Combined Martin-Gruber and complete Riché-Cannieu anastomoses disclosed during the electrodiagnostic evaluation of carpal tunnel syndrome

Background

Electromyographers are frequently confronted by anomalous innervations and some may challenge the interpretation of nerve conduction studies (NCS). Reports of 2 or more anomalous innervations in the same patient are rare. I describe the NCS in a patient referred for an evaluation of carpal tunnel syndrome (CTS) who was found to harbor a combined Martin-Gruber anastomosis (MGA) and complete Riché-Cannieu anastomosis (RCA).

Case presentation

This 31-year-old man was referred for electrodiagnostic studies following several months of intermittent right hand numbness and tingling. Clinical exam was normal. Median and ulnar motor NCS showed evidence of a combined MGA and complete RCA. Prolongation of the median sensory peak latency and median-2nd lumbrical motor distal latency provided the electrodiagnostic clues in support of CTS.

Discussion

In summary, this report describes the rare occurrence of a combined MGA and complete RCA in a patient with CTS, demonstrates how NCS can sort out this dual anomaly, and discusses the electrodiagnostic and cadaveric literature on the topic.