Post on 21-Jan-2016
Facial Nerve
Prof. Dr. Norberto V. Martinez
Faculty of Medicine and Surgery
University of Santo Tomas
Six Anatomical Segments
• Intracranial
• Meatal
• Labyrinthine
• Tympanic
• Mastoid
• extratemporal
Facial Nerve Surgery & Decompression
4 functional components
• Motor nucleus (efferent)• Parasympathetic fibers-greater superficial
petrosal nerve & chorda tympani ( Nervus Intermedius)
• Special Visceral Afferent from Nucleus Tractus Solitarius(afferent)
• General Sensory Afferent-cutaneous sensation to external ear & postauricular area (afferent)
Supra nuclear pathway
• Motor function origin begins at cerebral cortex
• Primary somatomotor cortex in the precentral gyrus (brodmann area4,6,8)
Facial Nucleus and Brainstem
• Facial nucleus lies within the reticular formation at the lower level of the pons
• There is distinctly ipsi & contalateral cortical input within the facial nucleus
superior or ventral – receives bilateral input
inferior or dorsal – receives contralateral input
INTERNAL AUDITORY CANAL(meatal)
• Traverse crest divides IAC into superior and inferior
• Superior portionfacial nerve anteriorly superior vestibular nerve posteriorly
• Inferior portion cochlear nerve anteriorlyinferior vestibular nerve posteriorly
FALLOPIAN CANAL
• Facial canal is approximately 30 mm long
• From Bills bar up to the stylomastoid foramen
• 3 intratemporal regionlabyrinthinetympanic mastoid
Labyrinthine segment
• Shortest segment (3-4mm)• Lies between labyrinth and cochlea • Beginning from fundus of IAC extending upto
geniculate ganglion*• Narrowest portion of fallopian canal is the
meatal foramen (junction bet IAC and Labyrinthine segment)• Labrynthine segment terminates in the
genicultae ganglion and will make a 40 to 80 turn(1st genu)
Mastoid Segment
• From 2nd genu to stylomastoid foramen
• Descends inferiorly and becomes more lateral *
• 2 branches- nerve to stapedius and chorda tympani
• Angle between chorda tympani and vertical portion is 30 degrees(facial recess)
Extra Temporal Segment
• 3 minor branches after leaving the stylomastoid foramen
• post auricular nervebranch to digastric musclestylohyoid muscle
• Further arborization occurs with frequent anastomosis occurs in the intraparotid course
• Five classic branches- temporal,zygomatic,buccal,mandibular,cervical
Blood Supply
• Blood supply is segmented derived from 3 arterial sources Nager 1953
brainstem to IAC: AICA
perigeniculate segment: Mid. meningeal artery
mastoid –tympanic: stylomastoid branch of post auricular artery
House Brackmann Facial Nerve Grading System
I. Normal• Normal facial function in all areas
House Brackmann Facial Nerve Grading System
II. Mild Dysfunction• Gross
– Slight weakness noticeable in close inspection . May have very slight synkinesis. At rest normal symmetry and tone.
• Motion– Forehead: moderate to good function– Eye: complete closure with minimal effort – Mouth: slight assymetry
House Brackmann Facial Nerve Grading System
III. Moderate Dysfunction• Gross
– Obvious, but not disfiguring difference between the two sides. Noticeable but not severe synkinesis, contracture, or hemifacial spasm. At rest, normal symmetry and tone.
• Motion– Forehead: slight to moderate movement– Eye: complete closure with effort– Mouth: slightly weak with maximum effort
House Brackmann Facial Nerve Grading System
IV. Moderately severe Dysfunction• Gross
– Obvious weakness and/or disfiguring assymetry. At rest, normal symmetry and tone.
• Motion– Forehead: none– Eye: incomplete closure– Mouth: assymetric with maximum effort
House Brackmann Facial Nerve Grading System
V. Severe Dysfunction• Gross
– Only barely perceptible motion• Motion
– Forehead: none– Eye: incomplete closure– Mouth: slight movement
House Brackmann Facial Nerve Grading System
VI. Total Paralysis• No movement
ELECTROPHYSIOLOGIC TESTING
1. Nerve Excitability Test
2. Maximal stimulation test
3. Electroneurography
4. Electromyography
• Electrical excitability test percutaneous stimulation of the facial nerve until muscle contraction is observed.
Electroneurography (ENoG)
Electroneurography (ENoG)
ENoG - Normal ENoG - Paralysis
Electromyography (EMG)
EMG – Normal
EMG – fibrillation potentials
Electromyography (EMG)
Electromyography (EMG)
EMG – polyphasic neurogenic potential
Facial Nerve InjuryIncidence
1% - Primary Otological Surgery
4 – 10% - Revision Cases
Primary Reason:
• 80% lack of familiarity with surgical anatomy
• Tear of Facial Nerve
• High facial ridge in CWD
Management Protocol
1. Complete post-op palsy• Immediate re-exploration• Decompression• Re-approximation severely
damaged• Interposition grafting loss of neural
tissue
Management Protocol
2. Delayed onset observation
Hilger minimal stimulation test after 72
hours, if (-) response at 5 mA ENOG >80 % neural degenerationExplore & decompression
Transmastoid Decompression
Thank You!