BOLD and perfusion changes during epileptic generalised spike wave activity.

Area of Science:

• Neuroscience
• Epilepsy Research
• Functional Neuroimaging

Background:

• The relationship between brain activity and blood flow (neurovascular coupling) during epileptic seizures is not fully understood.
• Functional magnetic resonance imaging (fMRI) studies have observed negative BOLD responses (NBR) during generalized spike wave activity (GSW), but their cause is debated.
• Understanding neurovascular coupling is crucial for accurate interpretation of fMRI data in epilepsy.

Purpose of the Study:

• To investigate whether neurovascular coupling is preserved during epileptic discharges, specifically generalized spike wave activity (GSW).
• To determine if negative BOLD responses (NBR) during GSW reflect decreased cerebral blood flow (CBF).
• To assess the correlation between BOLD and CBF changes during GSW and normal electroencephalography (EEG).

Main Methods:

• Simultaneous electroencephalography (EEG) with blood oxygen level-dependent (BOLD) and arterial spin label (ASL) fMRI at 3 Tesla.
• Four patients with generalized epilepsy (two idiopathic, two secondary) were studied.
• BOLD and CBF responses were measured during GSW and normal background EEG.

Main Results:

• GSW-related NBR were observed in frontal, parietal, and posterior cingulate cortices.
• A positive correlation was found between simultaneously measured BOLD and CBF throughout the imaged volume, indicating preserved neurovascular coupling.
• Reproducible GSW-associated BOLD responses were observed, consistent with previous lower-field fMRI studies.

Conclusions:

• Neurovascular coupling is preserved during generalized spike wave activity in patients with generalized epilepsy.
• The findings support the use of fMRI in epilepsy research, with cortical activations potentially reflecting discharge generation and deactivations reflecting altered resting state activity.
• This study validates the interpretation of fMRI signals during epileptic events.