Directional connectivity patterns in SEEG recorded epileptiform transitions in mesial temporal lobe epilepsy.

Abstract

<i>Objective</i>. Epilepsy is characterized by dynamic disruptions in brain networks, yet the spatiotemporal organization of directional interactions underlying ictal transitions remains incompletely understood. This study investigates peri-ictal transition patterns in mesial temporal lobe epilepsy (MTLE) by characterizing directional connectivity dynamics from intracranial stereo-electroencephalography (SEEG) seizure recordings.<i>Approach</i>. We analyzed SEEG data from 10 patients with MTLE who subsequently achieved seizure freedom following surgical resection. We quantified directional connectivity using directed transfer function measures across preictal, ictal, and post-ictal phases. We then applied clustering analyses to identify reproducible dynamical connectivity patterns and evaluated their consistency across seizures and patients.<i>Main results</i>. We identified distinct out-degree connectivity patterns across seizure phases, each associated with specific anatomical regions. Regions corresponding to the epileptogenic zone exhibited elevated out-degree during the preictal and early ictal periods, whereas non-resected regions showed increased out-degree during ictal termination and postictal phases. These patterns remained consistent across patients and seizures, demonstrating a structured and phase-dependent organization of directional information flow during seizure evolution.<i>Significance</i>. This study identifies stereotypical and reproducible peri-ictal directional connectivity patterns in MTLE. By characterizing how information flow evolves across seizure phases, our findings advance network-level understanding of ictal transitions and provide a reproducible framework for future studies of seizure network dynamics.