Magnetoencephalography

Magnetoencephalography (mag-NEE-toe-en-sef-uh-low-graf-ee) is a technique that checks brain function. For example, it can assess the magnetic fields that arise from electrical currents in the brain to pinpoint the parts of the brain that cause seizures. It also can help identify the location of important things such as speech or motor function. Magnetoencephalography is often called MEG.

When surgery is needed, it's best that your healthcare team members understand all they can about your brain. MEG is a noninvasive way to understand areas of the brain that cause seizures and areas that affect your brain functions. MEG also helps your care team identify areas of the brain to avoid. The data that MEG provides makes it easier to plan surgery precisely. In the future, MEG may be helpful in diagnosing stroke, traumatic brain injury, Parkinson's disease, dementia, chronic pain, brain disease that results from liver disease and other conditions.

MEG does not use any magnets. Rather, the test uses very sensitive detectors to measure magnetic fields from your brain. There are no known risks of having these measurements performed. However, having metal in your body or your clothes may prevent accurate measurements and could damage the MEG sensors. Your care team checks to see that you have no metal on your body before the test.

You may need to limit food and water intake before the test. You may also need to stop taking your regular medicines before the test. Follow any instructions you get from your care team. You must wear comfortable clothing without metal buttons, rivets or threads. You may need to change into a gown before the test. Don't wear jewelry, metal accessories, and makeup and hair products because they may contain metallic compounds. If having equipment around your head makes you nervous, ask your care team about taking a light sedative before the test. Infants and children may receive sedation or anesthesia to help them remain still during MEG. Your healthcare professional can explain your child's needs and options.

The equipment used in MEG testing fits over the head much like a motorcycle helmet. Your care team checks the fit of your head in the machine before doing the test. A member of your care team may give something to put on your head to help position the machine properly. You sit or lie flat while your care team checks the fit. The MEG test takes place in a room built to block magnetic activity that could make the test less accurate. You are alone in the room during the test. You can talk with the care team members during and after the test. Usually, MEG tests are painless. Your healthcare professional may perform an electroencephalogram (EEG) at the same time as the MEG. If so, your care team will place other sensors on your head using a cap or tape. If you will have an MRI scan as well as MEG, your care team likely will do MEG first to reduce the chance that the strong magnets used in MRI affect the MEG test.