Comparative morphometry of myelinated nerve fibres in the normal and pathologically altered human sural and tibial nerve.

To assess neuropathological changes in human nerves, biopsies are usually performed on the sural nerve or other nerves supplying only a small area of skin. It is not yet clearly understood to what extent the changes found in this sensory nerve correspond to the changes found in other distal sensomotory nerves. To answer this question, we made a comparative morphometric analysis of the sural and tibial nerve. In 39 autopsy cases (aged 22 - 90 years) the sural and the tibial nerve were subject of image analysis. The histological picture in this study group was clearly influenced by neuropathological changes as well as age-related changes. For each morphometric parameter in the sural and tibial nerve, we evaluated Pearson's correlation. The highest coefficient of correlation (r) was seen in those parameters that represented the condition of the myelin sheath area: the density of nerve fibre area (sum of measured nerve, fibre areas/analyzed endoneural area) (r = 0.86) and the density of myelin sheath area (sum of measured myelin areas/analyzed endoneural area) (r = 0.86). Similar correlations were obtained for the mean of axon diameter (r = 0.82), the numerical density of nerve fibre count (nerve fibre count/analyzed endoneural area) (r = 0.77), the mean of nerve fibre diameter (r = 0.77) and the mean of myelin sheath thickness (r = 0.72). Our results revealed a good or very good statistical correlation of morphometric parameters between the two examined nerves. They support the assumption that the sural nerve sufficiently reflects the histological changes in other distal sensomotoric nerves. This is valid at least in systemic neuropathological diseases and age-dependent processes.