Temporal bone histopathologic findings in Down's syndrome.

We report the results of a histopathologic study of 12 temporal bones from seven patients with Down's syndrome and of a dimensional study of the cochlea and the vestibular apparatuses of most of these specimens. Histopathologic study disclosed numerous abnormalities of the middle ear but only a limited number of inner ear abnormalities. The dimensional study showed that, while in the majority of cases the cochlea was shortened, most of the vestibular measurements were within the normal range. We also discuss hearing loss in patients with Down's syndrome and present our hypothesis that remnants of mesenchymal tissue in the round window niche might cause a certain degree of conductive hearing loss in such cases.