重复神经电刺激疲劳试验在全身型重症肌无力中的应用价值

Application value of exercise test of repetitive nerve stimulation in evaluating myasthenia gravis

目的观察重复神经电刺激（RNS）及疲劳试验对全身型重症肌无力fMG）的诊断应用价值，探讨提高RNS诊断阳性率的方法。方法广州医学院荔湾医院神经内科自2008年1月至2012年6月45例收治的全身型MG患者45例，首先在休息状态下对每位患者的口轮匝肌、肘肌、三角肌和小指展肌分别用低频（1Hz、3Hz、5Hz）和高频（10Hz、20Hz、30Hz）超强电流进行RNS检查；之后肌肉强直收缩，疲劳后再以同样电流进行RNS检查，观察阳性率的变化。结果疲劳试验前4块肌肉综合统计低频刺激下RNS阳性率[60．0％（27／45）]，高于高频刺激下RNS阳性率[17．78％（8／45）]，差异有统计学意义（X2=16．878，P=0．000）；与疲劳试验前比较，疲劳试验后肘肌、三角肌的RNS阳性率增加，差异有统计学意义（P〈0．05）；口轮匝肌、小指展肌的RNS阳性率无明显变化，差异无统计学意义（胗0．05）；4块肌肉综合统计低频刺激下RNS阳性率增高，差异有统计学意义（P〈O．05）。结论（1）重复神经电低频刺激在MG疾病诊断中具有重要的价值，低频刺激阳性率高，具诊断价值；（2）不同肌肉的阳性率不同，同时做4块肌肉可明显提高RNS的阳性率及灵敏度；（3）疲劳试验可显著提高三角肌、肘肌和低频刺激下4块肌肉综合统计的RNS阳性率，从而提高诊断的灵敏度。

Objective To evaluate the diagnostic utility of repetitive nerve stimulation （RNS） and the effect of exercise test in RNS, as well as to find the way to improve the diagnostic sensitivity of RNS in myasthenia gravis （MG）. Methods A total of 45 patients with generalized MG, admitted to our hospital from January 2008 to June 2012, were chosen in our study; they, firstly, underwent RNS test in orbicularis otis, anconeus, deltoid and musculus abductor digiti minimi with low frequency （1, 3 and 5 Hz） and high frequency （10, 20 and 30 Hz） supramaximal current, and then, till the muscle tetanic contraction （fatigue）, RNS test at the same frequency was performed again; the diagnostic sensitivity of RNS in MG was compared. Results Before exercise test, the comprehensive positive rate of the four muscles on low-frequency RNS test was 60.0% （27/45）, which was significantly higher than that on high-frequency RNS test （17.78%, 8/45） ff2=16.878, P=-0.000）. As compared with that before exercise test, the RNS positive rate of anconeus and deltoid after exercise was significantly higher （P〈0.05）, while no significant difference was noted on orbicularis otis and abductor digiti minimi between before exercise test and after exercise test （P〉0.05）. Increased comprehensive positive rate of four muscles in low-frequency RNS test was showed as compared with that in high-frequency RNS test （P〈0.05）. Conclusion RNS has important diagnosis value in MG, and low-frequency RNS enjoys high positive rate; different muscles have different positive rate of RNS, and RNS for the four muscles at the same time can obviously increase the positive rate and detection sensitivity; exercise test can significantly improve the diagnostic sensitivity of RNS in anconeus and deltoid, as well as the comprehensive positive rate offour muscles in low-frequency RNS test.