FACIAL NERVE PARALYSIS

DR. DAVIS THOMAS

ANATOMY OF FACIAL NERVEFacial nerve is the 7th cranial nerve.It is a mixed nerve.Has a motor & a sensory root.Motor root supplies all the mimetic muscles of the face which develop from the 2nd branchial arch.

Sensory root (nerve of Wrisberg) carries secretomotor fibres to the lacrimal, submandibular & sublingual glands.Also to nose & palate.Carries taste sensation to the anterior 2/3rd of the tongue.General sensation of the concha & retroauricular skin.

NUCLEUS OF FACIAL NERVE

Motor nucleus – pons. Receives fibres from

precentral gyrus. Upper part of the nucleus

which innervates forehead muscles receives fibres from both the cerebral hemispheres.

Lower part supplies the lower face gets only crossed fibres from one hemisphere.

Function of forehead preserved in supranuclear lesions.

COURSE OF FACIAL NERVE

Motor fibres take origin from the nucleus of 7th nerve,hook around the nucleus of 6th nerve and are joined by the sensory root.

Leaves brainstem at ponto-medullary junction.

Travels through posterior cranial fossa.

Enters the internal acoustic meatus.

At the fundus of the meatus , nerve enters the bony facial canal,traverses the temporal bone & comes out of the stylo mastoid foramen.

INTRACRANIAL PART: from pons to internal acoustic meatus.

INTRATEMPORAL PART:from internal acoustic meatus to stylomastoid foramen. Meatal segment: within the acoustic meatus. Labyrinthine segment: from the fundus of meatus to

the geniculate ganglion. takes a turn posteriorly forming a “genu”.

The bony canal in the labyrinthine segment is the narrowest & is prone for compression in bell’s palsy.

Tympanic/horizontal segment:from the geniculate ganglion to just above the pyramidal eminence.

it lies above the oval window& below the lateral semicircular canal.

Mastoid/vertical segment:from pyramid to stylomastoid foramen.b/n the tympanic & mastoid parts 2nd genu is seen.

EXTRACRANIAL PART: from stylomastoid foramen to the termination branches.

Upper temporofacial Lower cervicofacialFurther divide into-TemporalZygomaticBuccalMandibularcervical

BRANCHES OF FACIAL NERVE GREATER SUPERFICIAL PETROSAL NERVE: it arises from the

geniculate ganglion and carries the secretomotor fibres to the lacrimal gland and the glands of nasal mucosa.

NERVE TO STAPEDIUS: it arises at the level of second genu and supplies the stapedius muscle.

CHORDA TYMPANI: it arises from the middle of vertical segment

-passes between the incus and neck of malleus and leaves the tympanic cavity through petrotympanic fissure.

-carries secretomotor fibres to sublingual and submandibular salivary glands and brings taste to anterior 2/3rd of the tongue.

COMMUNICATING BRANCH:it joins the auricular branch of vagus and supplies the concha,retroauricular groove,posterior meatus and the outer surface of the tympanic membrane.

POSTERIOR AURICULAR NERVE:it supplies the muscles of pinna, occipital belly of occipitofrontalis nad communicates with auricular branch of vagus.

MUSCULAR BRANCHES:stylohyoid and posterior belly of digastric.

PERIPHERAL BRANCHES.

SURGICAL LANDMARKS OF FACIAL NERVE

FOR EAR & MASTOID SURGERY

1) Processus cochleariformis-it demarcates the geniculate ganglion which just lies anterior to it.tympanic segment of the nerve starts at this level.

2) Oval window & horizontal canal-it runs above the stapes and below the horizontal canal.

3) Short process of incus-it lies medial to the short process of incus at the level of aditus.

4) Pyramid-it runs behind the pyramid and the posterior tympanic sulcus.

5) Tympanomastoid suture-in mastoid segment nerve runs behind this suture.

6) Digastric ridge-it leaves the mastoid at the anterior end of digastric ridge.

FOR PAROTID SURGERY:

1) Cartilaginous pointer-it lies 1cm deep and slightly anterior and inferior to the pointer.it is sharp triangular piece of cartilage of pinna and points to the nerve.

2) Tympanomastoid suture-it lies 6-8mm deep to this suture.

3) Styloid process-it crosses lateral to styloid process

4) Posterior belly of digastric-if posterior belly of digastric is traced backwards along its upper border to its attachment to the digastric groove,nerve is found to lie between it and the styloid process.

TOPOGRAPHICAL ANATOMY OF FACIAL NERVE

ETIOLOGY OF FACIAL PARALYSIS

CENTRAL: -brain abscess -pontine gliomas -poliomyelitis -multiple sclerosis INTRACRANIAL PART: -acoustic neuroma -meningioma -congenital cholesteatoma -metastatic carcinoma -meningitis

INTRATEMPORAL PART: Idiopathic -bell’s palsy -melkersson’s syndrome Infections -asom -csom -herpes zoster oticus -malignant otitis externa Trauma -surgical:mastoidectomy stapedectomy -accidents:fractures of temporal bone neoplasms -facial nerve neuroma -glomus jugulare tumours -malignancies of external and

middle ear

EXTRACRANIAL PART: malignancy of parotid surgery of parotid accidental injury in parotid

region neonatal facial injury.

