Diffusion abnormalities of the corpus callosum in patients with malformations of cortical development and epilepsy

Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) technique that can characterize white matter (WM) architecture and microstructure. DTI has demonstrated extensive WM changes in patients with several epileptic syndromes, but few studies have focused on patients with malformations of cortical development (MCD). Our aim was to investigate the quantitative diffusion properties of the corpus callosum (CC), a major commissural bundle critical in inter-hemispheric connectivity, in a large group of patients with MCD.

Thirty-two MCD patients and 32 age and sex-matched control subjects were evaluated with DTI at 3.0 T. We analyzed the three major subdivisions of the CC (genu, body, and splenium) with deterministic tractography to yield fractional anisotropy (FA), mean diffusivity (MD), parallel diffusivity (λ||) and perpendicular diffusivity (λ⊥). We further assessed the CC with region of interest (ROI)-based analyses and evaluated different subgroups of MCD (polymicrogyria/schizencephaly, heterotopia, and cortical dysplasia). Partial correlations between diffusion changes and clinical parameters (epilepsy duration and age at disease onset) were also queried.

There were significant reductions of FA, accompanied by increases in MD and λ⊥ in all segments of the CC in the patients group with both analytical methods. The absolute differences in FA were greater on ROI-analyses. There were no significant differences between the MCD subgroups, and no correlations between clinical parameters of epilepsy and FA.

Our study indicates DTI abnormalities consistent with microstructural changes in the corpus callosum of MCD patients. The findings support the idea that patients with epilepsy secondary to cortical malformations present widespread WM changes that extend beyond the macroscopic MRI-visible lesions.