tDCS in patients with disorders of consciousness: sham-controlled randomized double-blind study

We assessed the effects of left dorsolateral prefrontal cortex transcranial direct current stimulation (DLPF-tDCS) on Coma Recovery Scale-Revised (CRS-R) scores in severely brain-damaged patients with disorders of consciousness.

In a double-blind sham-controlled crossover design, anodal and sham tDCS were delivered in randomized order over the left DLPF cortex for 20 minutes in patients in a vegetative state/unresponsive wakefulness syndrome (VS/UWS) or in a minimally conscious state (MCS) assessed at least 1 week after acute traumatic or nontraumatic insult. Clinical assessments were performed using the CRS-R directly before and after anodal and sham tDCS stimulation. Follow-up outcome data were acquired 12 months after inclusion using the Glasgow Outcome Scale-Extended.

Patients in MCS (n = 30; interval 43 ± 63 mo; 19 traumatic, 11 nontraumatic) showed a significant treatment effect (p = 0.003) as measured by CRS-R total scores. In patients with VS/UWS (n = 25; interval 24 ± 48 mo; 6 traumatic, 19 nontraumatic), no treatment effect was observed (p = 0.952). Thirteen (43%) patients in MCS and 2 (8%) patients in VS/UWS further showed postanodal tDCS-related signs of consciousness, which were observed neither during the pre-tDCS evaluation nor during the pre- or post-sham evaluation (i.e., tDCS responders). Outcome did not differ between tDCS responders and nonresponders.

tDCS over left DLPF cortex may transiently improve signs of consciousness in MCS following severe brain damage as measured by changes in CRS-R total scores.

This study provides Class II evidence that short-duration tDCS of the left DLPF cortex transiently improves consciousness as measured by CRS-R assessment in patients with MCS.