Facial Nerve Paralysis..

OutlinesAnatomyClassificationEvaluation Electrodiagnosis testingManagementBells palsy ,Ramse Hunt syndromeTemporal bone fracture

Anatomy of Facial nerveThe facial nerve contains approximately 10,000 fibers7000 myelinated fibers innervate the muscles of facial expression, stapedius muscle, postauricular muscles, posterior belly of digastric muscle, and platysma3000 fibers form the nervus intermedius (Nerve of Wrisberg)sensory fibers (taste) from the anterior 2/3 of the tonguetaste fibers from soft palate via palatine and greater petrosal nerveparasympathetic secretomotor fibers to the parotid, submandibular, sublingual, and lacrimal gland

Anatomy of Facial nerve1) Intracranial partSupranuclear segmentNuclear segmentInfranuclear segmentCerebellopontine angleInternal acoustic canalLabyrinthine segmentTympanic segmentMastoid segment2) Extracranial part

Supranuclear segmentCerebral cortex Corticobulbar tract Facial nucleus (pons)Upper face crossed & uncrossedLower face crossed only

Nuclear segmentFacial motor nucleuslower 1/3 of Ponsabducent nucleusOut from brain stem at pons recess between olive and inferior cerebellar peduncle

Nervous intermediusParasympathetic secretory fibers arise from superior salivatory nucleusThese preganglionic fibers travel to the submandibular ganglion via the chorda tympani nerve to innervate the submandibular and sublingual glandsAnd to sphenopalatine ganglion via greater superficial petrosal nerve to innervate lacrimal, nasal, and palatine gland

Nervous intermediusSecretory fibers of lesser superficial petrosal nerve tranverse tympanic plexus, synapse in otic ganglion, and travel via auriculotemporal nerve to innervate parotid glandTaste fibers from anterior 2/3 of tongue reach geniculate ganglion via chorda tympani nerve and from there travel to the nucleus of the tractus solitarius

Infranuclear segmentCerebellopontine angleInternal acoustic canalLabyrinthine segmentTympanic segmentMastoid segment

Cerebellopontine angleThe facial nerve and nervus intermedius exit the brain stem at the pontomedullary junction and travel with CN VIII to enter the internal acoustic meatus

Internal acoustic canalMotor facial nerve (medial)Nervus intermedius (between)Acoustic nerve (lateral)

Labyrinthine segmentFallopian canal Shortest & Narrowest partTemporal bone Facial nerve enter fallopian canal until middle earFirst genu Geniculate ganglionBranchesGreater superficial petrosal nerve lacrimal glandLessor superficial petrosal nerve parotid gland

Tympanic segmentFirst genu above oval window stapesSecond genu beyond middle earOut of cranium through stylomastoid foramen

Mastoid segmentStylomastoid foramenBranchesMotor nerve to stapedius muscleChorda tympani nerve between malleus and incus secretomotor : Submandibular & Sublingual glandtaste fiber : anterior 2/3 of tongue

Extracranial segmentPosterior auricular nerve : auricularis, occipitalis and sensation at auricular, post auricular area Branch to posterior belly of digastric muscle and stylohyoid muscleTemporal branch : muscle above zygomaZygomatic branch : orbicularis occli Buccal branch : buccinator and upper lipMarginal mandibular branch : orbicularis oris and lower lipCervical branch : platysma

PhysiologyEfferent fibers : from the motor nucleus innervate muscles of facial expression, post-auricular, stylohyoid, posterior digastric, and stapedius musclesEfferent fibers : ANS (preganglionic parasympathetic fiber) sphenopalatine ganglion to lacrimal glands and mucinous glands of nosesubmandibular ganglion to submandibular and sublingual glands

PhysiologyAfferent fibers convey taste from anterior two-thirds of tongue to nucleus tractus solitarius via lingual nerve, chorda tympani, and nervus intermedius. Afferent fibers mediate sensation from posterior external auditory canal, concha, ear lobe, and deep parts of face

Classifications of facial nerve injury

Seddon classification of nerve injury

NeuropraxiaAxonotmesisNeurotmesis

ClassificationsSunderland classification of nerve injury1 damage = Compression2 damage = Interruption of axoplasm3 damage = Disruption of myelin4 damage = Disruption of perineurium, myelin and axon5 damage = Transection of nerve

