Abstracts

Rationale: Focal cortical dysplasia (FCD) is the most common cause of surgically remediable epilepsy in children. FCD-related epilepsy often begins before age 5 years. Some FCD exhibit later seizure-onset, extending into adulthood. The brain is organized into distinct distributed functional networks that can be identified by functional connectivity analysis. We hypothesize that FCD location within and/or disruption of these established cortical networks underlies the temporal distribution of epilepsy onset in FCD-related epilepsy.

Methods: This is an international (20 centers), retrospective cohort design study from the Multi-centre Epilepsy Lesion Detection project. Patients were included if >3 years old, had 3D preoperative T1 MRI (1.5 or 3T) with radiologic diagnosis of FCD, or histopathological confirmation, and underwent epilepsy surgery. We tracked age epilepsy onset (t1), age preoperative scan (t2), duration epilepsy (t2-t1), and ILAE histopathologic classification. Images were processed using a standardized pipeline (MELD protocol https://www.medrxiv.org/content/10.1101/2021.02.01.21250734v1) and FCDs masked with 3D regions of interest (ROI) on T1 images. The ROIs were projected onto individual FreeSurfer surfaces then registered to fsaverage sym, a bilaterally symmetrical template. FCD dominant (top) network co-localization (median 64% overlap) within one of the seven distributed functional cortical networks (Yeo atlas (J Neurophysiol 2011;106(3);1125-1165) projected on fsaverage_sym template) was determined. Two-way Chi-Square test examined association between network and binned age of epilepsy onset ( < 3y, 3 to < 10y, 10 to < 16y, ≥ 16y). Negative binomial regression was used to evaluate the effect of network on the age of epilepsy onset, controlling for the lesion size. From this model, predictive age of epilepsy onset was calculated for each network across the lesion size range.