300 Section - Phase-Synchronized Closed-Loop Transcranial Electrical Stimulation for Patients with Parkinson's Disease

Parkinson’s disease (PD), a neurodegenerative disorder, causes gait impairment and reduced mobility. We developed a closed-loop transcranial electrical stimulation (tES) method that synchronizes stimulation with the individual gait cycle and the most comfortable gait phase, aiming to optimize neural modulation during walking. This study evaluates whether phase-synchronized closed-loop tES improves motor symptoms and gait function in patients with PD compared with non-synchronized tES.

Design:

32 patients with PD were included in the phase-synchronized group (mean age 72.6±9.6 years) and 12 in the non-synchronized group (mean age 69.8±8.8 years). All patients received transcranial alternating current stimulation (±1 mA) at gait-cycle frequency, delivered to the most affected cerebellum. Patients underwent 10 sessions (16 minutes/session; 4 × 4 minutes; twice weekly for 5 weeks). In the phase-synchronized group, the patients walked for 6 minutes under tES, and heel-contact signals from pressure sensors were analyzed to determine the most frequent stimulation phase at which heel contact occurred. Motor function (Unified Parkinson’s Disease Rating Scale III [UPDRS-III]) and spatiotemporal gait parameters were assessed pre- and post-intervention. Analyses were performed using paired and independent t-tests or nonparametric equivalents.

Results:

Walking speed, cadence, and stance variability and swing times improved significantly in both groups. UPDRS-III scores improved significantly in the phase-synchronized group (17.9±8.1 to 15.3±7.3; p=0.003; Cohen’s d = -0.56), whereas no significant change was observed in the non-synchronized group (19.0±7.7 to 18.5±7.6; p=0.139; Cohen’s d = -0.14).

Conclusion:

Phase-synchronized closed-loop tES, aligned with the most comfortable gait phase, enhanced motor performance in patients with PD. Optimizing the stimulation timing according to individual gait phase may strengthen gait-related neural networks, and maximize therapeutic efficacy of closed-loop tES. Phase synchronization may represent a key factor in future neuromodulation-based rehabilitation strategies for patients with PD.