Virtual reality and non-invasive brain stimulation in stroke: How effective is their combination for upper limb motor improvement?

Upper limb (UL) hemiparesis is frequently a disabling consequence of stroke. The ability to improve UL functioning is associated with motor relearning and experience dependent neuroplasticity. Interventions such as non-invasive brain stimulation (NIBS) and task-practice in virtual environments (VEs) can influence motor relearning as well as adaptive plasticity. However, the effectiveness of a combination of NIBS and task-practice in VEs on UL motor improvement has not been systematically examined. The objective of this review was to examine the evidence regarding the effectiveness of combining NIBS with task-practice in VEs on UL motor impairment and activity levels. A systematic review of the published literature was conducted using standard methodology. Study quality was assessed using the PEDro scale and Down's and Black checklist. Four studies examining the effects of a combination of NIBS (involving transcranial direct current stimulation; tDCS and repetitive transcranial magnetic stimulation; rTMS) were retrieved. Of these, three studies were randomized controlled trials (RCTs) and one was a cross-sectional study. There was 1a level evidence that the combination of NIBS and task-practice in a VE was beneficial in the sub-acute stage. A combination of training in a VE with rTMS as well as tDCS was beneficial for motor improvements in the UL in sub-acute stage of stroke (1b level). The combination was not found to be superior compared to task practice in VEs alone in the chronic stage (1b level). The results suggest that people with stroke may be capable of improving levels of motor impairment and activity in the sub-acute stage if their rehabilitation program involves a combination on NIBS and VE training. Emergent questions regarding the use of more sensitive outcomes, different types of stimulation parameters, locations and training environments still need to be addressed.