Prevalence of Martin-Gruber Anastomosis – an Electrophysiological Study

Abstract

Objective: Martin-Gruber anastomosis (MGA) is a median-to-ulnar nerve communication in the forearm; three types of MGA occur. Typically, motor fi bres course through the median nerve in the upper arm and elbow, however, they supply the ulnar-innervated muscles of the hand: abductor digiti minimi (ADM) – MGA-I; fi rst dorsal interosseous (FDI) – MGA-II; or adductor pollicis – MGA-III. The objective was to determine the prevalence of MGA in a study group of healthy volunteers. Methods: Two hundred and ninety-two healthy participants (457 arms) were enrolled. Motor and sensory nerve conduction studies of the ulnar and median nerves were performed. Ulnar and median nerve compound muscle action potential amplitudes were obtained on stimulation at the elbow and wrist. Results: We found 109 cases of MGA in 90 arms (MGA-I in 30 arms; MGA-II in 57 arms; MGA-III in 22 arms). We found isolated MGA types in 73 arms, a combination of two types in 15 arms, and occasionally (2 arms) a simultaneous combination of all three types. Conclusion: The prevalence of MGA was 19.7%. Most frequently, we found MGA-II (prevalence = 12.5%). Signifi cance: MGA does not produce any clinical signs. However, it can change EMG results. The neurophysiologist must be able to logically interpret such fi ndings.