Long-term outcomes in epilepsy surgery: antiepileptic drugs, mortality, cognitive and psychosocial aspects

Abstract

Assessment of long-term outcomes is essential in brain surgery for epilepsy. Little information exists on long-term non-seizure outcomes after epilepsy surgery. We perform a systematic review and meta-analysis of the evidence on this topic. Our aim was to provide evidence-based estimates of antiepileptic drug, psychosocial, neuropsychological and mortality long-term outcomes following epilepsy surgery, and to identify sources of variation in published results. We searched Medline, Index Medicus, the Cochrane database, bibliographies of reviews, original articles, and book chapters, to identify articles published from 1991 to 2005, containing > or =20 patients of any age, undergoing resective or non-resective epilepsy surgery, and followed for a mean/median of > or =5 years. Two reviewers independently assessed study eligibility and extracted data, resolving disagreements through discussion. Standard meta-analytical techniques were used to pool data. Of the 159 potentially eligible articles reviewed in full-text, 35 (22%) fulfilled eligibility criteria; 6 (17%) were controlled studies; 15 (36%) explored antiepileptic drug outcome; 6 (17%) explored mortality; 11 (31%) reported psychosocial outcomes; and 7 (20%) explored neuropsychological outcomes. On an average, 14% [95% confidence interval (CI(95)) = 11-17] of the patients with temporal lobe surgery achieved long-term antiepileptic drug (AED) discontinuation, 50% (CI(95) = 45-55) achieved monotherapy, and 33% remained on polytherapy (CI(95 =) 29-38). In analyses including all types of surgery, on average, 20% (CI(95) = 18-23) achieved long-term AED discontinuation, while 41% (CI(95) = 37-45) were on monotherapy and 31% (CI(95) = 27-35) remained on polytherapy. Children achieved better AED outcomes than adults. Seizure freedom after surgery was associated with lower mortality, but inconsistent mortality outcomes precluded making strong inferences. Non-controlled studies consistently reported improved long-term psychosocial outcomes, but the effect was less clear in controlled studies. Intelligence was unchanged by surgery, but long-term memory outcomes were associated with seizure freedom and side of temporal lobe resection. Few long-term, controlled studies exist. Longer follow-up was associated with lower rates of AED discontinuation, reflecting lower seizure-free rates over time. Cognitive and psychosocial outcomes were similar to those of short-term studies, and the results were influenced by the presence of controls.