Abstracts

Rationale: To review the literature to assess what criteria have been used to select patients for resective epilepsy surgery and examine whether these have changed since the publication of the first epilepsy surgery randomized controlled trial. The objectives of this study were to provide estimates of the standard criteria that are used for recruiting patients for epilepsy surgery and to identify sources of heterogeneity between studies. Methods: A systematic review was conducted using PubMed and EMBASE, bibliographies of reviews and book chapters identifying focal epilepsy resective series between 1965 and 2008. Abstract, full text review and data abstraction (i.e. indications for surgery) were performed independently by two reviewers. Descriptive analysis of the following were done to examine indications over time: epilepsy duration, frequency of seizures, disabling seizures, resistance to AEDs, duration of AED failure, number of AEDs failed, intolerable side effects to AED, absence of developmental delay, absence of psychiatric conditions/serious medical conditions/progressive neurological conditions, prior surgery, EEG criteria, neuroimaging criteria. Results: Out of 5061 articles related to epilepsy surgery, 384 articles met all eligibility criteria. Most common criteria for selecting patients for evaluation for resective surgery in decreasing frequency were: AED resistance (n=303, most commonly >2 AEDs=46), epilepsy duration (n=51, most commonly >1 year=37) and seizure frequency (most commonly at least one seizure/month, n=39). Criteria to select patients for surgery evolved over time, and studies pre-year 2000 vs. post-year 2000 were examined. Concentrating on the prospective data we found that a higher proportion of centers over time reported criteria of seizure frequency (Pre-year 2000: 14% vs. Post-year 2000: 23%) and number of AEDs failed (Pre-year 2000: 21% vs. Post-year 2000: 32%). The most important and rather disquieting outcome of the analysis was that, for the vast majority of studies inclusion criteria were incompletely documented for pre-surgical evaluation. Conclusions: The two main criteria that were used to define surgical candidacy in the published series reviewed are: seizure frequency and failure to anti-seizure medications. However, the terms are loosely defined and display significant intra-study variation. Overall, having one seizure per month and failure of two or more AEDs were the commonest specific criteria. Yet, seizure frequency should not be one of the sole determinants of surgical candidacy, as infrequent seizures may still pose significant risks and impair quality-of-life. Important variations between studies make it difficult to identify consistent objective criteria to determine surgical candidacy. Moreover, this review provides convincing data on the often incomplete data on criteria for pre-surgical evaluation. Development of accepted standard criteria for surgical candidacy including clear definitions of eligibility criteria are needed in order to ensure timely referrals to epilepsy centers and to allow for comparison of outcomes between centers.