[Structural changes in the peripheral nerves over a lifetime. Morphometric studies of the sciatic and sural nerves]

Investigations were conducted on topographically identical tissue samples from the sciatic and sural nerves. 22 autopsies on individuals free of any severe disorder provided the material for this study (stillborn babies and deaths of unnatural causes). The material was selected with the view to having all age groups of human life represented. preferably two or more subjects of each decade. The overall cross-section and the cross-section of each bundle were planimetrically measured, using magnified photographs of celloidin sections, 30 micron in thickness. Depending on age, the sum of the cross-sections of all bundles was found to percentually decrease by about one fifth in all nerves relative to the overall cross-section. Alterations in the sural nerve and in the smaller portion of the sciatic nerve (N. peronaeus communis) were characterised by linear regression of measurements with a negative correlation, but non-linear regression could be estimated for the larger portion (N. tibialis). Semi-thin sections of methacrylate-embedded material were used to ascertain the numerical density of Schwann cell nuclei on all cases and to study fibre calibre distribution on three selected subjects. The averaged numerical density of Schwann cell nuclei decreased by about 80% from birth to the age of five years and varied between the second and fifth decades within a relatively small range described by a hyperbolic regression. No unambiguous correlation was found to exist beyond the fifth decade.(ABSTRACT TRUNCATED AT 250 WORDS)