Anatomical characteristics of the fossula fenestrae vestibuli.

Anatomical characteristics of the fossula fenestrae vestibuli were tested and analysed precisely on 200 samples of temporal bones. The fossula is usually ovoid and shallow but can be, exceptionally, elongated, narrow and deep. It is surrounded by four walls. In 45.5 per cent of cases the upper wall is formed only by the facial canal and in 54.5 per cent of cases a bony lamella is found beneath the facial canal; the promontory forms the lower wall; the front wall is formed by the bony lamella and part of the processus cochleariformis; the back wall is clearly defined in only 22.8 per cent of cases and is formed by the bony lamella of the medial wall of the tympanic cavity. In 13.2 per cent of cases the floor of the fossula partially covers the prominence of the facial canal and in two per cent the eminentia pyramidalis. Bony recesses in this region occur fairly frequently: sinus subfacialis in 60 per cent, sinus retrofenestralis in 77.2 per cent, and sinus subrostralis in 25 per cent of the cases. These anatomical variations can influence the result of surgical intervention.