Objective: Communication between the median and ulnar nerves in the forearm (Martin-Gruber anastomosis) proved by anatomical and nerve conduction studies. The knowledge of these anastomosis is of major importance for assessment of traumatic or entrapment lesions of the median and ulnar nerve. Thus the prevalence of Martin-Gruber anastomosis (as the main purpose) must be determine in any population. The present prospective study was made in Shohada-e-tajrish hospital in 2002. 

Materials & Methods: Data were collected from 212 arms tested for carpal tunnel syndrome, compression ulnaropathy, polyneuropathy to exclude abnormalities. Supramaximal stimuli were given at distal and proximal sites of the median and ulnar nerves. Bar electrodes on define sites were used to record CAMP from thenar, first dorsal interosseous and hypothenar muscles, with stimulation of median and ulnar nerves. Diagnostic criteria for MGA have been proposed:1.CAMP over A.P.B higher in elbow than on wrist stimulation of median nerve. 2. CAMP over A.D.M. higher significantly on wrist than elbow stimulation of ulnar nerve.3.Recording of negative CAMP over A.D.M. of F.D.I. on elbow stimulation of median nerve ( not at wrist).

Results: The study comprised 212 arm(50% left,50% right). The mean age of patients was 26 years (range:15-45years) 52 were women . Eleven subjects has MGA (Prevalence: 10.3%). The sex ratio was 7 females to 4 males.

Conclusion: According to the method of our investigation the prevalence of MGA were 10.3% . More recently nerve conduction studies stated a prevalence of 31-34%. In our study the comparatively small prevalence of MGA must be documented by other studies in our populations.