Background. Transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (lDLPFC) was reported to promote the recovery of signs of consciousness in some patients in a minimally conscious state (MCS), but its electrophysiological effects on brain activity remain poorly understood. Objective. We aimed to assess behavioral (using the Coma Recovery Scale—Revised; CRS-R) and neurophysiological effects (using high density electroencephalography; hdEEG) of lDLPFC-tDCS in patients with prolonged disorders of consciousness (DOC). Methods. In a double-blind, sham-controlled, crossover design, one active and one sham tDCS (2 mA, 20 min) were delivered in a randomized order. Directly before and after tDCS, 10 min of hdEEG were recorded and the CRS-R was administered. Results. Thirteen patients with severe brain injury were enrolled in the study. We found higher relative power at the group level after the active tDCS session in the alpha band in central regions and in the theta band over the frontal and posterior regions (uncorrected results). Higher weighted symbolic mutual information (wSMI) connectivity was found between left and right parietal regions, and higher fronto-parietal weighted phase lag index (wPLI) connectivity was found, both in the alpha band (uncorrected results). At the group level, no significant treatment effect was observed. Three patients showed behavioral improvement after the active session and one patient improved after the sham. Conclusion. We provide preliminary indications that neurophysiological changes can be observed after a single session of tDCS in patients with prolonged DOC, although they are not necessarily paralleled with significant behavioral improvements.

中文翻译：

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长期意识障碍患者单次前额叶tDCS的神经生理学相关性：一项双盲随机对照试验研究。

背景。据报道，在一些处于最低意识状态（MCS）的患者中，在左背外侧前额叶皮层（lDLPFC）上进行经颅直流电刺激（tDCS）可以促进意识征象的恢复，但对脑活动的电生理作用仍知之甚少。目的。我们旨在评估长期意识障碍（DOC）患者的lDLPFC-tDCS的行为（使用昏迷恢复量表（修订版）； CRS-R）和神经生理效应（使用高密度脑电图； hdEEG）。方法。在双盲，假控制的交叉设计中，以随机顺序交付了一个主动和一个假tDCS（2 mA，20分钟）。紧接tDCS之前和之后，记录了10分钟的hdEEG，并进行了CRS-R。结果。这项研究招募了13名严重脑损伤患者。我们发现，在活跃的tDCS会话后，中央区域的α波段以及额叶和后部区域的θ波段中的组水平上的相对功率更高（未校正的结果）。在左和右顶壁区域之间发现了较高的加权符号互信息（wSMI）连接性，并且在alpha波段中都发现了较高的额顶壁加权相位滞后指数（wPLI）连接性（未校正的结果）。在组水平上，未观察到明显的治疗效果。活动期后三名患者表现出行为改善，假手术后一名患者得到了改善。结论。 我们提供的初步迹象表明，DOC延长的患者在单次tDCS疗程后可以观察到神经生理学改变，尽管不一定与行为改善相提并论。