Histometric evaluation of branches of peroneal nerve: Technique for combined biopsy of muscle nerve and cutaneous nerve

A technique for combined biopsy of muscular and cutaneous branches of the common peroneal nerve is described. Nerves studied were the nerve to the peroneous brevis, the lateral fasciles of the deep peroneal (to the extensor digitorum brevis) nerve and the cutaneous branches of the superficial peroneal nerve. These nerves from normal subjects of various ages were evaluated by histometric techniques. Degenerative changes affecting teased myelinated fibers were infrequent, but their incidence increased significantly with age. Teased-fiber measurements were analyzed to provide the average internode length (IL) and internode diameter (ID) of the large and small fiber populations of the nerve. Estimates of the IL of the whole nerve were adjusted for sampling error inherent in fiber teasing. Values for lateral fascicles of the deep peroneal nerve from persons 18 years and older (IL) and 10 years and older (ID) are: mean IL, small fibers, all nerves, 338 μm; mean IL, large fibers, all fibers, all nerves, 962 μm; mean IL, all nerves, 602 μm; mean ID, small fibers, all nerves, 5.1 μm; mean ID large fibers, all nerves, 10.8 μm; mean ID, all nerves, 7.7 μm. Values for the superficial peroneal nerve from persons 18 years and older are: mean IL, small fibers, all nerves, 328 μm; mean IL, large fibers, all nerves, 873 μm; mean IL, all nerves, 554 μm. The adjusted mean IL of the lateral fascicles of the deep peroneal nerve and the superficial peroneal nerve decreased with increasing age. Variation in IL increased signficantly with age and was greater in small fibers than in large fibers. Although histograms made from tested-fiber measurements of the nerve to the peroneus brevis were bimmodal, accurate separation of fibers into large and small groups was not possible. The fiber density (number of fibers/sq.mm) in the lateral fascicles and in the superficial peroneal nerve decreased significantly with age; the averages for adults were 6,838 and 8,648/sq. mm, respectively. Fiber-diameter histograms revealed that the superficial peroneal nerve contained the largest number of small fibers, the nerve to the peroneus brevis contained the least, and the lateral fascicles of the deep peroneal nerve contained an intermediate number.