Sunderland Classification of nerve injury

Nerve injuryneurapraxia ~ Sunderland grade 1axonotmesis ~ Sunderland grade 2-3neurotmesis ~ Sunderland grade 4-5

DegenerationInterruption of the continuity of the axon separates the distal axon from its metabolic source, the neuron or cell bodyWallerian degeneration of the distal axon and myelin sheath begins within 24 hours Macrophages phagocytose degraded myelin and axons

RegenerationComplete Partial Simple misdirectionClinical expression: synkinesis or associated movementComplex misdirectionClinical expression: mass movement

Differential DiagnosisExtracranialIntratemporalIntracranial

Extracranial 1. Traumatic Facial lacerations Blunt forces Penetrating wounds Mandible fractures Iatrogenic injuries Newborn paralysis

Extracranial 2. Neoplasm Parotid tumors Tumors of the external and middle ear Facial nerve neurinomas Metastatic lesions 3. Congenital absence of facial musculature

Intratemporal 1. Traumatic Fractures of petrous pyramid Penetrating injuries Iatrogenic injuries 2. Neoplastic Cholesteatoma Facial neurinomas Hemangiomas Meningiomas Acoustic neurinomas

Intratemporal3. Infectious Herpes zoster oticus Acute otitis media Chronic otitis mediaMalignant otitis externa 4. Idiopathic Bell's palsy Melkersson-Rosenthal syndrome 5. Congenital: osteopetroses

Intracranial 1. Iatrogenic injury 2. Neoplastic 3. Congenital Mobius syndrome Absence of motor units

HistoryOnsetPrevious symptomsComplete or incompleteUnilateral or bilateralPainUnderlying disease (vestibulocochlear)Associate symptomsAlteration in taste or lacrimation

HistoryFamily historyTraumaHx of viral infectionVaccinationDMHTNPregnancy

Physical examinationENT examNervous systemLocation Severity

Evaluation of Facial paralysisClinical feature Central VS Peripheral facial paralysis Complete head and neck examination Cranial nerve evaluation

Electrodiagnostic testing

Topographic diagnosis

Central facial paralysisUpper motor neurone lesion Movements of the frontal and upper orbicularis oculi tend to be sparedBecause of uncrossed contributions from ipsilateral supranuclear areasInvolvement of tongueInvolvement of lacrimation and salivation

Peripheral paralysisLower motor neurone lesion At rest :less prominent wrinkles on forehead of affected side, eyebrow drop, flattened nasolabial fold, corner of mouth turned down Unable to : wrinkle forehead, raise eyebrow, wrinkle nasolabial fold, purse lips, show teeth, or completely close eye

House-Brackmann grading system Grade I - Normal Grade II - Mild dysfunction, slight weakness on close inspection, normal symmetry at rest Grade III - Moderate dysfunction, obvious but not disfiguring difference between sides, eye can be completely closed with effort Grade IV - Moderately severe, normal tone at rest, obvious weakness or asymmetry with movement, incomplete closure of eye Grade V - Severe dysfunction, only barely perceptible motion, asymmetry at rest Grade VI - No movement

Topographic DiagnosisTo determine the anatomical level of a peripheral lesion Lacrimation Geniculate ganglionStapedius reflex motor nerve of stapedius muscleTaste chorda tympani

Schirmer's Test Geniculate ganglion & petrosal nerve function testSchirmers test +ve whenAffected side shows less than half the amount of lacrimation seen on the normal sideSum of the lengths of wetted filter paper for both eyes less than 25 mmLesion at or proximal to the geniculate ganglion

Stapedius reflex Nerve to stapedius muscle testImpedance audiometry can record the presence or absence of stapedius muscle contraction to sound stimuli 70 to 100 dB above hearing thresholdAn absence reflex or a reflex less than half the amplitude is due to a lesion proximal to stapedius nerve

Taste (Electrogustometry)Chorda tympani nerve testSolution of salt, sugar, citrate, quinine or Electrical stimulationCompares amount of current require for a response each side of tongueNormal : difference < 20 uAmp (thresholds differening by more than 25%= abnormal)Total lack of Chorda tympani : No response at 300 uAmpDisadvantage : False +ve in acute phase of Bells palsy

Minimal stimulation test

neurapraxia axonotmesis neurotmesis

Minimal stimulation test 3.5 mA Wallerian degeneration

Maximal stimulation test (MST) neurapraxia axon axonotmesis axon neurotmesis

Maximal stimulation test (MST) 5 mA 2 facial nerve 12 73 facial nerve misdirection

