Changes in nerve conduction with ulnar lesions at the elbow.

Ulnar nerve lesions at the elbow can usually be recognized by a characteristic combination of physical signs. In the hand, there is wasting and weakness of ulnar-innervated muscles with or without sensory loss of appropriate distribution; in the forearm there is often weakness of the ulnarinnervated portion of the flexor digitorum profundus and sometimes of the flexor carpi ulnaris. Further confirmation may be provided by the presence of deformity or arthritic change in the elbow joint with palpable thickening of the nerve trunk in the ulnar groove. In such cases ancillary methods of diagnosis are seldom necessary, but in others the physical signs may be less obvious and any technique which assists localization deserves serious consideration. Changes in motor nerve conduction in a patient with an ulnar nerve lesion at the elbow were first reported by Simpson (1956) who found that conduction was slowed through the affected region but that it was relatively normal both above and below it. A different approach to the study of nerve conduction was provided by the work of Dawson and Scott (1949) and Dawson (1956) on the direct recording of nerve action potentials, and Gilliatt and Sears (1958) showed that in patients with ulnar nerve lesions at the elbow abnormalities of the nerve action potential were present which might be particularly valuable in the diagnosis of mild cases. Since January, 1956, we have studied 14 patients in each ofwhom the presence of an ulnar nerve lesion at the elbow was well established on clinical grounds. In these patients we have used the techniques developed by Simpson and by Dawson to study nerve conduction and our results form the subject of the present paper. In addition we have found it necessary to obtain more information about the range of normal variation and have made a series of control observations which will be described.