The superficial radial nerve: techniques for evaluation

S U M M A R Y Several methods for obtaining radial nerve sensory responses have been compared. A technique for antidromic latency measurement over a fixed distance most consistently produced responses which were easy to obtain, reliable and well tolerated by the subjects. The radial nerve may be damaged by trauma along its rather exposed course and by toxins or vascular lesions due to systemic disease. Elec-trophysiologic evaluation of radial nerve func-tion has been performed, but with many different methods and varying results.1-5 Measurement of motor conduction velocity of the radial nerve was described first by Gassel and Diamontopoulos ¢ and by Jebsen. Downie and Scott ' measured conduction of radial sensory fibres in the forearm, finding a velocity similar to that of the median and ulnar nerves, but a very low amplitude of response (average 3-8 tLv). Other techniques have used different anatomical landmarks (the proximal phalanx of the thumb,4 the "anatomical snuffbox,"2 the wrist;'), have employed either needle5 or skin electrodes2 4 8; and have differed as to the distance over which the measurement is made. Feibel and Foca4 used a set distance of Il cm for measurement of distal latency, but reported low amplitudes of response (6 6 +±Lv). The present study was undertaken with the aim of developing a method for determining radial nerve sensory responses which would be technically simple to perform, relatively painless, and give reliable recordings of sufficiently high amplitude to avoid the need for an electronic averager. Materials and methods A TECA TE4 electromyograph (White Plains, New York) was used to elicit and record responses on photosensitive paper for measurement. The high frequency filter setting was 3 2 KHz; the low fre-quency filter setting, 32 Hz