Abstracts

Rationale: Focal cortical dysplasia (FCD) is a common cause of drug-resistant epilepsy and is potentially amenable to epilepsy surgery. Most studies reporting post-surgery seizure outcomes in patients with FCD-associated drug-resistant epilepsy comprise MRI-negative cases, in whom the FCD was only demonstrated on histopathological examination. This hampers the applicability of these results to real-world clinical practice, which relies on pre-operative investigations including MRI. To address this knowledge gap, we conducted a systematic review and meta-analysis of studies assessing surgical outcomes in patients with MRI-diagnosed FCD. Methods: Two authors (AW and AAB) performed a literature search of Medline via PubMed, Web of Science and Ovid EMBASE in compliance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Prospective or retrospective randomized controlled trials, cohort studies, or case series of >10 patients undergoing epilepsy surgery for FCD diagnosed pre-operatively on MRI were included. Other inclusion criteria were ≥12 months of post-operative follow-up and a clearly defined study population. Unpublished data and patients with FCD associated with other epileptogenic lesions (dual pathology) were excluded. Any discrepancy between the two reviewers was solved by a third author (PP). The Effective Public Health Practice Project (EPHPP) tool was used for evaluation of bias risk and quality of studies. Results: A total of 3,341 references were initially identified and, of these, 261 were removed because they were duplicates. The remaining 3,080 references were screened by abstract review. 195 full-text articles were then reviewed, of which 168 were excluded (among those 95 were conference abstracts; 42 did not correlate surgery outcomes to MRI diagnosis; 10 included <10 patients). Currently, 11 articles, comprising 322 patients, are included in the analysis. One article reported surgical outcomes in adults (68 patients), three in children (57 patients), and the remaining articles included all age groups (197 patients). Most of the studies (n=8) reported surgical outcomes using Engel’s classification, while others reported “seizure-freedom” as the outcome without specifying the classification system used. Meta-analysis revealed an overall effect size of 0.72 (95% CI 0.63-0.80), but also a high degree of heterogeneity (I2 =64.58%, p=0.00) (Fig.1). Conclusions: Preliminary results indicate that while reported seizure outcomes in MRI-diagnosed FCD surgery are encouraging, overall evidence is limited and most of the literature is highly heterogeneous with variability across studies in patient populations and surgical outcome reporting. We suggest more detailed and systematic reporting of outcomes in future surgical studies, as well as describing surgical outcomes according to pre-operative variables. Funding: No external funding was sought for this systematic review and meta-analysis. A.W. is supported by Monash University RTP Scholarship. P.P. is supported by an Early Career Fellowship from the National Health and Medical Research Council (APP1163708), and by the Viertel Clinical Investigator Award from the Sylvia and Charles Viertel Charitable Foundation. T.O’B. is supported by a Program Grant from the National Health and Medical Research Council of Australia (APP1091593), and the Royal Melbourne Hospital Neuroscience Foundation. P.K. is supported by a Medical Research Future Fund from the National Health and Medical Research Council of Australia (APP1136427).