Labyrinthine trauma during ear surgery.

Surgical trauma inflicted upon the membranous labyrinth is an uncommon, but often catastrophic, complication of chronic ear surgery. Areas most vulnerable to injury are the oval window and the lateral semicircular canal. Methods of injury include subluxation of the footplate, fracture of the lateral canal by drill or chisel, and accidental opening of a fistula. Three cases of labyrinthotomy of the lateral canal during ear surgery are presented. Two occurred while drilling, and the other was associated with a dehiscence of the bony and membranous labyrinth from a cholesteatoma. The cases are documented by pre and postoperative audiograms, vestibular function tests, and photographs. Of interest is the fact that in none of these cases was cochlear function compromised. In one case the hearing actually improved. The dictum that an accidentally opened labyrinth will automatically result in a dead ear is shown to be not necessarily true. Possible explanations for this phenomenon are discussed.