P 172. Focal tDCS in Chronic Stroke patients: A pilot study of physiological effects using TMS and concurrent EEG

Abstract

Motor dysfunction is known to be a prominent residual impairment in stroke survivors. There is evidence supporting short-term behavioral changes correlated with electrophysiological changes using electric brain stimulation. Studies suggest that altering cortical excitability may prime the cortex for subsequent training and improve functional activity. Using Neuroelectrics’ Starstim novel multichannel wireless device, which allows for simultaneous electroencephalography (EEG), 3D accelerometry and transcranial direct current stimulation (tDCS) using relatively small, gelled, Ag/AgCl electrodes (1 cm diameter), we aimed to determine the effects of anodal stimulation tDCS on EEG and transcranial magnetic stimulation (TMS) response, as well as kinematic movement performance in chronic stroke survivors with residual motor deficit in the arm. Fifteen chronic stroke patients with hemiparesis following a first single unilateral lesion received 20 min of bilateral 1 mA anodal tDCS over the motor cortex of the lesioned hemisphere. Four neurophysiological and motor evaluations were conducted during the experiment: one prior to stimulation and three at different time points following stimulation. Evaluations consisted of a 5 min EEG recording at rest and assessment of cortical excitability properties of the lesioned hemisphere using TMS. During the TMS evaluations, motor evoked potentials (MEP) were recorded via surface electromyography (EMG) electrodes both at rest and during maximal voluntary contraction. In addition, EEG was recorded during tDCS stimulation. We report results of MEPs, EEG, and motor behavior. We show, for the first time, that tDCS and EEG recording can be concurrently applied in stroke patients. Bilateral M1 stimulation using small Ag/AgCl electrodes is well tolerated and can augment corticospinal excitability in the affected hemisphere. In the literature, there is only one prior studying using concurrent EEG recording during cathodal tDCS in healthy subjects and two patients with epileptic encephalopathy (Faria et al., 2012). As far as we know, no studies have applied tDCS simultaneous with EEG recording in chronic stroke patients. We report the first study investigating feasibility and proof-of-concept of tDCS in 15 chronic stroke patients using EEG recording simultaneously with tDCS. With continuous EEG recording and neurophysiological data, we hope to gain insight into the mechanisms of biological responses to tDCS and the behavioral changes resulting from stimulation.