Efficiency Of Transcranial Direct Current Stimulation Of The Dorsolateral Prefrontal Cortex In Patients With Disorder Of Consciousness

Part Ⅰ Efficiency of anodal transcranial direct current stimulation of the dorsolateral prefrontal cortex in patients with disorder of consciousness:An EEG study based on phase locking valueObjective:Anodal transcranial direct current stimulation(a-tDCS)of the left dorsolateral prefrontal cortex(DLPFC)has been reported to improve the conscious state of patients with disorder of consciousness(DOC).While the effects of a-tDCS of the rightDLPFC as well as the electrophysiological effect of tDCS in patients with DOC are yet to be investigate.The primary objective of the present study is to explore the electrophysiological effect of a-tDCS of the left and rightDLPFC.The second objective is to research the effects of the stimulation on behavioral assessment.Methods:The present study was randomized sham-controlled designed.15 patients with chronic DOC were separated into three groups(i.e.left a-tDCS,right a-tDCS and sham stimulation).All patients received 10 sessions of stimulation.EEG and JFK Coma Recovery Scale-Revised(CRS-R)assessments were conducted at baseline and immediately after the last session of stimulation respectively.Phase locking value(PLV)was adopted to analyse the functional connectivity according to EEG data.Results:Electrophysiological assessment results: left a-tDCS strengthened the functional connectivity of the cortex in patients with DOC,while right a-tDCS showed less effectiveness and sham stimulation had no effect on neural connectivity.Behavioral assessment results: 2 patients were improved after left a-tDCS and none of patients who received right or sham stimulation showed any improvement.However,no significant difference was detected between 3 groups.Conclusions:A-tDCS of the DLPFC might enhance the cortical neural connectivity in patients with DOC.Moreover,the preliminary result revealed the possibility of hemispheric asymmetry of tDCS effects in patients with DOC: LeftDLPFC might be a better target compared to the contralateral site.Researches with larger sample sizes are needed to determine whether a-tDCS contributes to behavioral recovery in patients with DOC.Part Ⅱ Efficiency of anodal transcranial direct current stimulation of the dorsolateral prefrontal cortex on behavioral consciousness in patients with disorder of consciousnessObjective:A-tDCS of the left or rightDLPFC might enhance the cortical neural connectivity in patients with DOC.However,it still needs researches with large sample sizes to determine the behavioral effect of tDCS in patients with DOC.Furthermore,the safety and effect of double source anodal tDCS(bs-a-tDCS)of the bilateral DLPFC in patients with DOC remain unknown.This research was performed to investigate the efficiency of a-tDCS of the DLPFC in DOC treatment,and to compare the safety,tolerance,and the potential effect on behavioral consciousness between the different a-tDCS of the left,right,and bilateral DLPFC in patients with DOC.Methods:The present randomized sham-controlled study enrolled 72 patients with DOC which including unresponsive wakefulness syndrome(UWS)and minimally conscious state(MCS).According to the groups: a)left a-tDCS;b)right a-tDCS c)bilateral a-tDCS and d)sham stimulation,each patient received 10 sessions of stimulation.JFK Coma Recovery Scale-Revised(CRS-R)assessments were performed at baseline and immediately after the last session of stimulation.The changes of CRS-R scores and the difference between groups were analyzed.The safety and tolerance of each type of stimulation were observed as well.Results:None of patients had severe side effects during and after the stimulation.65 out of72 patients completed 10 sessions of intervention.Groups received left,right and bilateral stimulation revealed significant improvement of CRS-R total score(p <0.0125),while sham stimulation was less effective on behavioral assessment(p=0.066).One-way ANOVA and post hoc suggested that the improvements of left and bilateral stimulation groups were significantly higher than that of sham group(p <0.05),while right stimulation group showed no difference with sham group(p= 0.735).Moreover,only the group received bilateral a-tDCS showed a tendency toward improvement in UWS patients.Conclusions:A-tDCS of the left,right and bilateral DLPFC in patients with DOC were relatively safe.A-tDCS of the DLPFC might improve the behavioral consciousness level,and left or bilateral stimulation might be much effective than right stimulation.Moreover,bilateral stimulation,at least in UWS patients,might contribute to more improvements than unilateral stimulation do.Nonetheless,several sessions of a-tDCS were merely to produce a significant recovery which could change the diagnosis,amounts of patient with DOC showed no response to the stimulation,and the potential beneficiaries were quite difficult to detect before the treatment.