Invasive and Noninvasive Brain Stimulation in Parkinson's Disease: Clinical Effects and Future Perspectives.

In this review, we discuss the clinical and electrophysiological effects and the future directions of invasive and noninvasive brain stimulations in Parkinson's disease (PD). Deep brain stimulation (DBS) can improve motor symptoms in moderate to advanced PD. However, the optimal stimulation paradigm for nonmotor symptoms (NMS), freezing of gait, and the optimal timing of DBS are still under investigation. The findings of pathological oscillations and abnormal frequency to amplitude coupling provide models to develop adaptive DBS. Transcranial magnetic stimulation (TMS) revealed abnormal cortical excitability and plasticity in PD. Consecutive sessions of high-frequency, repetitive TMS on the motor cortex showed promising results. Paired TMS and DBS at specific times provided a novel way to investigate PD pathophysiology and have potential as a future treatment. Transcranial direct current stimulation or transcranial alternating current stimulation with multifocal electrodes or at specific phases of oscillation are also potential future strategies.