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Updated: Jul 19, 2026
Network Analysis of the Default Mode Network Using Functional Connectivity MRI in Temporal Lobe Epilepsy
Published on: August 5, 2014
Reduced neocortical thickness and complexity mapped in mesial temporal lobe epilepsy with hippocampal sclerosis
Jack J Lin1, Noriko Salamon, Agatha D Lee
1Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA. linjj@uci.edu
Abstract:
We mapped the profile of neocortical thickness and complexity in patients with mesial temporal lobe epilepsy (MTLE) and hippocampal sclerosis. Thirty preoperative high-resolution magnetic resonance imaging scans were acquired from 15 right (mean age: 31.9 +/- 9.7 standard deviation [SD] years) and 15 left (mean age: 30.8 +/- 8.4 SD years) MTLE patients who were seizure-free for 2 years after anteriomesial temporal resection. Nineteen healthy controls were also scanned (mean age: 24.8 +/- 3.9 SD years). A cortical pattern matching technique mapped thickness across the entire neocortex. Mesial temporal structures were not included in this analysis. Cortical models were remeshed in frequency space to compute their fractal dimension (surface complexity). Both MTLE groups showed up to 30% bilateral decrease in cortical thickness, in the frontal poles, frontal operculum, orbitofrontal, lateral temporal, and occipital regions. In both groups, cortical complexity was decreased in multiple lobar regions. Significant linkages were found relating longer duration of epilepsy to greater cortical thickness reduction in the superior frontal and parahippocampal gyrus ipsilateral to the side of seizure onset. The pervasive extrahippocampal structural deficits may result from chronic seizure propagation or may reflect other causes such as initial precipitating factors leading to MTLE.
Insights
Mesial temporal lobe epilepsy (MTLE) is linked to widespread neocortical thinning and reduced complexity, affecting areas beyond the temporal lobe. These changes may stem from chronic seizures or initial causes of MTLE.
Area of Science:
- Neuroimaging
- Epilepsy Research
- Structural Brain Analysis
Background:
- Mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis is a common epilepsy syndrome.
- Neocortical involvement in MTLE is increasingly recognized but not fully characterized.
- Understanding extrahippocampal changes is crucial for comprehending MTLE's full impact.
Purpose of the Study:
- To map neocortical thickness and complexity in MTLE patients.
- To investigate bilateral cortical changes.
- To explore correlations between epilepsy duration and structural deficits.
Main Methods:
- High-resolution MRI scans from 30 MTLE patients and 19 controls.
- Cortical pattern matching for thickness analysis (excluding mesial temporal structures).
- Fractal dimension calculation for cortical complexity (surface complexity).
Main Results:
- MTLE patients exhibited up to 30% bilateral cortical thickness reduction in frontal, temporal, and occipital regions.
- Cortical complexity was decreased across multiple lobar regions in both MTLE groups.
- Longer epilepsy duration correlated with greater cortical thinning in specific frontal and parahippocampal areas.
Conclusions:
- MTLE is associated with pervasive bilateral neocortical structural deficits.
- These extrahippocampal changes may result from chronic seizure activity or underlying etiological factors.
- Findings highlight the widespread impact of MTLE on brain structure beyond the hippocampus.
