Imaging in Acute Facial Nerve Paralysis

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Imaging in Acute Facial Nerve Paralysis

• M Castillo, MD, FACR
• Department of Radiology
• University of North Carolina, Chapel Hill

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Overview of Presentation

• Introduction
• Review of facial nerve anatomy
• Clinical and Imaging features of Bells palsy
• Typical
• Atypical
• Other causes of acute facial paralysis

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Introduction

• Bells palsy accounts for 75 of cases of acute
  facial nerve (7th cranial nerve) paralysis
• Imaging is not needed in majority of patients
  unless they have atypical features
• W/atypical features, MR CT may demonstrate
  potentially treatable lesions affecting facial
  nerves
• Facial nerves can be affected anywhere along
  their course

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Anatomy Review

• Facial nerve nuclei lie in reticular formation of
  brainstem, ventral to floor (tegmentum) of 4th
  ventricle(4)
• Motor Nuclei
• Efferent fibers surround nuclei of CN VI form
  small mounds on floor of 4th ventricle
  
  (facial colliculi)
• Non-Motor Nuclei
• Salivatory
• Solitary

Facial colliculus
5

• Efferent fibers surround 6th CN nucleus exit at
  cerebellopontine angle (CPA)
• 7th nerve courses into internal auditory canal
  (IAC)
• Within superior anterior quadrant(6)

Ant
Post
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Fallopian Canal

• Exits IAC via Fallopian canal
• Narrowest point throughout entire course
• Felt to be culprit in facial nerve compression in
  Bells palsy other causes of nerve swelling

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Geniculate ganglion

• Progress to geniculate ganglion
• Gives rise to greater superficial petrosal nerve
• Contains taste axons from tongue somatic fibers

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• Fibers then course posteriorly under lateral
  semicircular canal in middle ear (tympanic
  portion)
• Fibers angle back inferiorly at second genu
  diving the descending canal
• Here last somatic parasympathetic fibers
  separate from facial nerve via the chorda tympani
  nerve

Mastoid segment
Tympanic Portion
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• Facial nerve exits skull base at stylomastoid
  foramen
• Facial nerve angles superiorly anteriorly
  behind posterior margin of vertical mandibular
  ramus
• Just before entering parotid gland, inferior
  branches originate
• Posterior auricular, digastric stylohyoid
• Within substance of parotid gland, superior
  branches arise
• Temporal, zygomatic, buccal, orbicularis oris,
  mandibular cervical

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Clinical Signs Suggesting Site of Facial Nerve
Lesion

• Upper facial territory is supplied by bilateral
  motor cortices
• Lower facial territory is supplied only by
  contralateral motor cortex
• Therefore, unilateral central lesions spare upper
  face
• Lesions distal to geniculate ganglion
• Mostly motor abnormalities
• Lesions proximal to geniculate ganglion
• Motor, gustatory autonomic abnormalities

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Typical Bells Palsy

• Incidence
• 1530 per 100,000
• Usually during winter
• Etiology not entirely understood
• Possibly viral (Herpes Simplex Virus) or
  idiopathic
• Viral infection of facial nerve results in
  demyelination, inflammation swelling
• Traps nerve in narrow confines of fallopian canal
• Diagnosis of exclusion
• Made only when clinical imaging (if necessary)
  findings are supportive

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Typical Bells Palsy

• Usually a clinical diagnosis
• Acute onset unilateral (lower or upper) facial
  paralysis, posterior auricular pain, decreased
  tearing, hyperacusis (30) disturbances of
  taste
• By physical examination, Bells palsy divided
  according to classification by House and Brackman
• Grades 1 2 have better outcomes with worse
  outcome as grade increases.
• 80-90 recover completely
• Over age 60, only 40 recover completely

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Imaging in Typical Bells Palsy

• Imaging in typical Bells palsy is not usually
  necessary
• When necessary, MRI is best
• Normal facial nerve distal to geniculate ganglion
  may enhance
• Facial nerve proximal to geniculate ganglion does
  not normally enhance
• In patients with Bells palsy, enhancement of
  facial nerve in fallopian ICA is typical

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C/o Dr. M. Michel, Wisconsin
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Atypical Bells Palsy

• Clinical features
• Slower onset of symptoms
• Bilateral
• Recurrence
• Numbness is not unusual
• Progression beyond seven days suggests another
  cause

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Imaging in Atypical Bells Palsy
C/o Dr. M. Michel, Wisconsin
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Alternative Causes of Acute Facial Nerve Paralysis