Electroneurography (ENOG ) MST summating potential amplitude amplitude SP 5-10 90-95 facial nerve misdirection

Electromyography (EMG) facial palsy 10 Wallerian degeneration fibrillatioin facial nerve motor unit potential

Limitation of Electrodiagnostic testing 72 EMG 10 ( EMG)

ManagementExtracranial etiologyTraumaIatrogenicNeoplasm

Intratemporal etiology Fracture Iatrogenic Neoplasm Idiopathic (Bells palsy) Infection

Idiopathic facial palsy (Bell's Palsy)

Most common cause of facial paralysis (>50% of case)Most age 25-30 yrs.Male : Female = 1 : 1 Left side : Right side = 1 : 1Unilateral > bilateralIncrease risk in pregnancy 3.3 times DM 4.5 times Recurrent rate 10%60% have previous URI

EtiologyUnknown Microcirculatory failure of vasa nervorumViral infection (HSV)Ischemic neuropathyAutoimmune reactionEntrapment theory

DiagnosisBy exclusionCriteria :Paralysis or paresis of all muscle groups of one side of the faceSudden onsetAbsence of signs of CNS diseaseAbsence of signs of ear or CPA disease

Medical treatmentCorticosteroids : prednisolone 1 mg/kg/day 7-10 days Corticosteroids combine with antiviral drug is betterAcyclovir 400 mg 5 times/day Famciclovir and valacyclovir 500 mg bid

Surgical treatmentFacial nerve decompressionIndication Completely paralysisENOG less than 10% in 2 weeksAppropriate time for surgery is 2-3 weeks after paralysis

Herpes Zoster Oticus (Ramsay Hunt Syndrome)3rd most common of peripheral facial paralysis (10%)Aged > 60 yrs. or low immune (low CMIR)Virus travels to the dorsal root extramedullary cranial nerve ganglionInfected of HZV at auricular, external canal or faceProdromal symptoms very similar to those seen in Bell's palsybut usually more severe

Herpes Zoster Oticus (Ramsay Hunt Syndrome)Symptoms include severe otalgia, facial paralysis, facial numbness, and a vesicular eruption on the concha, external auditory canal, and palateFacial paralysis + hearing loss + vertigo canal paralysisPathophysiology & treatment liked in Bell s palsy

Temporal bone fractures Longitudinal fractureTransverse fracture Mixed fracture

Temporal bone fractures Signsbleeding from the external canalhemotympanumstep-deformity of the osseous canalconductive hearing loss (longitudinal fracture)sensorineural hearing loss (transverse fracture)CSF otorrheafacial nerve involvement (20% of longitudinal fractures and 50% of transverse fractures)

Longitudinal VS Transverse

Type of injuryLongitudinalTransverseIncidence 70-90%10-20%Site of injury

Temporal , Parietal areaOccipital , Frontal area

Origin of fracture siteTemporal squamaForamen magnumDirection of injuryPosterosuperior of EAC cross roof of middle ear along carotid canal anterior to labyrinthine capsuleBetween various foramen Jugular F. Hypoglosal F. Labyrinthine capsule

Insertionmiddle cranial fossamiddle cranial fossa

Tympanic mb.Middle earInner ear, hemotympanumHearing loss

VertigoCHL

NoSNHL

Common

Facial paralysis Onset20-25 %Delayed,transient50%Immediate,permanentSite of lesionTympanic segment , Perigeniculate ganglionLabyrinthine segmentCSF otorrheaNoCommon

Cardinal S&S1.Bleeding from ear2.CHL3.Battles sign1.Vertigo&Nystagmus2.SNHL3.Facial paralysis4.HemotympanumCT-scanAxial & sagital sectionCoronal & 20degree coronal oblique section

PrognosisImmediate onset paralysis : poor prognosis Delayed onset paralysis : good prognosisAll case of paralysis electrical testing

TreatmentSurgery is treatment of choiceIndications for facial nerve exploration incomplete paralysis iatrogenic paralysis Contraindications : any case have no poor prognostic factors

ComplicationsComplications of facial nerve decompression dural tearsconductive or sensorineural hearing lossvestibular function losspersistent CSF leaksmeningitisinjury to the anterior inferior cerebellar artery (AICA) or its branches