Objective: We aimed to compare the acute and retention effects of motor training alone versus its combination with transcranial direct current stimulation (tDCS) on motor symptoms in Parkinson’s disease (PD) patients.

Background: Recent studies suggest that tDCS may enhance the effects of motor training, potentially yielding greater improvements in motor function than motor training alone. However, previous findings have been inconsistent, likely attributable to small sample sizes and heterogeneous study designs, particularly the variability in tDCS protocols. In addition, it remains unclear whether these effects are sustained over time and which specific motor symptoms in PD are responsive to this combined intervention. A comprehensive synthesis of the available evidence is needed to clarify its therapeutic potential.

Method: Two independent reviewers searched for randomized controlled trials that applied motor training with active tDCS versus sham tDCS with motor function as an outcome measure for patients with PD. Random-effects meta-analyses were conducted to calculate standardized mean differences and 95% confidence intervals between the effects of motor training with active tDCS versus sham tDCS on motor function. A total of 16 randomized controlled trials (344 PD patients) were eligible for meta-analysis, resulting in 75 motor function comparisons for data synthesis.

Results: Motor training/active tDCS showed significant positive acute effects on overall motor function compared to motor training/sham tDCS, particularly improving step length and gait speed. Moderator variable analyses indicated that these acute effects persisted regardless of the number of sessions or the targeted brain regions for tDCS. Meta-regression analysis showed that a higher proportion of female participants and shorter PD duration were associated with greater acute effects. However, no significant retention effects of motor training/active tDCS on overall motor function were observed compared to motor training/sham tDCS.

Conclusion: Our results suggest that combining motor training with tDCS improves motor function, particularly in gait-related parameters, in PD patients. However, these effects were not sustained over time, highlighting the temporary nature of the benefits. Sex differences may influence the acute effects of combined motor training and tDCS interventions.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/transcranial-direct-current-stimulation-combined-with-motor-training-for-motor-symptoms-in-parkinsons-disease-a-systematic-review-and-meta-analysis/