Comparison of Fixed Distance Stimulation and Distal Wrist Crease Stimulation in Median Motor Conduction Study

OBJECTIVE: To determine optimal stimulation site for median motor conduction study, we compared fixed distance (7 cm proximal to the recording electrode) stimulation method and distal wrist crease stimulation method. METHOD: Nerve conduction studies were performed in 65 hands of 36 healthy adults without neurologic abnormality. Median motor responses were recorded from abductor pollicis brevis (APB) with the stimulations at the point 7 cm proximal to the recording electrode and at the distal wrist crease. The distal latencies and onset-to-peak amplitudes were measured and compared between two techniques. The distal latencies were also compared to that of ulnar compound muscle action potential (CMAP) obtained with fixed distance stimulation (7 cm proximal to the recording electrode). And we measured median nerve actual length from distal wrist crease to APB muscle motor point by anatomic dissection of 12 hands. RESULTS: The distal latencies of median CMAP to APB with 7 cm fixed distance stimulation and distal wrist crease stimulation were 2.91+/-0.37 ms and, 2.75+/-0.41 ms respectively. The differences were statistically significant. The distal latency of ulnar CMAP was 2.50+/-0.32 ms. Differences in distal latencies between ulnar CMAPs and not only 7 cm fixed distance median stimulation but also distal wrist crease median stimulation were also statistically significant. The mean length of median nerve from distal wrist crease to APB motor point was 5.91+/-0.77 cm. CONCLUSION: We suggest that the median motor nerve conduction study using distal wrist crease stimulation was an easier and more rapid procedure than fixed distance median motor nerve conduction study.

Usefulness of Wrist Crease Stimulation Method in Diagnosis of Carpal Tunnel Syndrome

OBJECTIVE: The previously established method of carpal tunnel syndrome (CTS) diagnosis is relatively troublesome and risk of misleading due to uncertainty of exact distance measurement for stimulation. If we use the wrist crease, an anatomical landmark, there might not be error in length measurement for stimulation at any wrist position. This study was performed to evaluate the wrist stimulation method in the diagnosis of CTS for it's convenience and reducing the errors. METHOD: Seventy healthy adults and sixty-five patients with clinical and electrophysiologic evidence of CTS were studied. Sensory nerve action potentials (SNAPs) in second and fifth digit were recorded antidromically with stimulation at a distance of 14 cm from recording electrode and stimulation at wrist crease. The ratio and difference of distal latency and ratio of amplitude between median and ulnar SNAPs were assessed. RESULTS: The ratio and difference of distal latency and ratio of amplitude in the 14 cm stimulation method were 1.52+/-0.28, 1.59+/-0.91 msec, 1.26+/-0.27 in the right, 1.43+/-0.14, 1.29+/-0.42 msec, 1.18+/-0.20 in the left, respectively in the men patients, and those of women patients were 1.48+/-0.35, 1.43+/-1.04 msec, 1.18+/-0.30 in the right, 1.53+/-0.30, 1.46 0.80 msec, 0.75+/-0.36 in the left. In wrist crease stimulation, those of men patients were 1.72+/-0.39, 1.74+/-0.98 msec, 1.22+/-0.24 in the right, 1.53+/-0.21, 1.31+/-0.46 msec, 1.25+/-0.29 in the left, and those of women patients were 1.67+/-0.46, 1.56+/-1.01 msec, 0.63+/-0.32 in the right, 1.68+/-0.37, 1.56+/-0.82 msec, 0.68+/-0.30 in the left. These results showed a significant positive correlation between the patients group and the control group in two stimulation methods (p<0.001). CONCLUSION: Based on the result of this study, wrist crease stimulation method is a quick and easy procedure, which would be recommended in the early diagnosis of CTS.