Seven patients aged 29 to 76 years with various clinical subtypes of chronic inflammatory demyelinating polyneuropathy (CIDP) were investigated. Sural nerve biopsies were performed between 7 months and 19 years after onset of disease. Quantitative electron microscopy revealed involvement of primary unmyelinated fibers (UF) in all cases. When compared with age-matched controls from the literature and two controls of our own, there was an increase of degenerating primary UF in all cases, a definite decrease of density per mm2 or number per nerve after subtraction of regenerates of myelinated and unmyelinated fibers in five cases, an increase of denervated Schwann cell complexes of the unmyelinated type in three cases, and an increased incidence of a high ratio (greater than or equal to 3) of primary UF per Schwann cell complex in five cases. Presumably due to the small number and heterogeneity of cases, the results did not correlate with type and duration of CIDP, but were obviously influenced by the degree of demyelination. The possible causes of UF damage in CIDP are discussed.

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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.