Cannieu-Riche anastomosis of the ulnar to median nerve in the hand: case report.

We observed in a male cadaver the presence of a new type of very long Cannieu-Riche anastomosis between the proximal portion of the deep branch of the ulnar nerve for the adductor pollicis and ramus of the recurrent branch of the median nerve to the superficial head of the flexor pollicis brevis. The clinical relevance of such a communication is the possible preservation of the function of all or part of thenar muscles from the ulnar nerve in case of median nerve lesion. The ignorance of that anomaly can induce obscure clinical, surgical and electroneuromyographical findings. We report on the incidence, the double innervation and the clinical significance of Cannieu-Riche anastomosis and provide a new classification of the various types of this nerval connection.