Brain Stimulation and Tailored Interventions to Promote Recovery in Stroke Survivors

The functional impact of impairment to UL following a stroke is critical given the close association between residual strength at the affected UL and performance in activity post-stroke. Exercise is a key element to recovery, even in chronic stroke survivors. However, the response to exercise is quite variable between individuals, reflecting the fact exercise intervention is often based on stroke survivors' clinical score as opposed to their potential for recovery. Accordingly, clients with comparable clinical presentations will often receive a similar intervention, even though they may exhibit very different potential for recovery. Hence, using a suitable prognostic tool of post-stroke recovery to individualize interventions based on individual potential for recovery is essential. One such tool is non-invasive transcranial magnetic stimulation (TMS). TMS elicits motor evoked potentials (MEP), which in turn provide a measure to conveniently assess the integrity of the corticospinal pathway. MEP is currently recognized as a good prognosis for post-stroke potential recovery. Another factor that can improve response to exercise is by modulating the excitability of sensorimotor circuits in the brain by the use of transcranial Direct-Current Stimulation (tDCS). Studies have shown that priming the motor cortex with tDCS before or during an intervention can promote motor recovery in stroke patients.

Goals: 1) To assess if an MEP amplitude stratification, used to guide exercise prescription, can optimize UL function in chronic stroke survivors; 2) To evaluate whether adding tDCS to a more individualized exercise intervention can further improve UL function.

Methods: Participants will be stratified based on their MEPs amplitudes at the affected hand. Within each stratum, participants will be further randomized into two tDCS groups: tDCS real and tDCS sham. The strength training program will target the affected upper limb and will last 4 weeks (3 times/week).The tDCS will be applied to an anodal montage during each training session (12 sessions; 2 mA) for 20 minutes (tDCS real group) or 30 seconds (tDCS sham group).

Inclusion criteria

• have had solely one supratentorial stroke
• be in a chronic stroke phase (>6 months)

Exclusion criteria

• a significant spasticity at the affected upper limb (score > 3 on the modified Ashworth scale);
• a significant pain intensity at the affected upper limb (≥ 4/10 on the Visual Analog Pain Scale);
• a major sensory deficit (a score ≤ 25/34 on the Nottingham Sensory Assessment);
• a presence of hemineglect (> 70% of unshaded lines on the same side as the motor deficit on the Line Cancellation Test);
• an apraxia (score >2.5 on the Alexander Test);
• the presence of a neurological disorder other than a stroke;
• concomitant orthopaedic problems at the affected upper limb and
• any contraindication to TMS and/or tDCS.