16-24 – Individualised Fibre-Ball White Matter Imaging Analysis of Drug Resistance in Focal Epilepsy

The pathomechanisms underlying drug resistance in (focal) epilepsy are poorly understood, but hypothesised to be network-based. Whilst several grey matter structural abnormalities have been linked to drug resistance previously, white matter biomarkers remain elusive despite an abundance of research. We leveraged a novel combination of DWI data acquisition and analysis to investigate individual white matter abnormalities associated with drug resistance in focal epilepsy. Fibre-ball DWI was acquired in 30 people with epilepsy (15 well-controlled, 15 drug-resistant) and 15 healthy controls at the (University of) Liverpool Magnetic Resonance Imaging Centre. We then implemented a modified version of the fixel-based analysis pipeline, including estimation of fibre and scalar metrics. We first assessed the utility of fibre-ball imaging data for tractography, then, following group comparisons, identified white matter abnormalities associated with drug-resistance in epilepsy, which were used to seed local and distributed networks. Finally, we compared fibre and scalar metrics in our individual patients against our control-defined normative average, across 72 TractSeg-defined tracts. Evidence for reductions of fibre metrics was found in the posterior of the right cingulum and the right middle longitudinal fascicle of the drug-resistant patients. Similarly, abnormalities specific to the well-controlled patients were identified in the left-projecting isthmus of the corpus callosum and the left middle longitudinal fascicle. We also report scalar-metric differences alongside potential networks of drug resistance, and present individual tract-based metric profiles. We first demonstrate the relationship between angular resolution and tractography performance, then further characterise the white matter abnormalities that may underlie drug-resistance networks in focal epilepsy, and expand on previous attempts to synthesise individualised quantitative DWI evaluation.