M.E.G.MagnetoEncphaloGraphyDefinition MEG identifies brain activity by measuring small electrical currents arising from the neurons of the brain. These currents produce magnetic fields. MEG generates an accurate location of the magnetic fields produced by the neurons. . How the test is performed The test begins by recording magnetic fields generated by neurons in the brain. The magnetic fields are detected by a sophisticated technology based on super-conducting detectors and amplifiers known as SQUIDs. The magnetic field is then analyzed to find the locations of the neuronal source within the brain. How to prepare for the test The test is approximately two hours. An EEG is done a the same time as the MEG. Electrodes will be placed on the patient’s scalp using paste which is water soluble. All electronic items or items with a magnetic strip, i.e. cell phones, credit cards will be removed. Also all metal above the waist should be removed, such as under wire bra, shirts with zippers or snaps, jewelry and wrist watches. During the MEG test, the patient is in a specially shielded room. The patient lays in a bed the head resting in the helmet-like MEG scanner (it looks like a hair dryer at the beauty salon). The MEG scanner is passive, so it does not emit radiation or magnetic fields. It only detects and amplifies magnetic signals produced by the brain. There are video and intercom systems in the room. The technician can see, hear and communicate with the patient at all times. During the scan the patient must keep their head still or the results will be inaccurate. We immobilize the patient's head using sponges placed on both sides of the head. We ask most patients to arrive sleep deprived. We hope to record their brain activity in the awake, drowsy, and sleep states. How the test will feel The test causes no discomfort. The scanner does not make noise (it is quiet, but it is always on). The patient is able to have someone in the room with them during the test, but they must also remove electronic and metallic objects. Why the test is performed MEG can provide invaluable information to clinicians for i localization of seizure focus and evaluation for candidacy of seizure surgery. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright ©2005. Any duplication or distribution of the information contained herein is strictly prohibited. Please discuss with your doctor any questions or concerns you may have. |
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Copyright © 2005 University of California, San Francisco - Department of Neurology
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