[Electromyography in children with polymyositis (author's transl)].

: Findings of repeat electromyography (EMG) in 15 children with polymyositis or dermatomyositis are reported. The data classically provided by EMG in these conditions is recalled. Emphasis is put on the contribution of stimulodetection to the diagnosis of primary disease of the muscle. With this procedure, EMG showed myogenic signs in all patients, at the first examination. Electrical anomalies are widespread from the start. A long-term study in 12 patients shows that electrical anomalies remain present long after clinical recovery. EMG disturbances are the last anomalies to disappear. EMG returns to normal when recovery is longstanding. EMG signs reappear if relapse occurs.