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A Multimodal Imaging- and Stimulation-based Method of Evaluating Connectivity-related Brain Excitability in Patients with Epilepsy
Published on: November 13, 2016
Characterization of resting functional MRI activity alterations across epileptic foci and networks
Lucas E Sainburg1,2, Aubrey A Little3, Graham W Johnson1,2
1Department of Biomedical Engineering, Vanderbilt University, Nashville, TN 37212, USA.
Abstract:
Brain network alterations have been studied extensively in patients with mesial temporal lobe epilepsy (mTLE) and other focal epilepsies using resting-state functional magnetic resonance imaging (fMRI). However, little has been done to characterize the basic fMRI signal alterations caused by focal epilepsy. Here, we characterize how mTLE affects the fMRI signal in epileptic foci and networks. Resting-state fMRI and diffusion MRI were collected from 47 unilateral mTLE patients and 96 healthy controls. FMRI activity, quantified by amplitude of low-frequency fluctuations, was increased in the epileptic focus and connected regions in mTLE. Evidence for spread of this epileptic fMRI activity was found through linear relationships of regional activity across subjects, the association of these relationships with functional connectivity, and increased activity along white matter tracts. These fMRI activity increases were found to be dependent on the epileptic focus, where the activity was related to disease severity, suggesting the focus to be the origin of these pathological alterations. Furthermore, we found fMRI activity decreases in the default mode network of right mTLE patients with different properties than the activity increases found in the epileptic focus. This work provides insights into basic fMRI signal alterations and their potential spread across networks in focal epilepsy.
Insights
Mesial temporal lobe epilepsy (mTLE) increases functional magnetic resonance imaging (fMRI) activity in the epileptic focus and connected brain networks. This heightened fMRI activity spreads through brain networks and correlates with disease severity.
Area of Science:
- Neuroimaging
- Epilepsy research
- Brain network analysis
Background:
- Resting-state functional magnetic resonance imaging (fMRI) is widely used to study brain network alterations in epilepsy.
- Characterizing fundamental fMRI signal changes in focal epilepsy, particularly mesial temporal lobe epilepsy (mTLE), remains underexplored.
Purpose of the Study:
- To investigate how mTLE impacts fMRI signals within epileptic foci and associated brain networks.
- To understand the spread of altered fMRI activity in mTLE patients.
Main Methods:
- Acquisition of resting-state fMRI and diffusion MRI data from 47 unilateral mTLE patients and 96 healthy controls.
- Quantification of fMRI activity using the amplitude of low-frequency fluctuations (ALFF).
- Analysis of regional activity relationships, functional connectivity, and white matter tract involvement.
Main Results:
- Increased fMRI activity (ALFF) observed in the epileptic focus and connected regions in mTLE patients.
- Evidence of fMRI activity spread along white matter tracts, linked to functional connectivity and disease severity.
- Decreased fMRI activity detected in the default mode network of right mTLE patients, distinct from focal increases.
Conclusions:
- mTLE significantly alters fMRI signals, with increased activity originating from the epileptic focus and spreading across brain networks.
- These findings offer crucial insights into the pathophysiology of fMRI signal changes in focal epilepsy.
- The study highlights the potential of fMRI to reveal network-level disruptions in mTLE.
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