Bilateral M1 anodal transcranial direct current stimulation in post traumatic chronic minimally conscious state: a pilot EEG-tDCS study

Objective: We tested the preliminary effects of bilateral anodal transcranial direct current stimulation (tDCS) in patients with disorders of consciousness. Design: Open label pilot study. Subjects: Ten chronic (greater than 12 months) patients in a minimally conscious state (MCS) following severe traumatic brain injury. Methods: The patients received 10 sessions of bilateral M1 anodal tDCS. Behavioural changes were assessed with the Coma Recovery Scale-Revised (CRS-R) before stimulation (T-1, T0), after five sessions (T1), at the end of the stimulation (T2), after two weeks (T3) and after three months (T4). Moreover, an EEG assessment was conducted. Results: Eight out of 10 patients showed new clinical signs of consciousness; specifically, a 2-point CRS-R improvement was detected in the last follow-up (p = 0.004). EEG upper α bandwidth was greater in the parietal site at T1 (p < 0.034). In addition, we found a significant correlation between behavioral and EEG indices at T1 (r =  0.89; p =  0.001). Conclusion: This preliminary study presents several limitations (small sample size and no control group). However, it provides important initial data that can be used to design randomized clinical trials testing this novel approach in MCS and to further explore EEG as a neural marker for the effects of tDCS.