title: Interhemispheric microstructural connectivity in bitemporal lobe epilepsy with hippocampal sclerosis.
abstract: Temporal lobe epilepsy (TLE) is the most common form of focal epilepsy. The most frequent pathologic finding in this condition is hippocampal sclerosis (HS). In addition, in a small proportion (14-23%) of refractory TLE patients, the presence of HS is bilateral. TLE involves grey matter (GM) and white matter (WM) abnormalities in a wide cortico-subcortical network. However, the impact of neuronal loss on specific WM fiber pathways and associated functional systems as well as seizure propagation pathways remains unclear. There is still much controversy regarding the role of the commissures (corpus callosum, hippocampal commissure and anterior commissure) in interhemispheric seizure propagation. This study aimed to investigate the integrity of WM interhemispheric connectivity in a singular sample of patients with TLE and bilateral HS using structural magnetic resonance imaging (MRI). We performed multimodal structural MRI [high resolution T1-weighted and diffusion tensor imaging (DTI)] analyses of seven patients with medically refractory TLE with bilateral HS, fourteen unilateral left TLE patients and fifteen matched healthy individuals. Whole-brain voxel-wise analysis techniques were used. These patients evidenced WM derangement [reduced fractional anisotropy (FA), increased mean diffusivity (MD) or reduced WM volume] in temporal and extratemporal tracks, but also in commissural pathways, compared to the unilateral left TLE patients and the control group. Presence of reduced FA or increased MD in the fornix, cingulum and uncinate fasciculus in addition to reduced WM volume in the fornix was also encountered. Neuropsychological assessment was performed without significant correlations with structural data. The current results support the idea that commissural pathways play a contributory role in interhemispheric TLE seizure propagation in bilateral HS and offer new perspectives about the long-term effects on interhemispheric connectivity associated with seizure propagation patterns in TLE patients.
authors.affiliation: Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute-IDIBELL, L'Hospitalet (Barcelona), Spain; Epilepsy Unit, Neurology Section, Hospital Universitari de Bellvitge (HUB), L'Hospitalet (Barcelona), Spain.
authors.forename: Júlia
authors.initials: J
authors.lastname: Miró
authors.affiliation: Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute-IDIBELL, L'Hospitalet (Barcelona), Spain.
authors.forename: Ane
authors.initials: A
authors.lastname: Gurtubay-Antolin
authors.affiliation: Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute-IDIBELL, L'Hospitalet (Barcelona), Spain; Department of Basic Psychology, Campus Bellvitge, University of Barcelona, L'Hospitalet (Barcelona), Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Ripollés
authors.affiliation: Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute-IDIBELL, L'Hospitalet (Barcelona), Spain; Department of Basic Psychology, Campus Bellvitge, University of Barcelona, L'Hospitalet (Barcelona), Spain.
authors.forename: Joanna
authors.initials: J
authors.lastname: Sierpowska
authors.affiliation: Epilepsy Unit, Neurology Section, Hospital Universitari de Bellvitge (HUB), L'Hospitalet (Barcelona), Spain.
authors.forename: Montse
authors.initials: M
authors.lastname: Juncadella
authors.affiliation: Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute-IDIBELL, L'Hospitalet (Barcelona), Spain; Department of Basic Psychology, Campus Bellvitge, University of Barcelona, L'Hospitalet (Barcelona), Spain.
authors.forename: Lluís
authors.initials: L
authors.lastname: Fuentemilla
authors.affiliation: Image Diagnosis Center, Hospital Clínic, Barcelona, Spain.
authors.forename: Verónica
authors.initials: V
authors.lastname: Sánchez
authors.affiliation: Epilepsy Unit, Neurology Section, Hospital Universitari de Bellvitge (HUB), L'Hospitalet (Barcelona), Spain.
authors.forename: Mercè
authors.initials: M
authors.lastname: Falip
authors.affiliation: Cognition and Brain Plasticity Group, Bellvitge Biomedical Research Institute-IDIBELL, L'Hospitalet (Barcelona), Spain; Department of Basic Psychology, Campus Bellvitge, University of Barcelona, L'Hospitalet (Barcelona), Spain; Catalan Institution for Research and Advanced Studies, ICREA, Barcelona, Spain. Electronic address: antoni.rodriguez@icrea.cat.
authors.forename: Antoni
authors.initials: A
authors.lastname: Rodríguez-Fornells
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003337:Corpus Callosum / Q000473:pathology*; D056324:Diffusion Tensor Imaging; D004833:Epilepsy, Temporal Lobe / Q000473:pathology*; D005260:Female; D020712:Fornix, Brain / Q000473:pathology*; D006179:Gyrus Cinguli / Q000473:pathology*; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology*; D012598:Sclerosis; D066127:White Matter / Q000473:pathology*
keywords: Commissural pathways; Diffusion tensor imaging; Interhemispheric seizure propagation; Mesial temporal lobe epilepsy; White matter