 Magnetoencephalography (MEG)
or
Magnetic Source Imaging (MSI)
Magnetoencephalography (MEG), also known as Magnetic Source Imaging (MSI), is a non-invasive scanning technique which provides information about the structure and function of the brain. It is a safe and painless procedure that detects small biomagnetic signals produced by the brain, recording magnetic fields over the surface of the head. These signals provide information about the location of active brain areas. This allows us to see how different areas of the brain interact with one another.
MEG can help to identify the areas of the brain that are emitting abnormal electric currents that are causing the seizures. Often patients perform cognitive tasks during the MEG, which helps to localize the learning and memory areas of the brain. The MEG produces a high resolution image of the brain that relates the functioning of the brain with behaviour.
One advantage that MEG has over PET and fMRI, which depend on changes in blood flow in the brain, is that it is fast enough to provide information about the millisecond by millisecond changes in neuronal firing, which PET and fMRI cannot. MEG records magnetic signals that are produced by the responding neurons, enabling us to see rapid brain potentials
Before an MEG/MSI
- No special diet is required. You can eat and drink as usual.
- Dress in comfortable clothing on the day of the test.
- You should wash your hair before the test and do not use hairspray, gel or other hair products.
- Do not wear any metal objects (jewellery, piercings, belts etc.).
During an MEG/MSI
- You will be placed in a shielded room away from fan motors, elevators and other sources of magnetic "noise".
- You will either lie down on a bed or sit in a chair.
- An electrical device, known as a neuromagnetometer, will be placed near your head. This instrument acts as an antenna to pick up the magnetic fields emerging from the brain, and takes a snapshot every millisecond.
Payment
This test is covered by the Ontario Health Insurance Plan (OHIP).
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