Virginia Commonwealth University, Biomedical Engineering, Rehabilitation Engineering to Advance Ability Lab (REALab), Biotech Eight, Room 421, 737 North 5th Street, Richmond, VA 23219, United States.
Virginia Commonwealth University, Biomedical Engineering, Rehabilitation Engineering to Advance Ability Lab (REALab), Biotech Eight, Room 421, 737 North 5th Street, Richmond, VA 23219, United States.
Neurophysiol Clin. 2022 Oct;52(5):366-374. doi: 10.1016/j.neucli.2022.07.002. Epub 2022 Jul 26.
The purpose of this study was to determine the effect of common transcranial magnetic stimulation (TMS) waveforms (monophasic and biphasic) on resting motor threshold (RMT), active motor threshold (AMT), and motor evoked potential (MEP) amplitudes in the biceps and first dorsal interosseous (FDI) because waveforms may affect motor targets differently. We also determined test-retest reliability.
Ten individuals participated in two sessions of TMS delivered to the motor cortex. Monophasic stimulation to induce a posterior-anterior current in the brain (mono) and biphasic posterior-anterior then anterior-posterior (bi) were applied in each session in random order. In each session, there were four blocks of measurements (2 muscles × 2 waveforms) of RMT, AMT and MEPs at the hotspot location. MEPs were normalized to the maximum EMG signal.
RMTs and AMTs were lower for mono compared to bi stimulation for the biceps (p<0.01) and FDI (p<0.01). Normalized MEPs were greater for mono compared to bi stimulation in the FDI (p=0.01) and not different in the biceps (p=0.86). Motor thresholds were not different between sessions suggesting high reliability (p<0.01). Normalized MEPs had very low reliability across sessions in the FDI, and moderate reliability in the biceps.
Preliminary investigation suggests the effect of TMS waveform on motor thresholds is similar in upper limb proximal and distal muscles, but the effect differs per motor target for MEPs. Further, test-retest reliability of waveform effects was sensitive to target muscle. These findings may contribute to improve the efficacy and reliability of TMS for clinical use.
本研究旨在确定常见的经颅磁刺激（TMS）波形（单相和双相）对肱二头肌和第一背侧骨间肌（FDI）静息运动阈值（RMT）、主动运动阈值（AMT）和运动诱发电位（MEP）幅度的影响，因为波形可能会以不同的方式影响运动靶点。我们还确定了测试-重测信度。
10 名个体参加了两次 TMS 刺激运动皮层的试验。在每次试验中，以随机顺序施加单相刺激以在大脑中产生后前电流（单）和双相后前然后前向后（双）。在每次试验中，有四个测量块（2 块肌肉×2 种波形）的 RMT、AMT 和热点位置的 MEP。MEP 被归一化为最大肌电图信号。
与双相刺激相比，单相刺激时肱二头肌（p<0.01）和 FDI（p<0.01）的 RMT 和 AMT 较低。与双相刺激相比，单相刺激时 FDI 的 MEP 归一化值更大（p=0.01），而肱二头肌则无差异（p=0.86）。运动阈值在两次试验之间无差异，提示可靠性高（p<0.01）。在 FDI 中，MEP 的归一化值在两次试验之间的可靠性非常低，而在肱二头肌中则为中度可靠性。
初步研究表明，TMS 波形对运动阈值的影响在上肢近端和远端肌肉中相似，但对 MEP 的运动靶点的影响则不同。此外，波形效应的测试-重测可靠性对靶肌肉敏感。这些发现可能有助于提高 TMS 在临床应用中的疗效和可靠性。
