Magnetoencephalography  (MEG)

Magnetoencephalography (MEG) is a test that measures the tiny magnetic fields created by your brain's electrical activity. Doctors use it to study how your brain works and to find the areas causing seizures.

MEG scans are safe and painless for both children and adults. Unlike the loud noises associated with MRI machines, MEG is completely silent. The process does not involve needles, incisions, radiation or strong magnets, resulting in a more comfortable and less stressful experience.

MEG provides more detailed brain activity maps than standard EEG tests. However, it is usually used alongside other tests like MRI scans and EEG to get a full picture of the brain.

MEG is also helpful in research on brain disorders like autism, Alzheimer’s, PTSD and traumatic brain injuries.

At ACH, our brain specialists—including neuroradiologists, neurologists and neurosurgeons—use MEG scans to map brain function before surgery. MEG helps us find the exact spot in the brain where seizures or other problems are happening.

We combine MEG with MRI, which shows the brain's structure. Together, these images help us map areas of normal and abnormal brain activity. This information allows us to make brain surgery safer and more effective by targeting the problem areas while protecting healthy tissue.

Our brain specialists use MEG scans to identify and map:

• The parts of the brain that control language, movement and sensory functions
• The areas where epileptic seizures start
• The exact location of brain tumors and other abnormalities

We often recommend MEG studies for people who are undergoing brain surgery for conditions such as:

• Epilepsy
• Brain tumors

Your doctor will tell you if you need to stop eating, drinking or making changes to your medications before the test. Before undergoing a MEG scan, we need to follow special requirements to obtain better brain signals. Prepare by observing the following tips:

• Avoid wearing makeup or using hair products, as these can affect the results.
• Don’t wear any metal items, like jewelry, glasses, hairpins, underwire bras, or clothes with any metal zippers, buttons or magnetic parts. If needed, we’ll provide you with a medical gown to wear.

If you have any medical devices in or on your body, let our specialists know beforehand. If the device contains metal or could interfere with the test, you may not be able to proceed with the scan.

Please notify us if you or your child has:

• An electronic implant, such as a pacemaker or a vagus nerve stimulator (VNS), deep brain stimulator (DBS) or responsive neurostimulator (RNS)
• Metal braces
• A permanent retainer
• Permanent makeup or lash extensions
• Hair extensions
• Artificial limbs or metallic prosthetic joints
• Cardiac defibrillators and pacemakers
• Certain brain aneurysms
• Certain metal coils placed within blood vessels
• Cochlear implants
• Implanted drug infusion ports
• Implanted nerve stimulators
• Metal teeth braces
• Metal pins, screws, plates, stents or surgical staples
• Programmable shunts

The process of a MEG test can vary depending on the reason for it. In general, you can expect:

• You will remove all metal accessories from your body and change into a medical gown.

• Infants and young children may need sedation (medication that helps you relax) or general anesthesia to complete a MEG exam without moving. If this is the case, the provider will insert an IV for the medication.

• Our MEG specialists will attach five positioning coils to your head with temporary tape and make three small dots on your head with a washable marker.

• After we place these, we will touch your head, each marker, and coils with a special wand-like device. This helps the computer create a picture of the shape of your head and determine the location of your head in relation to the sensors in the helmet.

• Four electrodes (like stickers) will be placed on your face and chest to monitor eye movements and your heart activities. These electrodes and coils will be connected to the MEG machine.

• When the MEG coils are in place and the quality of the signal has been checked, your will walk to the MEG room and the scan is ready to begin. Although it is large, the MEG machine is very quiet and does not move.

• Your child will lie on a moveable exam table or sit in a special chair and your head will be positioned into the MEG machine, which is similar to a football helmet coming down over your ears but does not cover your face.

• Feelings of claustrophobia from wearing the helmet are very rare. It’s important to put your head as deep as possible into the helmet so your brain is close to the sensors in the MEG machine.

• The procedure is performed in a closed room, which may be scary to you, but you will be able to communicate with our specialists at all times. There’s a two-way intercom and video monitoring system in the room. If you express discomfort at any time, the testing can be stopped immediately.

• Depending on the reason for the test, you may lie still or even go to sleep. It’s important to try to keep your head still during the testing. If you’re having the test to map sensory areas of your brain, you’ll do certain activities, like listening to words or beeps or repeatedly pushing a button.

• Our MEG specialists may use a small electrical current to stimulate your finger to measure how your brain responds to it. You’ll feel a tingling sensation, but it won’t hurt.

• Once our MEG specialists have all the information they need, the test will be over and our MEG specialists will enter the room to disconnect everything from the MEG machine, and you will be walked out of the MEG room to remove and clean your skin from electrodes and coils.

• When the test is over, a MEG specialist will analyze the recordings.

• Some providers perform an electroencephalogram (EEG) or a magnetic resonance imaging (MRI) scan alongside a MEG test. If this is the case, there will be additional steps to the process.

• The test can take up to two hours, but the entire visit could last up to four hours.

If you or your child had sedation or anesthesia for the test, a healthcare provider will observe you for 30 minutes to two hours after the exam to ensure you recover well. You’ll need someone else to drive you home.

If you didn’t have sedation, there’s no recovery period. You can return to your usual activities.

There aren’t any known risks of a MEG test.

Reviewing the recordings from your MEG test can take several days or even weeks. This is because MEG is used to plan complex brain surgeries, and multiple specialists may collaborate to analyze the results. Once the review is complete, your healthcare team will discuss the findings with you and outline the next steps in your care.