Prevalence of histologic otosclerosis: an unbiased temporal bone study in Caucasians.

Background: 'Histologic otosclerosis' refers to a disease process without clinical symptoms or manifestations that can only be discovered by sectioning of the temporal bone at autopsy. 'Clinical otosclerosis' concerns the presence of otosclerosis at a site where it causes conductive hearing loss by interfering with the motion of the stapes or of the round window membrane. Various authors have studied the prevalence of histologic otosclerosis on laboratory collections of temporal bones. Some 12-15% of the temporal bones with histologic otosclerosis have demonstrated stapedial fixation. Using these figures for calculating the prevalence of clinical otosclerosis gives an extrapolated clinical prevalence of 0.99-1.2%. This does not correlate well with the clinical data on otosclerotic families from which a clinical prevalence of 0.3% has been estimated.

Objective: To study the prevalence of histologic otosclerosis in an unselected series of temporal bones.

Study Design: During a 1-year period, 118 consecutive pairs of temporal bones of deceased patients at a tertiary center were collected to determine the prevalence of otosclerosis. Although histology remains the gold standard 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 bones with suspected otosclerosis shown with these techniques were further analyzed by conventional histology.

Results: 2.5% of the 236 temporal bones (or 3.4% of patients) studied demonstrated histologic otosclerosis.

Conclusions: Although the prevalence of 2.5% is much lower than previously published figures on histologic otosclerosis, the extrapolated data (extrapolated clinical prevalence = 0.30-0.38%) correlate well with clinical studies of otosclerotic families. The previous studies based on laboratory collections were likely biased by the presence of hearing loss or other otological diseases.