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Updated: Jan 30, 2026
Network Analysis of the Default Mode Network Using Functional Connectivity MRI in Temporal Lobe Epilepsy
Published on: August 5, 2014
Structural and functional asymmetry of medial temporal subregions in unilateral temporal lobe epilepsy: A 7T MRI
Preya Shah1,2, Danielle S Bassett1,3,4,5, Laura E M Wisse6,7
1Department of Bioengineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, Pennsylvania.
Abstract:
Mesial temporal lobe epilepsy (TLE) is a common neurological disorder affecting the hippocampus and surrounding medial temporal lobe (MTL). Although prior studies have analyzed whole-brain network distortions in TLE patients, the functional network architecture of the MTL at the subregion level has not been examined. In this study, we utilized high-resolution 7T T2-weighted magnetic resonance imaging (MRI) and resting-state BOLD-fMRI to characterize volumetric asymmetry and functional network asymmetry of MTL subregions in unilateral medically refractory TLE patients and healthy controls. We subdivided the TLE group into mesial temporal sclerosis patients (TLE-MTS) and MRI-negative nonlesional patients (TLE-NL). Using an automated multi-atlas segmentation pipeline, we delineated 10 MTL subregions per hemisphere for each subject. We found significantly different patterns of volumetric asymmetry between the two groups, with TLE-MTS exhibiting volumetric asymmetry corresponding to decreased volumes ipsilaterally in all hippocampal subfields, and TLE-NL exhibiting no significant volumetric asymmetries other than a mild decrease in whole-hippocampal volume ipsilaterally. We also found significantly different patterns of functional network asymmetry in the CA1 subfield and whole hippocampus, with TLE-NL patients exhibiting asymmetry corresponding to increased connectivity ipsilaterally and TLE-MTS patients exhibiting asymmetry corresponding to decreased connectivity ipsilaterally. Our findings provide initial evidence that functional neuroimaging-based network properties within the MTL can distinguish between TLE subtypes. High-resolution MRI has potential to improve localization of underlying brain network disruptions in TLE patients who are candidates for surgical resection.
Insights
Mesial temporal lobe epilepsy (TLE) subtypes show distinct brain network differences. High-resolution MRI reveals unique volumetric and functional network asymmetries in TLE patients, aiding surgical candidate selection.
Area of Science:
- Neuroimaging
- Epilepsy Research
- Brain Network Analysis
Background:
- Mesial temporal lobe epilepsy (TLE) is a common neurological disorder impacting the hippocampus and medial temporal lobe (MTL).
- Previous research focused on whole-brain network changes, leaving MTL subregion functional architecture unexplored.
- Understanding MTL network alterations is crucial for TLE diagnosis and treatment.
Purpose of the Study:
- To investigate volumetric and functional network asymmetry in MTL subregions of TLE patients.
- To differentiate between mesial temporal sclerosis (TLE-MTS) and MRI-negative nonlesional (TLE-NL) TLE subtypes.
- To assess the utility of high-resolution MRI in localizing brain network disruptions for surgical planning.
Main Methods:
- Utilized high-resolution 7T T2-weighted MRI and resting-state BOLD-fMRI.
- Employed an automated multi-atlas segmentation pipeline to delineate 10 MTL subregions per hemisphere.
- Compared volumetric and functional network asymmetry between TLE-MTS, TLE-NL, and healthy controls.
Main Results:
- TLE-MTS patients showed significant volumetric asymmetry with ipsilateral hippocampal subfield volume reduction.
- TLE-NL patients exhibited no significant volumetric asymmetry, except for mild ipsilateral whole-hippocampal volume decrease.
- Functional network asymmetry differed between subtypes: TLE-NL showed increased ipsilateral connectivity, while TLE-MTS showed decreased ipsilateral connectivity in CA1 and whole hippocampus.
Conclusions:
- Functional neuroimaging reveals distinct network properties within the MTL that can differentiate TLE subtypes.
- High-resolution MRI shows promise in identifying specific brain network disruptions in TLE patients.
- These findings support the use of advanced MRI techniques for improved localization of epileptogenic networks in surgical candidates.
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