Hippocampal and thalamic atrophy in mild temporal lobe epilepsy: a VBM study
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Published on: August 5, 2014
A Labate1, A Cerasa, A Gambardella
1Cattedra ed UO di Neurologia, Università degli Studi Magna Graecia, Campus Universitario Germaneto, Catanzaro, Italy.
Background:
Patients with temporal lobe epilepsy (TLE) often have mild drug-responsive epilepsy which is frequently associated with MRI detectable mesial temporal sclerosis (MTS), indicating that MTS is not necessarily related to seizure severity. To better define the anatomic substrates associated with TLE, we applied voxel-based morphometry (VBM) analysis to patients with mild TLE.
Methods:
Optimized VBM was applied to the MRI brain images of 95 consecutive unrelated patients who were diagnosed with mild TLE and to 37 healthy controls. We complemented the investigation by calculating the gray matter volume of regions of interest (ROIs) in the bilateral hippocampus. Standard MRI scans revealed evidence of MTS (pTLE) in 34 patients, and no evidence of MTS in the remaining 61 (nTLE).
Results:
The VBM analysis provided evidence of a reduction in gray matter volume in the hippocampus and thalami. The gray matter volume reduction in the thalamic and hippocampal networks was significantly more severe in patients with pTLE than in the nTLE or the control groups (at a threshold of FWE-corrected p < 0.05). Patients with nTLE showed the same gray matter abnormalities at an uncorrected statistical threshold (p < 0.001) compared to normal controls. ROI analysis confirmed the ipsilateral hippocampal atrophy that was detected in routine MRI scans.
Conclusions:
The structural abnormalities seen in patients with mild temporal lobe epilepsy (TLE) demonstrate that a temporo-limbic pathway, which includes the thalamus, plays a major role in the pathogenesis of TLE. It is likely that other factors, especially genetic ones, play a major role in the causation and severity of TLE.
Insights
Mild temporal lobe epilepsy (TLE) involves structural changes in the hippocampus and thalamus. Voxel-based morphometry revealed gray matter reduction, particularly in patients with mesial temporal sclerosis (MTS), suggesting a temporo-limbic pathway
Area of Science:
- Neuroimaging
- Epilepsy Research
- Structural Brain Analysis
Background:
- Temporal Lobe Epilepsy (TLE) is often mild and drug-responsive.
- Mesial Temporal Sclerosis (MTS) is frequently observed in TLE but not always linked to seizure severity.
- Anatomic substrates of mild TLE require further definition.
Purpose of the Study:
- To investigate the structural brain abnormalities in patients with mild TLE using voxel-based morphometry (VBM).
- To compare gray matter volumes between TLE patients with and without MTS and healthy controls.
Main Methods:
- Voxel-based morphometry (VBM) applied to MRI scans of 95 mild TLE patients and 37 controls.
- Categorization of TLE patients into those with (pTLE, n=34) and without (nTLE, n=61) MTS.
- Region of Interest (ROI) analysis of bilateral hippocampus gray matter volume.
Main Results:
- VBM identified gray matter volume reduction in the hippocampus and thalami in mild TLE patients.
- Thalamic and hippocampal gray matter loss was more severe in pTLE patients compared to nTLE and controls (FWE-corrected p < 0.05).
- nTLE patients showed similar gray matter abnormalities compared to controls at an uncorrected threshold (p < 0.001); ROI confirmed ipsilateral hippocampal atrophy.
Conclusions:
- Structural abnormalities in mild TLE involve a temporo-limbic pathway, including the thalamus, crucial for TLE pathogenesis.
- Genetic factors likely play a significant role in TLE causation and severity.
- Mild TLE is associated with significant structural changes beyond just the hippocampus.
