Tympanoplasty, Mastoidectomy, Facial Nerve Decompression

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Tympanoplasty, Mastoidectomy, Facial Nerve
Decompression

• Hau Sin Wong
• Grand Rounds
• 10/27/04

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Tympanoplasty

• Definition operation involving tympanic membrane
  and evaluation of middle ear
• Whereas myringoplasty is an operation of the
  tympanic membrane
• Tympanoplasty can be accompanied with or without
  mastoidectomy

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Types of Tympanoplasty

• Type I restoration of normal ME with intact
  ossicles
• Type II Ossicular chain partially destroyed but
  preserved ad continuity restored

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• Type III TM lays on stapes suprastructure
• Type IV Round window protection with a small
  middle ear mobile footplate left exposed
• Type V Closed middle ear with round window
  protection fenestra in the horizontal
  semicircular canal coveredby a skin graft.

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Middle Ear Anatomy

• Ossicles Malleus, Incus, Stapes
• Ligaments sup malleolar ligament, stapedial
  tendon
• Cochlearform process, pyramidal process

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Technique

• Evaluate TM and ME if perforation present
• Create vascular strip
• Incise postauricular incision for mastoidectomy
• Mastoidectomy- identify lateral landmarks for
  drilling. Anterior boundary-post EAC, superior
  boundary- root of the zygoma, linea temporalis,
  inferior boundary- mastoid tip. Drill medially
  and saucerize, delineating Tegmen superiorly,
  thinning post EAC anteriorly, Sigmoid sinus
  posteriorly, Horizontal SCC medially
• Identify vertical segment of facial nerve between
  HSCC and digastric ridge
• Open facial recess boundaries are fossa incudus,
  facial nerve, chorda tympani
• Visualization of incus, malleus in antrum, incus
  and stapes in facial recess.

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Tympanomeatal flap

• EAC skin and TM elevated anteriorly

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• TM grafts
• 1. Cartilage 2. fools fascia (loose areolar
  fascia over temporalis fascia) 3. temporalis
  fascia
• Medial or lateral graft placement

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Facial Nerve Decompression
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Anatomy

• 5 segments
• Meatal- brainstem to IAC
• Labyrinthine- fundus of IAC to facial hiatus
  (includes fallopian canal-narrowest segment of
  facial canal)
• Tympanic- geniculate gangilion to pyraminal
  eminence
• Mastoid-pyramidal eminence to stylomastoid
  foramen
• Extratemporal- stylomastoid foramen to muscles of
  facial expression ( temporal, zygomatic, buccal,
  mandibular, cervical)

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Anatomy

• Arterial Supply
• Intracranial segment supplied by labyrinthine
  artery off the AICA
• Tympanic segment supplied by superficial petrosal
  artery off the middle meningeal artery
• Mastoid segment supplied by the stylomastoid
  artery off the external carotid artery

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Facial Nerve Decompression

• Eggshell the facial canal (vertical segment)
• Open Facial recess and extended the facial recess
  using a barber pole method
• Follow facial nerve to the tympanic segment
• Eggshell covering overlying facial nerved
  removed, exposing the sheath
• Sheath incised and facial nerve decompressed.

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