Cerebellar Transcranial Direct Current Stimulation for Motor Learning in People with Chronic Stroke: A Pilot Randomized Controlled Trial.

Nitika Kumari,Sharon Olsen,Usman Rashid,Nada Signal,Denise Taylor

doi:10.3390/brainsci10120982

Abstract

Cerebellar transcranial direct current stimulation (ctDCS) is a non-invasive brain stimulation technique that alters neural plasticity through weak, continuous, direct currents delivered to the cerebellum. This study aimed to evaluate the feasibility of conducting a randomized controlled trial (RCT) delivering three consecutive days of ctDCS during split-belt treadmill training (SBTT) in people with chronic stroke. Using a double-blinded, parallel-group RCT design, eligible participants were randomly allocated to receive either active anodal ctDCS or sham ctDCS combined with SBTT on three consecutive days. Outcomes were assessed at one-week follow-up, using step length symmetry as a measure of motor learning and comfortable over-ground walking speed as a measure of walking capacity. The feasibility of the RCT protocol was evaluated based on recruitment, retention, protocol deviations and data completeness. The feasibility of the intervention was assessed based on safety, adherence and intervention fidelity. Of the 26 potential participants identified over four months, only four were enrolled in the study (active anodal ctDCS n = 1, sham ctDCS n = 3). Both the inclusion criteria and the fidelity of the SBTT relied upon the accurate estimation of step length asymmetry. The method used to determine the side of the step length asymmetry was unreliable and led to deviations in the protocol. The ctDCS intervention was well adhered to, safe, and delivered as per the planned protocol. Motor learning outcomes for individual participants revealed that treadmill step length symmetry remained unchanged for three participants but improved for one participant (sham ctDCS). Comfortable over-ground walking speed improved for two participants (sham ctDCS). The feasibility of the planned protocol and intervention was limited by intra-individual variability in the magnitude and side of the step length asymmetry. This limited the sample and compromised the fidelity of the SBTT intervention. To feasibly conduct a full RCT investigating the effect of ctDCS on locomotor adaptation, a reliable method of identifying and defining step length asymmetry in people with stroke is required. Future ctDCS research should either optimize the methods for SBTT delivery or utilize an alternative motor adaptation task.

Highlights

Stroke is the second largest cause of disability in developing countries and the third largest cause of disability in developed countries [1]
While motor learning often refers to the acquisition of new motor skills, a process which can take weeks, months, or even years of practice [12], this paper focuses on a type of motor learning that occurs within a shorter time-frame, known as ‘motor adaptation’
The intent of the full randomized controlled trial (RCT) was to evaluate the effect of repeated anodal Cerebellar transcranial direct current stimulation (ctDCS) on motor learning in people with chronic stroke by measuring changes in motor performance in response to locomotor adaptation training

Summary

Introduction

Stroke is the second largest cause of disability in developing countries and the third largest cause of disability in developed countries [1]. Brain Sci. 2020, 10, 982 of individuals are left with functional limitations at six months post-stroke [6]. One of the common limitations that persist after stroke is the inability to walk [7], with as many as 45% unable to ambulate independently in the community one year post-stroke [8]. This restricts community integration and lowers the quality of life [9]. The underlying mechanism by which motor re-learning occurs is neural plasticity; a process in which the brain alters its structure and neural connections [11]

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