LIMITED LONGITUDINAL SLIDING OF THE MEDIAN NERVE IN PATIENTS WITH CARPAL-TUNNEL SYNDROME

During normal movements or changes in position of the limbs, nerve str uctures must accommodate the resulting changes in length of the nerve path. In patients with carpal tunnel syndrome, we monitored electrophy siologically the longitudinal adjustment of the median nerve to positi ons of extreme flexion and extreme extension of the wrist and elbow, b y measuring the differences induced in the latency of the sensory nerv e action potential (SNAP) recorded in the forearm and upper arm. In pa tients, the latency difference was significantly shorter than in norma l subjects (0.196 +/- 0.084 ms vs. 0.088 +/- 0.059 ms in the forearm, and 0.485 +/- 0.122 ms vs. 0.129 +/- 0.086 ms in the upper arm). These results indicate that the displacement of the source of the median ne rve SNAP with movements of flexion and extension is limited in patient s with carpal tunnel syndrome. Such an abnormality may partly underlie the pathophysiology of entrapment syndromes. (C) 1995 John Wiley and Sons, Inc.