Network pathology in temporal lobe epilepsy

Hippocampal sclerosis (HS), a frequent cause of drug resistant temporal lobe epilepsy (TLE), is often accompanied by widespread changes in ipsi and contra lateral white matter connectivity. Whereas most diffusion weighted tractography studies report alterations best explained with a loss of white matter integrity, recent evidence raises the question of pathologically enhanced structural connectivity. Here we probed connection patterns between hippocampus and thalamus in 44 patients (22 with right and 22 with left mesial temporal sclerosis) and 24 healthy control subjects with high resolution T1 imaging, memory fMRI and probabilistic DTI-tractography (FSL). After whole brain segmentation with freesurfer, streamline samples ('fibers') departing from the hippocampus and targeting the thalamus were drawn with FSL. We found a pronounced enhancement of connectivity between the sclerotic hippocampus and the ipsi lateral thalamus both in right and left HS as compared to control subjects,