for "atypical Bell palsy"
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- Imaging findings
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- T-bone CT: Normal facial nerve (CNVII) canal
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- T1 C+ MR: Intratemporal facial nerve enhances along entire course
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- T1 C+ MR other: Internal auditory canal (IAC) fundal "tuft" enhancement
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- Increasing role of 3D-FLAIR
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- 3D-FLAIR C-: Bright signal along canalicular CNVII
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- 3D-FLAIR C+: Avid enhancement of canalicular CNVII, particularly fundal "tuft"
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- High-resolution steady-state free precession T2 should **not** show mass-like nodular enlargement of CNVII
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- **Temporal Bone Fracture Involving Facial Nerve Canal**
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- Key facts
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- Fracture line crosses facial nerve canal
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- Fracture line may be difficult to see
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- Multiplanar reconstructions are essential
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- High-resolution T-bone CT is criterion standard for imaging but is imperfect tool
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- Posterior genu & mastoid segment fractures are challenging to identify on CT; easily overlooked
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- Imaging findings
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- T-bone CT: Fracture may affect geniculate ganglion, tympanic, or mastoid segment of facial nerve
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- Transverse fractures affect facial nerve more commonly than longitudinal fractures
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- **Intratemporal Facial Nerve Perineural Malignancy**
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- Key facts
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- If invasive parotid malignancy found on CT or MR, imaging of stylomastoid foramen & mastoid segment facial nerve is critical
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- Always look for perineural malignancy on intratemporal facial nerve
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- Imaging findings
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- T-bone CT: Normal to enlarged mastoid facial nerve canal ± opacification of adjacent mastoid air cells
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- T1 C+ MR: Enlarged & asymmetrically enhancing facial nerve segment(s)
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- Regardless of modality, scrutinize stylomastoid foramen & evaluate for loss of normal fat plane
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- On CT, look for soft tissue replacing normal fat density at stylomastoid foramen
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- On MR, look for loss of bright precontrast T1 signal at stylomastoid foramen
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- **Caution: Do not fat saturate precontrast T1 MR**
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- **Facial Nerve Venous Malformation ("Hemangioma")**
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- Key facts
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- May present with acute onset of peripheral facial nerve paralysis
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- May be subtle imaging finding early in disease course
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- Any focal facial nerve enhancement on MR should be investigated with T-bone CT
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- Imaging findings
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- Most common location: Geniculate fossa
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- T-bone CT: "Honeycomb" matrix (50%)
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- T1 C+ MR: Geniculate ganglion enhancing mass
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- Other MR findings: When large, spreads anteromedially along greater superficial petrosal nerve course
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- **Facial Nerve Schwannoma**
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- Key facts
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- 50% present with hearing loss
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- Facial nerve symptoms may be delayed
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- Imaging findings
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- Most common location: Geniculate fossa
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- Often affects multiple contiguous segments of intratemporal facial nerve
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- T-bone CT: Expanded, tubular facial nerve canal
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- T1 C+ MR: Enhancing mass along facial nerve
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- Intramural cystic change possible when large
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- ## Helpful Clues for Less Common Diagnoses
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- **Oval Window Atresia W****ith Ectopic Facial Nerve**
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- Key facts
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- May be seen with external auditory canal (EAC) atresia or as isolated lesion
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- Presents with conductive hearing loss with normal otoscopic exam
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- Key diagnosis to make, as facial nerve ectopia may preclude surgery
