Electrophysiological Evaluation and Clinical Implication of Martin-Gruber Anastomosis in Healthy Subjects

Abstract

Background: The aim of this study is to determine the prevalence of Martin-Gruber Anastomosis (MGA) in healthy Egyptian subjects, and to discuss the available literature regarding MGA subtypes and their clinical implications. Methods: An electrophysiological study was conducted in both forearms of 140 healthy subjects. This included the ulnar and median nerves. Compound muscle action potentials were recorded from abductor pollicis brevis, abductor digiti minimi, and first dorsal interosseous muscles. Other measurements included the compound motor action potential amplitude and its innervation ratio. Results: MGA was found in 56 of the 280 forearms. This included 20 men and 36 women. Type II MGA subtype was the most frequent in both genders. The MGA was bilateral in 6 subjects and more frequent on the right side. The highest mean amplitude and innervation ratio were recorded at first dorsal interosseus muscle. Conclusions: The prevalence of MGA in the studied sample of the Egyptian population is 20%. It is important for Hand, Orthopaedic and Neurosurgeons to be aware of this anatomic variation in order to explain paradoxical motor and sensory loss in patients.

Median-to-Ulnar Nerve Communication in Carpal Tunnel Syndrome: An Electrophysiological Study

“…A significant increase in the CMAP amplitude at the wrist, compared to the elbow could be easily found while stimulating the UN and recording from FDI and ADM, though not while recording from APB. In our cohort of MUC and CTS patients, there was not a more affected side, according to the existing evidence [5,6,26], although a few studies in healthy subjects have described a slight prevalence of MUC in the right hand [7,10]. Moreover, we reported MUC III in 60% of patients, and several MUC types often coexisted in the same limb (Table 3), in contrast with a majority of the existent studies [10,29].…”

“…In our cohort of MUC and CTS patients, there was not a more affected side, according to the existing evidence [ 5 , 6 , 26 ], although a few studies in healthy subjects have described a slight prevalence of MUC in the right hand [ 7 , 10 ]. Moreover, we reported MUC III in 60% of patients, and several MUC types often coexisted in the same limb ( Table 3 ), in contrast with a majority of the existent studies [ 10 , 29 ]. This aspect is very relevant because many studies on MUC have only considered recordings from APB [ 11 , 21 , 31 ] or ADM/FDI [ 18 , 20 , 26 ], and some concern may arise about mistakes in interpreting NCS findings if the possibility of different MUC subtypes is not considered.…”

“…Several studies have explored the prevalence and characteristics of the MUC among healthy subjects [ 3 , 4 , 7 , 10 , 13 , 22 , 28 , 29 , 30 ], whereas subjects with MN or UN injuries were often excluded. Only a few studies have explored the effects of such communication in a population of patients affected by CTS [ 5 , 11 , 12 , 21 ].…”

“…The median-to-ulnar communicating branch (MUC) [ 1 ], also known as “Martin-Gruber anastomosis/communication,” is a common anatomical innervation variant of the upper limb in which a crossover of axons passes from the median (MN) to the ulnar nerve (UN) in the forearm; this condition occurs asymptomatically in about 5–40% of the population and is bilateral in 10–40% of cases [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. MUC usually goes undetected, but sometimes it is revealed by the unusual distribution of a motor or sensory deficit after injuries of the MN and UN [ 11 ].…”

Marinacci Anastomosis: A Case Report

“…Some distal function may be spared by these anomalous intercommunications, in cases of ulnar and median nerve lesions, with the detour route bypassing the block in conduction [1]. These are usually asymptomatic and are incidentally discovered during surgery, following nerve injury, during routine electrodiagnostic tests, or during routine cadaveric dissections [1][2][3][4][5][6][7][8][9][10][11]. The common anomalous intercommunications in the forearm and hand include the Martin-Gruber and Marinacci anastomoses in the forearm and the Riche-Cannieu and Berrettini anastomoses in the hand.…”