眼轮匝肌刺激型单纤维肌电图在眼肌型重症肌无力的应用

Stimulation single fiber electromyography in orbicularis oculi in ocular myasthenia gravis

目的建立眼轮匝肌刺激型单纤维肌电图(SFEMG)正常对照组的颤抖参考值,并探索其应用于重复神经刺激(RNS)阴性眼肌型重症肌无力(OMG)患者的敏感度及其与各临床指标的关系。方法2019年1—12月于中山大学附属第一医院神经科肌电图室招募健康志愿者32名,以建立正常对照组的参考值。收集2019年12月至2023年1月中山大学附属第一医院RNS阴性的OMG患者36例。对患者进行定量MG评分(QMGS),记录其新斯的明试验、抗体及胸腺CT结果。使用一次性同心圆针电极对一侧眼轮匝肌进行刺激型SFEMG检测,计算平均连续波间期差(MCD),与正常对照组的MCD平均值及单个值上限对比以评估颤抖是否异常。将均值异常的MCD值分别与QMGS和抗体滴度进行Spearman相关分析。结果32名健康人中男性13名,女性19名,年龄(46.8±18.7)岁,MCD为(19.0±4.4)μs。所得MCD的参考值上限为平均27.7μs,单个37.4μs,超过平均值上限或单个值超过上限者占比超过10%为异常。36例OMG患者中男性20例,女性16例,年龄(37.2±17.0)岁,MCD为(29.9±14.7)μs。颤抖增宽者29例(81%),其QMGS为3(2,4)分;在检测了MG抗体的25例患者中有20例抗体阳性;进行了CT检查的26例患者中有6例胸腺增生、7例胸腺瘤。颤抖正常者7例(19%),其QMGS为3(2,4)分,其中检测了MG抗体的5例均为抗体阳性,进行了CT检查的6例中2例胸腺增生,未发现胸腺瘤。颤抖增宽与正常的两组患者间各临床指标差异无统计学意义。异常MCD均值与QMGS或抗体滴度未发现相关性。结论正常对照组的MCD平均值上限为27.7μs,单个值上限为37.4μs,其用于RNS阴性的OMG患者时敏感度为81%,异常MCD均值与各临床指标无显著相关性。颤抖异常提示神经肌肉接头传递障碍,是MG患者重要的神经电生理指标,适用于RNS阴性患者。眼轮匝肌刺激型SFEMG为神经肌肉接头的功能评估提供了可靠、敏感的电生理手段。

Objective To establish the reference values of stimulation single fiber electromyography(SFEMG)in orbicularis oculi,and to explore its sensitivity in repetitive nerve stimulation(RNS)negative ocular myasthenia gravis(OMG)patients,and the relationship between jitter and various clinical parameters.Methods Thirty-two healthy volunteers were included to establish the reference value of normal controls from January 2019 to December 2019.From December 2019 to January 2023,36 OMG patients with negative RNS were collected.Quantitative MG score(QMGS)was performed,neostigmine test and antibody titers as well as thymus CT results were recorded.One side of the orbicularis oculi muscle was tested with a disposable concentric needle electrode in stimulation SFEMG,and the mean consecutive difference(MCD)value was calculated,which was compared with the average MCD value and upper limit of individual values in normal controls to evaluate whether the jitter was abnormal.Spearman correlation analysis of abnormal mean MCD values with QMGS and antibody titer was conducted.Results Among the 32 healthy volunteers,there were 13 males and 19 females,the age was(46.8±18.7)years,and the MCD was(19.0±4.4)μs.The upper limit of the reference value was 27.7μs for average MCD,and 37.4μs for 10%individual values.Among 36 OMG patients negative at RNS tests,20 were male and 16 were female,with a age of(37.2±17.0)years.The MCD was(29.9±14.7)μs,and Jitter was abnormal in 29 patients(81%).Among them,20(20/25)patients were antibody positive,6(6/26)patients had thymic hyperplasia,and 7(7/26)patients had thymoma.The QMGS was 3(2,4).There were 7 patients(19%)with normal jitter,whose QMGS was 3(2,4).Among the patients with normal Jitter,5(5/5)patients were antibody positive,2(2/6)patients had thymic hyperplasia.There was no statistically significant difference in clinical indicators between the two groups of patients with abnormal or normal jitter.There was no significant correlation in antibody titer or QMGS with abnormal mean MCD value.Conclusions The upper limit of the mean MCD value in the normal controls is 27.7μs.The upper limit of a single value is 37.4μs.Its sensitivity for OMG patients with RNS negative is 81%,and the abnormal mean MCD value does not show a significant correlation with various clinical indicators.Abnormal jitter indicates dysfunction of neuromuscular junction transmission,which is an important neuroelectrophysiological indicator for MG patients and is suitable for RNS negative patients.Orbicularis oculi muscle stimulation SFEMG provides a reliable and sensitive electrophysiological means for functional evaluation of neuromuscular junction.