A clinical and electrical study of ulnar nerve lesions in the hand.

Compression of the ulnar nerve at the wrist or in the palm gives rise to a distinctive clinical syndrome of weakness of the small muscles of the hand with or without associated sensory loss (Hunt, 1908; Harris, 1929; Russell and Whitty, 1947; Bakke and Wolff, 1948). Frequently there is a history of trauma which may be occupational and thus often repeated, although in other cases the onset appears to follow a single injury to the wrist or the hand. In the three-year period ending in November, 1958, nine patients with ulnar nerve lesions in the hand were referred to the Department of Applied Electrophysiology, and we propose to discuss the clinical and electrical findings in this series of patients. A series of normal values for ulnar nerve conduction in the hand has also been obtained and will be described. The ulnar nerve enters the hand superficial to the flexor retinaculum on the lateral side of the pisiform bone; more distally it overlies the piso-hamate ligament and occupies a groove on the medial aspect of the hook of the hamate. It divides into a superficial cutaneous and a deep muscular branch, the latter passing deeply through the hypothenar muscles, which it supplies, to gain the palm where it innervates the interossei, the medial two lumbrical muscles, and the adductor pollicis. From clinical and anatomical considerations it is possible to divide ulnar nerve lesions in the hand into three groups according to the clinical signs and the presumed site of the lesion. The first and largest group is characterized by weakness of the hand muscles supplied by the ulnar nerve with the exception of the hypothenar group; there is no sensory loss. This distribution of muscle weakness will arise from a lesion involving the deep palmar branch of the nerve after the branches to the hypothenar muscles have been given off. Russell and Whitty (1947) reported four such cases. A second group of cases has been described in which all the intrinsic hand muscles supplied by the ulnar nerve were