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 inspection Complete eye closure with minimal effort Slight asymmetry of smile with maximal effort Synkinesis barely noticeable, contracture, or spasm absent III Obvious weakness, but not disfiguring May not be able to lift eyebrow Complete eye closure and strong but asymmetrical mouth movement with maximal effort Obvious, but not disfiguring synkinesis, mass movement or spasm IV Obvious disfiguring weakness Inability to lift brow Incomplete eye closure and asymmetry of mouth with maximal effort Severe synkinesis, mass movement, spasm V Motion barely perceptible Incomplete eye closure, slight movement corner mouth Synkinesis, contracture, and spasm usually absent VI No movement, loss of tone, no synkinesis, contracture, or spasm

Simplified HB Score Grade Definition I Normal II Very mild weakness III Obvious weakness, asymmetry of mouth Complete eye closure Some spasms IV Incomplete eye closure Severe spasms V Very slight movement only VI No movement at all

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