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Network Analysis of Foramen Ovale Electrode Recordings in Drug-resistant Temporal Lobe Epilepsy Patients
Published on: December 18, 2016
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Epileptic networks in action: Synchrony between distant hemodynamic responses
Hui Ming Khoo1,2, Nicolás von Ellenrieder1, Natalja Zazubovits1
1Montreal Neurological Institute and Hospital, McGill University, Montreal, Canada.
Annals of Neurology
|June 7, 2017
Summary
This study demonstrates that functional magnetic resonance imaging (fMRI) detects synchronized neuronal activity in epileptic networks. This confirms that brain regions with hemodynamic responses during interictal epileptic discharges (IEDs) are indeed interconnected, validating the EEG-fMRI approach.
Area of Science:
- Neuroscience
- Epileptology
- Medical Imaging
Background:
- Focal epilepsy studies often show widespread abnormalities, suggesting epileptic networks.
- Direct evidence of neuronal interaction between these distributed regions has been lacking.
- Functional magnetic resonance imaging (fMRI) detects hemodynamic responses to interictal epileptic discharges (IEDs).
Purpose of the Study:
- To determine if distributed hemodynamic responses in fMRI correlate with synchronized neuronal activity.
- To investigate neuronal interactions within epileptic networks using simultaneous EEG-fMRI and intracerebral EEG (iEEG).
Main Methods:
- Studied 28 patients undergoing EEG-fMRI followed by iEEG.
- Analyzed synchrony (correlation) of IEDs between regions with and without hemodynamic responses.
- Coregistered hemodynamic responses to iEEG electrode positions.
Main Results:
- Intracerebral IED synchrony was significantly higher between regions with hemodynamic responses compared to those without (p < 0.0001).
- Synchrony differences were specific to periods with IEDs, not present during IED-free periods.
- Higher synchrony was observed between regions involved at seizure onset (p < 0.0001).
Conclusions:
- EEG-fMRI accurately reveals hemodynamic changes associated with IEDs across the brain.
- This study proves synchronized iEEG activity between hemodynamically responsive regions, confirming neuronally based epileptic networks.
- The findings validate the noninvasive EEG-fMRI method for mapping these interictal epileptic networks.
