Interest of computer tomography in the study of prognostic factors of otosclerosis.

Background: Otosclerosis is a primary osteodystrophy of the otic capsule that causes stapedo-vestibular ankylosis. Its diagnosis is suspected on the basis of clinical and audiometric elements, basically in the presence of conductive hearing loss with a normal eardrum. The CT-scan is an essential examination for the preoperative evaluation of otosclerosis. The aim of our study was to evaluate the use of CT-scanning in predicting the functional outcome of otosclerosis surgery by correlating postoperative audiometric results and preoperative CT findings.

Methods: We conducted a retrospective study at the ENT Department in association with the Medical Imaging Department of our hospital, over a period of 8 years, from January 2014 to December 2022 and involving 90 patients (104 ears).

Results: The average age of our patients was 40 years with extremes ranging from 22 to 61 years. We noted a sex ratio of 0.38. The preoperative CT-scan showed signs of otosclerosis in 87% of the cases and infra-radiological forms in 13% of the cases. Veillon stage II was the most frequent radiological stage encountered with a percentage of 48%. A good audiometric evolution, defined by a closure of postoperative Air Bone Gap (ABG ≤ 20 dB) and by an improvement of Bone Conduction (BC gain ≥ 0), was recorded in 86 cases (82.7%) for ABG and in 84 cases (80.8%) for BC gain. Scanographic predictive factors of poor postoperative outcome for ABG and BC gain were: advanced stages (Veillon stage III and IV), endosteal effraction, and round window involvement. According to multivariate analysis, only the extent of otosclerotic foci was directly and independently associated with the postoperative audiometric outcome.

Conclusion: The CT-scan is an essential examination in the preoperative evaluation of otosclerosis. It allows a positive diagnosis to be made and evaluate the extension of otosclerosis. Moreover, thanks to the analysis of the extent of the otosclerosis foci, mainly by the Veillon classification, the CT-scan allows to predict the postoperative audiometric prognosis.