Individual white matter fractional anisotropy analysis on patients with MRI-negative partial epilepsy

Thomas Duning (1) , Christoph Kellinghaus (2) , Siawoosh Mohammadi (1) , Hagen Schiffbauer (3) , Simon Keller (4) , Erich Bernd Ringelstein (1) , Stefan Knecht (1) , Michael Deppe (1)

1 Department of Neurology, University Hospital Muenster
2 Department of Neurology, Klinikum Osnabrueck
3 Department of Clinical Radiology, University Hospital Muenster
4 The Magnetic Resonance and Image Analysis Research Centre (MARIARC), University of Liverpool

Background: Conventional structural Magnetic Resonance Imaging (MRI) fails to identify a cerebral lesion in 25% of patients with cryptogenic partial epilepsy (CPE). Diffusion Tensor Imaging (DTI) is a 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 pre-surgical evaluation. Methods: We performed DTI at 3 Tesla 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 to 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 to 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.

Mots clés: EPILEPSY; MRI; cryptogenic partial epilepsy; diffusion tensor imaging; fractional anisotropy; white matter

Thomas Duning, Christoph Kellinghaus, Siawoosh Mohammadi, Hagen Schiffbauer, Simon Keller, et al.. Individual white matter fractional anisotropy analysis on patients with MRI-negative partial epilepsy. Journal of Neurology, Neurosurgery and Psychiatry, 2010, 81 (2), pp.136. ⟨10.1136/jnnp.2008.160820⟩. ⟨hal-00552723⟩