Plenary IV: Hot Off the Press: Late Breaking Science
Beyond the Seizure Diary: How Long-Term Bilateral Subscalp EEG Reveals the True Burden of Epilepsy
Saturday, January 24, 2026
1:15 PM - 1:25 PM PST
Location: Octavius Ballroom 4
Introduction: Accurate quantification of seizures is critical for the clinical management of epilepsy, evaluation of treatment efficacy in clinical trials, and the development of seizure forecasting systems. However, reliance on patient-reported seizure diaries is known to be fraught with inaccuracies, with both under- and overreporting commonly observed. The UMPIRE study was designed to evaluate the safety and performance of the Minder bilateral subscalp EEG system and to directly compare diary-reported seizures with objective electrographic recordings during extended monitoring.
Methods: The UMPIRE study was a prospective, multicenter, first-in-human trial enrolling 26 adults with focal or generalized epilepsy and a baseline seizure frequency of at least two per month. All participants were implanted with the Minder bilateral subscalp EEG device and monitored continuously for six months. In addition to ambulatory EEG recording, participants underwent simultaneous scalp video-EEG monitoring (VEM) at 4 and 24 weeks. This allowed direct comparison of self-reported seizure diary entries with electrographic events captured during VEM.
Results: During the VEM sessions, 25 electrographic seizures were recorded across eight participants. Of these, 56% (14/25) were not reported in the seizure diary. Conversely, 88 diary entries had no corresponding electrographic seizure, resulting in an overall diary accuracy of only 12% during monitored periods. Over the full six-month period, 600 seizures were recorded in diaries; subscalp EEG was available for 377 of these, of which only 115 (31%) had electrographic confirmation. Diary accuracy varied between individuals (0–100%), with some patients demonstrating substantial overreporting and others showing frequent unrecognized seizures. Unexpected bilateral seizure origin was often noted.
The Minder system captured extensive EEG data, with an average data completeness of 53% over six months, equating to more than 2,300 hours of recording across participants. This enabled detection of bilateral seizure foci, frequent unreported events, and differentiation between epileptic and nonepileptic episodes. In 23% of participants, bilateral recording altered diagnostic impressions, demonstrating the clinical utility of extended, bilateral EEG coverage.
Conclusion: This study confirms that patient seizure diaries often misrepresent actual seizure occurrence, with both significant under- and overreporting. Distribution of reported and unreported events matched that of larger studies examining video EEG data. Continuous, long-duration EEG recording using a subscalp device provides objective and clinically relevant data that substantially exceeds the temporal sampling of conventional inpatient monitoring. The Minder system was found to be safe and capable of high-fidelity recording, supporting its utility in clinical practice, research, and seizure forecasting. Replacing diary-based seizure reporting with continuous EEG may markedly improve the management and evaluation of epilepsy.
