What is an Electroencephalogram (EEG)?

An electroencephalogram (EEG) is a test that measures and records the electrical activity of your brain. Special sensors (electrodes) are attached to your head and hooked by wires to a computer. The computer records your brain’s electrical activity on the screen or on paper as wavy lines. Certain conditions, such as seizures, can be seen by the changes in the normal pattern of the brain’s electrical activity.

What happens during the test?

You will be asked to lie on your back on a bed or table or relax in a chair with your eyes closed. The EEG technologist will attach approximately 25 to 30 flat metal discs (electrodes) to different places on your head, using a sticky paste to hold the electrodes in place. The electrodes are hooked by wires to a computer that records the electrical activity inside the brain.

It is important that you lie still during the recording, and do not talk to the technologist unless you need to. The technologist may ask you to do different things during the test to record what activity your brain does at that time. You may be asked to breathe deeply and rapidly. If you are asked to breathe rapidly, you may feel lightheaded or have some numbness in your fingers. This reaction is normal. It will go away in a few minutes after you start breathing normally again.

An EEG is a very safe test and there is no pain with the test. The electrical activity of your brain is recorded, but at no time is any electrical current put into your body.

What Should I Expect after the test?

There are no side effects from this test.

The results will be studied by a neurologist who is a specialist in nerve and muscle diseases. The report of the findings will be sent to your physician who will discuss them with you.

How do I prepare for this test?

Before the day of the test, tell your doctor if you are taking any medicines. Your doctor may ask you to stop taking certain medicines before the test because some medicines can affect your brain’s usual electrical activity and cause abnormal test results.

Do not eat or drink foods that have caffeine for 8 hours before the test.

Please wake up at least two hours before your scheduled test time.

Please wear comfortable clothes. During the test you will be lying on a bed in the
EEG Lab.

Since the electrodes are attached to your scalp, it is important that your hair be clean and free of oils or lotions. Shampoo your hair and rinse with clear water before the test. Do not put any hair conditioner or oils on after shampooing. The testing time is usually one hour, however, some testing takes longer while some may be shorter so please eat a full meal before coming to the EEG lab.