Abstracts

Rationale: The core tenet of evidence based medicine (EBM) is the explicit integration of best research evidence, clinical expertise and patient values in the care of individual patients. It is unclear to what extent these principles have been applied to research detailing neuropsychological outcomes of epilepsy surgery. Using EBM principles, we assembled a rating system that users of neuropsychological outcomes literature could apply to assess validity and usefulness. The rating system was applied to a sample of studies describing neuropsychological outcomes of resective epilepsy surgery. Methods: The rating system incorporated elements from widely used criteria to assess the validity and usefulness of clinical research (e.g., JAMA Users Guides to the medical literature), methodological issues germane to neuropsychology, and experience of the authors. A systematic review of focal resective epilepsy surgery yielded 158 articles detailing neuropsychological outcomes. Of these, 10% of studies were randomly selected for evaluation using the EBM rating system.Results: The 28-item rating system assessed the following three EBM tenets: I. Are the results of this outcome study valid? II. Are the results of this outcome study important? III. Will the results help me in caring for my patients? The rating system was applied to the selected articles and identified important threats to validity (Question I), the most common of which were absence of a non-surgical comparison group (63%) and lack of randomization (94%). Most studies described inclusion/exclusion criteria (75%) and implemented a longitudinal design (88%) with sufficient follow-up (88%). Participants were well-described on many variables (e.g., age, epileptic focus or site of surgery, age of seizure onset, and post-operative seizure frequency). However, approximately half of studies provided no clear information regarding education, pathology, extent of resection, or detailed information regarding pre-operative intellectual function and language dominance. Very few studies included information on anti-epileptic medication use and psychiatric comorbidities (6%). Application of the rating system suggested the majority of studies had flaws that potentially limited the importance of findings (Question II). Specifically, only 63% of studies had adequate sample sizes, and only 13% used an empirically-based method of change measurement. All studies used normed or standardized cognitive measures with published reliability and validity evidence. Although all studies had some level of clinical relevance, no studies reported results in a manner that could be easily applied to predicting outcome in individual patients (Question III).Conclusions: The EBM rating system identified threats to validity, importance, and applicability of results of neuropsychological outcomes following epilepsy surgery. Many of these threats could be addressed by applying more rigorous study designs, attending to sample size and careful patient description, using empirically-based measures of change, and including methods that allow prediction of individual outcomes.