MEDIAN-ULNAR ANASTOMOSIS TO THENAR, HYPOTHENAR, AND FIRST DORSAL INTEROSSEOUS MUSCLES - COLLISION TECHNIQUE CONFIRMATION

Median-ulnar anastomosis (Martin-Gruber anastomosis; MGA) is tradition ally diagnosed based upon changes in compound muscle action potential (CMAP) amplitude following proximal stimulation. We describe a rare pa tient with a MGA innervating thenar, hypothenar, and first dorsal inte rosseous muscles. Proximal stimulation, however, evoked CMAPs with str iking changes in morphology and area but only minimal amplitude change s, due to concomitant diagnoses of carpal tunnel syndrome and polyneur opathy. Collision studies were therefore required for diagnostic confi rmation of the MGA. (C) 1997 John Wiley & Sons, Inc.