Correlations between CT scan findings and hearing thresholds in otosclerosis

Abstract

Conclusion: High-resolution computed tomography (CT) scan may reveal an isolated fenestral form of otosclerosis, and an extensive form, which involves multiple foci around the otic capsule. Pre- and postoperative hearing thresholds are poorer in patients with extensive otosclerosis and their chance of overclosure is reduced by 90%. Objectives: To evaluate the relationship between CT scan extension of otosclerotic foci and hearing thresholds in the operated ear, before and after stapedotomy. Methods: A preoperative CT scan was performed in 200 patients suspected of having otosclerosis. CT scan findings were categorized as negative, isolated fenestral otosclerosis, and extensive otosclerosis. Preoperative and 2 months postoperative air-conduction (AC) and bone-conduction (BC) thresholds were collected. Results: In the operated ear, 150 CT scans (75%) revealed an isolated fenestral otosclerosis; 35 (17.5%) were classified as extensive otosclerosis. Mean preoperative BC was significantly poorer in extensive otosclerosis (30.3 dB) than in isolated fenestral otosclerosis (24.6 dB). Mean postoperative BC remained lower in extensive otosclerosis (30.3 dB) than in isolated fenestral otosclerosis (21.2 dB). An overclosure greater than 10 dB was found in 20% of isolated fenestral otoscleroses and in 2.85% of extensive otoscleroses (chi-square: 5.5; p = 0.02).