Magnetoencephalography: Epilepsy and Brain Mapping
Magnetoencephalography (MEG) directly measures the magnetic fields created by neural electrical activity. Unlike functional magnetic resonance imaging (fMRI), which detects a tertiary effect of neural activation (change in local blood oxygenation level due to a change in blood flow), MEG is a more direct measure of brain functional activity. The temporal resolution of MEG is determined by the rate at which data rate can be acquired, and current systems are more than capable of acquisition speed that allows real-time assessment of brain function (typically up to 12-kHz sampling). This includes normal endogenous oscillatory activity (such as alpha oscillations in the occipital lobes) and isolated “spikes” or bursts of electrical discharges in the setting of epilepsy, both requiring temporal resolution measured on a millisecond scale. The high temporal resolution also allows for the determination of propagation of brain activity, to aid in the identification of epileptogenic foci in the setting of rapid generalization.
KeywordsVagal Nerve Stimulator Eloquent Cortex Wada Test Volumetric Magnetic Resonance Imaging Electromagnetic Activity
The authors would like to acknowledge the assistance of J. Christopher Edgar, PhD, William C. Gaetz, PhD, and Nicole Florance, MD, in obtaining the source material.
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