Magnetic Pulses to the Brain Ease Freezing of Gait in Parkinson’s Disease

For people living with Parkinson’s disease, few symptoms are as frightening or as disabling as freezing of gait, the sudden, involuntary inability to move the feet forward despite every intention to walk. Patients describe the sensation as though their shoes have been glued to the floor, and the episodes frequently lead to falls, injuries, and a progressive loss of independence. Now, a new study published in BMC Medical Imaging by a team of researchers based at the First Affiliated Hospital of Nanjing Medical University and Southeast University in China offers one of the most detailed looks yet at how a non-invasive brain stimulation technique can loosen that grip, and at the specific neural changes that accompany the improvement.

The technique in question is repetitive transcranial magnetic stimulation, or rTMS, a procedure in which rapidly pulsed magnetic fields are delivered through a coil held against the scalp. The magnetic pulses pass painlessly through the skull and induce small electrical currents in the underlying cortical tissue, nudging neurons toward greater or lesser activity depending on the stimulation parameters. Clinicians have long used rTMS targeting the primary motor cortex, the strip of brain tissue at the top of the head that commands voluntary movement, to treat a range of motor symptoms. What has remained frustratingly unclear is precisely how the stimulation remodels the brain’s locomotor circuitry when it is applied to freezing of gait, a symptom that does not respond to medication in the same way tremor or rigidity often do.

To answer that question, the research team assembled a carefully structured cohort. They enrolled 37 patients with Parkinson’s disease who experienced freezing of gait, 66 patients with Parkinson’s disease who did not, and 32 healthy controls. Every participant underwent a comprehensive baseline assessment, designated T0, combining transcranial magnetic stimulation paradigms with multimodal magnetic resonance imaging. This dual approach allowed the investigators to capture both the electrophysiological behavior of the cortex and the structural and functional architecture of the brain in the same individuals, on the same day, creating a detailed neurophysiological fingerprint of what distinguishes patients who freeze from those who do not.

The baseline findings were striking. Compared with both the non-freezing patients and the healthy controls, the freezing group showed decreased short-interval intracortical inhibition, a measure of how effectively inhibitory circuits within the motor cortex damp down excessive neural activity. In essence, the motor cortex of patients who freeze is running too hot, with its internal braking systems weakened. The same group also displayed excessive cortico-cortical coupling, meaning their motor cortex was functionally entangled with other cortical regions in an abnormally strong way, and reduced fractional anisotropy across extensive white matter bundles, a diffusion MRI marker indicating that the insulated fiber tracts connecting distant brain regions had lost structural integrity. Together, these three abnormalities paint a picture of a locomotor control system that is disinhibited, mis-wired, and structurally compromised.

With that baseline established, the researchers turned to treatment. The 37 patients with freezing of gait received ten add-on rTMS sessions targeting the lower limb region of the primary motor cortex, the portion of the motor map that controls the legs and feet. The stimulation protocol used a frequency of 10 hertz, meaning ten pulses per second, delivered at 90 percent of each patient’s resting motor threshold, the stimulation intensity calibrated individually to the minimum needed to evoke a measurable muscle response. Delivering high-frequency stimulation at this sub-maximal intensity is a standard approach for exciting the targeted cortex while keeping the procedure safe and tolerable. Because the sessions were added on top of existing care, the study could evaluate whether stimulation provided benefit beyond the patients’ usual treatment.

The results, measured one day after the final session and again at a one-month follow-up, showed meaningful improvements in objective gait indicators at both time points compared with baseline. This persistence is important: a therapy that only works for a few hours after the last session would be of limited clinical value, but the fact that gait measures remained improved a month later suggests that the stimulation produced changes that outlasted the treatment course itself. For a symptom that has historically been considered one of the most treatment-refractory features of Parkinson’s disease, the durability of the effect is a headline finding in its own right.

Just as importantly, the post-intervention assessments revealed what was happening inside the brain as patients improved. The team documented a constellation of neuromodulatory changes that partially reversed the abnormalities identified at baseline. Short-interval intracortical inhibition increased, indicating that the weakened inhibitory circuits within the motor cortex had been strengthened by the stimulation. Functional connectivity between the primary motor cortex and the occipital lobe, the visual processing region at the back of the brain, decreased, suggesting that the excessive cortico-cortical coupling seen before treatment had been dialed back. Perfusion, the blood supply reflecting neural activity, was reduced in the left precentral gyrus, the cortical region housing the motor representation of the body. And fractional anisotropy rose in the superior longitudinal fasciculus, a major white matter highway that links frontal, parietal, and temporal regions and plays a role in integrating motor planning with sensory feedback.

These mechanistic findings matter because freezing of gait has long resisted a simple explanation. It does not map cleanly onto the loss of dopamine that defines Parkinson’s disease, and it often persists even when other motor symptoms are well controlled by medication. The new data support a model in which freezing emerges from a network-level failure: a motor cortex that lacks adequate local inhibition, communicates abnormally with distant cortical areas including visual regions, and sits atop white matter pathways that can no longer relay signals efficiently. By strengthening cortical inhibition, normalizing the motor-occipital loop, reducing excessive perfusion, and remodeling the microstructure of key fiber tracts, rTMS appears to push this dysfunctional network back toward a healthier operating state.

The study also demonstrates the power of combining electrophysiology with multimodal imaging in a single experimental design. Transcranial magnetic stimulation paradigms provide a direct, quantitative readout of cortical circuit behavior in living humans, while diffusion and functional MRI reveal the structural scaffolding and functional coordination of the wider network. Measuring both before and after intervention allowed the researchers to link symptom change to specific, measurable neural mechanisms rather than relying on subjective reports alone. This kind of mechanistic transparency is increasingly seen as essential for moving brain stimulation from an empirical trial-and-error therapy toward a rationally targeted intervention.

There are, of course, limits to what a single study can establish. The intervention was evaluated in a defined cohort, and the authors note that the modulation of the identified abnormalities was partial rather than complete, meaning that stimulation improved but did not fully normalize the network disturbances underlying freezing. Larger and longer studies will be needed to determine optimal stimulation parameters, identify which patients are most likely to benefit, and confirm how long the effects can be sustained with maintenance treatment. Nevertheless, the work represents a significant step forward. It validates the primary motor cortex as a stimulation target for freezing of gait, identifies the cortical, connectivity, perfusion, and white matter changes that accompany clinical improvement, and offers a mechanistic framework that could guide the next generation of neuromodulation trials for one of Parkinson’s disease’s most feared symptoms.

Subject of Research: Neuromodulatory effects of repetitive transcranial magnetic stimulation on freezing of gait in Parkinson's disease

Article Title: Neuromodulatory mechanism of repetitive transcranial magnetic stimulation for freezing of gait in Parkinson’s disease

Article References: Gan, C., Sun, H., Cao, X., Si, Q., Wan, C., Ye, S., Shan, A., Gao, M., Shi, J., Wang, X., Ge, Y., Yuan, Y., Kong, Y., & Zhang, K. (2026). Neuromodulatory mechanism of repetitive transcranial magnetic stimulation for freezing of gait in Parkinson’s disease. BMC Medical Imaging. https://doi.org/10.1186/s12880-026-02800-7

Image Credits: AI Generated

DOI: 10.1186/s12880-026-02800-7

Keywords: Parkinson's disease, freezing of gait, transcranial magnetic stimulation, primary motor cortex, cortical excitability, multimodal MRI, white matter integrity, brain stimulation, neuromodulation, movement disorders, gait analysis, neurology