SYSTEMIC DISEASES:

diabetes mellitus hypothyroidism uraemia polyarteritis nodosa wegener’s

granulomatosis sarcoidosis leprosy leukemia demyelinating

disease

IDIOPATHIC BELL’S PALSY Idiopathic, peripheral facial paralysis of acute onset. Incidence male = female

< 13 yrs & > 65 yrs

Aetiology : Viral Herpes simplex, Herpes Zoster & Ebstein – Barr Virus Vascular ischemia Hereditary Auto immune disorder

Diagnosis : Always by exclusion Careful history, complete otological & head & neck examination,

x-ray studies, blood test Net & Topodiagnosis

CLINICAL FEATURES OF BELL’S PALSY

BELL’S PALSY Treatment : General : (1) Reassurance (2) Relief of ear pain by analgesics (3) Care of eye (4) Physotherapy or Massage of facial

muscles

Medical Management : -Steroids – Prednisolone 1 mg / kg / day divided into morning

& evening doses for 5 days -If recovery occurs, taper the dose. -Can be combined with acyclovir. -Other drugs – Vasodilators, mast cell inhibitors, vitamins

BELL’S PALSY

Surgical treatment : -Nerve decompression of vertical & tympanic

segment of nerve

Prognosis -85 – 90% recover fully.

INFECTIONS -Ramsay – Hunt Syndrome : Facial paralysis along with vesicular rash in EAC & Pinna Mgt. as in bells palsy

Infection of middle ear : ASOM – Bony canal in dehiscent inflammation of middle

ear spreads to epineurium & perineurium causing facial paralysis

Mgt : Treat ASOM - systemic antibiotics Myringotomy / cortical mastoidectomy

CSOM : due to cholesteatoma / penetrating granulation tissue.

Mgt : Urgent exploration of middle ear & mastoid

Trauma -Fracture of temporal bone -Common in transverse type. - Mgt. : Surgical decompression, re-

anastomosis of cut ends or cable nerve graft.

SUNDERLAND CLASSIFICATION

5 Classes of Injury

Class 1 : Partial block to flow of axoplasm ; no morphological changes are seen. Recovery of function is complete (Neuropraxia)

Class 2 : Loss of axoplasm ; but endoneural tube remain intact. During recovery axons will grow into the respective tubes and the result is good (axonotemesis)

Class 3 : Injury to endoneurium ; during recovery axons of one tube can grow into another synkinesis can occur (Neurotemesis)

Class 4 : Injury to Perineurium ; in addition to above scarring will impair regeneration of fibers (Partial Transection)

Class 5 : Injury to epineurium in addition to above.

(Complete nerve transection)

HOUSE – BRACKMANN FACIAL NERVE GRADING SYSTEM

INVESTIGATIONS Electrical Tests -Nerve Excitability test -Maximum stimulation test -Electroneurography -Blink reflex -Electro Myography -Antidromic potentials -Acoustic reflex evoked potential -Magnetic stimulation -Facial nerve monitoring

Topognostic Tests : -Lacrimal Function -Stapedius Reflex -Taste -Salivary flow -Salivary PH

NERVE EXCITABILITY TEST [NET] -When the difference between 2 sides exceed 3.5 MA the test

is positive for degeneration. -Degeneration of fibres cannot be detected earlier than 48 to

72 hours of its commencement

MAXIMUM STIMULATION TEST [MST] -The movements on the paralysed side are subjectively

expressed as a percentage (0%, 25%, 50%, 75% & 100%) of the movement on the healthy side.

ELECTRO NEUROGRAPHY [ENOG] Evoked electromyography Nerve is stimulated and the compound action potentials from facial

muscles are recorded and measured objectively & compared with normal side.

The average difference in healthy is only 3% > 30% considered as abnormal

BLINK REFLEX Stimulation of supra orbital branch of trigeminal nerve

elicits a reflex contraction (blink) of orbicular occuli muscle, which is innervated by facial nerve.

Used to identify subclinical facial nerve involvement

ELECTRO MYOGRAPHY : -It records spontaneous activity of facial muscles

by direct insertion of the electrode in to the muscle

-At rest, normal muscle does not show any electrical activity but on voluntary contraction, normal violational motor unit potential seen.

-Denervated muscles shows fibrillation potentials but they appear only 14-21 days after

TOPOGNOSTIC TESTS : Schirmer’s Tests -Decreased lacrimation indicates lesion proximal

to geniculate ganglion. Stapedial reflexs -It is lost in lesion above the nerve to stapedius. Taste test -Impairment of taste indicates lesion above

chorda tympani Submandibular Salivary flow test -Decreased salivation shows injury above the

chorda

COMPLICATIONS FOLLOWING FACIAL PALSY Incomplete recovery Exposure Keratitis – incomplete closure of eyes – leads to dryness – exposure keratitis & corneal ulcers - Prevented my methylcellulore drops, eye ointment & proper cover for the

eye at night Temporary tarsorrhaphy may also be indicated Synkinesis (mass movement) Tics & spasms Contractures Crocodile tears (gustatory lacrimation) -Treated by section of greater superficial petrosal nerve or tympanic

neurectomy Frey’s Syndrone (Gustatory sweating) Psychological & social problem

SURGICAL MANAGEMENT

Decompression End to end anastomosis Nerve graft – graft taken from greater

auricular, lateral cutaneous nerve of thigh or sural nerve

Hypoglossal facial anastomossis

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