Magnetoencephalography (MEG)


Magnetoencephalography (MEG) is a non-invasive brain mapping technique often used to plan surgery for epilepsy. Groups of brain cells that cause seizures exhibit abnormal electrical activity called spikes (or more generally epilepform discharges) which are usually observed with electroencephalography (EEG). These abnormal electrical discharges also generate tiny magnetic fields, which can be detected by MEG. In some cases, the abnormal brain cells and their associated abnormal activity are better identified by MEG, in comparison to EEG. In this fashion, MEG provides information that complements the data provided by EEG. MEG is able to detect magnetic fields with a highly specialized scanner placed in a room shielded from external magnetic fields. MEG is often used along with magnetic resonance imagining (MRI) to create magnetic source imaging (MSI). Data collected using MEG is superimposed on the structural image of the brain obtained by MRI to mark the magnetic sources. Therefore, MSI illustrates both anatomical and functional characteristics of the brain.

The images below illustrate electromagnetic abnormalities located in the left superior temporal lobe. 

MEG

An actual MEG scanner is seen below:

MEG2

The images above are courtesy of the Department of Radiology, University of California, San Diego, and used here with permission.


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