The fine structure of the sheaths of vestibular ganglion cells in the rat, monkey and man.

The fine structure of the sheaths of vestibular ganglion cells was studied in 8 rats, 4 baboons, and more than 400 operative specimens of human vestibular nerve. Human vestibular ganglion cells were all unmyelinated. In baboons the sheaths were predominantly composed of loose myelin, while compact myelin sheaths could be observed in rats. The pathophysiological consequences of the lack of myelin ensheathment around the cell bodies of human vestibular ganglia are discussed.