Quantitative relaxometry and diffusion MRI for lateralization in MTS and non-MTS temporal lobe epilepsy

Abstract

We developed novel methodology for investigating the use of quantitative relaxometry (T1, T2) and diffusion tensor imaging (DTI) for lateralization in temporal lobe epilepsy. Patients with mesial temporal sclerosis confirmed by pathology (N=8) and non-MTS unilateral temporal lobe epilepsy (N=6) were compared against healthy controls (N=19) using voxel-based analysis restricted to the anterior temporal lobes, and laterality indices for each MRI metric (T1, T2, fractional anisotropy (FA), mean diffusivity, axial and radial diffusivity) were computed based on the proportion of significant voxels on each side. The diffusivity metrics were the most lateralizing MRI metrics in MTS and non-MTS subsets, with significant differences also seen with FA, T1 and T2. Patient-specific multi-modal laterality indices were also computed and were shown to clearly separate the left-onset and right-onset patients. Marked differences between leftonset and right-onset patients were also observed, with left-onset patients exhibiting stronger laterality indices. Finally, neocortical abnormalities were found to be more common in the non-MTS patients. These preliminary results on a small sample size support the further investigation of quantitative MRI and multi-modal image analysis in clinical determination of seizure onset.The presence of more neocortical abnormalities in the non-MTS group suggests a role in seizure onset or propagation and motivates the investigation of more sensitive histopathological analysis to detect and delineate potentially subtle neocortical pathology.

Structural–functional coupling changes in temporal lobe epilepsy

“…Additionally, we found that SC–FC decoupling was mediated by changes in multiple focal regions in left TLE (right fusiform, left frontal inferior orbital gyrus, bilateral posterior cingulate, left anterior cingulate, left caudate), compared to a bilateral pattern of hippocampal abnormality in right TLE. Our finding of a more lateralized decoupling pattern in left TLE is consistent with previous research, which has found that both DTI (Khan et al, 2014) and fMRI (Dupont et al, 2002; Vlooswijk et al, 2010) changes are more lateralized in left TLE. The posterior cingulate gyrus appeared to play a major role in SC– FC decoupling, involving abnormalities in multiple functional topological properties (BC, LE, CC).…”

Preoperative automated fibre quantification predicts postoperative seizure outcome in temporal lobe epilepsy

“…In studies of the epileptogenic hippocampus in TLE, mean diffusivity has been shown to be a more sensitive marker of pathology compared to fractional anisotropy (Assaf et al , 2003; Salmenpera et al , 2006). Temporal lobe mean diffusivity has been shown to be a stronger predictor for the lateralization of the epileptogenic temporal lobe relative to temporal lobe fractional anisotropy (Khan et al , 2014). Despite that whole-brain mean diffusivity and fractional anisotropy may have lateralizing value, mean diffusivity alterations are more restricted to the hippocampus, fornix and cingulum, i.e.…”

Novel connectivity map normalization procedure for improved quantitative investigation of structural thalamic connectivity in temporal lobe epilepsy patients

“…The image acquisition and processing used in this work has been previously described. 28 In brief, T 1 and T 2 mapping with whole brain coverage at 1 mm isotropic resolution were estimated using driven equilibrium single pulse observations (DESPOT1. DESPOT2).…”