Gross dehiscence of the bone covering the facial nerve in the light of otological surgery.

Understanding the relationship between the anatomy of the fallopian canal and a variety of ear diseases is necessary. In this study, our purpose was to identify the incidence of facial nerve dehiscence in patients undergoing surgery for a variety of chronic ear diseases. The operative records of 219 patients were reviewed retrospectively for dehiscence of the facial canal. The diagnoses were cholesteatoma (n = 49), tympanosclerosis (n = 51), adhesive otitis media (n = 38), and chronic otitis media (n = 81). Only 17 of 219 who underwent tympanoplasty without mastoidectomy were excluded from the calculations. Dehiscence of the facial canal was encountered in 18 (8.9 per cent) of 202 patients. The dehiscence rate was highest with cholesteatoma, followed by adhesive otis media, chronic otis media and tympanosclerosis (p < 0.01). The canal dehiscence was mainly seen in the tympanic segment and second genu, and was rare in the mastoid segment. Labyrinthine fistula was the most common pathology that coexisted with the dehiscence. It was encountered in two (11.1 per cent) of 18 patients. In conclusion, the likelihood of dehiscent bone covering the tympanic segment of the fallopian canal is significantly higher in cholesteatoma than the other chronic ear diseases. The surgeon can feel somewhat more confident while performing surgery for tympanosclerosis as far as the dehiscence in the fallopian canal is concerned.