For many, the recovery of arm and hand movements is incomplete, even after undergoing standard stroke rehabilitation care. The concurrent application of transcranial direct current stimulation (tDCS) with upper limb exercises improves motor recovery more than exercises alone. However, not every person with stroke appears to benefit from this adjunctive therapy. This may relate to inter-subject variability in response to tDCS, stroke lesion characteristics and the use of one-size-fits-all protocols. 

Our study will determine how motor stroke severity, defined by the amount of corticospinal tract (CST) injury on magnetic resonance imaging, and tDCS type, influence motor learning responses in people with stroke. We will recruit individuals greater than 3 months after stroke with mild to severe motor deficits. They will practice goal-directed reaching while concurrently receiving tDCS. Each person will receive three types of tDCS (anodal, cathodal, sham) to the contralesional motor cortex, applied on a different days and separated by washout periods. Primary outcomes will be kinematic measures of reaching performance obtained before and after each tDCS+reaching session, and 24-hours later to assess retention. 

This study will elucidate which type of tDCS helps each person to optimize their own motor learning, and whether CST injury predicts these improvements. This knowledge will determine the effectiveness of the imaging biomarker, CST injury, for predicting individual responses to tDCS. The identification of such a biomarker is required for the development of personalized tDCS interventions in stroke rehabilitation clinical trials, which may yield more successful trial results.

Protocol: Towards a personalized approach to stroke motor recovery with transcranial direct current stimulation