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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右侧伸指总肌的低频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。
Objective To investigate the possible causes of different sensitivities of SFEMG and RNS in patients with myasthenia gravis (MG). Methods Sixty-seven patients with MG were selected. Each patient underwent the low-frequency RNS and autofrettaged SFEMG of the right extensor total muscle at the same time of the same day. Results The abnormal rate of SFEMG in 67 patients with MG was significantly higher than that of RNS (92.5%) (50.7%, P <0.01). There was a significant positive correlation between the amplitude of RNS amplitude reduction and the average jitter value, abnormal potential and blocking potential in SFEMG. Of the 34 patients with significantly decreased RNS amplitude, 2 showed no sign of block in SFEMG, with a maximum of 62% of the decrease in amplitude in 2 patients; whereas in the 33 patients with no decrease in RNS, The percentage of conduction block potential is up to 58%. Conclusion In the diagnosis of MG, SFEMG examination of the same muscle is more sensitive than the diagnosis of RNS. The magnitude of the amplitude decrease in the RNS test does not correspond exactly to the percentage of arrest potential in SFEMG. SFEMG may be more sensitive than RNS for two reasons. (1) The RNS test records the sum of the motor unit potential amplitudes of myofibers on the muscle surface, whereas SFEMG records the prolongation or arrest of the delivery time of a single motor endplate in the muscle fibers. (2) RNS and autonomic contractions SFEMG may be detected by different types of motor end-plates.