Abstracts

Rationale: Patients with pharmacoresistant epilepsies of different etiologies, including focal cortical dysplasias (FCDs), have abnormalities of white matter tracts (WMTs). However the the pattern of WMTs abnormalities, as well as its causes, in children with epilepsy and FCD remain unknown [1]. We aimed to evaluate the integrity of WMTs and its association with seizure semiology in children with pharmacoresistant epilepsy secondary to focal cortical dysplasia (FCD). Methods: We analyzed diffusion tensor imaging (DTI) acquired in a 3 Tesla MRI of 14 patients with pharmacoresistant epilepsy secondary to type II FCD (medium age 13 years, range 8.9-17.4, 10 female) and 29 age and sex-matched controls (medium age 13 years, range 9.4-17.7, 17 female). We selected 7 WMTs with the aim to cover all brain lobes: cortical spinal tract (CST), corpus callosum (CC), cingulum, fornix, uncinate fasciculus (UF), inferior longitudinal fasciculus (ILF) and inferior fronto-occipital fasciculus (IFOF). Images were analyzed with a semi-automatic protocol using ExploreDTI to obtain average fractional anisotropy (FA) and mean diffusivity (MD). Seizure semiology was obtained through prolonged video-EEG recordings and seizures were classified as motor tonic, motor clonic, automatisms, hipermotor and bilateral tonic-clonic. Statistical analysis was performed with SPSS 24. Results: Patients with FCD presented increase of MD in genu of CC (Two sample T-test and p < 0.001) and increase of FA (p=0.011) and MD (p=0.046) in splenium of CC; decrease of MD (p=0.009) of CST ipsilateral to the FCD and decrease of FA (p=0,001) of ILF ipsilateral to the FCD. Patients with bilateral tonic-clonic seizures presented more extensive WMTs abnormalities, including CC, CST and UF. Conclusions: Children with epilepsy and FCD have widespread abnormalities in WMTs and the pattern of abnormality differs among the tracts. These differences could be justified by the complex patterns of development and maturation of each tract [2,3]. The presence of bilateral tonic-clonic seizure is associated with a more extensive alteration. Our findings suggest that multiple causes could be associated with abnormalities of WMTs in children with FCD, including impairment of normal brain neurodevelopment but also the occurrence of bilateral tonic-clonic seizures.References: [1] - Widjaja E, Blaser S, Miller E, et al. Evaluation of subcortical white matter and deep white matter tracts in malformations of cortical development. Epilepsia 2007;48;1460-9. [2] - Hasan KM, Kamali A, Iftikhar A, et al. Diffusion tensor tractography quantification of the human corpus callosum fiber pathways across the lifespan. Brain research 2009;1249;91-100. [3] – Lebel C, Walker L, Leemans A, et al. Microstructural maturation of the human brain from childhood to adulthood. Neuroimage 2008;40;1044-55. Funding: Funding by Fundação CAPES.