Complete ulnar innervation of the thenar muscles combined with normal sensory fibres in a subject with no peripheral nerve lesion.

A complete ulnar innervation of all thenar muscles, including the opponens, have to our knowledge been described only in patients with severe traumatic lesions of the median nerve. The present study reports a subject with exclusive ulnar innervation of the thenar muscles in the right hand. The patient had no anamnestic or objective signs of peripheral nerve lesions. While his sensory and motor ulnar nerve fibres were normal, electrophysiological examination of the right median nerve showed normal course of the sensory fibres but apparently no motor fibres to the thenar muscles.