Abstracts

Rationale: Spatiotemporal network dynamics have been considered as central features in epilepsy. It is essential to understand the characteristic dynamic changes during preictal, ictal and postictal periods within epileptogenic zones as well as remote cortical areas. The present study aimed to investigate the spatial topology changes in continuous time domains from intracranial EEG recordings in intractable partial epilepsy with epilepsy surgery.Methods: Intracranial EEG data from 14 seizures in seven epilepsy surgery patients who had been seizure-free for at least one-year of postoperative follow-up were analyzed so far (3 females and 4 males, mean 39.3 year-old). Intracranial electrodes with ictal onset and propagation of ictal discharges were reviewed by two neurologists independently. Exact times of ictal onset and offset were also recorded for each seizure. Methods for time-frequency localization of signal powers, phase synchronization, and directionality of phase coupling within and outside of seizure onset electrodes were analyzed for different frequency components during time periods including at least 60 seconds before seizure onset and 60 seconds after seizure termination using MATLAB ver7.7.Results: Signal powers were dramatically increased near the seizure onset (ranged 9.5 sec in advance to 10.4 sec after, compared to visual analysis), and dropped abruptly at seizure offset across different frequency bands. In contrast, phase synchronization was somewhat variable before/around seizure onset and during seizure propagation but clearly increased towards seizure offset. Directional interactions showed distinct features within and surrounding ictal onset electrodes.Conclusions: This study analyzed spatial topology and temporal dynamic changes before, during and after seizures from intracranial EEG recordings. Spatiotemporal analysis of epileptic network dynamics may permit new insights into mechanisms involving spontaneous initiation and termination of seizures in chronic epilepsy.