Abstracts

Rationale: The responsive neurostimulator system (RNS System) allows evaluation of long-term ambulatory electrocorticography (ECoG) 1. Interrater agreement was 79% 2 in one ECoG study. The purpose of this retrospective study is to report outcomes of 10 patients treated with RNS and assess their ECoG relative to clinical outcome. Methods: Patient records of 10 individuals from 3/2005 to 3/2016 were reviewed with a focus on seizure response, electrocorticography, long episodes (LE), and saturations (Sats). The first six seizures were evaluated after 3 months and compared to 6 seizures at the time of last follow-up. The ECoG patterns were judged by 2 of the co-authors for agreement and divided into 4 seizure types: low voltage ictal fast, repetitive spiking, rhythmic slow, and mixed patterns (combined patterns over 5 seconds). Outcomes were correlated to the individual ECoG patterns for an association. Results: Ten patients (8 F) with a mean age of 38yrs (range 22-52) treated for epilepsy an average of 11.6 years (range 8-34) prior to RNS placement. 3 patients had prior epilepsy surgery. 6 patients were enrolled from the pivotal trial. Mean follow-up was 7 years (range 1-11 years). 84 seizures were reviewed for the ECoG pattern and number of LE. A mixed pattern was the most common ictal ECoG pattern at seizure onset in 5/10, 2/10 with low voltage fast, 1/10 rhythmic spiking, 2/10 with repetitive spiking. Mixed patterns were uncommon though 1 patient had 2 independent patterns. No patient had a change in pattern from the 3 months post implant to the last follow-up visit. 2/10 were seizure free, 6/10 were responders, and 4/10 had no appreciable benefit.. LE remained a stable pattern on ECoG as did saturations though they usually differed. Neither LE or Sats correlated with seizure outcome. . Conclusions: Mixed patterns were most common on ECoG in this cohort. Patterns of ictal ECoG onset remained stable from the first 6 seizures to the last 6 seizures. Long episodes and saturation did not consistently correlate to seizure freedom. Funding: N/A