Your brain is a highly complex organ made up of billions of cells. The brain cells send and receive messages to and from all parts of your body. These messages are electrical impulses that create brain waves.
How does an EEG work?
An EEG is a test that records the electrical impulses in your brain through metal discs placed on your scalp. EEG is the short name for electro-encephalogram (ee-LEK-tro-en-SEF-uh-low-gram). The test results show brain wave patterns in different parts of your brain and if the patterns are normal or abnormal. The EEG test helps to detect or rule out conditions such as epilepsy, stroke, brain tumors, trauma, coma, or brain death. An EEG is a safe, easy, and painless test. There are no known risks from an EEG.
How do I prepare for the test?
Wash your hair the night before the test. Do not use hair spray, conditioner, or gels. Your hair must be clean and oil free.
- Do not drink any caffeine drinks, such as tea, coffee, and sodas, for 24 hours before the test.
- You may eat a regular meal or snack 2 hours before the test.
- Before the day of your test, tell your doctor all the medicines you take. Do what your doctor tells you about taking your normal medicines.
What happens during the test?
An EEG technician will help you sit or lie down so you’ll be comfortable during the test. Flat metal discs about the size of a quarter will be placed on your scalp. The discs will be attached with a sticky paste that washes off with water. The discs are called electrodes (ee-LEK-trodes) and are connected by wires to the EEG machine. The machine will record your brain wave patterns on paper or in a computer.
Types of EEG Stimulation
During your test, brain wave activity will be stimulated in several different ways:
- You will be asked to breathe deeply and rapidly for a few minutes. It’s normal to feel mild dizziness or tingling while you breathe rapidly. This is called hyperventilation (HI-per-ven-til-LAY-shun).
- You may be asked to go to bed later the night before your test. You may be asked to get up earlier the morning of your test. You may also be given a mild sedative to help you doze off. These methods may be used to help you sleep during the test.
- A flash light or flickering lights may be placed in front of your closed eyes. You may see various colors or patterns for a few moments. This is called photo stimulation.
- You may put on earphones. You’ll hear clicks or tones that will sound many times per second, usually in one ear at a time. The test usually takes 1 to 1 1/2 hours.
What happens after the test?
After the test, the technician will clean your scalp to remove the paste. You may return to your normal activities, unless your doctor tells you otherwise.
How do I get my results?
Your doctor will discuss the results of the test with you. Ask your doctor or the testing center about how and when to get your results.
Questions and concerns
It’s normal to feel some anxiety before and during a test. But a diagnostic test should not be a frightening experience. Feel free to express concerns about your EEG. Please ask the medical staff any questions you may have.
My test appointment
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