OBJECTIVE: We comprehensively characterized a large pediatric cohort with focal cortical dysplasia (FCD) type 1 to expand the phenotypic spectrum and to identify predictors of postsurgical outcomes. METHODS: We included pediatric patients with histopathological diagnosis of isolated FCD type 1 and at least 1 year of postsurgical follow-up. We systematically reanalyzed clinical, electrophysiological, and radiological features. The results of this reanalysis served as independent variables for subsequent statistical analyses of outcome predictors. RESULTS: All children (N = 31) had drug-resistant epilepsy with varying impacts on neurodevelopment and cognition (presurgical intelligence quotient [IQ]/developmental quotient scores = 32-106). Low presurgical IQ was associated with abnormal slow background electroencephalographic (EEG) activity and disrupted sleep architecture. Scalp EEG showed predominantly multiregional and often bilateral epileptiform activity. Advanced epilepsy magnetic resonance imaging (MRI) protocols identified FCD-specific features in 74.2% of patients (23/31), 17 of whom were initially evaluated as MRI-negative. In six of eight MRI-negative cases, fluorodeoxyglucose-positron emission tomography (PET) and subtraction ictal single photon emission computed tomography coregistered to MRI helped localize the dysplastic cortex. Sixteen patients (51.6%) underwent invasive EEG. By the last follow-up (median = 5 years, interquartile range = 3.3-9 years), seizure freedom was achieved in 71% of patients (22/31), including seven of eight MRI-negative patients. Antiseizure medications were reduced in 21 patients, with complete withdrawal in six. Seizure outcome was predicted by a combination of the following descriptors: age at epilepsy onset, epilepsy duration, long-term invasive EEG, and specific MRI and PET findings. SIGNIFICANCE: This study highlights the broad phenotypic spectrum of FCD type 1, which spans far beyond the narrow descriptions of previous studies. The applied multilayered presurgical approach helped localize the epileptogenic zone in many previously nonlesional cases, resulting in improved postsurgical seizure outcomes, which are more favorable than previously reported for FCD type 1 patients.

Department of Circuit Theory Faculty of Electrical Engineering Czech Technical University Prague Prague Czech Republic

Department of Clinical Psychology 2nd Faculty of Medicine Charles University and Motol University Hospital full member of the European Reference Network EpiCARE Prague Czech Republic

Department of Neurosurgery 2nd Faculty of Medicine Charles University and Motol University Hospital full member of the European Reference Network EpiCARE Prague Czech Republic

Department of Pathology and Molecular Medicine 2nd Faculty of Medicine Charles University and Motol University Hospital full member of the European Reference Network EpiCARE Prague Czech Republic

Department of Pediatric Neurology 2nd Faculty of Medicine Charles University and Motol University Hospital full member of the European Reference Network EpiCARE Prague Czech Republic

Department of Pediatrics Martin University Hospital Jessenius Faculty of Medicine in Martin Martin Slovak Republic

Department of Radiology 2nd Faculty of Medicine Charles University and Motol University Hospital full member of the European Reference Network EpiCARE Prague Czech Republic

Department of Water Resources and Environmental Modeling Faculty of Environmental Sciences Czech University of Life Sciences Prague Prague Czech Republic

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