Effects Of Transcranial Direct Current Stimulation On White Matter Fibers And Consciousness Improvement In Patients With Chronic Disorders Of Consciousness

Objectie: There is increasing evidence of behavioral and neurological changes following transcranial direct current stimulation(tDCS)in patients with disorders of consciousness,but there is limited evidence of neuroimaging basis for functional changes.The purpose of this study was to investigate the effect of tDCS on promoting the recovery of consciousness in patients with chronic disorders of consciousness and its effect on the white matter fibers of the brain.Methods: This study used a randomized cross-controlled trial design.Each participant received,in a randomized order,10 sessions of active and 10 sessions of sham tDCS applied over the left prefrontal cortex for 2 weeks;separated by 2 weeks of washout.The coma recovery scale-revised(CRS-R)was used to assess the level of consciousness and diffusion tensor imaging was used to evaluate white matter.Results: A total of 6 patients with disorders of consciousness completed the study.In terms of behavior level,there was no significant change in the CRS-R scale between baseline and post-therapy(F=5.263,p>0.05).In terms of neuroimaging,track-based spatial statistics showed that the MD values in splenium of corpus callosum,genu of corpus callosum,forceps major,forceps minor,body of corpus callosum,bilateral internal capsule,bilateral external capsule and the RD values in genu of corpus callosum,forceps minor,forceps major,right internal capsule,right external capsule after sham stimulation were significantly higher than the baseline level(p< 0.05),but no significant difference was seen in imaging indicators after active tDCS treatment(p>0.05).Further imaging analysis of tract of interest showed that the RD average values of white matter fibers such as left cingulum(hippocampus)(sham stimulation: 0.56±0.08 vs.active stimulation: 0.52±0.05,p=0.007),left corticospinal tract(sham stimulation:0.62±0.08 vs.active stimulation : 0.59±0.08,,p=0.016)and forceps minor(sham stimulation: 0.87±0.06 vs.active stimulation: 0.84±0.05,p=0.036)after sham stimulation treatment were significantly increase comparing to the active stimulation.In addition,the correlation analysis between the white matter DTI indicators and consciousness level before and after the active stimulation treatment showed that the total score of CRS-R was significantly positively correlated with the MD average values(r =0.937,p=0.006)and RD average values(r =0.876,p=0.022)of the right anterior thalamic radiation,and showed significant negative correlation with the MD average value(r =-0.842,p=0.035)and RD average value(r =-0.914,p=0.011)of the left superior longitudinal fasciculus.Furthermore,significant correlations were observed between the imaging indicators of multiple tract of interest and the CRS-R subscale items.Conclusions: Although the use of active tDCS in the left dorsal lateral prefrontal cortex of patients with chronic disorder of consciousness don't show significant behavioral arousal effects,it causes changes in the imaging indicators of the relevant white matter regions,and the changes in these imaging indicators show a significant correlation with changes in behavior.tDCS may promote the recovery of brain structure network by slowing down the white matter fiber demyelination and cell edema,suggesting that tDCS has potential application value for improving consciousness.