Noninvasive Brain Stimulation for Parkinson's Disease: Therapeutic Applications and Clinical Perspectives

Noninvasive brain stimulation (NIBS), including repetitive transcranial magnetic stimulation (rTMS), transcranial direct current stimulation (tDCS), and transcranial alternating current stimulation (tACS), has been investigated as an adjunctive therapeutic approach for neurological and psychiatric disorders. In Parkinson's disease (PD), NIBS is of particular interest because several motor and nonmotor symptoms remain insufficiently controlled by pharmacological or surgical treatments. This review summarizes the mechanisms and clinical applications of NIBS in PD, with emphasis on cortical excitability, synaptic plasticity, and network oscillations. These physiological effects may contribute to therapeutic benefit, although clinical responses vary according to stimulation parameters, disease stage, and concurrent task or rehabilitation context. Among NIBS modalities, rTMS has the most consistent clinical evidence, particularly for improving motor symptoms, gait disturbance, depression, and selected cognitive outcomes when applied to the motor cortex, supplementary motor area, or dorsolateral prefrontal cortex. tDCS has shown limited and inconsistent efficacy as a monotherapy for motor symptoms but may have potential benefits for cognitive and mood-related outcomes, especially when combined with physical rehabilitation or cognitive training. tACS remains at an earlier stage of clinical investigation, with preliminary evidence suggesting that frequency-specific stimulation may modulate abnormal oscillatory activity and improve selected motor outcomes, such as tremor or motor stability. Safety, tolerability, and biomarker-guided personalization are important considerations for clinical translation. Further studies are needed to standardize stimulation protocols, assess long-term efficacy, and identify predictors of treatment response. Overall, NIBS represents a generally safe and noninvasive approach that may complement existing treatments for PD. This review summarizes the current evidence and future directions for NIBS-based interventions.