How does combining physical therapy with transcranial direct stimulation improve upper-limb motor functions in patients with stroke? A theory perspective.

More than half of stroke survivors suffer from upper-limb dysfunction that persists years after stroke, negatively impacting patients' independence and, therefore, affecting their quality of life. Intense motor rehabilitation is required after a stroke to facilitate motor recovery. More importantly, finding new ways to maximize patients' motor recovery is a core goal of stroke rehabilitation. Thus, researchers have explored the potential benefits of combining the effects of non-invasive brain stimulation with physical therapy rehabilitation. Specifically, combining transcranial direct stimulation (tDCS) with neurorehabilitation interventions can boost the brain's responses to interventions and maximize the effects of rehabilitation to improve upper-limb recovery post-stroke. However, it is still unclear which modes of tDCS are optimal for upper-limb motor recovery in patients with stroke when combined with physical therapy interventions. Here, the authors review the existing literature suggesting combining physical therapy rehabilitation with tDCS can maximize patients' motor recovery using the Interhemispheric Competition Model in Stroke. The authors focus on two main rehabilitation paradigms, which are constraint-induced movement therapy (CIMT) and Mirror therapy with and without tDCS. The authors also discuss potential studies to elucidate further the benefit of using tDCS adjunct with these upper-limb rehabilitation paradigms and its effectiveness in patients with stroke, with the ultimate goal of maximizing patients' motor recovery.