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Updated: Aug 5, 2026

Screening of Axonal Degeneration in Carpal Tunnel Syndrome Using Ultrasonography and Nerve Conduction Studies
Published on: January 11, 2019
Combined Martin-Gruber and complete Riché-Cannieu anastomoses disclosed during the electrodiagnostic evaluation of
1Department of Neuromuscular Medicine, Hospital for Special Care, 2150 Corbin Avenue, New Britain, CT, 06053 USA.
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.
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