Abstract
BackgroundThe treatment of patients in a minimally conscious state (MCS) remains challenging. Transcranial direct current stimulation (tDCS) is a non-invasive therapeutic method in treating neurologic diseases by regulating the cortical excitability. The aim is to investigate the effect of tDCS in patients with MCS in this study.MethodsEleven patients in MCS were enrolled in the study. All the patients received 5 daily sessions of 20-min sham tDCS, followed by 10 sessions of 20-min real tDCS. The anodal electrode and cathodal electrodes were placed over the left dorsolateral prefrontal cortex (DLPFC) and the right eyebrow, respectively. Assessment of Coma Recovery Scale-Revised (CRS-R) scores and resting-state functional MRI (rs-fMRI) scans was conducted three times in each patient: before tDCS (baseline, T0), post-sham tDCS at week 1 (T1), and post-real tDCS at week 2 (T2). The whole-brain functional connectivity (FC) was obtained by bilaterally computing FC from six seed regions: precuneus, middle frontal gyrus, supplemental motor area, angular gyrus, superior temporal gyrus, and occipital lobe. One-way repeated measure ANOVA was used to compare the differences of CRS-R scores and FC at T0, T1, and T2. The false discovery rate correction of p < 0.001 was adopted for controlling multiple comparisons in FC analysis.ResultsFive patients with MCS showed obvious clinical improvement represented by increased CRS-R scores post- 2-week real tDCS. The CRS-R scores did not change post- 1-week sham treatment. No side effects were reported during the study. The FC of the bilateral supplementary motor area, right angular gyrus, and right superior temporal gyrus were significantly enhanced after 2-week real tDCS compared with that after 1-week sham-tDCS. In addition, FC of bilateral occipital lobe and right precuneus were significantly enhanced post- 2-week real tDCS compared with the baseline.ConclusionOur findings indicated that tDCS over DLPFC could serve as a potentially effective therapy for improving the consciousness state in patients with MCS. The FC in rs-fMRI can be modulated by tDCS at both the stimulation site (left DLPFC) and the distant regions.
Highlights
Conscious state (MCS) is a disorder of consciousness (DoC), showing a partial retention of consciousness of self or environment, usually caused by neurological diseases, such as brain trauma, post-anoxic encephalopathy, and cerebrovascular accident tumor [1, 2]
We found the increase of coma recovery scalerevised (CRS-R) total scores and alterations of functional connectivity (FC) in rs-fMRI mediated by 2-week real Transcranial direct current stimulation (tDCS) in patients with Minimally conscious state (MCS)
Our findings showed that an increased FC in sensorimotor network, frontal parietal network, and auditory network post-2-week real tDCS, which provided another piece of evidence that improvement of FC in both nearby and distant of the stimulated brain regions could be induced by tDCS in patients with MCS [5, 36,37,38,39]
Summary
Conscious state (MCS) is a disorder of consciousness (DoC), showing a partial retention of consciousness of self or environment, usually caused by neurological diseases, such as brain trauma, post-anoxic encephalopathy, and cerebrovascular accident tumor [1, 2]. Research on non-pharmacological strategies for improving arousal outcome in MCS is highly warranted [2, 4]. Traditional non-pharmacological strategies, such as physical therapy and sensory stimulation, could promote arousal, to some extent, they cannot promote the recovery of the damaged consciousness-related neural networks in MCS [5]. With growing understanding of the neural network changes of consciousness disorders, the novel rehabilitation method, which directly modulates the cortical excitability and neural network, provides new opportunities for the treatment of MCS [6]. The treatment of patients in a minimally conscious state (MCS) remains challenging. Transcranial direct current stimulation (tDCS) is a non-invasive therapeutic method in treating neurologic diseases by regulating the cortical excitability. The aim is to investigate the effect of tDCS in patients with MCS in this study
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