Responsive neurostimulation detections: "Recognizing the unseen".

Background: Closed-loop responsive neurostimulation (RNS) is an established non-resective neuromodulatory therapy for individuals with drug-resistant epilepsy (DRE). RNS systems are typically programmed to detect and respond to predefined seizure onset patterns, with detector settings often remaining unchanged for extended periods.

Aims: To describe the delayed recognition of a novel seizure onset pattern in the acute and chronic clinical settings.

Methods: The case of a 35-year-old female with history of drug-refractory temporal lobe epilepsy who presented with increasing seizure frequency and headaches was reviewed.

Results: We demonstrate emergence of a new seizure onset pattern in a 35-year-old female with DRE who had undergone RNS implantation 5.5 years prior to presentation. Guided primarily by strong clinical suspicion, with live electrocorticography (ECoG) serving as a confirmatory tool, we identified a previously unrecognized seizure onset pattern linked to a rare, delayed intraparenchymal hemorrhage associated with an RNS lead. Longitudinal ECoG analysis in this patient, who experienced over a 95% reduction in seizures since implantation, revealed evolving seizure patterns over several years that contributed to delayed detections.

Conclusion: This case underscores the risk of misdiagnosis when acute changes in seizure patterns occur, in the context of detections programmed to identify specific patterns. Longitudinal analysis of ECoG in the same patient showed changes in seizure patterns over several years that were detected with delay, highlighting importance of vigilant detection monitoring.