Correlation of CT analysis and audiometry in Japanese otosclerosis

OBJECTIVE: To determine the extent of audiometric correlation with CT findings. METHODS: Forty-four patients (82 ears) with surgically confirmed otosclerosis underwent preoperative CT examination. Based on the computed tomography (CT) findings, the ears were classified into five groups as follows: Group A, the group with no pathological CT findings; Group B1, the group with demineralization localized in the region of the fissula antefenestram; Group B2, the group with demineralization extending towards the cochleariform process from the anterior region of the oval window; Group B3, the group with extensive demineralization surrounding the cochlea; and Group C, the group with thick anterior and posterior calcified plaques. RESULTS: There were 32 ears (39.0%) in Group A, 21 ears (25.6%) in Group B1, 16 ears (19.5%) in Group B2, 7 ears (8.5%) in Group B3, and 6 ears (7.3%) in Group C. The mean bone conduction levels were greater in the order of the extent of demineralization: Groups A, B1-B3 suggesting positive relationship between the cochlear function and the degree of labyrhinthine otosclerosis. CONCLUSION: A good correlation between the preoperative CT findings and audiometry findings suggests that CT with a slice intervals between 0.5 and 1mm could provide useful informations in assuming the extent of otosclerosis in the inner ear.