Anaesthesia with hypotension for fenestration.

The object of the fenestration operation is to overcome the obstruction offered to the transmission of sound-actuated waves by the fixation of the footplate of the stapes in the oval window by osteosclerotic bone. This is achieved by providing an opening in the wall of the bony labyrinth that will allow free movement of labyrinthine fluids in response to transmitted sound waves (Cawthorne, 1952). This was described as a one-stage endaural procedure by Lempert (1938). The operation itself falls naturally into two parts (Hall, 1945): (1) the preparation of the middle ear, i.e. essentially a modified radical mastoidectomy; and (2) the trephining of the bony labyrinth, which is carried out under lowpower magnification. The fenestra is then covered with a skin flap which is rotated from the wall of the external auditory