Let's learn about the MEG scan (Magnetoencephalography) that maps brain activity.

Do you or someone you know have a condition like epilepsy? Or have you ever wanted to know exactly where the important parts of the brain that control speech and movement are before undergoing brain surgery? Today we're talking about a very advanced, painless, and safe test that doctors use in times like these. It's called an MEG scan.

Simply put, what is this MEG?

MEG, or Magnetoencephalography, is a test that measures the very subtle magnetic fields generated by electrical signals emitted by our brain cells. To be precise, this is a method of brain mapping our brain activity.

The best part is that it is completely painless and noninvasive. This means that no needles are used, no cuts are made, and you are not exposed to any radiation, such as X-rays. MEG is the most advanced method in the world for recording and evaluating brain activity.

In what cases is an MEG test performed?

Neurologists and neurosurgeons use this MEG test for two main reasons.

Additionally, MEG is an indispensable tool in scientific research to gain a deeper understanding of the functioning of the human brain.

How does this machine work?

It's very simple. The neurons in our brain communicate with each other by generating very small electrical voltages. When these electrical currents flow, a magnetic field is created around them.

The MEG machine uses more than 300 highly sensitive sensors , which are placed on a helmet-like device that you wear on your head, to detect, record, and analyze these magnetic fields. These sensors are so sensitive that they can pick up even the smallest magnetic fields coming from our brains. These sensors are called SQUIDs (superconducting quantum interference devices).

These sensors and special computer software work together to record your brain activity millisecond by millisecond, whether you're sitting still or doing something (e.g., looking at pictures or reading words). Finally, this information is combined with an image of your brain, which is displayed on a computer screen as a "map" showing which parts of your brain are active.

How to prepare for the MEG test?

Your doctor will give you any special instructions you need before this test.

• The doctor will ask if you need to refrain from eating or drinking for a while before the test.
• They will also advise you on whether you need to make any changes to the medications you are taking.
• Do not wear makeup on the day of the test, and do not use any gel or spray on your hair. These things can interfere with the test results.
• You cannot bring any metal objects into the examination room. This means you must remove any jewelry, glasses, hairpins, or underwire bras. If necessary, the hospital will give you a special medical gown to wear.

Most importantly: Be aware of the metal parts in your body

If you have any medical devices permanently implanted inside or outside your body, you should definitely tell your doctor about them before the test. Some devices contain metal and may interfere with the magnetic field, so you may not be able to have this test.

What happens during the test?

The way an MEG test is performed can vary slightly depending on the reason for it, but it usually goes something like this.

1. Preparation: You will remove all metal objects from your body and put on the hospital gown.

2. For young children: For young children, it may be necessary to administer sedation or general anesthesia, as it may be difficult for them to remain still during the test.

3. Positioning: Measure the exact position of your head relative to the helmet, and apply three or four small positioning coils with temporary tape at three or four locations on your head.

4. Removing magnetic signals: Next, a circular device called a "degausser" is moved around your body to remove unwanted magnetic signals that may have accumulated in your body's environment.

5. Sitting for the test: You will then be made to sit in a special chair connected to the MEG machine, or you will be made to lie down on a bed.

6. Putting on the helmet: Now the helmet with the MEG sensors is placed on your head. This reduces the risk of claustrophobia. For best results, keep your head as close to the helmet as possible.

7. During the test: Sometimes you will be asked to sit still, and you may even fall asleep. In a brain scan, you will be asked to read words on a screen, answer questions, or do small tasks, such as pressing a button. Sometimes, your finger may be given a small electrical stimulus to measure how your brain responds. This may feel like a slight tickle, but it is not painful.

8. Communication: The testing room has an intercom and video system, so you can talk to the testing technician at any time.

This entire test takes about one or two hours.

What happens after the test?

If you or your child were given sedation, the medical staff will monitor you for about half an hour to two hours. You will need someone to help you go home.

If you are not sedated, there is no problem. You can continue with your usual activities as soon as the test is over.

What is the difference between MEG, MRI and EEG?

Although all three of these tests are performed on the brain, the information they measure and give us is different.

Sometimes doctors combine information from both MEG and MRI tests to create a functional map of brain activity. This is called MSI (Magnetic Source Imaging).