Noninvasive brain stimulation after stroke: it is time for large randomized controlled trials!

We here provide an update about studies published recently in the field of noninvasive neuromodulation of the motor system, aiming at facilitating recovery of function after stroke.

A number of longitudinal studies have confirmed that repeated stimulation of the motor cortex in combination with motor training improves performance compared with control or sham stimulation. In the early postacute stroke phase, enhancement of ipsilesional motor cortex excitability by means of repetitive transcranial magnetic stimulation (rTMS) seems to be a well tolerated and effective strategy to promote motor recovery. In contrast, recent studies suggest that transcranial direct current stimulation (tDCS) in the early poststroke phase does not facilitate motor recovery. In the chronic phase, however, both rTMS and tDCS have been shown to be beneficial when applied over several days combined with training. Interestingly, bihemispheric stimulation strategies (ipsilesional activation and contralesional suppression) seem to constitute effective protocols, especially when using rTMS.

Noninvasive brain stimulation seems to support motor recovery. However, to date randomised controlled trials (RCTs) that are sufficiently powered are lacking. Data suggest that the most promising protocols should now be tested in RCTs with sufficiently large samples taking into account the clinical heterogeneity of stroke.