Department of Neuropaediatrics and Muscular Disorders, University Medical Center Freiburg, Germany.
Brain Stimul. 2010 Apr;3(2):87-94. doi: 10.1016/j.brs.2009.10.003. Epub 2009 Oct 31.
One major attribute of transcranial magnetic stimulation (TMS) is the variability of motor-evoked potential (MEP) amplitudes, to which variations of coil positioning may contribute. Navigated TMS allows the investigator to retrieve a stimulation site with an accuracy of 2.5 mm and to retain coil position with low spatial divergence during stimulation.
The purpose of this study was to investigate whether increased spatial constancy of the coil using a navigational system decreases the variability of MEP amplitudes and increases their reproducibility between different points in time of investigation.
We investigated eight healthy subjects (mean age 23.8 +/- 1.2 years, range 22-25, four women, four men) at three different points in time with and without an optically tracked frameless navigational device, respectively. Input-output curves, motor threshold, and MEP amplitudes were recorded. We calculated the coefficient of variation as statistical parameter of variability. Reproducibility between different sessions was assessed via the MEP amplitude.
The coefficient of variance of MEP amplitudes did not show a distinct difference between navigated and non-navigated TMS in input-output curves. MEP amplitudes, indicating reproducibility, did not significantly differ between sessions with and without navigated TMS, either.
Our results do not support the hypothesis that increased spatial constancy using a navigational system improves variability and reproducibility of MEP amplitudes. Variability of MEPs might mainly be due to not influenceable neurophysiologic factors such as undulant cortical excitability and spinal desynchronization.
经颅磁刺激（TMS）的一个主要特征是运动诱发电位（MEP）幅度的可变性，这可能与线圈定位的变化有关。导航 TMS 允许研究人员以 2.5 毫米的精度检索刺激部位，并在刺激过程中保持线圈位置的低空间发散。
本研究旨在探讨使用导航系统是否可以增加线圈的空间稳定性，从而降低 MEP 幅度的可变性，并提高其在不同时间点的可重复性。
我们分别在三个不同的时间点对 8 名健康受试者（平均年龄 23.8 +/- 1.2 岁，范围 22-25 岁，4 名女性，4 名男性）进行了研究，分别使用和不使用光学跟踪无框架导航设备。记录输入-输出曲线、运动阈值和 MEP 幅度。我们计算了变异系数作为变异性的统计参数。通过 MEP 幅度评估不同时间段之间的可重复性。
在输入-输出曲线中，导航和非导航 TMS 之间的 MEP 幅度变异系数没有明显差异。MEP 幅度，即可重复性，在有和没有导航 TMS 的不同时间段之间也没有显著差异。
我们的结果不支持增加使用导航系统的空间稳定性可以提高 MEP 幅度的可变性和可重复性的假设。MEP 的可变性可能主要归因于不可影响的神经生理因素，如波动的皮质兴奋性和脊髓去同步化。
