Atrophy of the thumb web space in rheumatoid arthritis: clinical and electrodiagnostic studies.

One hundred and twenty definite or classical rheumatoid arthritis (RA) patients with an average duration of the disease of 12.1 years were studied. Sixty-two patients had distinct atrophy of the first dorsal interosseous of the hand without definite signs of carpal, cubital, or ulnar tunnel syndrome (group A); 43 patients showed neither distinct atrophy nor sensory disturbance of either hand (group B). Other patients had sensory and/or motor disturbances due to carpal, cubital, or ulnar tunnel syndrome and other neuropathies. Electrodiagnostic examinations revealed that there were differences in the distal latency to the first dorsal interosseous muscle from the wrist between 24 group-A patients and 14 normal controls (P less than 0.05), and between the group-A patients and 12 group-B patients (P less than 0.1). The results of this study indicate that some RA patients with atrophy of the thumb web space may have compression neuropathy of the most distal branches of the ulnar nerve.