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Epileptic spikes: magnetoencephalography versus simultaneous electrocorticography.
Makoto Oishi1, Hiroshi Otsubo, Shigeki Kameyama
1Departments of Neurosurgery, National Nishi-Niigata Central Hospital, and Brain Research Institute, Niigata University, Niigata, Japan. oishi@masa.go.jp
Epilepsia
|November 9, 2002
Summary
Extracranial magnetoencephalography (MEG) effectively detects over 50% of lateral frontal epileptic spikes, correlating with their spread. However, MEG shows lower sensitivity for basal temporal epileptic spikes, requiring larger discharge areas for detection.
Area of Science:
- Neuroscience
- Medical Imaging
- Epileptology
Background:
- Epileptic spikes are abnormal electrical discharges in the brain.
- Extracranial magnetoencephalography (MEG) measures magnetic fields produced by neural activity.
- Electrocorticography (ECoG) directly records brain activity using subdural electrodes.
Observation:
- Simultaneous MEG and ECoG recordings were performed in two epilepsy patients.
- MEG sensitivity for epileptic spikes was evaluated at different cerebral sites.
- Equivalent Current Dipoles (ECDs) of MEG spikes were estimated and localized.
Findings:
- MEG detected 53% of lateral frontal epileptic spikes, correlating with ECoG amplitude and electrode coverage.
- MEG detected only 26% of basal temporal epileptic spikes, with lower sensitivity for smaller discharges.
- MEG demonstrated significantly higher sensitivity for lateral convexity epileptic discharges compared to deep basal temporal discharges.
Implications:
- Extracranial MEG is a valuable tool for detecting epileptic spikes, particularly those originating from the lateral convexity of the brain.
- MEG's sensitivity is influenced by the location and spatial extent of epileptic discharges.
- Further research may refine MEG's utility in localizing epileptic sources in challenging brain regions.