Facial nerve disorders

Dr Raymond Ngo

2008

Function of the facial nerve

• Motor fibers – face and others

• Parasympathetic fibers to salivary glands

• Taste to anterior 2/3 of tongue

• Sensation to skin (periaural)

Anatomy of the facial nerve

• Intra-cranial - Brainstem to IAC

• Meatal – through the IAC to meatal foramen

• Labyrinthine – meatal to geniculate

• Tympanic – 1st genu to 2nd genu

• Mastoid – 2nd geno to stylomastoid

• Extratemporal

Otoscopic Exam

Clinical examination

• Face – House Brackmann Score

• Ears

• Oral examination

• Schirmer’s test

Grade Definition

I Normal symmetrical function in all areas

II Slight weakness noticeable only on close inspectionComplete eye closure with minimal effortSlight asymmetry of smile with maximal effortSynkinesis barely noticeable, contracture, or spasm absent

III Obvious weakness, but not disfiguringMay not be able to lift eyebrowComplete eye closure and strong but asymmetrical mouth movement with maximal effortObvious, but not disfiguring synkinesis, mass movement or spasm

IV Obvious disfiguring weaknessInability to lift browIncomplete eye closure and asymmetry of mouth with maximal effortSevere synkinesis, mass movement, spasm

V Motion barely perceptibleIncomplete eye closure, slight movement corner mouthSynkinesis, contracture, and spasm usually absent

VI No movement, loss of tone, no synkinesis, contracture, or spasm

Grade Definition

I Normal

II Very mild weakness

III Obvious weakness, asymmetry of mouthComplete eye closure Some spasms

IV Obvious weakness, asymmetry of mouthIncomplete eye closure Severe spasms

V Very slight movement only

VI No movement at all

Simplified HB Score

Investigations

• Audiometry

• CT or MRI

• ENoG– After day 4– At day 14– Role

Electroneuronography

ENoG Results

• Comparison of bad versus good side

• Response is – (amplitude of bad side / good side) x 100 %– 40/750 X 100 = 5.3%

• Degeneration is – 100 – 5.3% = 94.7% degenerated

Patient A

• 25 year old female

• Sudden onset – noticed food dribbling out of left corner of mouth

• Friends noticed change in appearance

• Rapid worsening over 2 days

• No past medical history

Bell’s Palsy

• Start Prednisolone, Acyclovir

• Protect the eye

• Prognosticate with ENoG

• Surgical decompression of facial nerve (optional)

• Await resolution

Patient A +

• Notice of ear examination vesicles in the ear canal and pinna

• Audiogram shows mild sensorineural hearing loss on left

• Patient develops dizziness several days later

Ramsay Hunt Syndrome

• Management same as Bell’s

• Prognosis less good

• Can be part of multiple cranial nerve neuropathy

Patient B

• 30 year old Indian construction worker

• Long history of ear problems

• Complains of left ear discharge many months

• Noticed a gradual onset left facial weakness

• Associated hearing loss

Mastoiditis Complication

• Start antibiotics

• Order CT Temporal Bone

• Consider myringotomy

• Consider mastoidectomy

Patient C

• 70 year old man• Long standing history

of right ear hearing loss – does not bother him

• Noticed mild weakness of right face

Exclude a CPA lesion

• Rare for CPA lesions to present with facial palsy

• Do MRI internal acoustic meatus

• Consider the diagnosis of facial nerve schwannoma

Patient D

• 58 year old man

• History of right parotid lump 1 year

• Getting bigger 4 cm but not painful

• Mild facial asymmetry

Parotid Tumor

• A parotid tumor with facial palsy is likely to be malignant

• Adenoid cystic especially• Benign tumors rarely

affect facial nerve• Facial nerve

schwannoma (extra-temporal) maybe very big before palsy appears

Patient E

• 20 year old RTA victim

• Sustained skull base injury – suspected

• Otorrhoea noted

• Referred for investigation of temporal bone fracture

• Patient is alert and able to communicate

Temporal Fractures

• Decision to decompress depends on onset of palsy

• Immediate onset – need to decompress

• Delayed onset – can observe

Iatrogenic Facial Injuries

• Parotid Surgery

• Head and Neck Surgery

• Ear Surgery

• Lateral Skull Base Surgery

Complications of Facial Palsy

• Eyes – exposure keratitis

• Oral function

• Crocodile tears

• Cosmesis issues

Facial Repair

• Facial slings

• Nerve grafting– End to end (sural / greater auricular)– Hypoglossal to facial nerve– Cross innervation