The core network in absence epilepsy. Differences in cortical and thalamic BOLD response

Area of Science:

• Neuroscience
• Epileptology
• Medical Imaging

Background:

• Absence seizures (AS) are common in children, characterized by brief lapses in awareness.
• The underlying neural networks and initiation points of AS are not fully understood.
• Previous studies suggest involvement of both cortical and subcortical structures.

Purpose of the Study:

• To investigate the cortical and subcortical regions involved in epileptiform activity during absence seizures (AS) in untreated children.
• To explore the temporal dynamics of brain activity preceding and during spike-and-wave events.
• To identify potential initiation sites of epileptiform discharges in AS.

Main Methods:

• Electroencephalography-functional Magnetic Resonance Imaging (EEG-fMRI) was performed on eleven children with confirmed AS.
• An event-related analysis was used to identify brain regions associated with epileptiform activity.
• Regions of interest (ROIs) were defined to analyze the time course of the blood oxygen level-dependent (BOLD) signal.

Main Results:

• Group analysis showed positive BOLD signal in the thalamus and negative BOLD signal in the parietal lobe, caudate nuclei, and brainstem reticular formation.
• BOLD signal changes occurred at or immediately after electrographic onset in subcortical structures.
• A subtle BOLD signal increase was observed in the parietal cortex 10 seconds prior to epileptiform activity onset, unlike other cortical regions.

Conclusions:

• A core network, including brainstem reticular structures, is involved in generalized epileptiform activity in children with AS.
• The parietal cortex exhibits preceding BOLD signal changes, suggesting a role in the initiation of epileptiform activity in AS.
• These findings enhance our understanding of the neurobiology of absence seizures.