Facial Nerve

ParalysisDr. 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)

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

Segments of Facial Nerve

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.: 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 ManifestationSupranuclear 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

Features Upper Motor Neuron Palsy

Lower Motor Neuron Palsy

Forehead wrinkling B/L present Same side absent

Eye closure B/L present Same side absent

Naso-labial fold Opposite side absent

Same 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

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 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

Sunderland Grading

EEMG response

Recovery begins in

House Brackmann grading

I Normal 1-4 wks I

II 25 % of normal

1-2 mth II

III < 10 % of normal

2-4 mth III or IV

IV No response 4-18 mth V

V No response 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

ElectromyographyRecords spontaneous activity of facial muscles

Electromyography ResponsesNormal 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 ProtocolUp 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

Thank You