Résumé
This case report describes an unusual communicating branch from radial to ulnar nerves in the axilla region on the right side of the Korean cadaver of a 59-year-old male. The brachial plexus containing the communicating branch were extracted en bloc. The extracted specimens were immersed in Guanidine-HCl (0.2 M) for two weeks and then treated several times with an ultrasonic cleaner for an hour to soften the connective tissue around the nerve bundles. The spinal root origins of this communicating branch were found to be largely C7 and some C8. Unexpectedly, the branches of the ulnar nerve innervated the medial two-third of the medial head of the triceps brachii muscle on the right side in the same cadaver. Numbers of nerve fibers of the communicating branch and the main distributing branch of the ulnar nerve to the triceps brachii muscle were 523 and 525, respectively. This result implies that nerve fibers moving from the radial to the ulnar nerves may innervate the original distributing territories of the radial nerve. Another possibility is that a part of radial muscular branch to the triceps beachii muscle may be fused to the ulnar nerve in their distributing territories.