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(Abst. 1.336), 2018

Outcomes After Mesial Temporal Lobe Resection Following Long-Term Ambulatory Recording by the RNS® System
Authors: Lawrence J. Hirsch, Yale University School of Medicine; Emily Mirro, NeuroPace, Inc.; Vincenta Salanova, Indiana University; Thomas C. Witt, Indiana University; Cornelia Drees, University of Colorado; Mesha-Gay Brown, University of Colorado; Ricky W. Lee, Via Christi Comprehensive Epilepsy Center; Toni L. Sadler, Via Christi Comprehensive Epilepsy Center; Elizabeth A. Felton, University of Wisconsin; Paul A. Rutecki, Middleton VA Medical Center; Hae Won Shin, University of North Carolina; Eldad Hadar, University of North Carolina; Christianne N. Heck, Keck School of Medicine of USC; Janet E. Greenwood, Keck School of Medicine of USC; Manu Hegde, University of California - San Francisco; and Vikram R. Rao, University of California - San Francisco
Content: Rationale: Chronic ambulatory electrocorticographic (ECoG) recording by the RNS® System (NeuroPace, Inc.) can provide information about lateralization of mesial temporal lobe (MTL) seizures, identifying patients who could benefit from mesial temporal ablative or resective procedures. In 20% of patients with MTL seizures who had bilateral hippocampal leads, the presumed seizure focus lateralization, as determined by standard localization testing, changed based on chronic ambulatory ECoG data (King-Stephens, et al., Epilepsia, 2015). Clinical outcomes are reviewed for patients treated with an MTL ablative or resective procedure based on long-term ambulatory ECoG data collected by the RNS System. Methods: This retrospective chart review examines patients who possibly or probably had bilateral MTL refractory epilepsy, were treated with the RNS System and bilateral MTL leads , and who were eventually offered and received a resective or ablative surgery based on RNS System recordings. Results: After bilateral MTL ambulatory monitoring with the RNS System, 9 patients at 7 epilepsy centers had MTL resections; none had laser ablations. The average time treated with the RNS System before resection was 54 months (range 11-117 months). Average post-resection follow-up was 28 months (range 6-67 months). At last follow-up, 8 of 9 patients (89%) were free of disabling seizures. Of these 8 patients, 4 had only unilateral seizure onsets stored by the RNS System prior to resection, and 4 had bilateral seizure onsets with a majority from one side. The remaining patient had a 50% seizure reduction; this patient had bilateral seizures recorded with the RNS System prior to the resection, continues to be monitored bilaterally, and receives treatment on the unresected side where seizures have been exclusively recorded.After resection, 8 of 9 patients continued to be treated with the RNS System. Six of the 8 had bilateral leads, including the side of resection, and 3 of these patients were receiving bilateral responsive stimulation therapy. Two continued treatment with unilateral leads. Three of the 9 patients had 1 AED discontinued, 1 patient had their VNS turned off, and 3 patients obtained their driver’s license. Conclusions: Long-term ambulatory ECoG monitoring of the MTL bilaterally with the RNS System provides data regarding lateralization of MTL epilepsy and may identify candidates for a unilateral mesial temporal resective or ablative procedure who were not previously considered. In some patients, the RNS System data indicated that seizure onsets were strictly unilateral. In other patients with bilateral onsets, ECoG monitoring suggested that a unilateral procedure would provide clinical benefit. The majority of patients (89%) in this small cohort became free of disabling seizures after these resections, some with ongoing brain-responsive neurostimulation. We are currently identifying and reviewing all patients with the RNS System who have undergone MTL resections for a larger cohort analysis. Funding: None.
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