CRANIAL NERVE VII

THE FACIAL NERVE

ANATOMY

Long complicated course:Cerebral cortexInternal capsuleBrainstem : nucleus in the lower PonsLeaves brainstem at cerebello-pontine angleInternal auditory meatus – Canal

CN VIICN VIIINervus intermediusInternal auditary artery and vein

ANATOMY (cont)

ANATOMY (cont)

Temporal boneLabyrinthine segmentHorizontal segment

Medial wall of middle earVertical segment

mastoid

Exits at stylomastoid foramen

ANATOMY (cont)

Turns to run through parotid gland

Divides into branches

ANATOMY (cont)

Motor supply to face and a few sensory fibres to earSecretomotor component-parasympathetic

ANATOMY (cont)

Fibres from contralateralhemisphere supply the nucleus in ponsMotor fibres from ipsilateral hemisphere supplies the portion of nucleus that innervates the forehead

UMN innervation of forehead - bilateral

GENERAL

Damage = facial weakness + cosmetic deformityLevel of damage is determined by clinical picture

UMN vs LMNDegree of recovery dependent on extent of damage

AETIOLOGY

UMN lesions = neurosurgeon/ neurologistLMN lesion = ENT surgeon

damage along pathway of nerve

CAUSES: NON TRAUMATIC

Bell’s palsy – most commonHerpes Zoster oticusTumors

Acoustic neuromaParotid tumors

Ramsey Hunt Syndrome

CAUSES: NON TRAUMATIC

InfectionsTBMastoiditisViral infections

CSOMAOM

CAUSES: CONGENITAL

TRAUMATICDifficult deliveryForcepsLarge infant

CAUSES: CONGENITAL

INHERITEDMyotonic Dystrophy

Autosomal dominantMuscle wasting + mental impairmentCNVII palsy = early sign

Albers-Schoenberg diseaseAutosomal recessive Affects bone metabolismOsteoperosis of bony canals

CAUSES: CONGENITAL

DEVELOPMENTALMoebius syndromeCharge syndromeOculo-auriculo- vertabral syndromeCongenital unilateral lower lip palsy

CAUSES: ACQUIRED

INFECTIONSRamsey Hunt SyndromeHerpes Zoster oticusOMETBMastoiditisSyphillisAIDS

CAUSES: ACQUIRED

NEOPLASTICSchwannomasAcoustic neuroma

CNVIIIParotid gland tumors

CAUSES: ACQUIRED

METABOLICDM HTPregnancyAutoimmune diseaseshypothyroidism

CAUSES: ACQUIRED

NEUROGBSMS

CAUSES: ACQUIRED

TRAUMATICSkull base #’sIatrogenic

Surgical injuriesSharp injuries

APPROACH:

TRAUMATIC AND NON-TRAUMATIC LMN

FACIAL NERVE PALSY

TRAUMATIC:

Post surgicalRequires urgent attention ? urgent surgery

Laceration to extra-temporal courseAssess:

Branches involved, how distal lesion is and degree of damage (paralysis, paresis and palsy)

Urgent referral to ENT/ plastic surgeon

TRAUMATIC (cont):

Petrous temporal bone #’s:Characteristics:

Hx of significant head traumaHaemotypanum / laceration of EAM

#’s:Longitudinal (90%)

Side blow; 20% facial nerve injuryTransverse (10%)

Frontal/occipital blow; 40% facial nerve injuryMay be bilateral, ass. with hearing loss

TRAUMATIC (cont):

Petrous temporal bone #’s…Mechanism of damage:

Bony spiculeIntraneural haematomaNeural contusionNerve transection

Possible complications:Facial nerve palsyDeafness (sensorineural/conductive)VertigoCSF leakage (otorrhoea)

TRAUMATIC (cont):

Petrous temporal bone #’s:Management: thorough neuro assessment

Immediate and complete palsy: refer to ENTCSF leakage: neurosurgical opinionSensorineural deafness and vertigo (inner ear)

Bedrest, labyrinthine sedatives and early mobilisationGuidelines for elective ENT referral:

Conductive deafness >1/12Partial or delayed facial nerve palsyAny signs of inner ear damage

NON-TRAUMATIC:

Mostly idiopathic (Bell’s)90% resolve spontaneouslyUsually no significant sequelae

NON-TRAUMATIC (cont):

EXCLUSION CRITERIA FOR BELL’S:Signs of a tumourBilateral simultaneous palsyVesiclesInvolvement of multiple motor CN’sHx or evidence of traumaEar infectionSigns of CNS lesionFacial palsy noted at birthTriad of IM (fever, sore throat, cervical LA)

BELL’S PALSY:

Unilateral facial palsyAcute onsetOther sx: pain, hearing loss85% begin to recover in 3 weeks

Usually recover fully15% recover after 3/12

Poor clinical result

BELL’S PALSY (cont):

Management: Prednisone 1mg/kg/day for 10 daysMust start within 14 days of onsetAcyclovir 400mg QID for 10 daysCorneal protection:

OintmentsEye dropsEye coverage

HERPES ZOSTER OTICUS:

Ramsay-Hunt syndromeVaricella zoster virusPoor prognosisPresents with severe otalgiaVesicles appear in 3-7 daysRx: steroids and acyclovir

ACUTE OTITIS MEDIA:

Palsy occurs in 2-3 daysRx: myringotomy and IV antibioticsIf acute mastoiditis: do mastoidectomyDo not decompress nerve

CHRONIS OTITIS MEDIA:

Acute infectious exacerbations of CSOM

IVI antibiotics and surgeryCholesteatoma

surgery

SPECIAL INVESTIGATIONS:

RADIOLOGICAL TESTS:

Not indicated for every ptHigh resolution CTMRI

ELECTROPHYSIOLOGIC TESTS:

Electroneuronography (EnoG):2 weeks of onset of sxMeasures and compares amplitudes of muscle summation potentialsCurrent applied over main trunk of facial nerveDetermines % degeneration

ELECTROPHYSIOLOGIC TESTS (cont):

Nerve excitability test (NET):Wave pulse applied to affected and unaffected facial nerveThresholds for min facial responses recorded and compared3-4mA difference abN

ELECTROPHYSIOLOGIC TESTS (cont):

Maximal stimulation test (MST):Stimulates ipsi- and contralateral facial musclesUse max stimulation to evaluate muscular responseSubjective observation

Electromyography (EMG):Determines muscle activity rather than nerve

ELECTROPHYSIOLOGIC TESTS (cont):

Audiometry:Evaluates conductive and SN hearing lossCo-existent in pt with CN VII palsies

Branches: Greater Superficial Petrosal Nerve:

Schirmer’s test: assess parasym innervation to lacrimal gland

Nerve to Stapedius: stapedius reflex (audiometry)Chorda tympani nerve: test for taste

CLASSIFICATION:

HOUSE-BRACKMANN SCALE:

I: N movementII: slight weakness, N symm and toneIII: obvious weakness, no disfiguring weakness, N symm and tone, complete eye closureIV: obvious weakness, possible disfiguring asymm, N symm and tone, incomplete eye closureV: min movement and asymmVI: total paralysis, no movement, obvious asymm at rest

TBH PROF’S CLASSIFICATION:

Score each of the following of of 20:ForeheadEyesNoseMouth

Total score out of 80Useful guide for follow-up and monitoring

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