BACKGROUND: The examination of sympathetic skin response is an important index for assessing the autonomic nerve function, and patients with myasthenia gravis are always accompanied by dysautonomia.Therefore, it will be important to know whether sympathetic skin response can be used as the index for the clinical evaluation of myasthenia gravis.OBJECTIVE: To investigate the diagnostic value of sympathetic skin response in the damage of autonomic nerve function of patients with myasthenia gravis.DESIGN: A case-controlled comparative observation.SETTING: Department of Neurology and Room of Nerve Electromyogram, the Affiliated Hospital of North Sichuan Medical College.PARTICIPANTS: Thirty outpatients or inpatients with myasthenia gravis were selected from the Department of Neurology, the Affiliated Hospital of North Sichuan Medical College from May 2006 to May 2007, including 9 males and 21 females, aged 8 - 72 years with a mean age of (28±5) years old. They were all accorded with the diagnostic standards of myasthenia gravis, accompanied by different severity of autonomic nerve symptoms, including poor skin nutrition, sweating of hands and feet, pyknocardia,persistent hypotension, abdominal pain, constipation, etc. They all had not taken any drug affecting the autonomic nerve function before the examination. Informed consents were obtained from all the patients.Meanwhile, 30 healthy physical examinees were enrolled as the normal control group, including 10 males and 20 females, aged 10 - 75 years with a mean age of (31±5) years old. Approval was obtained from the hospital ethic committee.METHODS: After admission, the patients were examined with sympathetic skin response using DANTEC keypoint 2.0 electromyography evoked potential apparatus (Danmark). The changes of the latency and wave amplitude of sympathetic skin response were observed. The subjects in the normal control group were examined with the same methods at physical examination. Abnormality was judged by the disappearance of wave form, latency longer than that in the normal control group by Mean±2.5SD, or wave amplitude lower than the average value in the normal control group by 50%.MAIN OUTCOME MEASURES: The results of the latency and wave amplitude of sympathetic skin response were compared between the patients with myasthenia gravis and normal controls.RESULTS: All the 30 patients with myasthenia gravis and 30 healthy physical examinees were involved in the final analysis of results. There were no significant differences between the left and right upper and lower limbs in both the myasthenia gravis group and normal control group (P ＞ 0.05). In the myasthenia gravis group, the abnormal rate of sympathetic skin response was 37% (11/30), the latency was prolonged and the wave amplitude was decreased as compared with those in the normal control group, and there were significant differences (P ＜ 0.01).CONCLUSION: Sympathetic skin response can be used as an electrophysiological index for judging the damages of autonomic nerve function in patients with myasthenia gravis.