Altered Functional Connectivity after Epileptic Seizure Revealed by Scalp EEG

Abstract

Epileptic seizures are considered to be a brain network dysfunction, and chronic recurrent seizures can cause severe brain damage. However, the functional brain network underlying recurrent epileptic seizures is still left unveiled. This study is aimed at exploring the differences in a related brain activity before and after chronic repetitive seizures by investigating the power spectral density (PSD), fuzzy entropy, and functional connectivity in epileptic patients. The PSD analysis revealed differences between the two states at local area, showing postseizure energy accumulation. Besides, the fuzzy entropies of preseizure in the frontal, central, and temporal regions are higher than that of postseizure. Additionally, attenuated long-range connectivity and enhanced local connectivity were also found. Moreover, significant correlations were found between network metrics (i.e., characteristic path length and clustering coefficient) and individual seizure number. The PSD, fuzzy entropy, and network analysis may indicate that the brain is gradually impaired along with the occurrence of epilepsy, and the accumulated effect of brain impairment is observed in individuals with consecutive epileptic bursts. The findings of this study may provide helpful insights into understanding the network mechanism underlying chronic recurrent epilepsy.

Hemodynamic correlates of emotion regulation in frontal lobe epilepsy patients and healthy participants

“…Focal damage in any of these regions could result in reduced abilities to activate this whole network and might thus be associated with more difficulties in all these domains. Furthermore, repeated seizures may have lasting effects on brain network activity, affecting also distant regions (Englot et al, 2015 ; Liang et al, 2020 ). It has been reported that chronic epilepsy can induce neural reorganization in adult brains (Elger et al, 2004 ).…”

Effects of seizure burden on structural global brain networks in patients with unilateral hippocampal sclerosis

“…Additionally, in patients with chronic epilepsy, a negative correlation has been found between clustering coefficient/local efficiency of white matter structural networks and cognitive function (Vaessen et al, 2012). Furthermore, epileptic activity can reduce long-range connectivity and enhance local connectivity in the postseizure functional connectivity compared to the preseizure functional connectivity (Liang et al, 2020).…”

“…Additionally, in patients with chronic epilepsy, a negative correlation has been found between clustering coefficient/local efficiency of white matter structural networks and cognitive function (Vaessen et al., 2012). Furthermore, epileptic activity can reduce long‐range connectivity and enhance local connectivity in the postseizure functional connectivity compared to the preseizure functional connectivity (Liang et al., 2020). As we included, in the current study, only patients using antiepileptic drugs, and some were well controlled for several months, this may also explain the absence of statistically significant differences in the global brain structural network properties between patients with hippocampal sclerosis and healthy controls.…”

Evaluation of EEG dynamic connectivity around seizure onset with principal component analysis

“…Within each segment, the power spectrum density was estimated using the Welch method in windows of 1 s, with overlap of 75% up to 40 Hz. As the literature suggests that the delta band is one of the most meaningful for seizure analysis [15], only the averaged connectivity matrices between 0.5 Hz and 4 Hz was analysed.…”