Riche-Cannieu Anastomosis Presenting in a Patient with Suspected Carpal Tunnel Syndrome: A Case Report


  • Patsaree Pattanasuwanna Rehabilitation unit of Nakhon Pathom Hospital, Nakhon Pathom, Thailand


carpal tunnel syndrome, electrodiagnosis, median-ulnar nerve communications, Riche-Cannieu anastomosis, ulnar-median anastomosis


Objectives: To present an anatomical variant detected from the non-clinical correlation of electrophysiologic findings in a patient suspected of carpal tunnel syndrome (CTS).

Study design: A case report.

Setting: Rehabilitation Unit of Nakhon Pathom Hospital, Nakhon Pathom, Thailand.

Subjects: A 77-year-old man with a history of numbness in both hands for six months who underwent electrodiagnostic evaluation of CTS.

Methods: The patient’s medical record was reviewed, and a nerve conduction study (NCS) was conducted.

Results: The nerve conduction study was conducted to rule out other forms of peripheral neuropathy. Despite the thenar muscles’ bulk and strength being preserved, it was not possible to record the left median compound muscle action potential (CMAP).  Further ulnar nerve stimulation at the wrist and elbow, recorded at the left abductor pollicis brevis (APB) muscle, revealed a normal CMAP response. Based on these results, Riche-Cannieu anastomosis in the left hand was suspected.

Conclusions: In the absence of other supportive evidence, Riche-Cannieu anastomosis should be excluded if the median CMAP response from the APB muscle cannot be obtained due to, e.g. motor weakness and muscle atrophy at the thenar eminence. Stimulation of the ulnar nerve while recording at the APB muscle can help avoid misdiagnosis


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