Non-invasive brain stimulation: a new strategy to improve neurorehabilitation after stroke?

SummaryBackgroundMotor impairment resulting from chronic stroke can have extensive physical, psychological, financial, and social implications despite available neurorehabilitative treatments. Recent studies in animals showed that direct epidural stimulation of the primary motor cortex surrounding a small infarct in the lesioned hemisphere (M1lesioned hemisphere) elicits improvements in motor function.Recent developmentsIn human beings, proof of principle studies from different laboratories showed that non-invasive transcranial magnetic stimulation and direct current stimulation that upregulate excitability within M1lesioned hemisphere or downregulate excitability in the intact hemisphere (M1intact hemisphere) results in improvement in motor function in patients with stroke. Possible mechanisms mediating these effects can include the correction of abnormally persistent interhemispheric inhibitory drive from M1intact hemisphere to M1lesioned hemisphere in the process of generation of voluntary movements by the paretic hand, a disorder correlated with the magnitude of impairment. In this paper we review these mechanistically oriented interventional approaches.What next?These findings suggest that transcranial magnetic stimulation and transcranial direct current stimulation could develop into useful adjuvant strategies in neurorehabilitation but have to be further assessed in multicentre clinical trials.