TEMPORAL BONE FINDINGS IN ALZHEIMERS-DISEASE

Sensorineural hearing loss has been reported in Alzheimer's disease (A D) and a topographically specific pattern of degeneration in the centr al auditory system has been described, Although peripheral visual and olfactory systems have been extensively studied, there is no report of peripheral auditory system abnormalities in AD patients. Comparison o f temporal bones from eight AD patients with those from eight non-AD c ontrols revealed a significant difference in the percentage of remaini ng hair cells, peripheral processes, and spiral ganglion cells in the basal cochlear turn but no significant differences in the overall perc entage between the two groups. Furthermore, special stains (thioflavin S and Bielschowsky's silver impregnation) of temporal bone nervous ti ssue from AD patients did not show neuritic plaques and neurofibrillar y tangles. It is unclear whether the differences between the two group s in the basal portion of the cochlea are due to AD or some other proc ess, such as presbycusis, However, lack of significant degeneration in other parts of the cochlea and absence of neurofibrillary tangles and neuritic plaques in all eight patients may suggest that the periphera l auditory system, unlike the peripheral visual and olfactory systems, is not involved in AD. A larger sample of AD patients is necessary to clarify the peripheral auditory system findings in the present study.