• Atypical signs symptoms which suggest etiology
  other than Bells palsy require imaging
• Clinical history is crucial in distinguishing
  etiologies
• Choice of imaging technique depends on clinical
  suspicion

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Lyme Disease

• Lyme disease (borreliosis)
• Endemic areas (Northeast USA, central Europe,
  Scandinavia, Canada)
• Consider in children w/atypical facial palsy
• Imaging small white matter lesions similar to
  multiple sclerosis, enhancement of facial other
  cranial nerves
• Bilateral facial paralysis 25
• Important to make diagnosis early because it is
  curable early w/antibiotics

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Ramsay Hunt Syndrome

• Caused by reactivation varicella zoster virus
  (herpes virus type 3)
• Facial paralysis hearing loss /- vertigo
• Herpes zoster oticus
• Two-thirds of patients have rash around ear
• Other cranial nerves, particularly trigeminal
  nerves (5th CN) often involved
• Worse prognosis than Bells (complete recovery
  50)
• Important cause of facial paralysis in children
• 6-15 years old

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C/o Dr. M. Michel, Wisconsin
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Infectious causes

• Acute facial paralysis may result from bacterial
  or tuberculous infection of middle ear, mastoid
  necrotizing otitis externa
• Incidence of facial paralysis with otitis media
  0.16
• Infection extends via bone dehiscences to nerve
  in fallopian canal leading to swelling,
  compression eventually vascular compromise
  ischemia
• Immune compromised patients are at risk for
  pseudomona infection
• Poor prognosis (complete recovery is lt 50)

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Tuberculosis
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Parotid peri-parotid disease
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HIV Infection
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Bezolds abscess coalescent mastoiditis
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Trauma

• Most acute post traumatic facial palsies are due
  to t-bone fractures
• Historically fractures classified as longitudinal
  or transverse with transverse carrying risk of
  permanent paralysis
• Longitudinal fracture usually leads to temporary
  paralysis from concussion swelling of nerve
• Transverse fracture can lead to transection of
  nerve
• In all types of paralysis due to fracture,
  usually the region of geniculate ganglion is
  involved

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Neoplasms

• 27 of patients with tumors involving the facial
  nerve develop acute facial paralysis
• Most common causes schwannomas, hemangiomas
  (usually near geniculate ganglion) perineural
  spread such as with head and neck carcinoma,
  lymphoma leukemia
• Other neoplasms can also involve the facial nerve
• Adults metatstatic disease, glomus tumors,
  vestibular schwannomas meningiomas
• Children eosinophilic granuloma sarcomas

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Hemangioma
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Hemangioma
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Facial Nerve Schwannoma
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Perineural Tumor Spread
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Glomus Tumor

• Glomus tumors arising from jugular bulb
  (jugulare) and/or middle ear (tympanicum) may
  involve the facial nerve

M
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Other tumors
Rhabdomyosarcoma squamous cell carcinoma of the
EAC
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Vestibular Schwannoma

• Common tumor
• However, facial nerve is resistant to compression
• Therefore, tends to produce facial paralysis
  mostly when they attain a large size

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Vestibular Schwannoma
-Common tumor -However, facial nerve is resistant
to compression, thus, tends to produce facial
paralysis mostly when they attain a large size
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Meningioma

• Second most common primary tumor of
  cerebellopontine angle
• Rarely results in facial paralysis

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Rhabdomyosarcoma
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Miscellaneous Causes
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Hypertrophic Polyneuropathy

• Hypertrophic polyneuropathies occasionally lead
  to facial paralysis

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Wegeners Granulomatosis
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Other Causes

• Guillain-Barre Syndrome
• Ascending paralysis
• Iatrogenic
• Temporal bone surgery
• Excision of vestibular schwannoma has lt10 chance
  of paralysis
• Middle ear surgeries
• Babies who required forceps delivery
• gt90 recovery

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Melkersson-Rosenthal Syndrome

• Acute episodes of facial paralysis
• Facial swelling
• Fissured tongue
• Scrotal tongue
• Very rare
• Familial but sporadic
• Usually begins in adolescence
• Leads to facial disfigurement
• No definite therapy

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Conclusion

• While Bells palsy does not typically require
  imaging for diagnosis, imaging evaluation is
  important in the work-up of patients with
  atypical or unusual presentations of acute facial
  nerve paralysis, identification of discreet
  lesions may lead to a change in management of
  these patients.