Transcranial Direct Current Stimulation on Supplementary Motor Area Enhances the Effects of Exercise Therapy for Proprioception and Balance in People with Parkinson’s: an Exploratory Pilot Trial

Background and Purpose Parkinson’s impairs movement control and proprioception. This pilot randomized controlled trial investigated whether anodal transcranial direct current stimulation (a-tDCS) combined with proprioceptive exercises improves these functions in people with Parkinson’s. Methods Twenty-four people with Parkinson’s were randomly assigned (1:1) to either active a-tDCS (2mA, 20 minutes, 3 sessions/week for 2 weeks) or sham stimulation, followed by standardized proprioceptive training. The primary outcome was ankle joint proprioceptive acuity. Secondary outcomes included postural sway, gait initiation parameters, and quality of life. Participants were blinded to group allocation. Results The active a-tDCS group showed significantly greater improvement in ankle joint repositioning error compared to the sham group (mean difference −2.9 degrees, 95% CI [−3.1, −2.7]; P = .012). Postural sway (elliptical sway area, eyes closed) was also significantly reduced in the active a-tDCS group (−2.6 cm², 95% CI [−4.6, −0.6]; P = .038). Gait initiation time decreased in both groups, but only the active a-tDCS group showed a significant reduction in step time (−168 ms, 95% CI [−175, −160]; P = .005). No significant between-group difference was found in quality of life ( P = .687). Discussion and Conclusions Multiple sessions of a-tDCS combined with proprioceptive exercises explored preliminary evidence of enhanced proprioceptive acuity and postural control in people with Parkinson’s. Gait initiation also improved with a-tDCS. All a-tDCS sessions were well-tolerated by participants, with no adverse effects reported. Further research is needed to explore long-term effects and underlying mechanisms. This pilot study provides preliminary evidence for a-tDCS as a potential adjunctive therapy, though larger trials are needed to confirm clinical efficacy. Clinical trial registration code: IRCT20230820059201N2 (Iranian Registry for Clinical Trials) Clinical trial registration URL: https://irct.behdasht.gov.