Disclosures: Meghan K. Hayes, MD: No financial relationships or conflicts of interest

Case Diagnosis: Asymmetric Riche–Cannieu anastomosis

Case Description: 52-year-old right hand dominate man with past medical history of bilateral carpal tunnel syndrome with right sided carpal tunnel release without improvement presented for evaluation of bilateral hand numbness and tingling. Examination showed preserved muscle strength and decreased pin-prick over palmar digits 2-5 bilaterally. Right median nerve testing showed normal motor responses and sensory responses with prolonged peak latencies and normal amplitudes. Left median nerve stimulation at typical nerve locations showed no motor response and sensory testing showed prolonged peak latencies and decreased amplitudes. Pick up over the abductor pollicus brevis showed a motor response with stimulation at the wrist over the ulnar nerve.

Setting: VA Medical Center Electrodiagnostic LaboratoryAssessment/

Results: This patient presented for evaluation of symptoms typically suggestive of carpal tunnel syndrome and was diagnosed with a Riche-Cannieu anastomosis.

Discussion: There are four commonly described anomalous connections between the median (MN) and ulnar nerves (UN); Martin Gruber anastomosis, Marinacci anastomosis, Barrettini anastomosis, and Riche-Cannieu anastomosis (UN to the MN in the hand). The fourth was observed in this patient with the left hand being predominantly more affected than the right. This abnormality was originally described by Riche and Cannieu in 1897 as a cross over in the palm between the deep branch of the UN and the recurrent branch of the MN. The incidence is predicted to be between 3.12–77% in cadaveric dissections. However, there are few case reports delineating the clinical picture and electrodiagnostic findings of this anomaly. This case adds to the current body of knowledge regarding this anomaly and also demonstrates the presence of significant asymmetry of this anomaly in this patient.

Conclusion: The identification of a Riche-Cannieu abnormality is important to prevent incorrect diagnosis of a more severe median mononeuropathy and potentially unwarranted surgical intervention.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/asymmetric-riche-cannieu-anastomosis-disguised-as-a-median-mononeuropathy-a-case-report/