Tympanoplasty, Mastoidectomy, Facial Nerve Decompression Hau Sin Wong Grand Rounds 10/27/04

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

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

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.

Middle Ear Anatomy Ossicles: Malleus, Incus, Stapes Ligaments: sup malleolar ligament, stapedial tendon Cochlearform process, pyramidal process

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.

Tympanomeatal flap EAC skin and TM elevated anteriorly

TM grafts: 1. Cartilage 2. fool’s fascia (loose areolar fascia over temporalis fascia) 3. temporalis fascia Medial or lateral graft placement

Facial Nerve Decompression

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)

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

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.