Seizure Outcome After Surgery for MRI-Diagnosed Focal Cortical Dysplasia: A Systematic Review and Meta-analysis

BACKGROUND AND OBJECTIVES: Focal cortical dysplasia (FCD) has been associated with poorer postsurgical seizure outcomes compared to other pathologies. FCD surgical series have been assembled on the basis of a histologic diagnosis, including patients with abnormal and normal preoperative MRI. However, in clinical workflow, patient selection for surgery is based on preoperative findings, including MRI. We performed a systematic review and meta-analysis of the literature to determine the rate and predictors of favorable seizure outcome after surgery for MRI-detected FCD. METHODS: We devised our study protocol in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and registered the protocol with PROSPERO. We searched MEDLINE, EMBASE, and Web of Science for studies of patients followed up for ≥12 months after resective surgery for drug-resistant epilepsy with MRI-detected FCD. Random-effects meta-analysis was used to calculate the proportion of patients attaining a favorable outcome, defined as Engel class I, International League Against Epilepsy class 1 to 2, or seizure-free status. Meta-regression was performed to investigate sources of heterogeneity. RESULTS: Our search identified 3,745 references. Of these, 35 studies (total of 1,353 patients) were included. Most studies (89%) followed up patients for ≥24 months after surgery. The overall postsurgical favorable outcome rate was 70% (95% confidence interval [CI] 64-75). There was high interstudy heterogeneity. Favorable outcome was associated with complete resection of the FCD lesion (risk ratio [RR] 2.42 [95% confidence interval (CI) 1.55-3.76], p < 0.001) and location of the FCD lesion in the temporal lobe (RR 1.38 [95% CI 1.07-1.79], p = 0.013) but not lesion extent, intracranial EEG use, or FCD histologic type. The number of FCD histologic types included in the same study accounted for 7.6% of the observed heterogeneity. DISCUSSION: Seventy percent of patients with drug-resistant epilepsy and MRI features of FCD attain a favorable seizure outcome after resective surgery. Our findings can be incorporated into routine preoperative counseling and reinforce the importance of completely resecting the MRI-detected FCD when safe and feasible.