White matter alterations in focal to bilateral tonic-clonic seizures

We sought to examine the microstructural white matter differences in patients with focal to bilateral tonic-clonic seizures (FBTCS), compared to those with focal epilepsy without FBTCS, and control participants. Using a superior tract segmentation model, we obtained track-weighted tensor-metrics (TW-TM), implemented through an automated pipeline for image analysis and tract reconstruction. Analysis of covariance was used to compare group differences in the TW-TM for whole-tract and hemispheric tract measurements. We identified several white matter regions that displayed significantly altered white matter in patients with focal epilepsy compared to controls. Further, patients without FBTCS had significantly increased white matter disruption in the inferior fronto-occipital fascicle and the striato-occipital tract. In contrast, patients with FBTCS were more similar to healthy controls in most regions, except for distinct alterations in the inferior cerebellar region compared to the non-FBTCS group and controls. Our study revealed marked alterations in a range of subcortical tracts widely considered critical in the genesis of seizures in focal epilepsy. Our application of TW-TM in a new clinical dataset enabled the identification of specific tracts that may act as a predictive biomarker to distinguish patients who are likely to develop FBTCS.