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Quantitative MRI in patients with idiopathic generalized epilepsy. Evidence of widespread cerebral structural changes
F G Woermann1, S M Sisodiya, S L Free
1National Society of Epilepsy and Epilepsy Research Group, University Department of Clinical Neurology, Institute of Neurology, London, UK.
Abstract:
In patients with idiopathic generalized epilepsy (IGE), visual inspection of routine MRI is normal. However, pathological studies have shown microdysgenesis in grey and white matter in a large percentage of autopsies from cases of IGE. Recently, widespread structural changes not evident on visual inspection of high resolution MRI have been shown using quantitative MRI in patients with apparently focal cerebral dysgenesis. We sought to determine whether similar quantitative changes might be present in patients with IGE, reflecting possible underlying structural abnormalities. Twenty patients with juvenile myoclonic epilepsy, 10 patients each with childhood absence epilepsy and juvenile absence epilepsy, five patients with tonic-clonic seizures on awakening and 30 control subjects had T1-weighted volume acquisition MRI scans on a 1.5T GE scanner. The cerebral hemispheres were segmented semi-automatically, allowing the comparison of normalized cortical and subcortical matter volumes between groups, and investigation of the regional distribution of cortical and subcortical matter in individual subjects. Patients with IGE had significantly larger cortical grey matter volumes than control subjects. Significant abnormalities of the regional distribution of cerebral grey and subcortical matter were found in eight out of 20 patients with juvenile myoclonic epilepsy, one out of 10 patients with childhood absence epilepsy, four out of 10 patients with juvenile absence epilepsy and two out of five patients with tonic-clonic seizures on awakening, but in none of the 30 control subjects. Using MRI-segmentation, we identified widespread cerebral structural changes in patients with various IGE syndromes. Quantitative MRI supports the existence of structural abnormalities in patients with IGE.
Insights
Idiopathic generalized epilepsy (IGE) patients show normal MRI visually, but quantitative MRI reveals widespread structural brain changes. These subtle abnormalities in grey and white matter suggest underlying cerebral dysgenesis in IGE syndromes.
Area of Science:
- Neuroimaging
- Epilepsy Research
- Quantitative MRI
Background:
- Idiopathic generalized epilepsy (IGE) typically shows normal visual MRI.
- Autopsy studies indicate microdysgenesis in grey and white matter in IGE.
- Quantitative MRI detects subtle structural changes in other epilepsy types.
Purpose of the Study:
- To investigate quantitative MRI for detecting structural brain abnormalities in IGE syndromes.
- To compare brain matter volumes and regional distribution in IGE patients versus controls.
Main Methods:
- Quantitative MRI (1.5T T1-weighted scans) on 20 juvenile myoclonic epilepsy, 20 absence epilepsy, 5 tonic-clonic seizure patients, and 30 controls.
- Semi-automated segmentation of cerebral hemispheres for volume and distribution analysis.
- Comparison of normalized cortical and subcortical grey and white matter volumes.
Main Results:
- Patients with IGE exhibited significantly larger cortical grey matter volumes than controls.
- Abnormal regional distribution of grey and subcortical matter was identified in 8/20 juvenile myoclonic epilepsy, 1/10 childhood absence epilepsy, 4/10 juvenile absence epilepsy, and 2/5 tonic-clonic seizure patients.
- No abnormalities were found in 30 control subjects.
Conclusions:
- Quantitative MRI reveals widespread cerebral structural changes in various idiopathic generalized epilepsy syndromes.
- These findings support the presence of underlying structural abnormalities in IGE, not visible on routine MRI.
- Quantitative MRI is a valuable tool for identifying subtle brain malformations in IGE.