Otosclerosis: Contribution of Computed Tomography and Radio-Anatomical Correlations

Abstract

Otosclerosis is an osteodystrophia of the otic capsule, responsible for hearing loss by blocking of the stapes footplate. The purpose of this study was to evaluate the reliability of computed tomography (CT) in the positive diagnosis of otosclerosis, to compare the radiological findings to those intraoperatively, and to seek a correlation between imaging data and postoperative audiometric results. This is a retrospective study of 60 patients having otosclerosis, treated in our department between 2009 and 2011. All patients underwent an otoscopic examination, pure tone and vocal audiometry, impedancemetry and petrous CT scan. At petrous CT scan, a footplate thickening was found in 9 cases. Labyrinthine bone hypodensity was noted in 51 cases. Sensitivity of CT in the diagnosis of otosclerosis was 100%. Regarding the operative findings and their correlation with imaging, we found that among the 7 facial canal procidences reported intraoperatively, CT had identified 6, with a sensitivity of 86%. Of the 53 facial nerve in normal position intraoperatively, CT had only identified 34, with a specificity of 64%. Regarding the ossicles, there were 6 cases of abnormalities of the incus, among them 3 were identified on CT, with a sensitivity of 50%. The 54 patients with normal ossicular chain intraoperatively were all identified as such on CT, with a specificity of 100% (p = 0.001). For correlation between imaging and postoperative results, it was found that patients with extended otosclerosis had lower postoperative audiometric improvement than those having localized disease (p < 0.05). Computed tomography is necessary for the diagnosis of otosclerosis. It also helps, with good sensitivity and specificity, seeking for anatomical variants that the surgeon could possibly encounter during surgical procedure. Finally, there is a statistically significant correlation between imaging data and postoperative audiometric results, allowing establishing a functional prognosis even before surgery.