Limited Add-On Effects of Unilateral and Bilateral Transcranial Direct Current Stimulation on Visuo-Motor Grip Force Tracking Task Training Outcome in Chronic Stroke. A Randomized Controlled Trial

Benedikt Taud,Robert Lindenberg,Marcus Meinzer,Ulrike Grittner,Dorothee Höfflin,Agnes Flöel,Robert Darkow,Jasmin Wevers

doi:10.3389/fneur.2021.736075

Abstract

Background: This randomized controlled trial investigated if uni- and bihemispheric transcranial direct current stimulation (tDCS) of the motor cortex can enhance the effects of visuo-motor grip force tracking task training and transfer to clinical assessments of upper extremity motor function.Methods: In a randomized, double-blind, sham-controlled trial, 40 chronic stroke patients underwent 5 days of visuo-motor grip force tracking task training of the paretic hand with either unilateral or bilateral (N = 15/group) or placebo tDCS (N = 10). Immediate and long-term (3 months) effects on training outcome and motor recovery (Upper Extremity Fugl-Meyer, UE-FM, Wolf Motor Function Test, and WMFT) were investigated.Results: Trained task performance significantly improved independently of tDCS in a curvilinear fashion. In the anodal stimulation group UE-FM scores were higher than in the sham group at day 5 (adjusted mean difference: 2.6, 95%CI: 0.6–4.5, p = 0.010) and at 3 months follow up (adjusted mean difference: 2.8, 95%CI: 0.8–4.7, p = 0.006). Neither training alone, nor the combination of training and tDCS improved WMFT performance.Conclusions: Visuo-motor grip force tracking task training can facilitate recovery of upper extremity function. Only minimal add-on effects of anodal but not dual tDCS were observed.Clinical Trial Registration: https://clinicaltrials.gov/ct2/results?recrs=&cond=&term=NCT01969097&cntry=&state=&city=&dist=, identifier: NCT01969097, retrospectively registered on 25/10/2013.

Highlights

1 Neurocure Cluster of Excellence, Charité University Medicine, Berlin, Germany, 2 Department of History, Philosophy and Ethics of Medicine, Heinrich Heine University, Düsseldorf, Germany, 3 Berlin Institute of Health at Charité, Charité University Medicine, Berlin, Germany, 4 Institute of Biometry and Clinical Epidemiology, Charité University Medicine, Berlin, Germany, 5 Department of Neurology, University Medicine Greifswald, Greifswald, Germany, 6 German Centre for Neurodegenerative Diseases, Site Greifswald/Rostock, Greifswald, Germany, 7 Center for Stroke Research, Charité University Medicine, Berlin, Germany. This randomized controlled trial investigated if uni- and bihemispheric transcranial direct current stimulation of the motor cortex can enhance the effects of visuo-motor grip force tracking task training and transfer to clinical assessments of upper extremity motor function
The present study aimed to address three open questions: [1] Does visuo-motor grip force tracking task training improve performance in the trained task, and/or generalizes to clinical assessments of upper extremity function in chronic stroke? [2] If immediate and long-term training gains occur, are they enhanced by concurrent unilateral or bilateral motor cortex transcranial direct current stimulation (tDCS)? [3] Does unilateral or bilateral tDCS result in differential transfer effects? We hypothesized that both anodal and dual tDCS would enhance motor training outcome and transfer to clinical assessments of upper motor function
Three month later the adjusted WMFT scores were: 0.66 (95%CI: 0.60–0.72) for sham, 0.62 (95%CI: 0.57–0.67, difference to sham: −0.04, 95%CI: −0.11 to 0.04, p = 0.323) for dual, and 0.60 (95%CI: 0.55–0.65, difference to sham: −0.05, 95%CI: −0.13 to 0.02, p = 0.161) for anodal. The results of this randomized, controlled clinical trial demonstrated that a visuo-motor grip force tracking task training, consisting of isometric abductions of the paretic thumb, improved control of the paretic thumb, and resulted in generalization to clinical assessments of upper extremity function such as Upper-Extremity Fugl-Meyer (UE-FM), but not WMFT, in chronic stroke patients

Summary

Introduction

This randomized controlled trial investigated if uni- and bihemispheric transcranial direct current stimulation (tDCS) of the motor cortex can enhance the effects of visuo-motor grip force tracking task training and transfer to clinical assessments of upper extremity motor function. The combination of behavioral treatment with repetitive transcranial magnetic stimulation (rTMS) or transcranial direct current stimulation (tDCS) can have positive effects on motor rehabilitation after stroke [11, 12]. Intensity, and duration of the stimulation, rTMS is able to increase or decrease cortical excitability [13]. Depending on the polarity of the current, tDCS can be used to increase or decrease cortical excitability [16], with anodal tDCS yielding a relative depolarization and cathodal tDCS yielding hyperpolarization of neuronal membranes [17]. The current study utilized tDCS because it can be administered concurrently with motor training, while offering a superior safety profile and placebo stimulation condition compared to rTMS [19]

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