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- If ectopic CNVII not recognized on preoperative imaging, may result in iatrogenic facial nerve injury
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- Imaging findings
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- T-bone CT: Oval window narrowed with bony atresia plate covering window itself
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- Tympanic segment facial nerve moves medially from normal location under lateral semicircular canal
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- Tympanic segment may be found on superior margin, within, or on inferior margin of atresia plate
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- **External Auditory Canal Atresia W****ith Ectopic Facial Nerve**
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- Key facts
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- Severity of external ear microtia directly related to degree of EAC-middle ear malformation
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- Mastoid segment is most commonly ectopic
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- Imaging findings
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- T-bone CT: EAC is dysplastic with mastoid segment facial nerve anterior to normal location
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- Other CT findings: EAC is stenotic or absent
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- Small middle ear with ossicle fusion mass ± oval window atresia
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- ## Helpful Clues for Rare Diagnoses
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- **Prolapsing Facial Nerve I****nto Middle Ear**
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- Key facts
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- Intratemporal facial nerve bordering middle ear cavity may have variable bone covering
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- If dehiscence of facial nerve is accompanied by protrusion of nerve into middle ear, there is high risk of injury during surgery
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- Imaging findings
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- T-bone CT: Tympanic segment facial nerve dehiscent ± nerve hanging into middle ear cavity
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- Other T-bone CT findings: Facial nerve may appear slightly enlarged when not in bony canal
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- **Ramsay Hunt Syndrome**
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- Key facts
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- Herpes zoster oticus affects facial nerve ± vestibulocochlear nerve ± inner ear
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- EAC vesicles usually precede facial nerve symptoms
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- When vesicular rash is delayed or mild, clinical confusion about diagnosis may be present
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- Imaging findings
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- T-bone CT: Facial nerve canal normal
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- T1 C+ MR: Enhancing facial nerve in IAC & T-bone
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- Increasing role of 3D-FLAIR
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- Bright 3D-FLAIR C- inner ear signal & 3D-FLAIR C+ cochlear nerve enhancement more commonly seen in Ramsay Hunt than Bell Palsy
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- Enhancement of inner ear structures & cochlear nerve is more variable on T1 C+ MR
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- **Lyme Borreliosis****of Intratemporal****Facial Nerve**
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- Key facts
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- Bacteria *Borrelia* is tick-borne systemic infection
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- May cause acute facial nerve paralysis
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- Imaging findings
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- T-bone CT: Normal facial nerve canal
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- T1 C+ MR: Entire intratemporal CNVII enhances
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- IAC-CPA CNVII enhancement may also be present
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## References
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# Selected References
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1. [Chen Y et al: Reliability of temporal bone high-resolution CT in patients with facial paralysis in temporal bone fracture. Am J Otolaryngol. 39(2):150-152, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=29258690%5Bpmid%5D)
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1. [Kirsch CFE et al: Practical tips for MR imaging of perineural tumor spread. Magn Reson Imaging Clin N Am. 26(1):85-100, 2018](http://www.ncbi.nlm.nih.gov/pubmed/?term=29128008%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. [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. [Saraiya PV et al: Temporal bone fractures. Emerg Radiol. 16(4):255-65, 2009](http://www.ncbi.nlm.nih.gov/pubmed/?term=18982367%5Bpmid%5D)
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1. [Okada K et al: Benign mass lesions deep inside the temporal bone: imaging diagnosis for proper management. Acta Otolaryngol Suppl. (559):71-7, 2007](http://www.ncbi.nlm.nih.gov/pubmed/?term=18340574%5Bpmid%5D)
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1. [Chan EH et al: Facial palsy from temporal bone lesions. Ann Acad Med Singapore. 34(4):322-9, 2005](http://www.ncbi.nlm.nih.gov/pubmed/?term=15937573%5Bpmid%5D)
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1. [Kress B et al: Bell palsy: quantitative analysis of MR imaging data as a method of predicting outcome. Radiology. 230(2):504-9, 2004](http://www.ncbi.nlm.nih.gov/pubmed/?term=14699179%5Bpmid%5D)
