J Korean Neurol Assoc.  1994 Mar;12(1):87-91.

The Electrodiagnostic Findings in Martin-Gruber Anastomosis

• Lee SA
• Kim KK
• Lee MC
• Sunwoo IN
• Kim KW

Abstract

A median-to-ulnar nerve communication in the forearm (Martin-Gruber anastomosis, MGA) is not rare. Awareness of this anastomosis is important in the clinical and electrodiagnostic evaluation of median and ulnar nerves. According to the muscles innervated by the crossover, three types have been classified. However, there are very few detailed studies of their incidence and combinations. Thus we studied detailed electrophysiologic aspects of MGA to determine their incidence and types. The crossing fibers were detected bilaterally with surface recording electrodes over thenar, hypothenar, and first dorsal interosseous muscles of 112 unselected subjects. 49 males and 63 fema]es. MGA was found in 37(33%) subjects, in 52(23%) limbs. The anomaly was bilateral in 15(41%) of the subjects. Type II was seen in all the MGAdetected 52 limbs (100%), type I in 24 (4696), and type m in 2(4%). From the viewpoint of MGA-detected pattern the pure form of type- II was in 27 limbs(52%), the combination of type II and I in 23(44%), the combination of type I, II and m in 1(2%), and the combination of type Il and m in 1(2%). The mean amplitude and amplitude ratio of the anomalous response were highest at the first dorsal interosseous muscle, which were 3.5mV and 22%. Since the crossing fibers in MGA innervate most commonly the first dorsal interosseous, recordig of this muscle is essential to evaluate the contribution of MGA to median and ulnar nerve lesions.

MeSH Terms

Electrodes
Extremities
Forearm
Humans
Incidence
Male
Muscles
Ulnar Nerve