Clinical utility of dorsal sural nerve conduction studies

A technique of testing sensory nerve conduction of the dorsal sural nerve i n the foot was used in 38 normal subjects and 70 patients with peripheral n europathies. The normal dorsal sural sensory nerve action potential (SNAP) had a mean amplitude of 8.9 muV (range 5-15 muV), mean latency to negative peak of 4.0 ms (range 3.2-4.7 ms), and mean conduction velocity of 34.8 m/s (range 30-44 m/s). Optimal placement of the recording electrodes to obtain a maximal nerve action potential was proximal to digits 4 and 5. Cooling t o below 25 degreesC prolonged the latency but did not decrease the SNAP amp litude. Among the patients with peripheral neuropathy, dorsal sural SNAP wa s absent in 68 (97%), whereas only 54 (77%) showed abnormalities of sural s ensory conduction. The diagnostic sensitivity of sensory nerve conduction s tudies in peripheral neuropathies may be significantly improved by the use of this technique for evaluating the action potential of the dorsal sural n erve. (C) 2001 John Wiley & Sons.