Abstracts

Rationale: There is no agreement as to what the ideal definition of surgical candidacy is in patients with partial epilepsy. Criteria for considering patients for surgical investigation and treatment vary significantly among institutions and epilepsy programs. The objective of this study is to provide evidence-based estimates of the standard criteria that are used for epilepsy surgery and to identify sources of variation between published studies. Methods: Medline, Index Medicus, bibliographies of reviews, original articles, and book chapters were searched to identify published articles since 1965. Two groups of studies were identified: any surgical studies describing outcomes in ≥20 patients of any age who underwent resective or non-resective epilepsy surgery. The second group of studies were reviews, consensus conferences and guidelines. Two reviewers independently assessed study eligibility and extracted the data. Disagreements were resolved through discussion. Results: 429 studies were reviewed in full text. 344 surgical series were included, the others were definitions from consensus conferences, guidelines, or review articles. 56 studies used a criterion of intractability based on the number of antiepileptic drugs (AEDs); 18 studies defined intractable epilepsy as failure to one AED, 24 to two, and 14 to three or more AEDs. All other studies only indicated failure of an adequate trial of AED without specifying the number of AEDs. 32 studies specified the length of time to AED failure: 10 studies used more than one year, 14 more than two years and 8 used between one or two years of failure. Other used AED criteria included intolerable side effects, persistent seizures despite several combinations of AEDs and adequate blood levels of AEDs. Forty-nine studies used the number of seizures as a criteria for intractability: 45 studies defined intractability as having more than one seizure per month, 2 used one per year, one study used one per week and one study one every two months. The others did not specify the actual number of seizures required. Other criteria included: disabling seizures and seizure type (mainly complex partial seizures), presence of focal lesion on neuro-imaging, absence of various conditions such as psychiatric conditions or developmental delay. Conclusions: This study shows that the two main criteria that are used to define surgical candidacy are the number of seizures and failure to antiseizure medications, but a wide variety of criteria are used to define these two aspects. Important variations between studies make it difficult to identify consistent quantitative criteria to determine surgical candidacy. Overall the most frequently used criteria are failure to two medications over one year and at least one seizure per month. Future studies are needed to determine the potential impact of having different inclusion criteria on surgical outcomes after epilepsy surgery. Developing standard accepted surgical candidacy criteria should allow for better comparability of outcomes among centers.