Unmyelinated fibers in human greater auricular and sural nerves: a comparative morphometric study

Abstract

Since normal structural details of human greater auricular nerve (GAN) have not as yet been studied with modern techniques, light and electron microscopic findings of seven presumably normal GANs, obtained from five patients during radical neck dissection, were compared with those of normal sural nerves (SNs). In GANs there was a tendency to higher densities per mm2 and a larger number of small-diameter fibers in myelinated fibers (MFs) and unmyelinated fibers (UFs) without obvious signs of de- or regeneration. UF histograms were unimodal in both groups, with mean UF diameters being somewhat smaller in GANS than in SNs. Schwann cell complexes containing several or even numerous UFs were more frequent in GANs than in SNs. In GANs, UF often occurred focally in great numbers within large Schwann cell complexes (polyaxonal complexes), not commonly seen in normal SNs. It is concluded that these structural peculiarities in GANs reflect natural conditions in short sensory nerves irrespective of any specific function.