Dynamic Neuromagnetic Network Changes of Seizure Termination in Absence Epilepsy: A Magnetoencephalography Study.

Wenwen Jiang,Wenchao Qiu,Jing Xiang,Caiyun Wu,Ailiang Miao,Shuyang Huang,Lu Tang,Qiqi Chen,Xiaoshan Wang,Zheng Hu

doi:10.3389/fneur.2019.00703

Abstract

Objective: With increasing efforts devoted to investigating the generation and propagation mechanisms of spontaneous spike and wave discharges (SWDs), little attention has been paid to network mechanisms associated with termination patterns of SWDs to date. In the current study, we aimed to identify the frequency-dependent neural network dynamics during the offset of absence seizures.Methods: Fifteen drug-naïve patients with childhood absence epilepsy (CAE) were assessed with a 275-Channel Magnetoencephalography (MEG) system. MEG data were recorded during and between seizures at a sampling rate of 6,000 Hz and analyzed in seven frequency bands. Source localization was performed with accumulated source imaging. Granger causality analysis was used to evaluate effective connectivity networks of the entire brain at the source level.Results: At the low-frequency (1–80 Hz) bands, activities were predominantly distributed in the frontal cortical and parieto–occipito–temporal junction at the offset transition periods. The high-frequency oscillations (HFOs, 80–500 Hz) analysis indicated significant source localization in the medial frontal cortex and deep brain areas (mainly thalamus) during both the termination transition and interictal periods. Furthermore, an enhanced positive cortico–thalamic effective connectivity was observed around the discharge offset at all of the seven analyzed bands, the direction of which was primarily from various cortical regions to the thalamus.Conclusions: Seizure termination is a gradual process that involves both the cortices and the thalamus in CAE. Cortico–thalamic coupling is observed at the termination transition periods, and the cerebral cortex acts as the driving force.

Highlights

Epilepsy is conventionally considered a functional brain disorder generated by excessive synchronization of large neuronal populations leading to a hypersynchronous state
Recent researches have demonstrated that synchronization increases at seizure onset and seizure termination, whereas it transiently decreases in between, which suggested that seizures are not so much a manifestation of hypersynchrony but instead courses of network reorganization [1,2,3,4]
Forty-three seizures were captured during MEG recording; only 33 seizures were eligible for the subsequent analysis, with an average ictal duration of 13.8 s

Summary

Introduction

Epilepsy is conventionally considered a functional brain disorder generated by excessive synchronization of large neuronal populations leading to a hypersynchronous state. Recent researches have demonstrated that synchronization increases at seizure onset and seizure termination, whereas it transiently decreases in between, which suggested that seizures are not so much a manifestation of hypersynchrony but instead courses of network reorganization [1,2,3,4]. Epilepsy is formulated as a network disorder that constitutes aberrant circuits between the thalamic input and the cortex that are facilitating generalized spike-and-waves (SWDs) according to the most recent definition of the International League Against Epilepsy (ILAE). Childhood absence epilepsy (CAE) is the most common pediatric epilepsy syndrome, occurring in 10–17% of all childhood onset epilepsy with a female preponderance [5]. Typical absence seizures appear as brief disruptions of responsiveness without warning, interruptions of ongoing behavior that are difficult to notice. Electroencephalography (EEG) reveals characteristic bilateral, symmetrical, and synchronous discharges of 3 Hz generalized SWDs on a normal background activity [5, 6]

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Results

Conclusion