Absence seizures: individual patterns revealed by EEG-fMRI

Area of Science:

• Neuroscience
• Epileptology
• Functional Neuroimaging

Background:

• Absence seizures feature abrupt generalized spike-wave discharges and unresponsiveness.
• Previous EEG-fMRI studies implicated the thalamus, default mode areas, and caudate nuclei in absence seizures.
• Animal models suggest cortical initiation of absences with secondary thalamic involvement.

Purpose of the Study:

• To investigate dynamic changes in brain activity throughout absence seizures using EEG-fMRI.
• To clarify the temporal evolution of brain region involvement during absence seizures.
• To explore the role of cortical and subcortical structures in absence epilepsy.

Main Methods:

• Utilized electroencephalography-functional magnetic resonance imaging (EEG-fMRI) in nine patients with absence epilepsy.
• Analyzed seventeen absence seizures using a sliding window approach to generate temporal BOLD response maps.
• Focused on generalized 3-4 Hz spike and wave discharges (GSWs) characteristic of absence seizures.

Main Results:

• Thalamic activation occurred in 94% of absences.
• Deactivation in default mode areas (88%) and caudate nuclei (59%) was observed.
• Patient-specific cortical activations were present in 59% of absences and preceded thalamic responses.

Conclusions:

• BOLD signal changes during absence seizures are highly patient-specific, akin to a fingerprint.
• Early cortical activations, though patient-specific, support the cortical focus theory of absence epilepsy.
• Dynamic analysis reveals a temporal sequence of brain involvement, starting with early cortical changes.