Electrodiagnostic investigation of the neuromuscular lesions in rheumatoid arthritis

85 muscles, in 30 rheumatoid arthritis patients, were examined by EMG. The patients were subdivided into steroid and non-steroid treated groups. In both groups, the EMG demonstrated myopathic, polymyositic and neuropathic lesions, the first two predominating. Similar changes were found regardless of the size of the muscle examined. A relatively high number of myopathic changes were observed in early RA. The activity of the disease did not seem to play an important role. No correlation with the condition of the adjacent joint was found. No patient had a normal EMG in all the muscles examined. The conduction velocity indicated an entrapment syndrome in four patients. Creatine phosphokinase was normal in 23 patients, while aldolase was moderately high in 9 of 23 cases.