A new variation of abductor digiti minimi accessorius.

An anomalous hypothenar muscle, similar to previous descriptions of an abductor digiti minimi accessorius, was discovered during routine cadaveric dissection. This muscle is unique in that it differs in its insertion from those described previously. In addition, the abductor digiti minimi presented with 2 heads that received innervation from the same ulnar nerve branch as the anomalous muscle rather than from the deep branch of the ulnar nerve. This knowledge is useful to the hand surgeon in diagnosing and surgically treating problems associated with Guyon's canal.