Interictal magnetoencephalography and the irritative zone in the electrocorticogram
Z Agirre-Arrizubieta1, G J M Huiskamp, C H Ferrier
1Department of Neurology and Clinical Neurophysiology, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Utrecht, The Netherlands. Z.AgirreArrizubieta@umcutrecht.nl
Brain : a Journal of Neurology
|June 6, 2009
Summary
Magnetoencephalography (MEG) reliably detects interictal ECoG spikes for epilepsy surgery planning. However, MEG misses many ECoG spikes, so it cannot replace ECoG for comprehensive evaluation.
Area of Science:
- Neuroscience
- Medical Imaging
- Epileptology
Background:
- Magnetoencephalography (MEG) is explored for epilepsy surgery planning, potentially aiding or substituting intracranial electrocorticography (ECoG).
- MEG recordings are typically interictal, reflecting interictal ECoG activity.
- Assessing the clinical utility of MEG requires understanding its correlation with interictal ECoG.
Purpose of the Study:
- To evaluate the clinical value of magnetoencephalography (MEG) in reflecting interictal activity recorded by electrocorticography (ECoG).
- To determine the reliability of MEG for planning intracranial electrode placement in epilepsy surgery candidates.
Main Methods:
- 38 epilepsy surgery candidates underwent 151-channel MEG and MRI.
- Interictal MEG spikes were identified, modeled (multiple signal classification), and co-registered to MRI.
- Interictal ECoG spikes were recorded, averaged, quantified, ranked, and mapped to brain regions.
Main Results:
- All identified interictal MEG spikes correlated with interictal ECoG spikes.
- 56% of all interictal ECoG spikes had a corresponding MEG counterpart.
- High correlation (>90%) was found in interhemispheric and fronto-orbital regions; lower correlation (~25%) in mesial temporal regions.
Conclusions:
- MEG is a dependable tool for identifying interictal ECoG spikes and can guide intracranial electrode placement for epilepsy surgery.
- MEG cannot substitute for ECoG due to its inability to detect a significant portion of interictal ECoG spikes.
