Myelination of the mouse vestibular ganglion.

Myelination of mouse vestibular ganglion cells and preganglionic fibres was examined by light and electron microscopy from gestation day 16 to postnatal day 23. Myelination of the preganglionic fibres occurred essentially during the first 2 days after birth and was almost complete by postnatal day 7. Myelination of the ganglion cells occurred later and lasted longer than that of the fibres. Its onset was observed on postnatal day 9 and the myelin sheaths had fully developed structures 2 weeks later. Thus, myelination of vestibular ganglion neurons appeared to be the latest event to take place in the maturation of the peripheral vestibular system. The sequences of myelination are discussed with respect to those of electrophysiological maturation.