Proximal Martin-Gruber anastomosis mimicking ulnar neuropathy at the elbow

We present a case of Martin-Gruber anastomosis (MGA) mimicking conduction b lock between the above- and below-elbow sites of ulnar nerve stimulation. W e review the anatomical and electrophysiological literature on this subject and discuss its clinical implications. The potential for a MGA to occur ve ry proximally in the forearm and thus mimic ulnar neuropathy at the elbow i s underrecognized. We recommend that a check for MGA be performed on all pa tients with an apparent conduction block at the elbow, and suggest that 3 c m distal to the medial epicondyle may be an optimal below-elbow ulnar nerve stimulation site. (C) 1999 John Wiley & Sons, Inc.