Brain-Responsive Neurostimulation Reduces Focal Seizures by 82% at Three Years

Advancing Neuromodulation for Refractory Focal Epilepsy

Managing drug-resistant focal epilepsy remains a significant clinical challenge, as approximately one-third of patients continue to experience seizures despite optimal antiseizure medication regimens [1, 2]. When resective surgery is not an option, clinicians often utilize neuromodulation therapies such as vagus nerve stimulation, deep brain stimulation, or responsive neurostimulation to reduce seizure burden [3, 4]. Meta-analyses of these interventions show that intracranial modalities (devices with electrodes implanted directly within the cranium) achieve higher one-year seizure reduction rates compared to extracranial vagus nerve stimulation [1, 3]. Long-term prospective data further support these findings, reporting sustained improvements in seizure frequency and a low rate of sudden unexplained death in epilepsy among patients treated with direct brain stimulation [2]. Given these outcomes, current expert consensus from the International League Against Epilepsy recommends that clinicians offer a surgical evaluation to every patient as soon as drug resistance is established to optimize long-term prognosis [5]. A recent prospective study now offers fresh insights into the real-world effectiveness of responsive neurostimulation, providing clinicians with updated expectations for long-term seizure control and patient safety.

Real-World Effectiveness and Seizure Reduction Rates

To evaluate the RNS System in a real-world clinical setting, researchers conducted an open-label, prospective, postapproval investigation across 32 US epilepsy centers. The study enrolled 324 adult patients (mean age 37.1 years; 59.6% female) with drug-resistant focal epilepsy. Of this initial cohort, 271 patients completed the three-year follow-up period. The primary effectiveness endpoint was the median percent change in seizure frequency at three years of treatment. The findings provide Class IV evidence (data derived from observational or open-label studies lacking a concurrent control group) that direct brain-responsive neurostimulation safely reduces seizure burden over time. Clinical outcomes demonstrated a progressive and significant improvement in seizure control. The median percent reduction in seizure frequency was 62% at six months, which further increased to 82% at three years (p < 0.0001; Wilcoxon signed-rank test). Beyond the median reduction, a substantial portion of the cohort achieved high-responder status, with 41% of participants reaching a 90% or greater reduction in seizure frequency by the three-year mark. The study also documented significant periods of complete seizure freedom, a primary goal for clinicians managing refractory epilepsy. The researchers found that 42.5% of participants experienced at least one seizure-free period lasting six months or more, and 22.0% of participants achieved sustained seizure freedom for 12 months or more. For practicing neurologists, these data confirm that brain-responsive neurostimulation can provide meaningful clinical relief and extended periods of seizure control in a real-world population that has already failed multiple antiseizure medications.

Consistency Across Seizure Onsets and Locations

The clinical utility of the RNS System appears robust regardless of the complexity of the patient's seizure profile or the anatomical origin of the epilepsy. The researchers found that effectiveness was consistent across patients with either one or two seizure onsets, indicating that the presence of dual foci does not diminish the therapeutic benefit of responsive neurostimulation. Furthermore, the study demonstrated that effectiveness was consistent across all onset locations, including the mesial temporal lobe (the inner region of the temporal lobe frequently involved in focal seizures), the neocortex (the outer layer of the cerebral hemispheres), or a combination of both mesial temporal and neocortical regions. This finding is particularly relevant for clinicians managing patients with multifocal epilepsy, confirming that the device provides reliable seizure reduction across diverse anatomical substrates. When compared to historical data, the outcomes in this prospective real-world study were notably improved. The seizure reductions observed were greater and were achieved faster than those reported in the original randomized controlled trials and subsequent long-term treatment trials. Specifically, the median reduction reached 62% by six months, a rate of improvement that exceeded the timelines seen in earlier investigations. These results were, however, similar to a more recent retrospective multicenter real-world study that analyzed existing patient records across multiple institutions. The authors suggest that these improved outcomes in contemporary practice likely reflect evolving clinical expertise and more effective device programming strategies developed since the initial regulatory trials.

