An EEG-fMRI Study on the Termination of Generalized Spike-And-Wave Discharges in Absence Epilepsy

Abstract

IntroductionDifferent studies have investigated by means of EEG-fMRI coregistration the brain networks related to generalized spike-and-wave discharges (GSWD) in patients with idiopathic generalized epilepsy (IGE). These studies revealed a widespread GSWD-related neural network that involves the thalamus and regions of the default mode network. In this study we investigated which brain regions are critically involved in the termination of absence seizures (AS) in a group of IGE patients.MethodsEighteen patients (6 male; mean age 25 years) with AS were included in the EEG-fMRI study. Functional data were acquired at 3T with continuous simultaneous video-EEG recording. Event-related analysis was performed with SPM8 software, using the following regressors: (1) GSWD onset and duration; (2) GSWD offset. Data were analyzed at single-subject and at group level with a second level random effect analysis.ResultsA mean of 17 events for patient was recorded (mean duration of 4.2 sec). Group-level analysis related to GSWD onset respect to rest confirmed previous findings revealing thalamic activation and a precuneus/posterior cingulate deactivation. At GSWD termination we observed a decrease in BOLD signal over the bilateral dorsolateral frontal cortex respect to the baseline (and respect to GSWD onset). The contrast GSWD offset versus onset showed a BOLD signal increase over the precuneus-posterior cingulate region bilaterally. Parametric correlations between electro-clinical variables and BOLD signal at GSWD offset did not reveal significant effects.ConclusionThe role of the decreased neural activity of lateral prefrontal cortex at GSWD termination deserve future investigations to ascertain if it has a role in promoting the discharge offset, as well as in the determination of the cognitive deficits often present in patients with AS. The increased BOLD signal at precuneal/posterior cingulate cortex might reflect the recovery of neural activity in regions that are “suspended” during spike and waves activity, as previously hypothesized.

Unravelling the brain networks driving spike‐wave discharges in genetic generalized epilepsy—common patterns and individual differences

“…Activity in this network decreases in various goal‐oriented tasks, which is why it is also called “task‐negative network” (for review see). It has been shown, that activity in the DMN also decreases during absence seizures and GSWD . This was discussed as hemodynamic correlate of impaired consciousness during absence seizures .…”

“…There is agreement in the existing literature that the thalamus plays a pivotal role in the pathophysiology of GSWDs. Several studies have demonstrated thalamic activations during absence seizures in animals and humans . However, its exact role in triggering and/or maintaining GSWDs remains a matter of debate .…”

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“…One prevailing feature among epilepsy patients was a decreased baseline DMN connectivity that is also correlated to seizure frequency . Additionally, the DMN demonstrated a reactive property given that there have been observations of DMN node deactivation at seizure onset and reactivation at seizure termination . This may suggest that this particular connectivity profile represents treatment resistant epilepsy, but further studies are required to fully characterize this network.…”