An EEG is a test that records the electrical impulses in your brain through metal discs placed on your scalp. 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 to 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 stop taking any prescribed medication unless specifically told to do so by your physician.

What to expect

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 paste that washes off with water. The discs are connected by wires to the EEG machine. The machine will record your brain wave patterns in a computer.

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
  
• 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 flashlight or flickering lights may be placed in front of your closed eyes. This is called photo stimulation.

The test usually takes 1 to 1 1/2 hours.