Dehiscences of the horizontal segment of the facial canal in otosclerosis.

Dehiscences of the bony horizontal segment of the facial canal are rather common in human adults. These facial canal dehiscences occur most often in the region of the oval window. This study presents the observations of the facial canal in the oval window region in 427 operations for otosclerosis. The incidence of dehiscences in the facial canal to the middle ear space in otosclerosis was studied. Dehiscences were observed in 14 of the 427 patients (3.27%) who had a stapedotomy. This incidence is very low compared to the anatomical studies of the facial nerve in human cadaver temporal bones. Dehiscences of the facial canal are a variation of the normal anatomy of the facial nerve and these dehiscences occur sporadically in otosclerosis.