Effects of Transcranial Direct-Current Stimulation on Gait Initiation in People with Parkinson’s Disease

Abstract

Background: Gait initiation is a major issue in Parkinson’s disease (PD). Moreover, the effect of current treatment on motor deficits vary alongside individual differences and disease severity. In some cases, postural instability has been documented as a major side-effect and refractory symptom to dopaminergic medication. Despite these shortcomings, research involving other forms of therapy including deep brain stimulation (DBS) and transcranial magnetic stimulation (TMS), has evidenced the improvement of postural deficits in PD. In this regard, there is a strong rational for the modulation of subcortical brain activity via the application of non-invasive transcranial direct current stimulation (tDCS) to interconnected cortical brain structures. Purpose: Therefore, we sought to determine the effect of tDCS applied to the supplementary motor area (SMA), on gait initiation preparation and performance in PD. Methods: A within subjects repeated measures quasi-experimental design was used to investigate the effects of a 10-minute sham-controlled tDCS intervention. Clinically diagnosed participants (n=12) with idiopathic PD were tested on medication during two sessions that bookended one week. Those who had previously undergone other forms of brain stimulation, had diabetes, severe freezing of gait, or any other neurological or functional limitations that could interfere with gait initiation were excluded from the study. Statistical Analyses/Results: Two-way repeated measures ANOVAs with Bonferroni corrections and a post-hoc analyses when appropriate, revealed a significant reduction in the magnitude of center of pressure (CoP) displacement and velocity in the mediolateral (ML) direction following tDCS. Conclusions: Findings from this study provide insights that may guide scientific research regarding the effects of tDCS on gait initiation among those with PD. Additionally, our work may highlight the importance of ML postural stability for individuals with comorbid and/or pharmacologically induced postural instabilities.