[Stapes surgery in anomalies of the course of the facial nerve].

In 548 stapes operations performed in Berne during the period 1994-1998, an anomaly of the course of the facial nerve was observed in 37 cases. 29 exhibited partial prolapse of the nerve over the oval window, with or without dehiscence of the bony canal, while 5 showed total prolapse of the nerve over the oval window. In one case the nerve was duplicated round the oval window and in a further instance the facial nerve was situated over the promontory and also over the oval window. In one other case the nerve was spread widely over the oval window. Concomitant anomalies of the stapes were frequently observed. The following surgical techniques were employed: in the case of partial prolapse of the nerve, a small piston was placed in the lower part of or in the oval window, which was widened towards the promontory. In cases of total prolapse of the facial nerve the prosthesis was drilled straight into the promontory. Where the nerve was duplicated the prosthesis was placed in the footplate between the nerve branches, and where the nerve ran over the promontory and over the oval window the prosthesis was placed above the oval window. In the case where the nerve was spread widely over the oval window, no prosthesis was inserted. 78% of patients had a residual air-bone gap of 20 dB or less; in only three cases did hearing fail to improve. One patient with Crouzon disease involving a complex anomaly had a hearing impairment of 22 dB. There was no deafness, facial paralysis or vertigo with nystagmus.