Department of Neuroscience, Imaging and Clinical Sciences, University "G. d'Annunzio", via L. Polacchi 11, 66100 Chieti, Italy; Institute for Advanced Biomedical Technologies (ITAB), University "G. d'Annunzio", via L. Polacchi 11, 66100 Chieti, Italy.
Unit of Neurology, Neurophysiology, Neurobiology, Department of Medicine, Università Campus Bio-Medico di Roma, via Álvaro del Portillo 21, 00128 Rome, Italy.
Neurophysiol Clin. 2019 Feb;49(1):19-25. doi: 10.1016/j.neucli.2018.12.003. Epub 2019 Jan 8.
Application parameters of transcranial direct current stimulation (tDCS) for therapeutic purposes are relatively restricted. The aim of this study was to assess safety and effects on motor cortex excitability of an intensive anodal-tDCS protocol.
In 26 healthy subjects, five 15-minute anodal-tDCS sessions were delivered, at increasing time intervals, over 24hours. Safety was defined as absence of serious adverse events including brain tissue alterations on magnetic resonance imaging. Effect on motor cortex excitability was evaluated by motor evoked potential (MEP) amplitude, measured eight times.
No serious adverse events occurred. Mild adverse events, such as reversible scalp erythema or transient metallic taste, were observed in 27% of subjects. MEP amplitudes did not change in any of the recording periods. When inter-individual variability was taken into account and threshold values defined, 50% of subjects were classified as responders, 15% were inverse responders, and 35% non-responders. In the responders, normalized MEP was increased by 57% 1hour after the first anodal-tDCS and increased by 50% three hours after two stimulations delivered 1hour apart. Intra-individual, inter-sessional consistency of MEP response over four measurements was 61-77%.
Five anodal-tDCS delivered in 24hours are safe and well tolerated, expanding the safety standard of tDCS. However, only half of subjects respond to anodal-tDCS with a robust and durable MEP augmentation. On the other hand, the response to a single anodal-tDCS predicts fairly well the response to other sessions in the same subject.
These findings should be considered in clinical trials utilizing repeated anodal-tDCS.
经颅直流电刺激（tDCS）的治疗应用参数相对受限。本研究旨在评估强化阳极 tDCS 方案的安全性和对运动皮层兴奋性的影响。
在 26 名健康受试者中，连续 24 小时内，每隔一段时间进行 5 次 15 分钟的阳极 tDCS。安全性定义为无严重不良事件，包括磁共振成像上的脑组织改变。通过测量 8 次运动诱发电位（MEP）振幅来评估运动皮层兴奋性的变化。
未发生严重不良事件。27%的受试者出现轻度不良事件，如可逆的头皮红斑或短暂的金属味。在任何记录期间，MEP 振幅均未发生变化。当考虑个体间变异性并定义阈值时，50%的受试者被归类为反应者，15%为反向反应者，35%为非反应者。在反应者中，第一次阳极 tDCS 后 1 小时，MEP 归一化增加了 57%，两次刺激间隔 1 小时，第三次刺激后增加了 50%。四次测量中，MEP 反应的个体内、会话间一致性为 61%-77%。
24 小时内给予 5 次阳极 tDCS 是安全且耐受良好的，扩大了 tDCS 的安全性标准。然而，只有一半的受试者对阳极 tDCS 产生强烈且持久的 MEP 增强反应。另一方面，单次阳极 tDCS 的反应很好地预测了同一受试者其他疗程的反应。
这些发现应在利用重复阳极 tDCS 的临床试验中加以考虑。
