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Abstract Background Martin–Gruber anastomosis (MGA) is one of the most common anomalous innervations of the upper limb. It may alter the usual clinical picture and electrophysiological characteristics of median nerve (MN) injury or ulnar nerve (UN) injury. Aim To determine the mutual relation between MGA and carpal tunnel syndrome (CTS) regarding their association and to explore whether certain patterns of MGA are more prevalent in patients with CTS. Methods This study included 100 forearms of 64 subjects. They were 37 subjects complaining of unilateral or bilateral clinical symptoms of idiopathic CTS according to the criteria of the American Academy of Neurology and 27 subjects healthy or having traumatic lesions in either the upper or lower limbs with no neurological disorders. Electrophysiological studies of the MN and UN for the confirmation of CTS as well as the validation of MGA were done. Results By electrophysiological examination, MGA was encountered in 22% forearms of all the studied groups, mostly females. MGA type II and type III were the commoner types, each occurring in 40.9%, while type I and type IV each occurred in 9.1%. MGA type II was prevalent in the control group, while type III associated subjects with only clinical CT symptoms. Conclusion MGA is not prevalent in patients with CTS. Different types of MGA are present in CTS, but MGA was not implicated in the occurrence, severity, or electrodiagnostic features of CTS.

The median-to-ulnar communicating branch (MUC) is an asymptomatic variant of the upper limb innervation that can lead to interpretation errors in routine nerve conduction studies. The diagnosis of carpal tunnel syndrome (CTS) or ulnar nerve lesions can be complicated by the presence of MUC. In this study, we describe electrophysiological features of MUC in CTS patients presenting to our clinic. We enrolled MUB cases from consecutive CTS patients referred to our laboratory between the years 2014 and 2019. MUC was present in 53 limbs (36 patients) from the studied population. MUC was bilateral in 53% of patients. MUC type II was the most common subtype (74%), followed by types III and I; more coexisting MUC types were found in the majority of tested limbs. A positive correlation was demonstrated between the severity of CTS and the presence of positive onset, faster CV, or a double component of the compound muscle action potentials. We emphasize the importance of suspecting the presence of MUC in CTS in the presence of a positive onset or a double component in routine motor conduction studies.

Introduction: Median and ulnar motor nerve conduction study recording from median-innervated 2nd lumbrical and ulnar-innervated 1st palmar and 2nd dorsal interossei is designated in electrodiagnostic evaluation of carpal tunnel syndrome. In this technique, both responses are recorded by the same surface recording electrode placing over their shared motor point in mid-palm. To the best of our knowledge, this technique has never been utilized in demonstration of Martin-Gruber anastomosis. Case reports: By applying this technique to the conventional CMAP comparison method, the authors accordingly demonstrated Martin-Gruber anastomosis in four cases. Three presented with focal mononeuropathies of the upper limbs, including a severe carpal tunnel syndrome, a mild to moderate carpal tunnel syndrome, and an ulnar neuropathy. One was a normal individual. Significance: This report described a new electrophysiological pattern of MGA. Adding the mid-palm recording to conventional CMAP comparison method provides a broader view in terms of innervation of MGA. This technique is not complicated and can be added to the electrophysiological investigation for complete studying of the innervated muscles in MGA.

Introduction Martin–Gruber anastomosis (MGA) is one of the most common anomalous innervations present in the body. Missing these anomalous innervations may easily be mistaken for technical pitfalls or even for actual pathology. Aim The aim of the current study was to determine the presence and the frequency of MGA by electrophysiological examination in a sample of Egyptian subjects. Subjects and methods It is a cross-sectional study of consecutive apparently healthy volunteers. The study included 200 forearms from 100 apparently healthy Egyptian volunteers in a single-center public-hospital-based electromyography laboratory. Electrophysiological studies in the form of motor conduction study for the median and ulnar nerves were performed by recording the hypothenar, first dorsal inerosseous, and thenar muscles. Qualitative data were analyzed using Pearson’s Chi-square test and Fisher’s exact test. Results The present study included 69 (69%) women. MGA was found in 39 (19.5%) forearms of 26 (26%) subjects electrophysiologically. There was no statistical significant difference between the occurrence of MGA in men versus women (P=0.127). The most common form was MGA to the first dorsal interosseous muscle. It was present in 30 (15%) forearms of 24 (24%) subjects. MGA to thenar muscles was present in 13 (6.5%) forearms of 12 (12%) subjects. MGA to the abductor digiti minimi muscle was present in five (2.5%) forearms of five (5%) subjects. Conclusion Martin–Gruber anastomosis is present in Egyptians. The frequency of occurrence of MGA in a sample of Egyptian subjects was found to be 26% in electrophysiological examination.