Summary

测量单脉冲经颅磁刺激诱导的对侧沉默期以研究M1皮质脊髓抑制

Published: August 23, 2022
doi:

Summary

对侧沉默期(cSP)评估是指示皮质兴奋性和治疗反应的有希望的生物标志物。我们展示了一种评估cSP的方案,用于研究上肢和下肢的M1皮质脊髓抑制。

Abstract

对侧沉默期 (cSP) 是在运动诱发电位 (MEP) 后由肌电图 (EMG) 捕获的背景肌肉电活动抑制期。为了获得这一点,通过传递到所选目标肌肉的主要运动皮层(M1)的超阈值经颅磁刺激(TMS)脉冲来引发MEP,而参与者则提供标准化的自愿目标肌肉收缩。cSP 是 MEP 后发生的抑制机制的结果;它提供了最初~50毫秒脊髓抑制的广泛时间评估,以及之后的皮质抑制。研究人员试图更好地了解cSP背后的神经生物学机制,以验证其作为不同神经精神疾病的潜在诊断,替代和预测生物标志物。因此,本文介绍了一种测量下肢和上肢M1 cSP的方法,包括目标肌肉的选择、电极放置、线圈定位、自主收缩刺激测量方法、强度设置和数据分析,以获得具有代表性的结果。它的教育目标是为下肢和上肢执行可行、可靠和可重复的 cSP 方案提供视觉指南,并讨论该技术的实际挑战。

Introduction

沉默期 (SP) 是在持续肌肉收缩期间应用经颅磁刺激 (TMS) 诱导的运动诱发电位 (MEP) 之后的肌电图 (EMG) 沉默期。超阈值TMS脉冲可以应用于目标肌肉的对侧或同侧初级运动皮层(M1),从中记录肌电图活动产生两种现象:对侧沉默期(cSP)和同侧沉默期(iSP)。

尽管 iSP 和 cSP 具有相似的功能,但它们反映的组件可能略有不同。第一种被认为反映了经胼胝体抑制,因此完全来自皮质12。相反,cSP 被研究为皮质脊髓抑制的可能替代物,最有可能由 M1345 内的 γ-氨基丁酸 (GABA) B 受体介导。

支持cSP在GABA介导的途径中的作用,以前的工作发现口服GABA增强成分后cSP持续时间增加5,678尽管如此,脊柱过程也参与改变其持续时间。cSP 的早期阶段(<50 ms)与 H 反射值3-a 反射降低有关,该反射是周围神经回路的产物,可量化脊髓神经元的兴奋性9。脊柱加工被认为是通过Renshaw细胞的活化,超极化后运动神经元和脊柱中间神经元的突触后抑制介导的101112,1314

尽管有脊柱贡献,cSP主要由皮质抑制神经元的激活引起,皮质抑制神经元负责产生cSP的后期(50-200毫秒)310,131516在这方面,cSP持续时间的早期部分与脊柱抑制机制有关,而长cSP需要更大的皮质抑制机制313,1718

因此,cSP 是治疗神经系统疾病引起的皮质脊髓适应不良的有希望的生物标志物候选者,而更显着的 cSP 持续时间可能反映皮质脊髓抑制的增加,反之亦然511。因此,以前的工作发现cSP持续时间与肌张力障碍,帕金森病,慢性疼痛,中风和其他神经退行性和精神疾病等病理之间存在关联1920,2122。为了说明这一点,在膝关节骨关节炎队列中,较高的皮质内抑制(由cSP索引)与蒙特利尔认知评估量表23中的年轻,更大的软骨变性和较低的认知表现有关。此外,cSP变化还可以纵向指数治疗反应和运动恢复2425,2627282930

尽管cSP在神经精神病学领域的作用很有希望,但其评估的一个具有挑战性的方面是它可能对方案变化过于敏感。例如,cSP 持续时间 (~100-300 ms)11 可区分上肢和下肢。Salerno等人发现,在纤维肌痛患者样本中,第一背侧骨间肌(FDI)的平均cSP持续时间为121.2毫秒(±32.5),胫骨前肌(TA)的平均cSP持续时间为75.5毫秒(±21)。因此,文献传达了用于引出cSP的参数的无数差异,这反过来又危及研究之间的可比性,并延迟了向临床实践的转化。例如,在类似的人群中,关于用于刺激M1和目标肌肉的超阈值TMS脉冲设置的协议是异质的。最重要的是,研究人员未能正确报告其协议中使用的参数。

因此,目标是提供有关如何应用可行,可靠且易于重现的cSP方案来评估上肢和下肢M1皮质脊髓兴奋性的视觉指南,并讨论该程序的实际方法学挑战。此外,为了帮助说明参数选择的理由,我们对Pubmed/MEDLINE进行了非详尽的文献综述,以确定已发表的关于慢性疼痛和康复人群cSP的论文,使用检索词:康复(Mesh)或康复或慢性疼痛或中风,以及经颅磁刺激和单脉冲或皮质沉默期等术语。没有为提取定义纳入标准,合并结果显示在 表1 中,仅供说明之用。

Protocol

该议定书涉及对人类受试者的研究,并与地方伦理委员会的机构和伦理准则以及《赫尔辛基宣言》保持一致。在研究中使用其数据时,获得了受试者的知情同意。 1. 实验前程序 筛选对象。筛查受试者的颅内植入物、癫痫、癫痫发作史和妊娠。使用问卷指南确保遵守最新的安全预防措施32.对于颅内植入铁磁材料(例如弹片、动脉瘤?…

Representative Results

按照分步程序后,传递超阈值TMS脉冲(RMT的120%)将在目标肌肉的EMG记录中引发可观察到的MEP,以及随后的大约150ms至300ms的背景EMG活动抑制(图2)。根据该 EMG 模式,可以计算 cSP 指标。报告最多的结局是相对和绝对SP的持续时间(在ms范围内)。相对SP是从MEP开始到肌电图活动重新出现的测量。一种替代方案是使用放大的电机激励输出(根据协议,MSO = RMT的120%)来确定相对SP…

Discussion

引出 MEP 和 SP 的默认 SI 可能因总体而异。低至 80% RMT 的强度已被证明可以在健康个体中引起 cSP39,但对健康和患病人群的研究仍然使用高达 150% RMT495051 的强度。尽管这种异质性来源可能是目标人群性质所固有的,但不应忽视,因为不同的SI已经显示出独立(无论肌肉收缩力如何)决定了MEP39…

Disclosures

The authors have nothing to disclose.

Acknowledgements

没有致谢。

Materials

Alcohol pads Medline Preparation with 70% isopropyl alcohol
Conductive gel Weaver and Company Used on the electrode
Echo Pinch JTECH medical 0902A302 Digital dynamometer.
Mega-EMG Soterix Medical NS006201 Digital multiple channel EMG with built in software.
MEGA-TMS coil Soterix Medical NS063201 8 shaped TMS coil
Mega-TMS stimulator Soterix Medical 6990061 Single Pulse TMS
Neuro-MEP.NET Soterix Medical EMG software used to analyse the muscles eletrical activity.
Swim cap Kiefer

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Cite This Article
Rebello-Sanchez, I., Parente, J., Pacheco-Barrios, K., Marduy, A., Pimenta, D. C., Lima, D., Slawka, E., Cardenas-Rojas, A., Rosa, G. R., Nazim, K., Datta, A., Fregni, F. Measuring Contralateral Silent Period Induced by Single-Pulse Transcranial Magnetic Stimulation to Investigate M1 Corticospinal Inhibition. J. Vis. Exp. (186), e64231, doi:10.3791/64231 (2022).

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