Transcranial direct current stimulation effects in disorders of consciousness

Abstract

Objective: To assess the efficacy of transcranial direct current stimulation (tDCS) on improving consciousness in patients with persistent unresponsive wakefulness syndrome (UWS) (previously termed persistent vegetative state [PVS]) or in a minimally conscious state (MCS).

Design: Prospective, case series trial with follow-up at 12 months.

Setting: General and research hospital.

Participants: Inpatients in a PVS/UWS or MCS (N=10; 7 men, 3 women; age range, 19-62y; etiology: traumatic brain injury, n=5; anoxia, n=4; postoperative infarct, n=1; duration of PVS/UWS or MCS range, 6mo-10y). No participant withdrew because of adverse effects.

Intervention: All patients received sham tDCS for 20 minutes per day, 5 days per week, for 1 week, and real tDCS for 20 minutes per day, 5 days per week, for 2 weeks. An anodal electrode was placed over the left primary sensorimotor cortex or the left dorsolateral prefrontal cortex, with cathodal stimulation over the right eyebrow. One patient in an MCS received a second round of 10 tDCS sessions 3 months after initial participation.

Main outcome measure: JFK Coma Recovery Scale-Revised.

Results: All patients in an MCS showed clinical improvement immediately after treatment. The patient who received a second round of tDCS 3 months after initial participation showed further improvement and emergence into consciousness after stimulation, with no change between treatments. One patient who was in an MCS for <1 year before treatment (postoperative infarct) showed further improvement and emergence into consciousness at 12-month follow-up. No patient showed improvement before stimulation. No patient in a PVS/UWS showed immediate improvement after stimulation, but 1 patient who was in a PVS/UWS for 6 years before treatment showed improvement and change of status to an MCS at 12-month follow-up.

Conclusions: tDCS seems promising for the rehabilitation of patients with severe disorders of consciousness. Severity and duration of pathology may be related to the degree of tDCS' beneficial effects.

Keywords: CRS-R; Coma Recovery Scale-Revised; DLPFC; Deep brain stimulation; FDG-PET; MCS; MCS+; MCS–; PVS; Persistent vegetative state; Rehabilitation; TBI; UWS; VS; [(18)F]-fluorodeoxyglucose positron emission tomography; dorsolateral prefrontal cortex; fMRI; functional magnetic resonance imaging; minimally conscious state; minimally conscious state minus; minimally conscious state plus; persistent vegetative state; rCBF; regional cerebral blood flow; tDCS; transcranial direct current stimulation; traumatic brain injury; unresponsive wakefulness syndrome; vegetative state.