Ultrastructure of the human vestibular ganglion.

Abstract

The fine structure of human vestibular ganglion cells was studied in serial sections under the electron microscope. Most of these cells were unmyelinated and bipolar but a few were myelinated. Two types of unmyelinated multipolar cells were also observed, one large, similar in size to the bipolar cells, and the other smaller. Nerve fiber synapses were found among the small multipolar cells. One of these terminals contained mostly nongranular, spherical vesicles, and was primarily located on dendrites. The other contained many nongranular and granular ellipsoidal vesicles and was found in the perikaryon or the dendrites. Whether these terminals are of the same or different origins is yet to be determined. However, the existence of multipolar cells and synapses among these cells correlates with the reports on the neurophysiology of interreceptor and efferent activities in the vestibular nerve system. Another consideration is the dual autonomic innervation of the vestibular ganglion cells based on the presence of two types of nerve terminals.