Martin-Gruber Anastomosis

The Martin-Gruber Anastomosis (or Martin-Gruber Connection) is a communicating nerve branch between the median nerve and the ulnar nerve in the forearm. It is the most common anastomotic anomaly that occurs between these two nerves.^[1] This connection carries motor nerve fibers. In cases of nerve lesions of the median or ulnar nerves the MGA can serve as a conduit for alternative innervation of portions of the forearm or hand. This inconstant pattern of connection can serve as explanation for a difficult or challenging differential diagnosis.^[2] In one study,^[3] the MGA was found in 22.9% of cadaver specimens. This relatively high incidence demonstrates the necessity for healthcare specialists to factor the MGA into their diagnoses.

Discussion:.[4]
   - motor nerve may cross over from the median to ulnar nerve in the forearm; (motor connections but not sensory connections);
   - it occurs in two patterns:
   - from median nerve in proximal forearm to ulnar nerve in middle to distal third of forearm, & from AIN to ulnar nerve;
   - other anastomoses between median nerve & ulnar nerve includes:
        - motor branch of median nerve to superficial head of FPB & ulnar nerve to the deep head of the FPB;
        - anastomosis, of median nerve & ulnar motor branches thru first lumbrical or thru innervation of & adductor pollicis;
        - branch of median nerve to third lumbrical joining neural branch to this muscle from deep branch of ulnar nerve;
        - median nerve may also form anastomoses w/ branch of radial nerve in  vicinity of  apb & have radial nerve innervate this muscle;
        - first dorsal interosseous, adductor pollicis, or even abductor digiti minimi may be innervated by the median nerve

References

• Standring, Susan (2008). Gray's Anatomy 40th ed. Elsevier. p. 854. ISBN 0443066841.