The Incidence of Dehiscence of the Tympanic Segment of the Facial Nerve Canal Estimated With Computed Tomography

Abstract

Abstract. In this study, we aimed to determine the presence and incidence of dehiscence of the tympanic segment of the facial nerve canal using the High Resolution Computed Tomography (HRCT) and to evaluate this variation in relation to gender and age. The retrospective-prospective study was performed at the Clinic for Radiology, University Clinical Center of Sarajevo. After the criteria for participation and non-participation in the study were applied, the study included 295 patients (160 women and 135 men) of ages ranging from 5 to 75, with performed computed tomography (CT) of the temporal bone as a part of a standard procedure due to the suspicion of pathological activity in that area. We divided the subjects into seven age groups. Each group included a ten-year period. The presence of dehiscence of the facial nerve canal was recorded and the obtained results were statistically analyzed. Of the total number of patients included in the study, the dehiscence of the tympanic segment of the facial nerve canal was found in 95 patients (32%). Of 590 temporal bones, there were 118 temporal bones with facial nerve canal dehiscence in the tympanic segment (20%). The dehiscence without stenosis of the oval window was noted in 110 temporal bones (18.6%). The dehiscence with stenosis of the oval window was noted in 8 temporal bones (1.4%). There was no statistically significant difference between age groups (p=0.245, Pearson's χ2 test). Also, there was no statistically significant difference between males and females (p=0.385, Pearson's χ2 test). The incidence of dehiscence of the facial nerve canal is high and the tympanic segment is the most frequent site of dehiscence localization. Almost one third of the patients with the suspicion of pathological processes on the temporal bone can have dehiscence of the tympanic segment of the facial nerve canal. HRCT is the best visual imaging technique for the evaluation of the facial nerve course within its osseous canal.