Controlled clinical trial of repeated prefrontal tDCS in patients with chronic minimally conscious state

OBJECTIVES: To assess the effects of repeated transcranial direct current stimulation (tDCS) sessions on the level of consciousness in chronic patients in minimally conscious state (MCS). METHODS: In this randomized double-blind sham-controlled crossover study, we enrolled 16 patients in chronic MCS. For 5 consecutive days, each patient received active or sham tDCS over the left prefrontal cortex (2 mA during 20 min). Consciousness was assessed with the Coma Recovery Scale-Revised (CRS-R) before the first stimulation (baseline), after each stimulation (day 1-day 5) and 1 week after the end of each session (day 12). RESULTS: A treatment effect (p = 0.013; effect size = 0.43) was observed at the end of the active tDCS session (day 5) as well as 1 week after the end of the active tDCS session (day 12; p = 0.002; effect size = 0.57). A longitudinal increase of the CRS-R total scores was identified for the active tDCS session (p < 0.001), while no change was found for the sham session (p = 0.64). Nine patients were identified as responders (56%). CONCLUSION: Our results suggest that repeated (5 days) left prefrontal tDCS improves the recovery of consciousness in some chronic patients in MCS, up to 1 week after the end of the stimulations.