Neuromodulation by task-concurrent dual transcranial direct current stimulation over the motor cortex in subacute stroke (P4.218)

Objective: To examine safety and efficacy of task-concurrent dual transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) in subacute stroke patients. Background: Dual tDCS to bilateral M1 has been suggested to enhance motor reaction time and corticospinal excitability compared with unilateral tDCS in healthy subjects. However, it remains unknown whether combination of dual tDCS and rehabilitation may affect cortical excitability and oscillations in subacute stroke patients. Design/Methods: Crossover sham-controlled design applied in 10 subacute patients with first-time, unilateral, subcortical ischemic stroke and 12 matched healthy controls. During exercising the paretic or non-dominant extensor carpi radialis, participants underwent two different tDCS conditions on separate days, i.e. real tDCS (anode over the ipsilesional or non-dominant M1, while cathode over the contralesional or dominant M1; 2 mA for 20 mins) and sham tDCS (same settings except for 2 mins). We compared the changes of motor evoked potentials (MEPs), ipsilateral silent period (iSP) for interhemispheric inhibition, short interval intracortical inhibition (SICI), and movement-related cortical oscillations using transcranial magnetic stimulation and magnetoencephalography. Results: Compared with sham stimulation, the real tDCS significantly increased MEPs, reduced SICI, and prolonged iSP of the anode-stimulated M1, while decreased MEPs and shortened iSP from the cathode-stimulated M1 in healthy controls for at least 30 mins. Interestingly, the real tDCS decreased post-movement event-related synchronization (ERS) in beta frequency over the anode-stimulated dorsal premotor cortex, suggesting cortical disinhibition. In stroke patients, the real tDCS similarly increased MEPs, reduced SICI, and prolonged iSP of the anode-stimulated ipsilesional M1, while decreased MEPs, increased SICI, and shorten iSP of the cathode-stimulated contralesional M1. By contrast, the real tDCS increased ERS amplitude in beta frequency over the anode-stimulated ipsilesional M1, suggesting altered post-stroke plasticity. Conclusions: Task-concurrent dual tDCS safely and synchronously modulated bilateral M1 excitability and interhemispheric inhibition, as well as ipsilesional beta ERS in subacute stroke patients. Disclosure: Dr. Tang has nothing to disclose. Dr. Kuo has nothing to disclose. Dr. Tsai has nothing to disclose. Dr. Lu has nothing to disclose. Dr. Lee has nothing to disclose.