Facial Nerve Paralysis Dr. Vishal Sharma

Gabriel Fallopius (1523-62)

Anatomy of Facial Nerve Motor root: 7000 axons Sensory root (Nervus intermedius / Wrisberg): 3000 axons. Joins motor root at fundus of I.A.C. Motor: predominantly to facial muscles Secretomotor: lacrimal, submandibular, sublingual Taste: anterior 2/3rd of tongue Sensory: Post-aural / concha / ext. auditory canal

Course of facial nerve

Parts of facial nerve Intracranial: within cerebello-pontine angle Intra-temporal  Meatal segment  Labyrinthine segment  Tympanic segment  Mastoid segment Extra-cranial  Extra-parotid  Intra-parotid (terminal)

Segments of Facial Nerve 1. Supranuclear: Fibers in cerebral cortex to brain stem 2. Brain stem: Motor nucleus of facial nerve (pons) 3. Intra-cranial (12 mm): Brain stem to entry into IAC 4. Meatal (10 mm): Within Internal Auditory Canal 5. Labyrinthine (4 mm): Fundus of I.A.C. to Geniculate gangl. 6. Tympanic (11 mm): Geniculate ganglion to pyramid 7. Mastoid (13 mm): Pyramid to stylomastoid foramen 8. Extra-temporal (15 mm): S.M. foramen to pes anserinus

Primary branches of facial nerve Intra-temporal: greater superficial petrosal, stapedius, chorda tympani Extra-parotid: post-auricular, stylohyoid, posterior belly of digastric Intra-parotid: temporal, zygomatic, buccal, marginal mandibular, descending cervical

Intra-cranial branches

Extra-cranial branches

Communicating branches to: Meatal: vestibulo-cochlear Tympanic: lesser petrosal  otic ganglion Mastoid: auricular branch of vagus Extra-parotid: glossopharyngeal, auriculotemporal, vagus, greater auricular, lesser occipital Terminal: branches of trigeminal

Surgical landmarks

Cochleariform process: small bony protuberance (from which tensor tympani muscle turns 900 to insert into malleus) lies 1 mm inferior to geniculate ganglion at anterior end of tympanic segment. Cog: bony ridge hanging from tegmen tympani lies 1 mm above & posterior to cochleariform process. Incus short process: 2 mm below lies external genu Lateral Semicircular Canal: 2 mm Antero-Infero-Medial lies external genu Oval window: 1 mm above lies external genu

Inferior edge of Posterior S. C. C Inferior edge of Posterior S.C.C.: 2 mm anterior & lateral lies mastoid segment of facial nerve Tympano-mastoid suture in posterior canal wall: 5-8 mm medial lies mastoid segment of facial nerve Digastric ridge in mastoid tip: leads antero-medially to mastoid segment of facial nerve Groove between mastoid & bony E.A.C. meatus: bisected by facial nerve Tragal pointer: 1 cm antero-infero-medial is facial nv Root of styloid process: lateral lies facial nerve Superior border of posterior belly of digastric: superior & parallel lies facial nerve

Surgical landmarks

Lesions of Facial Nerve

Lesion Manifestation Supranuclear C/L hemiplegia, ed jaw jerk Nuclear (pons) I/L 6th, 7th palsy + C/L hemiplegia In C.P. Angle I/L 5th, 7th, 8th palsy Supra-geniculate ed lacrimation, hyperacusis, loss of taste Supra-stapedial Hyperacusis, loss of taste Supra-chordal Loss of taste Infra-chordal Facial asymmetry only

Upper Motor Neuron Palsy Lower Motor Neuron Palsy Features Upper Motor Neuron Palsy Lower Motor Neuron Palsy Forehead wrinkling B/L present Same side absent Eye closure Naso-labial fold Opposite side absent Drooping of angle of mouth Opposite side Same side

Etiology of Facial Nerve Palsy

1. Idiopathic (55%): Bell’s palsy, Melkersson Rosenthal syndrome 2. Temporal bone trauma (25%): Road traffic accident 3. Infection (10%): C.S.O.M., Herpes Zoster oticus Malignant otitis externa 4. Neoplasm (5%): Parotid tumors, Acoustic Neuroma, Glomus tumors, Malignancy of ear 5. Congenital (4%): Moebius syndrome 6. Iatrogenic (rare): Mastoidectomy, Parotid surgery 7. Metabolic (rare): Diabetes mellitus, Hypertension

Sunderland’s Classification (1951)

Cross section of nerve

Partial block of axoplasm Injury to endoneurium or myelin sheath Grade Name Characteristics I Neuropraxia Partial block of axoplasm II Axonotemesis Injury to axon III Neurotemesis Injury to endoneurium or myelin sheath IV Partial transection Injury to perineurium V Complete transection Injury to epineurium

House Brackmann Classification (1 year post-injury)

Grade Characteristics I II III IV V VI Description Characteristics I Normal Normal facial function II Mild dysfunction Slight weakness seen only on close inspection III Moderate dysfunction Obvious asymmetry; complete eye closure IV Moderately severe dysfunction Obvious asymmetry; incomplete eye closure V Severe dysfunction Only minimal motion seen; asymmetry at rest VI Total paralysis No movement