Safety Profile and Reduced SUDEP Risk

The safety profile of the brain-responsive neurostimulation system in this real-world cohort aligned with findings from earlier regulatory investigations, providing further reassurance for clinicians managing refractory epilepsy. During the interim safety period, the researchers reported that no serious stimulation-related adverse events occurred among the 324 implanted patients. This finding supports the long-term tolerability of the device in a diverse clinical population. While these interim results are encouraging, the study protocol dictates that the primary safety endpoint analysis will be conducted at five years of follow-up to provide a more comprehensive assessment of long-term risks and device performance over time. Beyond general safety, the study addressed the critical issue of mortality in patients with drug-resistant epilepsy, specifically focusing on sudden unexplained death in epilepsy (SUDEP), defined as the sudden, unexpected, non-traumatic, and non-drowning death of a person with epilepsy. In a combined analysis of 645 patients across all RNS System trials, the SUDEP rate was 2.3 per 1,000 patient years. This rate is a vital clinical metric, as SUDEP remains a primary concern for patients with uncontrolled focal seizures. The researchers found that this SUDEP rate was significantly lower than predefined comparators (p < 0.05; 1-tailed χ2), which serve as established benchmarks for mortality in similar patient populations. For practicing physicians, these data suggest that the reduction in seizure frequency achieved through responsive neurostimulation directly correlates with a decreased risk of epilepsy-related mortality.

Optimizing Therapy Through Evolving Programming Practices

The observation that seizure reductions in this prospective study were greater and achieved more rapidly than in the original randomized controlled trials suggests a shift in clinical application. The researchers note that this improved efficacy may reflect evolved device programming practices that have matured since the system was first introduced. In the years following the initial regulatory trials, clinicians have gained significant experience in interpreting chronic electrocorticography data (direct recordings of electrical activity from the cerebral cortex provided by the implanted device). This experience allows for more sophisticated adjustments to detection sensitivity and stimulation parameters. This iterative refinement of programming likely contributes to the high rates of clinical response, including the finding that 41% of participants achieved a 90% or greater reduction in seizure frequency by the three-year mark. Looking ahead, the wealth of longitudinal intracranial recordings captured by the system offers a pathway toward even more personalized epilepsy management. The researchers emphasized that future research efforts will focus on using the brain data obtained by the device to optimize detection and stimulation paradigms for each individual patient. By leveraging these data, clinicians may be able to move beyond current programming standards to develop highly specific algorithms that anticipate and disrupt seizure activity with greater precision. This data-driven approach aims to further refine the therapeutic window for each patient, potentially increasing the 22.0% rate of 12-month seizure freedom observed in this real-world cohort.

References

1. Khorkhash KMM, El-Shazly AA, Fayed ZYI, Hefny SM. Responsive Neuro-Stimulation versus Deep Brain Stimulation in Drug Resistant Focal Epilepsy: A Systematic Review. The Quarterly journal of medicine. 2024. doi:10.1093/qjmed/hcae175.564

2. Eliashiv D, Rao VR, Jobst BC, et al. Postapproval Study for Brain-Responsive Neurostimulation for Drug-Resistant Focal Epilepsy: Three-Year Efficacy and Interim Safety Results.. Neurology. 2026. doi:10.1212/WNL.0000000000214875

3. Skrehot HC, Englot DJ, Haneef Z. Neuro-stimulation in focal epilepsy: A systematic review and meta-analysis.. Epilepsy & behavior : E&B. 2023. doi:10.1016/j.yebeh.2023.109182

4. Rolston JD, Englot DJ, Wang DD, Shih T, Chang EF. Comparison of seizure control outcomes and the safety of vagus nerve, thalamic deep brain, and responsive neurostimulation: evidence from randomized controlled trials. Neurosurgical FOCUS. 2012. doi:10.3171/2012.1.focus11335

5. Jehi L, Jetté N, Kwon C, et al. Timing of referral to evaluate for epilepsy surgery: Expert Consensus Recommendations from the Surgical Therapies Commission of the International League Against Epilepsy. Epilepsia. 2022. doi:10.1111/epi.17350