Morphometric analysis of intramuscular nerves.

Intramuscular nerves were obtained at autopsy from five adult controls and were morphometrically analyzed. The number of myelinated fibers was directly proportional to the diameter of the fascicles. The fascicles were grouped into six sizes according to diameter. For each group, the normal range of distribution of the number of myelinated fibers could be estimated. Fiber size distribution and myelinated fiber density were also calculated. A unimodal fiber size distribution was observed for the small fascicles (less than 50 microns in diameter), and a bimodal pattern was observed for the large fascicles. Total myelinated fiber density was high in the small fascicles, and it decreased as the fascicles became larger in size, approaching the values observed in the large peripheral nerves. This study will be helpful in objectively evaluating morphological changes of intramuscular nerves in adult neuromuscular disorders.