Angelakis et al. report an attempt to restore consciousness through the use of tDCS in patients with persistent unresponsive wakefulness syndrome (UWS) following a severe TBI. Five daily sessions of tDCS were administered with the anode over the left DLPFC or left primary sensorimotor cortex (1 mA/35 cm2 x 20 min) and the cathode over the right orbital region to participants (N = 10, four with TBI, open head TBI excluded) with varying degrees of consciousness (assessed by JFK Coma Recovery Scale-Revised, JFK CRS-R; monitored by EEG and fMRI/FDG-PET). A 22-year-old male patient with TBI sustained 6 months prior to treatment (baseline CRS-R: 9) showed immediate improvement after a week of (CRS-R: 17) and continued improvement after second participation 3 months later (CRS-R: 19). A 19-year-old female patient with a TBI sustained 6 years prior (baseline CRS-R: 8) to intervention demonstrated no immediate response to tDCS but improved at a 1-year follow-up (CSR-R: 9). Two patients (CRS-R: 6 and 9, respectively) did not show any immediate effects (no change in CRS-R) or changes at a 1-year follow-up. Both patients were males (aged 35 and 37) with severe TBIs sustained 7 and 10 years prior, respectively. Based on the response of all patients in the study (not just those with TBI), the authors observed that the efficacy of tDCS intervention seemed to be dependent on the severity of the disordered conscious, with MCS patients responding better than UWS, and the time since injury, with more recent injuries faring better.
Thibaut et al. performed a sham-controlled randomized double-blind study to determine the effect of tDCS on consciousness in patients with UWS (N = 25; 6 post-traumatic) and patients in a minimally conscious state (MCS; N = 30; 19 post-traumatic). The study employed a cross-over design in which each patient received one session of both sham and real tDCS in a randomized order. The anodal electrode was placed over the left dlPFC with the cathodal (reference) electrode over the right suborbital region (2 mA/35 cm2 x 20 min). A subset of patients showed a transient improvement in CRS-R score following a single session of tDCS. A group effect was seen for the MCS but not for the UWS patient group. Although the authors did not assess the effect of treatment specifically for post-traumatic patients, their presented data show that treatment had no significant effect for the 6 post-traumatic UWS patients but produced some improvement for 5 of the 19 post-traumatic MCS patients. No adverse tDCS-related side effects were observed.