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1. [Salzman KL et al: Dumbbell schwannomas of the internal auditory canal. AJNR Am J Neuroradiol. 22(7):1368-76, 2001](http://www.ncbi.nlm.nih.gov/pubmed/?term=11498429%5Bpmid%5D)
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1. [Caldemeyer KS et al: Imaging features and clinical significance of perineural spread or extension of head and neck tumors. Radiographics. 18(1):97-110; quiz 147, 1998](http://www.ncbi.nlm.nih.gov/pubmed/?term=9460111%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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1. [Parker GD et al: Clinical-radiologic issues in perineural tumor spread of malignant diseases of the extracranial head and neck. Radiographics. 11(3):383-99, 1991](http://www.ncbi.nlm.nih.gov/pubmed/?term=1852933%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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**Normal Facial Nerve Enhancement**
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*Axial T1 C+ FS MR shows the normal enhancement pattern of the facial nerves. Note mild symmetric enhancement of the geniculate ganglia <img src='img/arrows/WS.png'/> and anterior tympanic segments <img src='img/arrows/WO.png'/> but absent enhancement of the intracanalicular segments <img src='img/arrows/WC.png'/> bilaterally.*
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**Normal Facial Nerve Enhancement**
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*Axial T1 C+ FS MR shows the normal enhancement pattern of the facial nerves. Note mild symmetric enhancement of the geniculate ganglia <img src='img/arrows/WS.png'/> and anterior tympanic segments <img src='img/arrows/WO.png'/> but absent enhancement of the intracanalicular segments <img src='img/arrows/WC.png'/> bilaterally.*
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**Normal Facial Nerve Enhancement**
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*Axial T1 C+ MR reveals prominent but normal enhancement of the geniculate ganglion <img src='img/arrows/WS.png'/> and anterior tympanic segment of facial nerve <img src='img/arrows/WO.png'/>.*
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**Normal Facial Nerve Enhancement**
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*Axial T1 C+ MR reveals prominent but normal enhancement of the geniculate ganglion <img src='img/arrows/WS.png'/> and anterior tympanic segment of facial nerve <img src='img/arrows/WO.png'/>.*
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**Bell Palsy**
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*Axial T1 C+ FS MR in a patient with Bell palsy shows a "tuft" of enhancement at the fundus of the internal auditory canal <img src='img/arrows/WS.png'/> as well as abnormal enhancement along the labyrinthine segment <img src='img/arrows/WO.png'/> and anterior genu <img src='img/arrows/WC.png'/> of facial nerve.*
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**Bell Palsy**
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*Axial T1 C+ FS MR in a patient with Bell palsy shows a "tuft" of enhancement at the fundus of the internal auditory canal <img src='img/arrows/WS.png'/> as well as abnormal enhancement along the labyrinthine segment <img src='img/arrows/WO.png'/> and anterior genu <img src='img/arrows/WC.png'/> of facial nerve.*
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**Bell Palsy**
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*Coronal T1 C+ FS MR in a patient with Bell palsy shows a classic "tuft" of enhancement <img src='img/arrows/WS.png'/> at the fundus of the internal auditory canal above the crista falciformis <img src='img/arrows/WO.png'/>. Note additional enhancement of the tympanic segment <img src='img/arrows/WC.png'/> of facial nerve, which courses below the lateral semicircular canal.*
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**Temporal Bone Fracture Involving Facial Nerve Canal**
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*Axial bone CT shows a complex, longitudinally oriented fracture <img src='img/arrows/WS.png'/> of the right temporal bone, which traverses the anterior genu of the facial nerve canal <img src='img/arrows/WO.png'/>, resulting in ipsilateral facial paralysis. Note avulsion of the petrous ridge <img src='img/arrows/WC.png'/>.*
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**Intratemporal Facial Nerve Perineural Malignancy**
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*Coronal T1 C+ FS MR shows a small, high, intraparotid adenoid cystic carcinoma <img src='img/arrows/WC.png'/> centered just below the stylomastoid foramen <img src='img/arrows/WO.png'/>. Note avid enhancement of the mastoid segment of the facial nerve <img src='img/arrows/WS.png'/> from perineural tumor spread.*
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**Facial Nerve Venous Malformation ("Hemangioma")**
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*Axial bone CT shows a permeative expansile lesion <img src='img/arrows/WS.png'/> with a "honeycomb" matrix centered at the anterior genu of the facial nerve canal. Note extension into the widened labyrinthine <img src='img/arrows/WO.png'/> and anterior tympanic <img src='img/arrows/WC.png'/> segments of the facial nerve canal.*
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**Facial Nerve Schwannoma**
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*Axial bone CT demonstrates smooth enlargement of the geniculate fossa <img src='img/arrows/WS.png'/> and the anterior tympanic segment of the facial nerve canal <img src='img/arrows/WO.png'/>, which is typical of facial nerve schwannoma. Note that unlike a venous malformation, no internal matrix is seen.*
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**Oval Window Atresia With Ectopic Facial Nerve**
