Quantitative histological study in the sural nerves of children.

Measurements have been made of the diameters of both myelinated and ummyelinated fibers in the sural nerves obtained at autopsy from 10 children without neurological disorders. The distributions of the myelinated fiber diameters were unimodal, except for two cases in which showed bimodal patterns as seen in adults. The second peak in bimodal histograms may appear around age 2 years. The densities of both myelinated and unmyelinated fibers were calculated in the same nerves. The fascicular areas of the same nerves were also measured. The densities of both myelinated and unmyelinated fibers, and the estimated numbers of both myelinated and unmyelinated fibers showed a tendency toward decrease, but the fascicular areas did a tendency to increase with aging. Although a definite proposal regarding the correlation cannot be made at present, it is interesting that the ratio of unmyelinated to myelinated fibers decreases with age. This tendency may be related to development of myelination.