This project proposes to continue the long term objective of studying the temporal bone histopathology in specific and general disorders with overt or possible cochlear and/or vestibular disturbance. Hearing acuity of hospitalized patients will be monitored by the use of conventional audiometry. Vestibular and electrophysiologic tests will be available in most cases. Temporal bones and brains of thoroughly evaluated patients will be removed at the time of autopsy and then processed for light microscopy examination. The cochlear and vestibular sensory cells and the first order neurons innervating these structures will be quantitatively evaluated. Similarly, a quantitative study of cell population in the primary auditory nuclei will be carried out. Correlation will be sought between the histopathologic findings in human temporal bones with the patient's history, results of auditory and vestibular studies and therapy. These studies will lead to a better understanding of cochleo-vestibular diseases and possibly to more adequate clinical preventive and therapeutic measures.