Conduction studies in peripheral nerve.

Conventional nerve conduction studies assess only a small proportion of the fiber population in peripheral nerve. Nerve conduction velocity is a measure of the very fast conducting fibers and varies with temperature and age. The amplitude of the compound nerve action potential is determined by fibers 9-14 microns in diameter and is dependent on the number of active fibers. The amplitude of the normal sural nerve action potential varies by a factor of 3-4 due to the large variation in the number of large myelinated fibers (1700-3300 per nerve, 7-14 microns). Nerve conduction studies performed under adequate conditions are of value in ascertaining whether there is involvement of peripheral nerve. Due to the large variation in normal nerve these studies are, however, not well suited as screening procedures in individuals exposed to toxic substances.