1132 Phase 1 Correlates of Seizure Onset Zone for Prediction of sEEG Placement and Clinical Outcomes

Abstract

INTRODUCTION: Approximately 20 million people worldwide suffer from drug resistant epilepsy. Treatment of the seizure onset zone (SOZ) can reduce seizure burden. When phase 1 testing fails to identify a clear surgical lesion, stereo-electroencephalography (sEEG) offers a high-resolution spatial map of cortical and subcortical activity. However, each additional lead placed also increases the chances of a complication. Preoperative identification of optimal targets is crucial to minimizing the risk-benefit ratio of sEEG placement. METHODS: We studied epilepsy patients that underwent sEEG placement followed by resection, stimulation, or laser ablation at a single institution from 1/2012 to 11/2021. Leads were identified by their respective Phase 1 indications. Preoperative and 1-year postoperative clinical outcomes were compared. Hypothesis testing was performed via the Wilcoxon rank sum test and Fisher’s exact test. A logistic generalized linear mixed effect model was used for multivariate analysis. RESULTS: 101 patients had 1752 leads placed with 239 SOZs found and treated. Mean weekly seizure frequency decreased from 25.2 to 7.8 (p < 0.001). SOZ leads were more likely to have concordant findings (p < 0.001) across studies. Lesions with PET hypometabolism (OR 1.4), MRI abnormalities (OR 1.9), MEG Clusters (OR 1.9) and calcifications (OR 3.2) were significantly more likely to predict SOZ, though PET hypometabolism was not significant in multivariate analysis. While the reason for lead placement in the SOZ did not predict seizure outcomes, patients with other lesions that had MEG Clusters or Calcifications had an average 15% worse seizure reduction than those without (p < 0.005). CONCLUSIONS: Certain Phase 1 aspects of a putative lesion, such as MRI abnormalities, the presence of calcifications, or MEG clusters can predict SOZ and clinical outcomes.