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Network Analysis of the Default Mode Network Using Functional Connectivity MRI in Temporal Lobe Epilepsy
Published on: August 5, 2014
Individual white matter fractional anisotropy analysis on patients with MRI negative partial epilepsy
Thomas Duning1, Christoph Kellinghaus, Siawoosh Mohammadi
1Department of Neurology, University Hospital Muenster, Albert-Schweitzer-Str 33, 48149 Muenster, Germany. duningt@uni-muenster.de
Background:
Conventional structural MRI fails to identify a cerebral lesion in 25% of patients with cryptogenic partial epilepsy (CPE). Diffusion tensor imaging is an MRI technique sensitive to microstructural abnormalities of cerebral white matter (WM) by quantification of fractional anisotropy (FA). The objectives of the present study were to identify focal FA abnormalities in patients with CPE who were deemed MRI negative during routine presurgical evaluation.
Methods:
Diffusion tensor imaging at 3 T was performed in 12 patients with CPE and normal conventional MRI and in 67 age matched healthy volunteers. WM integrity was compared between groups on the basis of automated voxel-wise statistics of FA maps using an analysis of covariance. Volumetric measurements from high resolution T1-weighted images were also performed.
Results:
Significant FA reductions in WM regions encompassing diffuse areas of the brain were observed when all patients as a group were compared with controls. On an individual basis, voxel based analyses revealed widespread symmetrical FA reduction in CPE patients. Furthermore, asymmetrical temporal lobe FA reduction was consistently ipsilateral to the electroclinical focus. No significant correlations were found between FA alterations and clinical data. There were no differences in brain volumes of CPE patients compared with controls.
Conclusion:
Despite normal conventional MRI, WM integrity abnormalities in CPE patients extend far beyond the epileptogenic zone. Given that unilateral temporal lobe FA abnormalities were consistently observed ipsilateral to the seizure focus, analysis of temporal FA may provide an informative in vivo investigation into the localisation of the epileptogenic zone in MRI negative patients.
Insights
Diffusion tensor imaging reveals widespread white matter abnormalities in patients with cryptogenic partial epilepsy (CPE) who have normal conventional MRI scans. Temporal lobe fractional anisotropy (FA) reductions may help locate the seizure focus in these MRI-negative cases.
Area of Science:
- Neuroimaging
- Epilepsy Research
- White Matter Integrity
Background:
- Conventional MRI misses lesions in 25% of cryptogenic partial epilepsy (CPE) cases.
- Diffusion tensor imaging (DTI) quantifies white matter (WM) microstructural integrity via fractional anisotropy (FA).
- This study aimed to detect focal FA abnormalities in MRI-negative CPE patients.
Purpose of the Study:
- To identify focal fractional anisotropy (FA) abnormalities in patients with cryptogenic partial epilepsy (CPE) who had normal conventional MRI.
- To investigate the utility of diffusion tensor imaging (DTI) in detecting subtle white matter (WM) changes in epilepsy.
Main Methods:
- Diffusion tensor imaging (DTI) at 3 Tesla was conducted on 12 CPE patients with normal conventional MRI and 67 healthy controls.
- Voxel-wise statistical analysis of fractional anisotropy (FA) maps compared WM integrity between groups.
- High-resolution T1-weighted images were used for volumetric measurements.
Main Results:
- Patients with CPE showed significant reductions in FA across widespread WM regions compared to controls.
- Individual analyses revealed symmetrical FA reductions in CPE patients.
- Asymmetrical temporal lobe FA reduction was consistently ipsilateral to the electroclinical focus, with no correlation to clinical data or brain volumes.
Conclusions:
- White matter (WM) integrity abnormalities in CPE extend beyond the presumed epileptogenic zone, even with normal conventional MRI.
- Unilateral temporal lobe FA abnormalities, detected via DTI, may aid in localizing the epileptogenic zone in MRI-negative epilepsy patients.
- DTI offers a valuable in vivo tool for investigating WM integrity in epilepsy.
