Facial nerve paralysis

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Disorders of the facial nerve

• Dr. Krishna Koirala MBBS, MS ( ENT-HNS)
• Associate Professor
• Department of ENT
• Manipal College of Medical sciences
• Pokhara, Nepal

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Surgical Anatomy

• Mixed nerve having 10,000 neurons (7, 000 motor
  and 3,000 sensory)
• Three nuclei
• Motor nucleus Caudal Pons
• Superior salivatory nucleus Dorsal to motor
  nucleus
• Nucleus of solitary tract Medulla

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• Superior aspect of motor nucleus has both crossed
  and uncrossed input
• Upper motor neuron lesions - only the lower part
  of the face on the contralateral side will be
  affected due to bilateral control to the upper
  facial muscles (frontalis and orbicularis oculi)
• Inferior aspect Contralateral input
• Lower motor neuron lesions - both upper and lower
  facial weakness occurs on the same side of lesion

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Differences between UMN and LMN facial palsy
Features Upper Motor Neuron Palsy Lower Motor Neuron Palsy
Forehead wrinkling B/L present Absent on same side
Eye closure B/L present Absent on same side
Naso-labial fold Absent on opposite side Absent on same side
Drooping of angle of mouth Opposite side Same side
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Facial Nerve Trunk (5 fiber types)

• Special visceral efferent Muscles of facial
  expression, stapedius, stylohyoid, posterior
  belly of digastric
• General visceral efferent Lacrimal, nasal
  mucosa, sublingual and Submandibular glands
• Special sensory Taste from anterior 2/3 of
  tongue
• Somatic Sensory EAC and concha
• Visceral afferent Mucosa of nose, pharynx ,
  palate

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Course / parts of facial nerve
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F. N .Segment Location Length (mm)
Supranuclear Cerebral cortex NA
Brain stem Motor nucleus , superior salivatory nucleus NA
 Meatal segment Brain stem to IAC 13-15
Labyrinthine segment Fundus of IAC to geniculate ganglion 3-4
Tympanic segment Geniculate ganglion to pyramidal eminence 8-11
Mastoid segment Pyramidal eminence to Stylomastoid foramen 10-14
Extratemporal segment Stylomastoid foramen to pes anserinus 15-20
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• Intracranial Pons to porous of IAC (24 mm)
• Intratemporal
• Meatal
• Labyrinthine
• Shortest (4mm), narrowest (0.68 mm)
• From fallopian canal to geniculate ganglion (1st
  genu)
• Branch greater superficial petrosal nerve
• Lacks anastomosing arterial cascades Involved
  in nerve edema in fracture temporal bone and
  vascular compression ,embolic phenomena, low-flow
  states

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• Tympanic (Horizontal) - (13 mm)
• Geniculate ganglion to Pyramidal process (2nd
  genu)
• Commonly dehiscent (Damaged during surgery)
• Mastoid (Vertical) - 20mm
• Pyramid to stylomastoid foramen
• Second genu lies lateral and posterior to the
  pyramidal process
• Branches Nerve to Stapedius ,Chorda tympani
  ,Posterior auricular Muscular

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• Extracranial / Extratemporal
• Peripheral branches
• Temporal
• Zygomatic
• Buccal
• Marginal mandibular
• Cervical

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Surgical Landmarks of facial nerve

• Processus cochleariformis (small bony
  protuberance from which tensor tympani muscle
  turns 900 to insert into malleus) lies 1 mm
  inferior to geniculate ganglion
• Cog bony ridge hanging from tegmen tympani lies
  1 mm above posterior to processus
  cochleariformis
• Short process of incus 2 mm below it lies the
  external genu

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• Lateral Semicircular Canal 2 mm anteroinfero-
  medially lies the external genu
• Oval window 1 mm above lies the 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

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• Classification of Nerve injury
• Seddon (1943) Neuropraxia, Axonotmesis ,
  Neurotmesis
• Sunderland (1951)
• 10 -Neuropraxia - Complete recovery
• 20 - Axonotmesis - Usually complete
• 30 - Neurotmesis -Incomplete
• 40 - Partial transection
• 50 - Complete transection

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Causes of Otogenic Facial Nerve paralysis

• Traumatic
• Fracture temporal bone
• Penetrating injury to middle ear/ mastoid
• Facial injuries
• Iatrogenic
• Infective
• Herpes Zoster Oticus (Ramsay Hunt syndrome)
• Acute suppurative otitis media
• Chronic suppurative otitis media Atticoantral
  type
• Malignant otitis externa

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• Neoplastic
• Glomus tumors / Schwannoma
• Middle ear malignancies
• Metastatic carcinoma
• Idiopathic
• Bells Palsy

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Diagnostic Tests

• Topodiagnostic Tests
• Hearing and balance
• Schirmers test
• Stapedial Reflex
• SM salivary flow rate
• Taste
• Electrodiagnostic Tests
• Maximal nerve stimulation
• Electromyography
• Evoked EMG

• Radiological
• CT Scan
• MRI
• Immunological
• ANA
• RA Factor
• VDRL / Monospot
• ESR
• Bone marrow ( Leukemia, lymphoma)

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• Topodiagnostic tests
• To determine the anatomical level of a peripheral
  lesion
• Principle Lesions distal to the site of a
  particular branch of the facial nerve will spare
  the function of that branch
• Hearing and balance Defects at the IAC
• Schirmer's test
• Quantitative evaluation of tear production
• Lesion at or proximal to geniculate ganglion

