Longitudinal alterations in brain networks and thalamocortical connectivity in paediatric focal epilepsy: a structural connectomics pilot study

Epilepsy is an archetypal brain network disorder characterized by recurrent seizures and associated psychological, cognitive and behavioural sequelae. Progressive brain network dysfunction may contribute to poorer outcomes following treatment, but this has never been tested in humans. In this structural connectomics pilot study, we assess whether there is progressive brain network dysfunction in a cohort of 23 children undergoing repeated multi-shell diffusion tensor imaging as part of their pre-surgical evaluation of focal epilepsy prior to epilepsy surgery. We analyse global and nodal graph metrics and thalamocortical connectivity, comparing the longitudinal changes to a cross-sectional cohort of 57 healthy controls. We identify no robust longitudinal changes in global or nodal network properties over a median of 1.15 years between scans. We also do not identify robust longitudinal changes in thalamic connectivity between scans. On sensitivity analyses, we identify increases in weighted degree at higher scales of brain parcellation and a decrease in the proportion of nodes with a low participation coefficient, suggesting progressive increases in intermodular connections. These findings of no or subtle structural longitudinal brain network changes over a relatively short timeframe indicate that either there are no progressive structural brain network changes over time in epilepsy or the changes appear over longer timescales. Larger studies with longer timeframes between scans may help clarify these findings.