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Network Analysis of Foramen Ovale Electrode Recordings in Drug-resistant Temporal Lobe Epilepsy Patients
Published on: December 18, 2016
Focal to bilateral tonic-clonic seizures are associated with widespread network abnormality in temporal lobe epilepsy
Nishant Sinha1,2, Natalie Peternell2, Gabrielle M Schroeder2
1Faculty of Medical Sciences, Translational and Clinical Research Institute, Newcastle University, Newcastle Upon Tyne, UK.
Objective:
Our objective was to identify whether the whole-brain structural network alterations in patients with temporal lobe epilepsy (TLE) and focal to bilateral tonic-clonic seizures (FBTCS) differ from alterations in patients without FBTCS.
Methods:
We dichotomized a cohort of 83 drug-resistant patients with TLE into those with and without FBTCS and compared each group to 29 healthy controls. For each subject, we used diffusion-weighted magnetic resonance imaging to construct whole-brain structural networks. First, we measured the extent of alterations by performing FBTCS-negative (FBTCS-) versus control and FBTCS-positive (FBTCS+) versus control comparisons, thereby delineating altered subnetworks of the whole-brain structural network. Second, by standardizing each patient's networks using control networks, we measured the subject-specific abnormality at every brain region in the network, thereby quantifying the spatial localization and the amount of abnormality in every patient.
Results:
Both FBTCS+ and FBTCS- patient groups had altered subnetworks with reduced fractional anisotropy and increased mean diffusivity compared to controls. The altered subnetwork in FBTCS+ patients was more widespread than in FBTCS- patients (441 connections altered at t > 3, p < .001 in FBTCS+ compared to 21 connections altered at t > 3, p = .01 in FBTCS-). Significantly greater abnormalities-aggregated over the entire brain network as well as assessed at the resolution of individual brain areas-were present in FBTCS+ patients (p < .001, d = .82, 95% confidence interval = .32-1.3). In contrast, the fewer abnormalities present in FBTCS- patients were mainly localized to the temporal and frontal areas.
Significance:
The whole-brain structural network is altered to a greater and more widespread extent in patients with TLE and FBTCS. We suggest that these abnormal networks may serve as an underlying structural basis or consequence of the greater seizure spread observed in FBTCS.
Insights
Patients with temporal lobe epilepsy (TLE) and focal to bilateral tonic-clonic seizures (FBTCS) show more widespread brain network alterations. These widespread changes in structural networks may explain the greater seizure spread in FBTCS patients.
Area of Science:
- Neuroscience
- Medical Imaging
- Epilepsy Research
Background:
- Temporal lobe epilepsy (TLE) is a common neurological disorder.
- Focal to bilateral tonic-clonic seizures (FBTCS) represent a severe manifestation of TLE.
- Understanding structural network differences in TLE with and without FBTCS is crucial for targeted therapies.
Purpose of the Study:
- To investigate and compare whole-brain structural network alterations in TLE patients with and without FBTCS.
- To determine if the extent and localization of network abnormalities differ between TLE patients experiencing FBTCS and those who do not.
Main Methods:
- Utilized diffusion-weighted magnetic resonance imaging (DW-MRI) to construct whole-brain structural networks in 83 drug-resistant TLE patients and 29 healthy controls.
- Dichotomized TLE patients into FBTCS-positive (FBTCS+) and FBTCS-negative (FBTCS-) groups for comparative analysis against controls.
- Quantified network alterations by measuring fractional anisotropy and mean diffusivity, and assessed subject-specific abnormalities in brain regions.
Main Results:
- Both FBTCS+ and FBTCS- groups exhibited altered subnetworks compared to controls, indicated by reduced fractional anisotropy and increased mean diffusivity.
- FBTCS+ patients displayed significantly more widespread network alterations (441 connections) than FBTCS- patients (21 connections).
- Abnormalities were more extensive and globally distributed in FBTCS+ patients, while FBTCS- patients showed localized changes primarily in temporal and frontal areas.
Conclusions:
- Whole-brain structural networks are significantly more altered and widespread in TLE patients with FBTCS.
- These pronounced network abnormalities may represent the structural basis or consequence of increased seizure propagation in FBTCS.
- Findings highlight distinct network profiles in TLE based on seizure manifestation, informing potential diagnostic and therapeutic strategies.
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