House Brackmann grading Sunderland Grading EEMG response Recovery begins in House Brackmann grading I Normal 1-4 wks II 25 % of normal 1-2 mth III < 10 % of normal 2-4 mth III or IV IV No response 4-18 mth V Never VI

Diagnosis Topo-diagnostic Tests Electrical Tests Magnetic stimulation of intra-cranial facial nerve CT scan temporal bone: for progressive palsy MRI brain Surgical exploration

Topo-diagnostic tests Audiometry: cochlear nerve function Vestibulometry: vestibular function Schirmer’s test: Greater Superficial Petrosal Nerve Stapedial reflex test: Nerve to stapedius Electrogustometry: Chorda tympani Submandibular salivary flow: Chorda tympani Examination for terminal facial nerve branches

Schirmer’s Test Unilateral wetness ed by >30% of total amount of both eyes after 5 minutes = Schirmer test positive  lesion at or proximal to geniculate ganglion

Stapedial Reflex

Electrogustometry Measures minimum amount of current required to excite sensation of taste

Muscles supplied by terminal branches

Electrical tests

Nerve Excitability Test Stimulating electrode used over terminal branches of facial nerve Minimum current intensity required to produce minimal muscle movement is calculated Normal side compared to paralyzed side Difference > 3.5 mAmp = unfavorable prognosis

Maximal stimulation test Stimulating electrode used over terminal branches of facial nerve Minimum current intensity required to produce maximal muscle movement is calculated Normal side compared to paralyzed side Difference > 3.5 mAmp = unfavorable prognosis

Electro-neuronography Terminal branch of facial nerve stimulated & action potential recorded in appropriate muscle Paralyzed side compared to normal side (which is taken as 100%) Response > 10% = 85-95 % chance of recovery Response < 10% = 25 % chance of recovery

Electro-neuronography

Electro-neuronography

Electro-neuronography

Records spontaneous activity of facial muscles Electromyography Records spontaneous activity of facial muscles

Electromyography Responses Normal Polyphasic Fibrillation Electrical Silence

Response Interpretation Normal Motor Unit Action Potentials: Incomplete transection of facial nerve Poly-phasic Motor Unit Action Potentials: Re-innervation of facial muscles Fibrillation potentials: Denervation of muscles (2-3 weeks after trauma) Electrical silence: Atrophy / absence of muscle

Bell’s Palsy Acute onset, idiopathic, unilateral, self-limiting, non-progressive, peripheral facial nerve palsy 85% start recovering within 3 weeks Etiology: 1. Viral: Herpes simplex, Herpes Zoster 2. Ischemia of facial nerve: exposure to cold, emotional stress, nerve compression 3. Hereditary 4. Autoimmune

Sir Charles Bell

Clinical Features Loss of forehead wrinkles Inability to close eyes Wide palpebral fissure Epiphora Loss of naso-labial fold Drooping of angle of mouth Dribbling of food while chewing on affected side

Medical treatment Prednisolone (1mg/kg in 2 doses): for 2 - 3 weeks Acyclovir: 200-400 mg 5 times per day X 7days Eye care: Voluntary closure @ 2 / min. Ciplox eye drops 2 hourly & ointment H.S. Eye cover at night. Physiotherapy: moist heat + facial massage + facial muscle exercise Electrical stimulation of facial nerve & muscle Facial nerve decompression: Controversial

Moebius syndrome

Melkersson Rosenthal Syndrome Recurrent alternating facial palsy Fissured tongue Facio-labial edema Familial history

Melkersson Rosenthal Syndrome

Surgical Treatment for Facial Nerve Injury

A. Facial nerve decompression: till meatal foramen B. Neurorrhaphy (Nerve repair) 1. Direct end to end anastomosis 2. Interposition Cable grafting: sural, greater auricular C. Nerve Transposition: hypoglossal-facial D. Muscle Transposition: temporalis, masseter E. Micro-neuro-vascular muscle flaps F. Static Procedures: eyelid implant, fascial sling

Treatment Protocol Up to 3 weeks: Nerve decompression or Nerve repair 3 weeks – 2 year: Nerve Repair or Nerve Transposition > 2 year with fibrillation in Electromyography: Nerve Repair or Nerve Transposition > 2 yr with electrical silence in Electromyography: Muscle transposition / Eyelid implant / Fascial sling

Facial Nerve Decompression Cortical mastoidectomy done Facial nerve canal bone thinned in barber pole fashion with diamond burr. Drilling done: Posteriorly at mastoid segment, Laterally at external genu & Inferiorly at tympanic segment Avoids injury to chorda tympani & lateral S.C.C. Labyrinthine segment decompressed by middle cranial fossa approach

Barber Pole

Direct repair & Cable Grafting

Nerves used for cable grafting

Nerve Transposition

Nerve Transposition

Temporalis muscle transposition

Masseter muscle transposition

Gold Weight Eyelid Implant

Complications of facial nerve injury 1. Incomplete recovery 2. Exposure keratitis 3. Facial tics & spasms 4. Faulty regeneration of facial nerve a. Synkinesis: Mass movement of facial muscles b. Crocodile tear syndrome: gustatory lacrimation Salivary to lacrimal gland cross over c. Frey’s syndrome: gustatory sweating Secreto-motor to sympathetic cross over

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