Division of Neuropaediatrics and Muscular Disorders, Department of Paediatrics and Adolescent Medicine, University Hospital Freiburg, Freiburg, Germany.
Brain Stimul. 2012 Apr;5(2):148-54. doi: 10.1016/j.brs.2011.02.006. Epub 2011 Apr 19.
Previous studies have shown that the efficacy of transcranial magnetic stimulation (TMS) to excite corticospinal neurons depends on pulse waveform.
OBJECTIVE/HYPOTHESES: In this study, we examined whether the effectiveness of polyphasic TMS can be increased by using a pulse profile that consists of multiple sine cycles.
In eight subjects, single-pulse TMS was applied to the left primary motor hand area through a round coil attached to a stimulator device that generated polyphasic pulses consisting of one to six full-sine cycles with a cycle length of 86 μs. In different blocks, we varied the number of sine cycles per pulse and recorded the motor-evoked potential (MEP) from the right first dorsal interosseus muscle. For each stimulus type, we determined resting motor threshold (RMT), stimulus-response curve (SRC), and mean MEP amplitude evoked at maximal stimulator output to assess the efficacy of stimulation.
Multicycle pulses were more effective than a single full-sine cycle in exciting corticospinal neurons. TMS with multicycle pulses resulted in lower RMT, larger MEP amplitudes at maximal stimulator output and a steeper slope of the SRC relative to a TMS pulse consisting of a single-sine cycle. The increase in efficacy was already evident when two full-sine cycles were used and did not increase further by adding more cycles to the TMS pulse.
Increasing the number of full-sine cycles per pulse can improve the efficacy of TMS to excite corticospinal neurons, but there is no simple linear relationship between the number of cycles and TMS efficacy.
先前的研究表明，经颅磁刺激（TMS）激发皮质脊髓神经元的疗效取决于脉冲波形。
目的/假设：本研究旨在检验多相 TMS 能否通过使用由多个正弦周期组成的脉冲来提高疗效。
在 8 名受试者中，通过附着在刺激器装置上的圆形线圈施加单脉冲 TMS，该刺激器装置产生的多相脉冲由一个至六个完整正弦周期组成，周期长度为 86 μs。在不同的刺激块中，我们改变了每个脉冲中的正弦周期数，并记录了来自右侧第一背间骨间肌的运动诱发电位（MEP）。对于每种刺激类型，我们确定了静息运动阈值（RMT）、刺激反应曲线（SRC）和最大刺激器输出时诱发的平均 MEP 幅度，以评估刺激的疗效。
多周期脉冲比单个完整正弦周期更能有效地激发皮质脊髓神经元。与由单个正弦周期组成的 TMS 脉冲相比，多周期脉冲的 TMS 导致更低的 RMT、在最大刺激器输出时更大的 MEP 幅度以及 SRC 的斜率更陡。当使用两个完整正弦周期时，已经可以看到疗效的增加，并且通过向 TMS 脉冲中添加更多周期，疗效并没有进一步增加。
增加每个脉冲中的完整正弦周期数可以提高 TMS 激发皮质脊髓神经元的疗效，但周期数与 TMS 疗效之间没有简单的线性关系。
