重症肌无力患者伸指总肌的单纤维肌电图和重复电刺激检测的对比性研究

目的探讨重症肌无力（MG）患者自主收缩单纤维肌电图（SFEMG）和重复电刺激（RNS）检测结果敏感性不同的可能原因。方法选择67例MG患者，每例患者均在同一天的同一时段依次进行有侧伸指总肌的低频RNS和自主收缩SFEMG检查。结果67例MG患者SFEMG的异常率（92．5％）明显高于RNS的异常率（50．7％）（P〈0．01）。RNS波幅递减值与SFEMG中的平均颤抖（Jitter）值、异常电位对和阻滞电位对百分比均呈显著的正相关。RNS检测示波幅明显递减的34例患者中，有2例在SFEMG中未发现阻滞电位，这2例患者的波幅递减值最高达62％；而RNS检测示无波幅递减的33例患者中，传导阻滞电位对百分比最高达58％。结论在诊断MG时，同一肌肉的SFEMG检查较RNS的诊断敏感性高。RNS检测中波幅递减幅度与SFEMG中的阻滞电位对百分比并非完全对应。SFEMG检查较RNS敏感性高可能有两个方面的原因：（1）RNS检测记录的是肌肉表面肌纤维运动单位电位幅度的总和，而SFEMG记录的是肌纤维单个运动终板传递时间的延长或阻滞；（2）RNS和自主收缩SFEMG所检测的可能是不同类型的运动终板。

A comparative study of single fiber electromyography and repetitive nerve stimulation of the same extensor digitorum communis muscle in patients with myasthenia gravis

Objective To investigate the possible causes of the different diagnostic sensitivity of voluntary single fiber electromyography (SFEMG) and repetitive nerve stimulation(RNS) in patients with myasthenia gravis (MG). Methods The voluntary SFEMG and RNS at low rates were recorded successively from the same extensor digitorum communis (EDC) muscle on the same day in 67 patients with MG. Results The diagnostic sensitivity of SFEMG and RNS was 92.5% and 50.7%, respectively, with the former statistically significantly higher than the later. The percentage of decrement of RNS was positively correlated with 3 SFEMG parameters, i.e. the mean jitter, percentage of abnormal pairs of potential and percentage of impulse blocking. Among the 34 cases with significant decrement on RNS, 2 had no impulse blocking and the maximum decrement reached 62%, while 33 cases with normal RNS had up to 58% of impulse blocking. Conclusion The voluntary SFEMG was more sensitive than RNS in diagnosing MG even in the same muscle. The blocking phenomenon observed in voluntary SFEMG was not completely corresponding to the decrement in RNS.The possible explanations were partly because that RNS recorded the total muscle fibers response in surface of the muscle and SFEMG examined the increasing or blocking at individual motor end-plates, and partly because that the voluntary SFEMG and RNS might explored endplates belonging to different motor units.