[Electrophysiological study of the lateral dorsal cutaneous nerve: technical applicability and normal values]

The distal nerve conduction study of the long nerve in the leg is more efficient to work with so that it can establish the early diagnosis of the majority of polyneuropathies. The main purpose of this study is the technical applicability of the orthodromic neural conduction examination of the dorsal cutaneous branch of the sural nerve (lateral dorsal cutaneous nerve) on healthy people, and define the normal values used as references to compare with the proximal segment. Forty five persons mean age 41.56 years old (range 19-75) were examined, and the sensory nerve action potentials were registered from ninety feet. The active recording superficial electrode was placed below and behind the lateral malleolus and the stimulating electrode was placed 10 cm distal to the recording superficial electrode at the dorsal lateral aspect of the feet. The mean value for the lateral dorsal cutaneous nerve conduction velocity was 47.35 +/- 4.8 m/s and for amplitudes 4.19 +/- 1.9 microV. The sensory conduction velocity in the distal segment was 14% lower than the proximal one. The sensory nerve action potential amplitude of the distal segment was 73% lower than the proximal one. The lower normal limit recommended for conduction velocity of this nerve plus correction for skin temperature of 34 degrees C is 38 m/s. Some differences in amplitude and conduction velocity among group ages are to be considered.