Relative frequency of nerve conduction abnormalities at carpal tunnel and cubital tunnel in France and the United States: importance of silent neuropathies and role of ulnar neuropathy after unsuccessful carpal tunnel syndrome release.

The two most frequently diagnosed nerve compression syndromes of the upper extremities are carpal tunnel syndrome and cubital tunnel syndrome. In order to determine the relative frequencies of nerve conduction abnormalities at the carpal tunnel and cubital tunnel in France and the United States, we evaluated all patients (nFR = 882 and nUS = 818) who had nerve conduction studies of the upper extremities over a six-yearFR or three-yearUS interval. In both France and the United States, the risk of electrophysiological abnormalities was 2 to 1 for the wrist relative to the elbow. Abnormal median nerves were twice as likely to be symptomatic as were abnormal ulnar nerves (silent ulnar neuropathy). Thus, the clinical risk for carpal tunnel syndrome relative to cubital tunnel syndrome was approximately 4 to 1. In many cases of persistent hand symptoms following carpal tunnel release, the problem may actually be related to an undiagnosed ulnar nerve lesion. Thus, a complete neurophysiological evaluation of the upper extremity necessitates both median and ulnar studies.