[Quantitative analysis of motor unit potential in patients with dermatomyositic disease]

To diagnose dermatomyositic disease well, we adopted the method of EMG in an investigation of 37 patients. Their electrophysiologic parameters of 220 muscles were determined. The results showed that the parameters, including the average DUR, AMP, RISE, AREA, AR/AM and SI of motor unit potentials (MUPs) were significantly lower than those of the controls (P < 0.05 or P < 0.01), especially AREA and SI (P < 0.01). But no remarkable difference was found between the muscles on the two sides of the diseased extremties. These findings suggest that quantitative analysis of MUPs is of importance to diagnosis of dermatomyositic disease and the parameters such as AREA and SI may provide more valuable information.