Intrinsic epileptogenicity in polymicrogyric cortex suggested by EEG-fMRI BOLD responses

Area of Science:

• Neuroscience
• Neurology
• Developmental Neuroscience

Background:

• Polymicrogyria (PMG) is a common cortical malformation.
• PMG is frequently associated with epilepsy and electroencephalogram (EEG) spikes.
• The underlying mechanisms of epileptogenicity in PMG are not well understood.

Purpose of the Study:

• To investigate the relationship between EEG spikes and brain activity in patients with Polymicrogyria.
• To assess the blood oxygenation level-dependent (BOLD) response to spikes in relation to the PMG lesion.
• To explore the intrinsic epileptogenicity of the Polymicrogyria cortex.

Main Methods:

• Simultaneous electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) were performed on nine patients with Polymicrogyria.
• The BOLD response was analyzed in relation to detected EEG spikes.
• Activation patterns were mapped and correlated with the location and extent of the PMG lesion.

Main Results:

• Sixteen out of 18 studies demonstrated significant BOLD responses to EEG spikes.
• In 61.5% of these responsive studies, the maximum activation was observed within the PMG lesion.
• However, the activated areas often constituted only a small portion of the overall lesion, indicating focal epileptogenicity.

Conclusions:

• The findings suggest that specific, small regions within the Polymicrogyria cortex possess intrinsic epileptogenic properties.
• These localized areas of intrinsic epileptogenicity likely contribute to the generation of seizures in patients with PMG.
• Simultaneous EEG-fMRI is a valuable tool for understanding the neurobiological basis of epilepsy in cortical malformations like PMG.