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

ABSTRACT

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.