title: Early and late age of seizure onset have a differential impact on brain resting-state organization in temporal lobe epilepsy.
abstract: Temporal lobe epilepsy (TLE) is associated with abnormalities which extend into the entire brain. While the age of seizure onset (SO) has a large impact on brain plasticity, its effect on brain connectivity at rest remains unclear, especially, in interaction with factors such as the presence of mesial temporal sclerosis (MTS). In this context, we investigated whole-brain and regional functional connectivity (FC) organization in 50 TLE patients who underwent a resting-state fMRI scan, in comparison to healthy controls, using graph-theory measures. We first classified TLE patients according to the presence of MTS or not. Then, we categorized the patients based on their age of SO into two subgroups (early or late age of SO). Results revealed whole-brain differences with both reduced functional segregation and increased integration in the patients, regardless of the age of SO and MTS, relative to the controls. At a local level, we revealed that the connectivity of the ictal hippocampus remains the most impaired for an early SO, even in the absence of MTS. Importantly, we showed that the impact of age of SO on whole-brain and regional resting-state FC depends on the presence of MTS. Overall, our results highlight the importance of investigating the effect of age of SO when examining resting-state activity in TLE, as this factor leads different perturbations of network modularity and connectivity at the global and local level, with different implications for regional plasticity and adaptive organization.
authors.affiliation: Department of Neurology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: Gaëlle E
authors.initials: GE
authors.lastname: Doucet
authors.forename: Ashwini
authors.initials: A
authors.lastname: Sharan
authors.forename: Dorian
authors.initials: D
authors.lastname: Pustina
authors.forename: Christopher
authors.initials: C
authors.lastname: Skidmore
authors.forename: Michael R
authors.initials: MR
authors.lastname: Sperling
authors.forename: Joseph I
authors.initials: JI
authors.lastname: Tracy
mesh_terms: D000328:Adult; D017668:Age of Onset; D001921:Brain / Q000254:growth & development / Q000473:pathology / Q000503:physiopathology*; D001931:Brain Mapping; D004833:Epilepsy, Temporal Lobe / Q000473:pathology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000254:growth & development / Q000473:pathology / Q000503:physiopathology; D012146:Rest; D012598:Sclerosis / Q000473:pathology / Q000503:physiopathology; D012640:Seizures / Q000473:pathology / Q000503:physiopathology*; D012815:Signal Processing, Computer-Assisted