Abstract
Sensory nerve conduction studies of the radial, median and ulnar nerves were carried out in healthy normal subjects by conventional techniques using surface electrodes.
Sensory nerve conduction velosity (SCV) and the amplitude of sensory nerve action potential (SNAP) were measured by both the orthodromic and antidromic techniques. Electrodes were placed on the elbow, the wrist and thumb, index and little fingers, respectively. SCV was calculated by the latency time which was taken as the time from stimulus artifact to the first deflection. The amplitude from negative peak to positive peak was considered the amplitude of SNAP.
The mean SCV did not show the significant difference between two techniques in the three nerves. On the other hand, the amplitude of SNAP in antidromic measurement was 2 or 3 times higher than that in orthodromic one. But, in the antidromic study of ulnar nerve, M wave overlapped SNAP as the stimulation voltage increased. Consequently, in order to get high amplitude of SNAP, the antidromic technique was preferable, but one had to examine the ulnar nerve carefully because M wave often overlapped.
One could also pick up the SNAP from the other nerve at the wrist or elbow, when the digital nerve was stimulated. This phenomenon could be caused by the anatomical abnormality, spread of the SNAP or the overflow of the stimulus current. Therefore, one must carefully perform the sensory nerve conduction study, since this phenomenon was noted between the radial and median nerves and between the median and the ulnar nerves as well.
