Abstracts

In recent years, advances in surgical techniques have allowed patients without identifiable neuroimaging abnormalities to undergo epilepsy surgery. However, there is a notion that patients with normal MRI or histopathology may have worse surgical outcomes than those with lesional epilepsy. The objective of this study is to provide evidence-based estimates of the surgical outcome in patients with non-lesional epilepsy and to identify sources of results variation between published studies, Medline, Index Medicus, bibliographies of reviews, original articles, and book chapters were searched to identify published articles since 1991, describing outcomes in [ge]5 patients of any age who underwent resective or non-resective epilepsy surgery without an identifiable structural lesion by imaging or histopathology. Two reviewers independently assessed study eligibility and extracted the data. Disagreements were resolved through discussion., Twenty-nine articles fulfilled eligibility criteria and described outcomes in 655 patients with non-lesional epilepsy surgery. Non-lesional status was defined by MRI in 56% of studies and by histopathology in 44%. Overall, 24% of patients described were non-lesional. The median proportion of seizure-free patients was 44% (95% CI 39-49) in non-lesional cases vs. 61% (95% CI 58-64) in those with lesions. The corresponding proportion was 46% (95% CI 39-53) if non-lesional status was defined by MRI, versus 42% (95% CI 35-49) if defined by histopathology. In non-lesional patients with temporal lobe surgery, 40% (95% CI 33-46) were seizure free. We explore aspects related to the validity of these results., Overall, non-lesional epilepsy surgery has inferior results compared with lesional cases (44% vs 61% respectively). The response after surgery was the same whether lesional status was defined using MRI or histopathology. Sources of heterogeneity are explored.,