Definition
Magnetoencephalography, or MEG, is an imaging technique that identifies brain activity and measures small magnetic fields produced in the brain. The MEG scan is used to help doctors pinpoint the source of seizures.
An electroencephalogram (EEG) may also be performed at the same time as the MEG.
How the test is performed
A MEG scanner has 275 superconducting quantum interference device (SQUID) sensors, located inside an apparatus that looks like a helmet. These sensors silently collect information about the magnetic fields produced by brain activity.
How to prepare for the test
Your child should arrive for the sleep-deprived or tired, so that we can record their brain activity in the awake, drowsy and sleep states. Your child can eat normally before the scan and should take medications as usual.
Because metals can interfere with the scan, your child should not wear any clothing with metal zippers or snaps above the waist and shouldn't wear jewelry or a watch. Electronic items with a magnetic strip also aren't allowed.
If you remain with your child during the test, you also must remove all metal and electronic items.
Please notify the MEG department in advance if your child wears braces or a permanent retainer, or has an electronic implant, such as a pacemaker or a vagus nerve stimulator.
How the test will feel
The MEG test causes no discomfort. When the scanner is on, it makes no noise. It takes about two hours and is performed in the Biomagnetic Imaging Laboratory in a specially shielded room that is equipped with video and intercom systems. This is so a technician can see, hear and communicate with your child at all times.
Electrodes will be placed on your child's scalp, and held in place with a water-soluble paste. The electrodes may feel sticky and strange on their scalp but should not cause any other discomfort.
Your child will lie on a MEG bed with their head resting on the helmet-like MEG scanner. Their head will be held still and immobilized by sponges placed on both sides. During the scan, your child may be asked to move parts of their body or to feel, listen to, look at or read something to create brain activity.
Why the test is performed
MEG is a non-invasive brain imaging procedure that helps pinpoint the area of the brain where a seizure occurs. It is commonly used to measure brain activity in between epileptic seizures to help doctors determine which areas of the brain can safely be removed to help control future seizures.
Test results
The MEG scan can provide valuable information used by doctors to locate the seizure focus and determine if your child is a candidate for seizure surgery. Results from the MEG test are matched with the results of a magnetic resonance image (MRI).
Together, the MEG and MRI create a map, or magnetic source image (MSI), that shows areas of normal and abnormal activity in your child's brain.
