Abstracts

Rationale: Our objective is to disclose which neurophysiologic seizure-onset information on scalp EEG and intracerebral EEG (iEEG) is significantly associated with postoperative outcome in a large series of patients with focal epilepsy who underwent resective surgery. Methods: We retrospectively analyzed 75 consecutive patients with focal epilepsy, who first underwent scalp EEG recording and then iEEG investigation for presurgical assessment, and who finally had resective surgery at Montreal Neurological Institute and Hospital between November 2004 and October 2015. We analyzed the following neurophysiologic scalp EEG and iEEG seizure-onset information: seizure-onset zone related to MRI-visible lesion (lesional epilepsy vs non-lesional epilepsy), seizure-onset patterns on scalp EEG and iEEG, localized nature of scalp seizure onset, anatomical location of iEEG seizure-onset zone, concordance of iEEG clinical and electrographic seizure-onset zone, extent of seizure-onset zone (measured by the number of seizure-onset contacts). To determine the independent prognostic factors, we used univariate (chi-square or Fisher two-tailed exact test for categorical variables and Mann-Whitney U test for continuous non-parametric data of the extent of seizure-onset zone) and standard multivariate logistic regression analyses (forward selection method and likelihood ratio test). Since scalp EEG and iEEG were recorded asynchronously, we matched scalp seizures with intracerebral seizures for each patient using strict criteria. Results: A total of 3057 seizures were assessed. Forty-eight percent (36/75) of patients had favorable outcome (Engel’s class I-II) after follow-up of at least one year. The results of each factor are given in table 1 and figure 1. By univariate analysis, a localized scalp EEG seizure onset (p Conclusions: Our study showed that localization at scalp seizure onset and multilobar seizure-onset zone were identified as strong predictors of surgical outcome. These predictors can help to select the better candidates for resective surgery. Funding: This research was supported from Canadian Institute of Health Research (grant FDN-143208).