Nerve supply to the inner sensory cells in a human cochlea.

A choclear apical turn taken from a 66-year-old woman showed an area with marked decrease in number of the inner sensory cells. After observation by scanning electron microscope, the same specimen was thin-sectioned tangentially to the osseous spiral lamina. Numbers of myelinated nerve fibers were counted and the thickness of the fiber was measured by computed measuring equipment. Compared to the area with inner sensory cells intact, the area without inner sensory cells showed a 70% decrease in number of myelinated fibers. These degenerated fibers might have had intimate relationship with the inner sensory cells, probably being the afferent nerve supply to the inner sensory cells.