Electrographic Correlates of Clinical Seizures (S53.007)

Objective: To assess electrographic differences between upper and lower response quartile patients treated with the RNS® System (NeuroPace, Inc.) for refractory focal epilepsies. Background: Identifying electrographic features differentiating patients with the most favorable response to treatment will aid in discovering disease biomarkers and treatment endpoints. Design/Methods: 179 adults had ≥ 6 months of clinical seizure data at year 7 post-implant and were included in this analysis. Patients in the upper (n=45: MTL=16, Neocortical=27, MTL + neocortical=2) and lower (n=45: MTL=16, Neocortical=26, MTL + neocortical=3) response quartiles were determined by ranking mean clinical seizure rates in year 7 compared to baseline. Electrographic features (interictal spikes, total spectral power and band spectral power) were extracted from 76,570 scheduled (putatively interictal baseline) ambulatory 4-channel electrocorticographic records (each ~90 seconds) collected in these patients over 7 years since implant. Differences in electrographic features and clinical seizures over time in the upper and lower response quartile patients were measured. Results: Electrographic feature trends over time (6 months to 7 years post-implant) closely followed clinical seizure rate trends in both MTL and neocortical groups, with higher feature values significantly (p −25 ) in the MTL group followed by spectral power in theta band (4 – 8 Hz). In the neocortical group, high gamma (50 –125 Hz) emerged as the strongest feature (p −20 ) followed by low gamma (25 – 50 Hz). Conclusions: ECoGs from patients in the upper quartile of response had significantly smaller feature values compared to those patients in the lower quartile. Spike rate and high gamma emerged as the features most correlated with clinical seizures in the MTL and Neocortical groups respectively. Disclosure: Dr. Desai has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with NeuroPace. Dr. Tcheng has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with NeuroPace. Dr. Morrell has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with NeuroPace. Dr. Morrell holds stock and/or stock options in NeuroPace, which sponsored research in which Dr. Morrell was involved as an investigator.