Abstract
Background: In nerve conduction laboratory, various types of cases are encountered. These are generally referred for electrophysiological investigation of the most common syndromes such as carpel tunnel syndrome where there is partial or total sparing of the thenar muscles from the effect of compression of their nerve supply. So for the assessment of traumatic and entrapment lesions of median and ulnar nerves, the knowledge of these anastomosis is important.

Aims and Objectives: The purpose of this study was to assess the prevalence of this anastomosis in healthy individuals, to draw attention of clinicians or surgeons from neurophysiology field to this anastomosis, and to avoid misinterpretations of different studies of needle electromyography and other nerve conduction studies.

Materials and Methods: A total of 150 healthy volunteers were selected from the medical students aged 17–30 years. Surface recording electrodes were placed on the hand abductor pollicis brevis, abductor digiti minimi, and the first dorsal interossei (FDI) of each subject. Using surface electrodes, we percutaneously stimulated the median and ulnar nerves at the wrist and the elbow. Rectangular pulses of 0.2 ms duration were used and the stimulus strength was supramaximal. Compound muscle action potential (CMAP) was recorded. CMAP from the FDI, hypothenar, and thenar muscles larger (at least 1.0 mV) on median nerve stimulation at the elbow than at the wrist and that from one or more of these sites larger (at least 1.0 mV) on stimulation of ulnar nerve at the wrist than at the elbow were accepted as indicators of the presence of the MGA. Analysis was carried out using Statistical Package for Social Sciences, version 10.0. P-value <0.05 was considered as statistically significant.

Results: The type of anastomosis frequently observed was type II, which was observed in 12 subjects; type I was observed in 3; type I + II was observed in 2; and type III was observed in 1 subject.

Conclusion: Because of its high incidence and different electrodiagnostic considerations, MGA should be considered to be of great clinical significance for correct diagnosis and for planning appropriate therapy in peripheral lesions of median and ulnar nerves.

Key words: Compound Muscle Action Potential; Median Nerve; Ulnar Nerve; Martin–Gruber Anastomosis