Superficial and deep white matter diffusion abnormalities in focal epilepsies

Author(s)

Urquia-Osorio, Hebel ; Pimentel-Silva, Luciana R. ; Rezende, Thiago Junqueira Ribeiro ; Almendares-Bonilla, Eimy ; Yasuda, Clarissa L. ; Concha, Luis ; Cendes, Fernando

• Document type: Journal article
• Source: Epilepsia; v. N/A, p. 13-pg., 2022-06-25.

Abstract

Objective This study was undertaken to evaluate superficial-white matter (WM) and deep-WM magnetic resonance imaging diffusion tensor imaging (DTI) metrics and identify distinctive patterns of microstructural abnormalities in focal epilepsies of diverse etiology, localization, and response to antiseizure medication (ASM). Methods We examined DTI data for 113 healthy controls and 113 patients with focal epilepsies: 51 patients with temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS) refractory to ASM, 27 with pharmacoresponsive TLE-HS, 15 with temporal lobe focal cortical dysplasia (FCD), and 20 with frontal lobe FCD. To assess WM microstructure, we used a multicontrast multiatlas parcellation of DTI. We evaluated fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), and assessed within-group differences ipsilateral and contralateral to the epileptogenic lesion, as well as between-group differences, in regions of interest (ROIs). Results The TLE-HS groups presented more widespread superficial- and deep-WM diffusion abnormalities than both FCD groups. Concerning superficial WM, TLE-HS groups showed multilobar ipsilateral and contralateral abnormalities, with less extensive distribution in pharmacoresponsive patients. Both the refractory TLE-HS and pharmacoresponsive TLE-HS groups also presented pronounced changes in ipsilateral frontotemporal ROIs (decreased FA and increased MD, RD, and AD). Conversely, FCD patients showed diffusion changes almost exclusively adjacent to epileptogenic areas. Significance Our findings add further evidence of widespread abnormalities in WM diffusion metrics in patients with TLE-HS compared to other focal epilepsies. Notably, superficial-WM microstructural damage in patients with FCD is more restricted around the epileptogenic lesion, whereas TLE-HS groups showed diffuse WM damage with ipsilateral frontotemporal predominance. These findings suggest the potential of superficial-WM analysis for better understanding the biological mechanisms of focal epilepsies, and identifying dysfunctional networks and their relationship with the clinical-pathological phenotype. In addition, lobar superficial-WM abnormalities may aid in the diagnosis of subtle FCDs. (AU)

• FAPESP's process: 16/05985-3 - Voxel-based diffusion tensor imaging in patients with focal epilepsies: comparative analyses of microstructural damage and anatomical connectivity between benign and refractory mesial temporal lobe epilepsy and frontal lobe epilepsy
• Grantee: Hebel Oziel Urquia Osorio
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 13/21056-4 - Proton MRS evaluation of inflammatory and drug refractoriness biomarkers in temporal lobe epilepsy.
• Grantee: Luciana Ramalho Pimentel da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 13/07559-3 - BRAINN - The Brazilian Institute of Neuroscience and Neurotechnology
• Grantee: Fernando Cendes
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC