Introduction: Anatomical variations in the innervation of intrinsic hand muscle are well known as Martin - Gruber anastomosis (MGA) that spread from the median to the ulnar nerves in the forearm. Although anatomical studies have shown that a crossover of sensory fibers is not rare in forearm MGA, it has been electrophysiologically described only in rare subjects. We hypothesized that the sensory fibers are not rare in MGA, and often follow the motor fibers.
Subjects and methods: The study included 59 of subjects with a total of 111 arms, with electrodiagnostically confirmed the presence of MGA on the forearm for motor fibers. In order to demonstrate the presence of sensory fibers in MGA, we stimulated the median nerve at the elbow and recorded the antidromic sensory potential from ulnar innervated digit (5th finger).
Results: Sensory MGA were present in 42 out of 111 arms (37.8%) with CI 95. There were 54 left hands with motor MGA, of which 18 (33.3%) had sensory fibers MGA, and 57 right hands with motor MGA, and 24 (42.1%) of which had sensory MGA.
Conclusion: This electrophysiologically study demonstrated the high incidence of sensory fibers in MGA anastomosis. Presence of sensory fibers as a possible anatomical variation should be taken into consideration during electroneurography analysis, diagnosis and surgical therapy.