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*Axial NECT shows a medialized course of the facial nerve tympanic segment <img src='img/arrows/WS.png'/> overlying the oval window, which has a prominent bony atresia plate <img src='img/arrows/WO.png'/> abutting the facial nerve.*
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**Oval Window Atresia With Ectopic Facial Nerve**
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*Coronal bone CT in a child with a complex ear malformation shows an atresia plate at the oval window <img src='img/arrows/WS.png'/> with associated ectopic course of the facial nerve <img src='img/arrows/WO.png'/>, which is positioned more medial than usual along the atresia plate. Note additional hypoplastic lateral semicircular canal <img src='img/arrows/WC.png'/> as well as EAC atresia <img src='img/arrows/BS.png'/> with microtia.*
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**External Auditory Canal Atresia With Ectopic Facial Nerve**
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*Coronal bone CT in a child with EAC atresia shows an aberrant course of the facial nerve canal <img src='img/arrows/WS.png'/> that is positioned inferolateral to its expected course immediately beneath the lateral semicircular canal <img src='img/arrows/WO.png'/>. A BB marks the expected location of the absent auricle.*
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**Prolapsing Facial Nerve Into Middle Ear**
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*Axial bone CT shows a typical case of midtympanic segment facial nerve prolapse into the middle ear cavity <img src='img/arrows/WS.png'/>. The facial nerve is sagging into the oval window niche.*
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**Ramsay Hunt Syndrome**
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*Axial T1 C+ FS MR reveals linear internal auditory canal <img src='img/arrows/WS.png'/> and intracochlear <img src='img/arrows/WO.png'/> enhancement, in addition to prominent enhancement of the tympanic segment <img src='img/arrows/WC.png'/> of the facial nerve. The patient had external ear vesicles at the time of imaging.*
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**Lyme Borreliosis of Intratemporal Facial Nerve**
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*Axial T1WI C+ FS MR in a patient with Lyme borreliosis of facial nerve demonstrates intense enhancement of labyrinthine <img src='img/arrows/WS.png'/>, geniculate <img src='img/arrows/WO.png'/>, and anterior tympanic <img src='img/arrows/WC.png'/> segments of the left intratemporal facial nerve. Note that the IAC-CPA segment also enhances faintly.*
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### Additional Images
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**Normal Facial Nerve Enhancement**
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*Axial T1 C+ FS MR shows normal enhancement of anterior tympanic segment <img src='img/arrows/WS.png'/> and geniculate ganglion <img src='img/arrows/WO.png'/> portions of intratemporal facial nerve in this asymptomatic patient.*
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**Bell Palsy**
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*Axial T1 C+ FS MR reveals an internal auditory canal fundal "tuft" of facial nerve enhancement <img src='img/arrows/WO.png'/> along with enhancement of the labyrinthine segment <img src='img/arrows/WS.png'/> and geniculate ganglion <img src='img/arrows/WC.png'/> in this patient with Bell palsy.*
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**Bell Palsy**
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*Axial T1 C+ FS MR shows the midmastoid segment of the facial nerve enhancing avidly <img src='img/arrows/WS.png'/>. A normal mastoid segment never enhances to this degree.*
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**Temporal Bone Fracture Involving Facial Nerve Canal**
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*Axial bone CT demonstrates a transverse fracture through the inner ear. The fracture line <img src='img/arrows/WS.png'/> passes anteriorly through the labyrinthine segment of the facial nerve canal <img src='img/arrows/WO.png'/>.*
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**Facial Nerve Venous Malformation ("Hemangioma")**
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*Axial bone CT shows a C-shaped venous malformation of the labyrinthine segment <img src='img/arrows/WO.png'/> and geniculate ganglion <img src='img/arrows/WS.png'/> segments of the facial nerve. The anterior surface of the petrous apex <img src='img/arrows/WC.png'/> is also involved.*
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**Oval Window Atresia With Ectopic Facial Nerve**
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*Coronal bone CT shows a typical case of oval window atresia with aberrant facial nerve <img src='img/arrows/WS.png'/> overlying the site of the oval window. Any attempt to repair this atresia will result in injury to CNVII.*
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**Oval Window Atresia With Ectopic Facial Nerve**
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*Axial bone CT demonstrates the tympanic segment of the facial nerve <img src='img/arrows/WS.png'/> overlying the oval window, which has an atresia plate visible <img src='img/arrows/WO.png'/>.*
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**External Auditory Canal Atresia With Ectopic Facial Nerve**
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*Axial bone CT demonstrates that the mastoid segment of the facial nerve is anterior to its normal location <img src='img/arrows/WS.png'/> as a result of atresia of the EAC.*
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**Lyme Borreliosis of Intratemporal Facial Nerve**
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*Axial T1 C+ FS MR shows intense enhancement <img src='img/arrows/WS.png'/> of the tympanic segment of the facial nerve in this patient with Lyme borreliosis of intratemporal facial nerve.*
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