Peripheral nerve tumors associated with Martin-Gruber anastomosis

Anomalous communications between median and ulnar nerve in the forearm have been widely described during the years. The most common of these anastomosis, known as Martin–Gruber anastomosis (MGA), consists in a neural connection between median and ulnar nerve in the forearm, usually in its proximal part, that results in an anomalous course of the fibers innervating the intrinsic muscles (and rarely cutaneous region) of the hand. Its frequency, firstly described by Gruber in 1870 as 15.2% in 250 studied arms, is currently estimated through neurophysiological and anatomical studies to range between 10% and 40% (Amoiridis, 1992; Rodriguez-Niedenführ et al., 2002; Lee et al., 2005). Much rarer is ulnar to median communication, known as Marinacci communication, where fibers from the ulnar nerve cross over to the median nerve in the forearm (Marinacci, 1964). The knowledge of such anatomical variants is important to explain some electrodiagnostic (EDX) findings. Moreover, its identification is crucial for reaching a correct diagnosis and providing information on prognosis and treatment. We report on two patients who presented with the coexistence of median–ulnar anastomosis and nerve tumors.