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Widespread and intense BOLD changes during brief focal electrographic seizures
E Kobayashi1, C S Hawco, C Grova
1Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada. eliane.kobayashi@mail.mcgill.ca
Neurology
|April 12, 2006
Summary
Brief focal seizures in a patient with gray matter nodular heterotopia caused widespread blood oxygenation level dependent (BOLD) changes lasting 30 seconds. These findings suggest even subtle seizures can impact behavior and brain activity.
Area of Science:
- Neuroimaging
- Epileptology
- Functional MRI
Background:
- Combined EEG-fMRI reveals blood oxygenation level dependent (BOLD) signal changes during interictal epileptic spikes.
- Limited understanding of BOLD signal alterations during actual seizures within an MRI scanner.
Observation:
- EEG-fMRI recorded brief focal electrographic seizures in a patient with right temporo-parietal gray matter nodular heterotopia.
- Analysis of 25 seizures revealed polyspike activity in the right temporal region lasting 2-6 seconds.
Findings:
- Widespread BOLD signal activation observed, encompassing the heterotopia and overlying cortex, with a peak in the angular gyrus.
- Bilateral BOLD signal deactivation noted, predominantly in occipital regions.
- Hemodynamic response function indicated a 30-second return to baseline BOLD signal post-seizure.
Implications:
- Brief focal seizures can elicit significant, widespread BOLD responses with prolonged return to baseline.
- These BOLD changes may correlate with behavioral consequences, even without apparent clinical manifestations.
- A focal BOLD peak distant from the EEG discharge suggests potential seizure initiation in deeper or less visible cortical areas.
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