Voxel-based diffusion tensor imaging in focal epilepsies: comparative analyses of microstructural damage in pharmacoresponse of mesial temporal lobe epilepsy and frontal lobe epilepsy

Abstract

The diffusion tensor image (DTI) is an MRI technique that allows noninvasive evaluation of white matter (WM). It describes the magnitude (mean diffusivity-MD) and directionality (fractional anisotropy-FA) of the movement of water molecules. Widespread WM changes measured by DTI has been described in focal epilepsies, however their relation to the etiology and pharmacological response is unclear. To analyze DTI images in pharmacoresponsive or pharmacoresistant patients with mesial temporal lobe epilepsy (gMTLE and rMTLE, respectively), all with hippocampal sclerosis (HS), frontal lobe epilepsy (FLE) with focal cortical dysplasia (FCD) and normal controls. We enrolled 97 patients (29 with gMTLE, 48 with rMTLE, 20 with FLE-FCD) and 70 controls. MRI was performed on a Phillips 3.0 T scanner. The DTI images were processed using MRICloud.org. We applied Kruskall-Wallis with Dunn-Bonferroni post-hoc comparisons to examine FA and MD values in regions-of-interest (ROI). We set p<0.05 as significant, corrected for false discovery rate. We found a significant reduction in ipsilateral and contralateral FA, and an increase of MD in both groups of patients with MTLE in almost all ROIs compared to controls. Patients with FLE-FCD had less diffuse DTI changes, consisting mainly by bilateral FA reduction in corpus callosum compared to controls (Table 1). WM microstructural are more widespread in patients with MTLE-HS than in FLE-FCD. gMTLE and rMTLE patients presented similar patterns of abnormalities. However, rMTLE patients had WM more intense changes in limbic tracts.