Transcranial Direct Current stimulation for post-stroke gait rehab

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Current rehabilitation methods fail to restore normal gait for many stroke survivors leading to dependence on others, recurrent falls, limitations in community ambulation and poor quality of life. The main objective of this study is to test both efficacy and neurophysiological mechanisms of a novel approach to treat persistent gait deficits after stroke with a combination of simultaneous non-invasive brain stimulation with transcranial Direct Current Stimulation (tDCS) and gait training. Rationale: Peripherally directed gait therapies are driven by functional brain changes. tDCS has been shown to enhance functional brain changes during rehabilitation and improve outcomes. Its ease of use and safety makes tDCS an ideal technology to pair with simultaneous gait training methods. Upper limb studies showed that 10-session bihemispheric tDCS in combination with movement therapy produced clinically meaningful improvement compared with minor changes after therapy alone. We conducted pilot studies that demonstrated both feasibility and tolerability of the proposed intervention. Our first single-session crossover pilot study demonstrated a potential benefit of tDCS combined with gait training compared with gait therapy alone. Our second 10-session pilot study showed feasibility of the intervention and demonstrated clinical improvements. The next important step is to test it in a randomized control study. We will use a bihemispheric tDCS montage that can address a key adaptive neuroplastic mechanism involved in post-stroke motor recovery, that is rebalancing interhemispheric interaction by 1) facilitation of the residual ipsilesional motor output pathways for the lower extremity and 2) suppression of transcallosal inhibition from the contralesional motor regions. Study Design: We will enroll 50 chronic stroke subjects (>6 months) with gait deficits. Subjects will be randomized to 10 sessions of either active tDCS+gait training or sham tDCS+gait training. Gait training will be accomplished in the treadmill-based Virtual Reality environment targeting longer single limb stance with the paretic limb. Aim 1 is to determine whether the combination of simultaneous tDCS and gait training produces greater improvement in gait performance compared to gait training alone. The primary outcome measure will be both gait speed as measured by 10- Meter Walk test (TMWT) and paretic single limb stance duration. Secondary outcome measures will assess various components of gait-related functional domains and will include the following: spatiotemporal gait asymmetry; another gait-speed-related measure (Timed Up and Go (TUG)); Ground Reaction Force; gait kinematics; a measure of gait coordination (Gait Assessment and Intervention Tool); a measure of sensory- motor impairment (Fugl-Meyer); a functional gait measure (Functional Gait Assessment); and dynamic balance (miniBEST test). Aim 2 is to characterize the neuroplastic brain changes in response to bihemispheric tDCS combined with gait training. Outcome measures are 1) ipsilateral corticospinal excitability (motor evoked potential recruitment curve (MEP-rc)),2) asymmetry of interhemispheric excitability (bilateral MEP-rc ratio), 3) functional connectivity between bilateral primary motor regions (resting state functional Magnetic Resonance Imaging (rs-fMRI)). Aim 3 is to identify factors that predict gait improvement in response to tDCS with gait training. We will evaluate the relationship between changes in gait speed and paretic single limb stance duration and baseline assessment of structural and functional reserve (according to corticospinal tract lesion load, clinical impairment, functional connectivity) and tDCS induced current density modeling. Significance: This study will address an important problem for the VA patient population. We will test for the first time whether bihemispheric tDCS can enhance gait training in chronic stroke and evaluate neuroplastic mechanisms involved in this therapeutic approach. Combination of tDCS and efficient VR-based gait training is a novel therapeutic approach that is being driven by promising preliminary data and supported by multidisciplinary expertise.