Can Transcranial Ultrasound Stimulation Ease Parkinson’s Symptoms?
Parkinson’s disease affects brain circuits that connect deep structures, including the basal ganglia, with the motor cortex, which controls voluntary movement. Although medication can help, many people continue to experience disabling motor symptoms.
Deep brain stimulation of the internal globus pallidus (GPi) is an established Parkinson’s disease treatment, but it requires surgically implanted electrodes. Researchers are therefore investigating whether focused ultrasound for Parkinson’s disease could offer a non-invasive way to influence similar brain circuits.
In a study led by Yi-Ying Lin and Robert Chen, researchers tested low-intensity transcranial ultrasound stimulation (TUS), which delivers focused sound waves through the skull. They compared stimulation of the motor cortex (M1), stimulation of the GPi, and simultaneous stimulation of both regions. They hypothesised that targeting the GPi would produce stronger improvements because it is already a recognised clinical target for movement disorders.
How Focused Ultrasound Targets Deep Brain Structures
Unlike stimulation of the motor cortex, which sits close to the skull, GPi stimulation required a system capable of delivering energy with enough depth, precision, and control to reach a clinically relevant structure without using implanted electrodes.
The NeuroFUS CTX-500 uses a four-element annular array, with concentric rings that can be driven at slightly different timings. This allows the focal point to be adjusted electronically, so the beam can be shaped for targets at different depths rather than relying on a fixed focus. That capability was especially important for the GPi condition, where accurate targeting was needed to test whether a deep movement-circuit node could be modulated non-invasively.
The CTX-500 was central to the study because it made it possible to focus ultrasound beyond the cortical surface and towards the GPi, a small and deep target within the basal ganglia.
The system also supported pairing ultrasound with TMS measurements, allowing the researchers to examine whether stimulation of a deep basal ganglia target produced downstream changes in motor cortex excitability.
Study Design: Testing Ultrasound Stimulation in Parkinson’s Disease
The study included 13 participants, with a mean age of 62.6 years and a mean disease duration of 7.5 years. Each completed three sessions involving 120 seconds of theta-burst stimulation.
Motor symptoms were assessed using the Movement Disorder Society Unified Parkinson’s Disease Rating Scale Part III, while transcranial magnetic stimulation measured brain excitability before and after stimulation.
Key Findings: GPi Stimulation and Parkinson’s Motor Symptoms
Motor scores improved in 12 participants after GPi stimulation, compared with six after M1 stimulation and eight after dual-site stimulation. The strongest improvement was seen in bradykinesia, the slowness of movement associated with Parkinson’s disease. Together, these results suggest that the deeper GPi target produced the clearest short-term motor benefit.
These findings matter because earlier work had mainly focused on the motor cortex, where similar stimulation patterns are known to increase excitability. In contrast, this study suggests that targeting a deeper node in the movement circuit may be more effective for improving symptoms. Stimulating both sites did not outperform GPi stimulation alone, which strengthens the case that the benefit came primarily from the deep target.
The TMS findings support this interpretation. After GPi stimulation, a stronger magnetic pulse was needed to produce a standard muscle response at the 10-minute time point, suggesting reduced motor cortex excitability. Although the ultrasound was aimed deep in the brain, the effect appeared to carry through the basal ganglia–thalamus–motor cortex loop, linking the deep target to measurable changes at the cortical level.
Because the GPi is already an established DBS target, showing that ultrasound can influence this region without surgery is an important step. If confirmed in larger trials, TUS could become an option for people who are not suitable for surgery, or a way to test whether someone may benefit from DBS before committing to an implanted device.
Clinical Implications and Limitations of Ultrasound Treatment
These findings suggest that TUS could become a promising non-invasive adjunct to medication for Parkinson’s disease. However, the study was small and measured only short-term effects, so larger trials are needed.
Participants with severe tremor or dyskinesia were excluded, and all continued dopaminergic medication, meaning future research must test how TUS performs across broader patient groups and alongside existing treatments.
REFERENCES:
Lin, Y.-Y., Raies, N., Grippe, T., Gunraj, C.A., Sarica, C., Saha, U.K., Bhattacharya, A., Darmani, G. and Chen, R. (2026), Transcranial Ultrasound Stimulation of Internal Globus Pallidus Region and Motor Cortex in Parkinson's Disease. Mov Disord, 41: 416-425. https://doi.org/10.1002/mds.70095
