[Anatomical observations in the spiral ganglion of human newborns (author's transl)].

Four temporal bones of human newborns were studied light- and electron-microscopically. Different parts of the spiral ganglion were examined but absolutely no myelinization of the large (type I) and small (type II) ganglion cells could be seen. Between the ganglion cells dense bundles of mixed nerves are detected, some of the unmyelinated nerves show synaptic-like contact zones to the surface of type II-cells. The small type II cells are mainly located at the periphery of the ganglion cell complex. Between the spiral ganglion and the osseous spiral lamina large bundles of unmyelinated nervecomplexes are crossing the mainly myelinated radial fibers. The nerve fibers running from the modiolus to Rosenthal's channel contain bout 12% unmyelinated nerves whereas the nerve fascicles crossing the osseous spiral lamina reveal a population of 22-25% unmyelinated nerve fibers. About 2% of the small unmyelinated nerve fibers (diameter 200-500 nm) which run between the ganglion cells contain dense core vesicles.