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

The technique behind the finding is conceptually elegant. Transcranial magnetic stimulation uses a focused magnetic coil held over the scalp to induce small electrical currents in the underlying cortex, briefly provoking neurons and recording the muscular response, typically a twitch in a hand or arm muscle detected by electromyography. By systematically stimulating a grid of positions over the primary motor cortex and measuring the minimum stimulation intensity needed to evoke a response at each spot, clinicians can build a functional map of the motor system without opening the skull. When this procedure is combined with neuronavigation, which tracks the coil’s position against the patient’s magnetic resonance imaging, the resulting map can be used both to plan surgery and, as this study demonstrates, to extract quantitative measures of how excitable the motor cortex has become in the presence of a tumor.

The London group distilled their nTMS recordings into two composite metrics. The first, the IntraM1 Excitability Score, or IMES, summarizes excitability measures within the primary motor cortex itself, the region conventionally labeled M1. The second, the Cortical Excitability Score, or CES, aggregates a broader profile of excitability across the mapped cortical area. Higher IMES values and lower CES values both point toward a motor cortex that retains more of its normal responsiveness to stimulation. The team reasoned that if a growing glioblastoma progressively disrupts the physiological state of the tissue it invades, then the degree of that disruption, captured electrically, might reflect how aggressively the disease is behaving.

The results bore out that reasoning with unusual clarity for a single-center retrospective cohort. Among the seventy-seven patients, who ranged widely in age with a mean of 55.4 years, median and mean overall survival clustered around 20.5 months, consistent with contemporary glioblastoma outcomes after maximal safe resection and standard chemoradiotherapy. On simple univariate comparisons, patients with lower IMES scores and higher CES scores died sooner. But the more important test came afterward: the researchers entered both excitability scores into Cox proportional hazards regression models alongside the classical prognostic variables, asking whether the electrical signatures still carried independent information. They did. A higher IMES was associated with a hazard ratio of 0.16, meaning substantially better survival for each increment on the score, with a p-value of 0.003. A higher CES, by contrast, carried a hazard ratio of 2.63, indicating roughly two-and-a-half-fold increased risk of death, with a p-value of 0.034.

Those numbers deserve unpacking for readers less familiar with survival statistics. In a Cox regression, a hazard ratio describes how the instantaneous risk of death changes with a one-unit increase in a given variable, holding all other variables constant. A hazard ratio below one is protective; a ratio above one is harmful. The fact that IMES and CES remained significant after adjustment for age, sex, neurological status, MGMT methylation and extent of resection means the excitability measures are not merely proxy readings of tumor size or patient fitness. They appear to encode something biologically distinct, plausibly the functional footprint of tumor infiltration into the motor network, a process that anatomical imaging and even molecular classification do not fully capture.

This interpretation fits into a fast-moving body of research on what some investigators call the onco-biological signature of brain tumors in motor systems. A landmark 2023 study in Nature showed that glioblastoma actively remodels the neural circuits it invades and that the degree of neuronal integration correlates with shortened survival, suggesting the tumor exploits neuronal activity as a trophic signal. Parallel work has documented microstructural abnormalities in the corticospinal tract and in the apparently normal white matter of the opposite hemisphere, while connectome analyses have quantified how invasion along fiber tracts predicts outcome. The nTMS excitability measures used in the London study can be understood as a functional complement to those structural metrics: rather than measuring the wiring, they measure how responsive the circuitry remains to direct stimulation.

One additional finding adds practical weight to the study. When the researchers compared excitability mapping restricted to one hemisphere against mapping that included both hemispheres, the bilateral approach improved the accuracy of twelve-month survival prediction. This detail matters biologically as well as statistically. Glioblastoma is notorious for occult crossing of midline structures such as the corpus callosum, producing so-called butterfly patterns of spread that conventional magnetic resonance imaging can underestimate. If excitability changes on the opposite, radiologically normal hemisphere carry prognostic signal, then bilateral stimulation may be sensing functional consequences of tumor infiltration that imaging alone misses, offering a cheap and repeatable window onto disease extent.

The clinical implications extend beyond prognosis into surgical decision-making. nTMS is already used in many neurosurgical centers to map motor pathways preoperatively, stratify surgical risk and plan the boundaries of resection, with a substantial literature confirming its value in reducing postoperative deficits. The new study suggests that the same data, collected routinely as part of surgical planning, could be repurposed at essentially no additional cost or burden to the patient as a prognostic tool. In an era when treatment intensification, clinical trial enrollment and even the extent of resection are calibrated to expected survival, having an objective, physiology-based biomarker available on the day of admission could meaningfully change how individualized treatment plans are drawn.

The authors and outside observers alike are careful about what the study does and does not establish. It is retrospective, comes from a single institution, and involves a modest sample of seventy-seven patients, so the hazard ratios, however compelling, require validation in independent and ideally prospective cohorts before excitability profiling enters routine practice. There are also technical considerations: motor threshold measurements can vary with coil type, limb dominance and stimulation parameters, and the field continues to debate the best standardized protocols for using motor threshold as a dependent variable in research. The King’s College team addressed methodological rigor by reporting their work in line with established guidance for prognostic marker studies and prediction models, and by adjusting for the classical covariates, but replication remains the essential next step.

Even with those caveats, the study marks a conceptual milestone in neuro-oncology. For a century, prognosis in glioma has been built from what pathologists and radiologists can see: cellular appearance, molecular markers, tumor volume and resection extent. This work adds a different dimension entirely, the living electrical behavior of the motor cortex confronting a tumor, and shows that this dimension carries information about survival that the standard battery of tests does not. If larger studies confirm the finding, the humble magnetic coil, currently valued for mapping where things are, may become equally valued for revealing how sick the system is, bringing a functional, physiologically grounded biomarker to the bedside of one of medicine’s most daunting cancers.

Subject of Research: Preoperative cortical excitability measured with navigated transcranial magnetic stimulation as a prognostic biomarker for overall survival in motor-eloquent glioblastoma

Article Title: nTMS-determined cortical excitability is associated with overall survival in patients with motor-eloquent glioblastoma

Article References: Lavrador, J. P., Mirallave-Pescador, A., Patel, S., Al-Banna, Q., Fayez, F., Prasad, V., Baig Mirza, A., Sinosi, F. A., Prakashvel, S., Rajwani, K., Kalyal, N., Chowdhury, Y. A., Marchi, F., Elhag, A., Ferrari, L., Baamonde, A. D., Mosquera, J. S., Ashkan, K., Bhangoo, R., & Vergani, F. (2026). nTMS-determined cortical excitability is associated with overall survival in patients with motor-eloquent glioblastoma. Journal of Neuro-Oncology, 179(3), Article 100. https://doi.org/10.1007/s11060-026-05806-x

Image Credits: AI Generated

DOI: 10.1007/s11060-026-05806-x

Keywords: glioblastoma, navigated transcranial magnetic stimulation, cortical excitability, overall survival, motor cortex, prognosis, brain tumor, neuro-oncology, motor mapping, biomarker, MGMT methylation, extent of resection