The all ulnar motor hand without forearm anastomosis.

Anomalous ulnar innervation of intrinsic hand muscles, inferred in a number of clinical series, has been documented only rarely in electrophysiological studies. Using near-nerve and standard conduction studies we evaluated 2 cases with nearly exclusive ulnar innervation of hand muscles. There was no evidence of anomalous communication in the forearm. Digital sensory fibers were normally distributed in median and ulnar nerves. The anomalous motor innervation most likely results from palmar communication between ulnar and median branches (Riche-Cannieu anastomoses). The normal distribution of digital afferents suggests that such anastomoses are formed primarily by motor axons.