Large-Scale Brain Networks Are Distinctly Affected in Right and Left Mesial Temporal Lobe Epilepsy

Mesial temporal lobe epilepsy ( MTLE) with hippocampus sclerosis ( HS) is associated with functional and structural alterations extending beyond the temporal regions and abnormal pattern of brain resting state networks ( RSNs) connectivity. We hypothesized that the interaction of large-scale RSNs is differently affected in patients with right-and left-MTLE with HS compared to controls. We aimed to determine and characterize these alterations through the analysis of 12 RSNs, functionally parceled in 70 regions of interest ( ROIs), from resting-state functional-MRIs of 99 subjects ( 52 controls, 26 right-and 21 left-MTLE patients with HS). Image preprocessing and statistical analysis were performed using UF 2 C-toolbox, which provided ROI-wise results for intranetwork and internetwork connectivity. Intranetwork abnormalities were observed in the dorsal default mode network ( DMN) in both groups of patients and in the posterior salience network in right-MTLE. Both groups showed abnormal correlation between the dorsal-DMN and the posterior salience, as well as between the dorsal-DMN and the executive-control network. Patients with left-MTLE also showed reduced correlation between the dorsal-DMN and visuospatial network and increased correlation between bilateral thalamus and the posterior salience network. The ipsilateral hippocampus stood out as a central area of abnormalities. Alterations on left-MTLE expressed a low cluster coefficient, whereas the altered connections on right-MTLE showed low cluster coefficient in the DMN but high in the posterior salience regions. Both right-and left-MTLE patients with HS have widespread abnormal interactions of largescale brain networks; however, all parameters evaluated indicate that left-MTLE has a more intricate bihemispheric dysfunction compared to right-MTLE. (C) 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.