Prevalence of otosclerosis in an unselected series of temporal bones

Background: Histologic otosclerosis is a disease process without clinical s ymptoms or manifestations that can be discovered only by sectioning of the temporal bone at autopsy. Clinical otosclerosis is otosclerosis at a site w here it causes conductive hearing loss by interfering with the motion of th e stapes or of the round window membrane. Various authors have studied the prevalence of histologic otosclerosis on laboratory collections of temporal bones. Some 12% to 15% of temporal bones with histologic otosclerosis have demonstrated stapedial fixation. Using these figures for calculating the p revalence of clinical otosclerosis gives an extrapolated clinical prevalenc e of 0.99% to 1.2%. This does not correlate well with the clinical data on otosclerotic families, from which a clinical prevalence of 0.3% has been es timated. Objective: To study the prevalence of histologic otosclerosis in an unselec ted series of temporal bones, Study Design: During a 1-year period, 118 consecutive pairs of temporal bon es of deceased patients at a tertiary care center were collected to determi ne the prevalence of otosclerosis. Although histology remains the gold stan dard for evaluation of otosclerosis, the gross observation of temporal bone slices combined with microradiography was used to screen for otosclerotic lesions more rapidly and with a lower cost/benefit ratio. The temporal bone s, which were suspected of having otosclerosis with these techniques, were further analyzed by conventional histology. Results: 2.5% of the 236 temporal bones (or 3.4% of patients) studied demon strated histologic otosclerosis. Conclusions: Although the prevalence of 2.5% is much lower than previously published figures on histologic otosclerosis, the extrapolated data (extrap olated clinical prevalence = 0.30% to 0.38%) correlate well with clinical s tudies of otosclerotic families. The previous studies based on laboratory c ollections were likely biased by hearing loss or other otologic diseases.