Imaging in Imaging in Acute Facial Nerve ParalysisAcute Facial Nerve Paralysis

M Castillo, MD, FACR

Department of Radiology

University of North Carolina, Chapel Hill

Overview of PresentationOverview of Presentation

• Introduction• Review of facial nerve anatomy• Clinical and Imaging features of Bell’s

palsy– Typical – Atypical

• Other causes of acute facial paralysis

IntroductionIntroduction

• Bell’s 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

Anatomy ReviewAnatomy 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

• 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

• Exits IAC via Fallopian canal– Narrowest point

throughout entire course – Felt to be culprit in facial

nerve compression in Bell’s palsy & other causes of nerve swelling

Fallopian Canal

• Progress to geniculate ganglion– Gives rise to greater

superficial petrosal nerve

• Contains taste axons from tongue & somatic fibers

Geniculate ganglion

• 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

Tympanic Portion

Mastoid segment

• 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

Clinical Signs Suggesting Site of Clinical Signs Suggesting Site of Facial Nerve LesionFacial 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

Typical Bell’s PalsyTypical Bell’s Palsy

• Incidence – 15–30 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

Typical Bell’s PalsyTypical Bell’s 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, Bell’s 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

Imaging in Typical Bell’s PalsyImaging in Typical Bell’s Palsy

• Imaging in typical Bell’s 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 Bell’s palsy, enhancement of facial nerve in fallopian & ICA is typical

C/o Dr. M. Michel, Wisconsin

Atypical Bell’s PalsyAtypical Bell’s Palsy

• Clinical features– Slower onset of symptoms– Bilateral– Recurrence

• Numbness is not unusual• Progression beyond seven days

suggests another cause

Imaging in Atypical Bell’s PalsyImaging in Atypical Bell’s Palsy

C/o Dr. M. Michel, Wisconsin

Alternative Causes of Acute Alternative Causes of Acute Facial Nerve ParalysisFacial Nerve Paralysis

• Atypical signs & symptoms which suggest etiology other than Bell’s palsy require imaging

• Clinical history is crucial in distinguishing etiologies

• Choice of imaging technique depends on clinical suspicion

Lyme DiseaseLyme 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

Ramsay Hunt SyndromeRamsay 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 Bell’s (complete recovery: 50%)• Important cause of facial paralysis in children

6-15 years old

C/o Dr. M. Michel, Wisconsin

Infectious causesInfectious 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 < 50%)

TuberculosisTuberculosis

Parotid & peri-parotid diseaseParotid & peri-parotid disease

HIV InfectionHIV Infection

Bezold’s abscess & coalescent Bezold’s abscess & coalescent mastoiditismastoiditis

TraumaTrauma

• 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

NeoplasmsNeoplasms

• 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

HemangiomaHemangioma

HemangiomaHemangioma

Facial Nerve SchwannomaFacial Nerve Schwannoma

Perineural Tumor SpreadPerineural Tumor Spread

Glomus TumorGlomus Tumor

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

Other tumorsOther tumors

Rhabdomyosarcoma & squamous cell carcinoma of the EAC

Vestibular SchwannomaVestibular Schwannoma

• Common tumor

• However, facial nerve is resistant to compression– Therefore, tends to produce facial paralysis mostly when

they attain a large size

Vestibular SchwannomaVestibular Schwannoma

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

MeningiomaMeningioma

• Second most common primary tumor of cerebellopontine angle

• Rarely results in facial paralysis

RhabdomyosarcomaRhabdomyosarcoma

Miscellaneous CausesMiscellaneous Causes

Hypertrophic PolyneuropathyHypertrophic Polyneuropathy

• Hypertrophic polyneuropathies occasionally lead to facial paralysis

Wegener’s GranulomatosisWegener’s Granulomatosis

Other CausesOther Causes

• Guillain-Barre Syndrome– Ascending paralysis

• Iatrogenic– Temporal bone surgery

• Excision of vestibular schwannoma has <10% chance of paralysis

• Middle ear surgeries– Babies who required forceps delivery

• >90% recovery

Melkersson-Rosenthal SyndromeMelkersson-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

ConclusionConclusion

• While Bell’s 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.