Therapies for motor recovery after stroke or traumatic brain injury are still not satisfactory. To date the best approach seems to be the intensive physical therapy. However the results are limited and functional gains are often minimal. The goal of motor training is to minimize functional disability and optimize functional motor recovery. This is thought to be achieved by modulation of plastic changes in the brain. Therefore, adjunct interventions that can augment the response of the motor system to the behavioural training might be useful to enhance the therapy-induced recovery in neurological populations. In this context, noninvasive brain stimulation appears to be an interesting option as an add-on intervention to standard physical therapies. Two non-invasive methods of inducing electrical currents into the brain have proved to be promising for inducing long-lasting plastic changes in motor systems: transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). These techniques represent powerful methods for priming cortical excitability for a subsequent motor task, demand, or stimulation. Thus, their mutual use can optimize the plastic changes induced by motor practice, leading to more remarkable and outlasting clinical gains in rehabilitation. In this review we discuss how these techniques can enhance the effects of a behavioural intervention and the clinical evidence to date.

Background . Recovery of motor function after stroke may depend on a balance of activity in the neural network involving the affected and the unaffected motor cortices. Objective . To assess whether transcranial direct current stimulation (tDCS) can increase the training-induced recovery of motor functions. Methods . In an exploratory study, 14 patients with chronic stroke and mean Fugl-Meyer Upper Extremity Motor Assessment of 29 (range = 8-50) entered a double-blind sham-controlled study, aimed to investigate neurophysiological and behavioral effects of bihemispheric tDCS (cathodal stimulation of the unaffected motor cortex and anodal stimulation of the affected motor cortex), combined with constraint-induced movement therapy (CIMT). Results . Patients in both groups demonstrated gains on primary outcome measures, that is, Jebsen Taylor Hand Function Test, Handgrip Strength, Motor Activity Log Scale, and Fugl-Meyer Motor Score. Gains were larger in the active tDCS group. Neurophysiological measurements showed a reduction in transcallosal inhibition from the intact to the affected hemisphere and increased corticospinal excitability in the affected hemisphere only in the active tDCS/CIMT group. Such neurophysiological changes correlated with the magnitude of the behavioral gains. Both groups showed a reduction in corticospinal excitability of the unaffected hemisphere. Conclusions . CIMT alone appears effective in modulating local excitability but not in removing the imbalance in transcallosal inhibition. Bihemispheric tDCS may achieve this goal and foster greater functional recovery.

The field of transcranial electrical stimulation (tES) has experienced significant growth in the past 15 years. One of the tES techniques leading this increased interest is transcranial direct current stimulation (tDCS). Significant research efforts have been devoted to determining the clinical potential of tDCS in humans. Despite the promising results obtained with tDCS in basic and clinical neuroscience, further progress has been impeded by a lack of clarity on international regulatory pathways. Therefore, a group of research and clinician experts on tDCS were convened to review the research and clinical use of tDCS. This report reviews the regulatory status of tDCS and summarizes the results according to research, off-label, and compassionate use of tDCS in the following countries: Australia, Brazil, France, Germany, India, Iran, Italy, Portugal, South Korea, Taiwan, and the US. Research use, off label treatment, and compassionate use of tDCS are employed in most of the countries reviewed in this study. It is critical that a global or local effort is organized to pursue definite evidence to either approve and regulate or restrict the use of tDCS in clinical practice on the basis of adequate randomized controlled treatment trials.