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• Significant when unilateral wetness is reduced
  by more than 30 of the total amount of both eyes
  after 5 minutes or when bilateral tearing is
  reduced to less than 25 mm after a 5-minute
  period
• Stapedius reflex test
• Absence of the reflex - lesion proximal to
  stapedius nerve
• Submandibular flow test
• Taste test

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• Electrodiagnostic Tests
• Nerve Excitability Test
• Technique using a stimulating electrode over
  the terminal ramifications of the facial nerve,
  increase the current (milliamperes) until
  movement in the appropriate muscle group is just
  visible
• Normal values (unaffected side of face) compared
  to the side of paralysis
• Interpretation A difference of 3.5 mamp or more
  - unfavorable prognosis

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• Electromyography ( EMG)
• Prognostic value in traumatic facial nerve
  injury
• Principle A denervated muscle produces
  spontaneous electrical potentials (fibrillations)
  after 14 -21 days
• Presence of voluntary motor unit action
  potential (VMAP) sign of incomplete paralysis
• Early presence of VAMP ( 10-14 days) Better
  clinical outcome suggesting no need for surgical
  decompression

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• Electroneurography (Evoked Electromyography)
• Interpretation The difference in amplitude of
  the potentials of the intact and involved side of
  the face correlate with the percentage of
  degenerated motor fibers (denervation)
• Advantage Quantitative analysis of amount of
  degeneration
• Disadvantage Amplitudes are a 24-48 hour delayed
  representation of actual events occurring at site
  of lesion

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Clinical applications

• Facial nerve subjected to traumatic injuries of a
  magnitude requiring surgical repair undergo 90
  degeneration within six days of injury
• In cases of Bell's Palsy, a poor prognosis can be
  anticipated in patients reaching 95 or more
  degeneration within 14 days of onset of the palsy

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• Common disorders

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• Bells Palsy
• Most common cause of LMN facial palsy (80)
• Acute, idiopathic, unilateral, peripheral LMN
  facial paralysis
• ? Viral prodrome ( Herpes simplex) , ? Vascular
• No sex predilection ,no side predilection
• 5th - 6th decade-Common
• 10 family history
• Pathophysiology
• Nerve swelling within the facial canal

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Clinical Features

• Unilateral LMN Facial Paralysis Progresses to
  maximal deficit over 3 to 72 hours
• Pain (50) Near the mastoid process
• Excess tearing (33) ,hyperacusis, dysgeusia
• Facial weakness
• All branches of nerve Upper Lower ,
  Unilateral
• Degree Partial (30) Complete (70)
• Affected side - flat and expressionless ,twisted
  intact side, palpebral fissure wide, eye does not
  close

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• Stapedius dysfunction (33) Hyperacusis
• Lacrimation Mildly affected in some
  patients
• Taste -- No clinically significant changes in
  most patients
• Sensory loss
• Mild or None
• May be present on face or tongue on side of
  paralysis

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• Natural History
• Complete / Incomplete
• Recovery begins within three weeks
• Full recovery by 6 months in 84 ( 60 in HZO )
• Recurrence 12 ( Rare IN HZO)
• Decrease in Response to electrical testing
• - Peaks in 5-10 days (10-14 days In HZO)

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• Herpes Zoster Oticus (Ramsay Hunt syndrome)
• Acute LMN facial paralysis caused due to Herpes
  zoster virus infection of the geniculate ganglion
  of the facial nerve
• Viral prodrome
• Severe pain in and around the ear
• Vesicles in pinna, face , neck ,oral cavity
  (100)
• SNHL and /or vertigo (40)

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• Treatment
• 1)For all cases of facial paralysis
• Reassurance
• Physical Therapy Heat, massage
• Psychosomatic Therapy
• Physiotherapy of the face
• Eye care

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• Eye care
• Corneal protection
• Antibiotic eye drops e.g.. Ciprofloxacin 2 drops
  in the eye TDS
• Antibiotic ointment at night
• Natural tears, isotonic saline and
  methylcellulose drops
• Strips of skin tape to help close the eye
• Temporary patching
• Tarsorraphy
• Comfort

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• 2)For Bells Palsy
• Steroid Therapy
• Prednisone 1mg/kg/day ( 60-80 mg) to begin 24 to
  48 h after onset and given for 1 wk, then
  decreased gradually over the 2nd wk
• Helps to reduce residual paralysis
• Improves recovery
• Antiviral agents
• Acyclovir, famciclovir

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• 3)For HZO (Ramsay- Hunt)
• Antiviral agents
• Acyclovir 800mg 5 times a day for 7 days
• Best results - treatment started within three
  days after symptoms appear
• Steroids
• Carbamazepine 200-600 mg TDS
• Vaccines
• Varicella vaccine
• Zostavax (helpful in preventing viral
  reactivation)

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• 4) Other modalities
• Cosmetic restoration( Static Procedures)
• Fascial slings Fascia Lata
• Tarsorraphy
• Gold weight prosthesis
• Temporalis muscle transposition
• Eyelid springs/ implants

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Fascial Slings
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Surgical treatment of facial nerve palsy

• Facial Nerve Decompression ( till meatal
  foramen)
• Nerve Repair ( Neurorraphy)
• End to end anastomosis
• Cable grafting( Sural, greater auricular)
• Nerve Transposition
• Facial - Hypoglossal anastomosis
• Muscle Transposition Temporalis, masseter
• Micro- neurovascular muscle flaps

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Treatment Protocol

• Up to 3 weeks Nerve decompression or repair
• 3 weeks 2 years
• Nerve repair or nerve transposition
• gt 2 year with fibrillation in Electromyography
• Nerve repair / nerve transposition
• gt 2 yr with electrical silence in
  Electromyography
• Muscle transposition / Eyelid implant / Fascial
  sling