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FACIAL NERVE PARALYIS
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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