Introduction: Responsive neurostimulation (RNS) has recently emerged as a promising neuromodulation therapy in patients with drug resistant epilepsy (DRE). RNS is a closed loop device which provides a reliable source of long-term monitoring of ictal and interictal electrical activity. While evidence suggests that reduction in clinical seizure may be as high as 70%, the impact of RNS on the burden of electrographic seizures has not been analyzed.
Methods: We performed a retrospective review of patients with DRE implanted with RNS at our institution between 2017 and 2024 with at least six month and collected patient demographics, medical and surgical histories. The PDMS and nSight interface of Neuropace was utilized to review ECoGs, thereby calculating electrographic seizures. Postoperative clinical seizures were calculated by patient’s reported frequency in addition to magnet swipes noted on ECOG in correlation with ongoing electrographic seizure. Data was collected on every patient having a follow up of at least six months, with a minimum of two RNS programming sessions post-implantation.
Results: 45% of patients had bilateral hippocampal lead implantation (n=10). 64% (n=14) patients were considered to be responders (subjective >50% reduction in seizures) whereas 36% (n=8) patients were considered to be subjective non-responders. Overall mean seizure reduction rate was 70%. At one year post-op, subjective responders had an average of 2 electrographic and one clinical seizure per month compared to 8 electrographic and 2 clinical seizures per month in the non-responder group.
Conclusion : There is evidence to suggest that there is both subjective reduction in clinical seizures and objective reduction in electrographic seizures based on real long term ECOG interpretation. Further investigation is needed to assess differential seizure reduction contingent upon RNS programming.
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