The prevalence of Martin-Gruber anastomosis in Iranian subjects by electrodiagnostic criteria

Median–ulnar anastomosis [Martin–Gruber anastomosis (MGA)] is a common anatomic variant. The crossover often occurs in mid-forearm. Median fibers that have crossed then run with distal ulnar nerve to innervate any of following ulnar muscle: (i) Abductor digiti minimi (ADM), (ii) first dorsal interosseous (FDI), (iii) adductor pollicis, (iv) deep head of flexor pollicis brevis, or (v) combination of these. The FDI is the most common termination (34%), followed by hypothenar (15.5%) and then Thenar (12%) musculature.1 This anomaly is asymptomatic. It seems to have less prevalence in our population, however, we did not find any published document regarding the prevalence of this anomaly, so the main goal of this study was to estimate the frequency of MGA in referred subjects to academic electrodiagnostic (EDX) clinics of physical and rehabilitation (PM and R) department. This descriptive cross sectional study was performed in subjects referred to our EDX clinics of PM and R department. Ninety subjects were recruited who had normal neurological exam. The subjects with median or ulnar nerves injuries due to trauma or polyneuropathy were excluded by supra max stimulate at wrist and elbow. The median nerve compound muscle action potential (CMAP’s) was recorded from abductor pollicis brevis (APB), ADM, and FDI. Afterward, the ulnar nerve was stimulated at wrist and below elbow recording from abductor ADM and FDI and APB muscles. The examinations were conducted in both sides. After recording these CMAP’s, four conditions may have occurred: (1) All the tests were within normal range; (2) while stimulating ulnar nerve and recording from FDI, > 20% decline in amplitude between wrist and elbow was detected and recording from ADM was normal, then median was stimulated in antecubital fossa whereas recording from FDI; provided that MGA was present, the amplitude difference of ulnar stimulation between elbow and wrist was recorded from FDI and when median was stimulated in wrist whereas recording from FDI a small positive wave record from volume conduction of nearby muscles; (3) during stimulating ulnar nerve and recording from ADM, more than 20% of amplitude decline was detected between elbow and wrist; then median was stimulated in antecubital fossa whereas recording from ADM; provided that MGA was present, the amplitude difference of ulnar stimulation between elbow and wrist was recorded from ADM and when median was stimulated in wrist whereas recording from ADM, a Iranian Journal of Neurology