Relationship between high-resolution computed tomography densitometry and audiometry in otosclerosis

Abstract Objective The aim of this study is to evaluate the usefulness of high-resolution computed tomography (HRCT) densitometry in the diagnosis of otosclerosis and to investigate the relationship between CT densitometry and audiometry. Methods HRCT findings and audiometry were compared among 34 patients (34 ears, the otosclerosis group) with surgically confirmed otosclerosis between January 2007 and December 2007 and 33 patients (33 opposite normal ears, the control group) with facial paralysis diagnosed at the same period of time. Seven regions of interest (ROI) were set manually around the otic capsule on the axial slice of 0.75-mm-thick CT image. The mean CT values of these seven regions were measured. In each ROI, the mean CT value of the otosclerosis group and that of the control group were compared. Based on the CT findings, the ears with otosclerosis were classified into two groups: Group A showed no pathological CT findings; Group B showed low density around the cochlea. In the otosclerosis group, the relationship between the findings of CT and the results of audiometry was analyzed. Results The mean CT values in the area posterior to the oval window and anterior to the oval window were significantly lower for the otosclerosis group compared with the control group (the former t = −2.030, p = 0.046; the latter Z = −4.979, p < 0.01). Group A consisted of 30 patients, 7 of which (23.33%) exhibited conductive hearing loss, and 23 of which (76.67%) exhibited mixed hearing loss; Group B had 4 patients, all with mixed hearing loss. For the otosclerosis group, the mean CT value in the area posterior to the oval window was positively correlated with the mean air conduction threshold ( r = 0.4273, p = 0.0117) and with the mean air-bone gap ( r = 0.3995, p = 0.0192). Conclusion Quantitative evaluation of CT with slices less than 1 mm in thickness may provide important information for the diagnosis and assessment of otosclerosis which are unattainable through other methods.