TDCS Of The Precuneus In MCS Patients: A Randomized Double-blind Clinical Trial

Background:Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has been shown to transiently improve signs of consciousness in patients in minimally conscious state (MCS) after a stimulation of the prefrontal cortex. Due to the precuneus has been described as a critical hub for consciousness recovery by previous studies, we here assessed the effect of the stimulation of repeated sessions of tDCS over the precuneus.Methods:This is a randomized double-blind sham controlled crossover study. Two sessions were performed, one real and one sham in a randomized order. Patients were stimulated once a day for five days using a current of 2mA during 20 minutes and separated by five days of washout, anode was positioned over the Pz and the cathode over the right supra orbicular cortex in MCS patients. The effects were assessed with the Coma Recovery Scale-Revised (CRS-R) at baseline, after the end of the stimulation session and five days later in order to assess the treatment effect and long-term effects. Followup outcome data were acquired 1 month,3 month,6 month and 1 year after the treatment sessions using the CRS-R.Results:33 MCS patients completed the study (mean age:57±11 years; interval since insult:6±5 months; 20 posttraumatic injury). We found a treatment effect after the 5 days of stimulations (p=0.012), but the effects did not last 5 days after the end of the stimulation (p=0.135). We identified 6 responders (i.e., new sign of consciousness during the 5 days of real tDCS and kept displaying this behavior 5 days later, that was not present at baseline, neither during the sham session) who had significant difference on time since interval (p=0.024) but not on age, gender or etiology. There is also no significant difference of treatment effect and long-term effect of tDCS responders and non-responders on CRS-R total scores or subscales. For the followup outcome data, there is no significant difference on CRS-R total scores or subscales both for all the patients and between tDCS responders and non-responders.Conclusion:Our results showed that 5 days of tDCS over the precuneus slightly and transitory improve signs of consciousness in a few proportion of patients in MCS.