Lee Soo Ho, Yoo Yeun Jie
Department of Rehabilitation Medicine, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Suwon, Korea.
Brain Neurorehabil. 2024 Nov 28;17(3):e24. doi: 10.12786/bn.2024.17.e24. eCollection 2024 Nov.
Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulatory technique with potential in stroke rehabilitation by modulating cortical excitability. However, the optimal parameters, including electrode placement, current intensity, stimulation duration, and electrode size, remain poorly understood, and the interactions among these factors contribute to mixed results in motor recovery post-stroke. This review explores the various stimulation parameters and their impact on enhancing corticospinal excitability (CSE) and motor function recovery. Different electrode placement (montages), such as anodal, cathodal, and bi-hemispheric stimulation, have demonstrated varying effectiveness in restoring motor function. Bihemispheric stimulation demonstrated a larger effect size compared to other unihemispheric (anodal or cathodal) stimulation; however, its relative superiority remains inconclusive. Inter-individual anatomical variations, such as skull thickness, lesion location, and cortical atrophy, can affect tDCS outcomes, highlighting the need for personalized electrode placement guided by computational modeling based on brain imaging. Furthermore, stimulation intensity, typically 1-2 mA, exhibited nonlinear effects on CSE, contrasting with the dose-response relationships observed in earlier studies. Stimulation duration is also critical, with evidence suggesting that prolonged stimulation may reverse excitability-enhancing effects beyond a certain threshold. While smaller electrodes enhance focality, an appropriately sized electrode is necessary to effectively modulate electrical activity in the target region, with evidence suggesting a dose-response relationship between electrode size and motor recovery. Overall, the interplay among these parameters underscores the need for personalized and optimized tDCS protocols to achieve consistent motor recovery in stroke patients. Future research should focus on refining these parameters to maximize the therapeutic benefits of tDCS.
经颅直流电刺激（tDCS）是一种非侵入性神经调节技术，通过调节皮层兴奋性在中风康复中具有潜力。然而，包括电极放置、电流强度、刺激持续时间和电极尺寸在内的最佳参数仍知之甚少，这些因素之间的相互作用导致中风后运动恢复的结果参差不齐。本综述探讨了各种刺激参数及其对增强皮质脊髓兴奋性（CSE）和运动功能恢复的影响。不同的电极放置（组合方式），如阳极、阴极和双半球刺激，在恢复运动功能方面已显示出不同的效果。与其他单半球（阳极或阴极）刺激相比，双半球刺激显示出更大的效应量；然而，其相对优势仍无定论。个体间的解剖变异，如颅骨厚度、病变位置和皮质萎缩，会影响tDCS的结果，这突出了基于脑成像的计算模型指导下进行个性化电极放置的必要性。此外，刺激强度通常为1-2 mA，对CSE表现出非线性效应，这与早期研究中观察到的剂量反应关系形成对比。刺激持续时间也很关键，有证据表明，超过一定阈值的长时间刺激可能会逆转兴奋性增强效应。虽然较小的电极可增强聚焦性，但需要适当尺寸的电极才能有效调节目标区域的电活动，有证据表明电极尺寸与运动恢复之间存在剂量反应关系。总体而言，这些参数之间的相互作用强调了需要个性化和优化的tDCS方案，以在中风患者中实现一致的运动恢复。未来的研究应专注于优化这些参数，以最大限度地提高tDCS的治疗益处。
