Abstract
Generalized seizures engage bilateral networks from their onset at a low temporal scale. Previous studies findings have demonstrated focal/local brain activity abnormalities in the patients with generalized tonic-clonic seizures (GTCS). Resting state functional magnetic resonance imaging (fMRI) allows the detection of aberrant spontaneous brain activity in GTCS. Little is known, however, about alterations of dynamics (temporal variability) of spontaneous brain activity. It also remains unclear whether temporal variability of spontaneous brain activity is associated with disease severity. To address these questions, the current study assessed patients with GTCS (n = 35), and age- and sex-matched healthy controls (HCs, n = 33) who underwent resting state fMRI. We first assessed the dynamics of spontaneous brain activity using dynamic amplitude of low-frequency fluctuation (dALFF). Furthermore, the temporal variability of brain activity was quantified as the variance of dALFF across sliding window. Compared to HCs, patients with GTCS showed hyper-temporal variability of dALFF in parts of the default mode network, whereas they showed hypo-temporal variability in the somatomotor cortex. Furthermore, dynamic ALFF in the subgenual anterior cingulate cortex was positively correlated with duration of disease, indicating that disease severity is associated with excessive variability. These results suggest both an excessive variability and excessive stability in patients with GTCS. Overall, the current findings from brain activity dynamics contribute to our understanding of the pathophysiological mechanisms of generalized seizure.
Highlights
Genetic generalized epilepsy (GGE), characterized by generalized spike-and slow waves, polyspikes, and polyspikes and waves on scalp electroencephalography (EEG) comprises a group of epileptic disorders [1]
Temporal variability of dynamic amplitude of low-frequency fluctuation (dALFF) was quantified for each voxel for the Generalized tonic-clonic seizures (GTCS) patients and HCs (Fig 1, S1 & S2 Files)
The largest temporal variability of dALFF was located in the heteromodal association cortex, whereas the lowest variability was located in the limbic cortex
Summary
Genetic generalized epilepsy (GGE), characterized by generalized spike-and slow waves, polyspikes, and polyspikes and waves on scalp electroencephalography (EEG) comprises a group of epileptic disorders [1]. GSWDs are highly synchronized, the thalamocortical network does not demonstrate abnormal functional connectivity as assessed by resting-state functional MRI (rsfMRI) in patients with GGE including GTCS, juvenile absence epilepsy, eyelid myoclonia with absences, juvenile myoclonic epilepsy, and absences epilepsy [5]. Inconsistent with this finding, Ji et al have demonstrated that patients with GTCS-only exhibit a wide range increase in functional connectivity in four thalamocortical networks [6]. GTCS can been considered a brain network disorder rather than a single source pathology [8]
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