Electroencephalogram (EEG)

What is an electroencephalogram (EEG)?

An electroencephalogram (EEG) is a test during which the electrical signals of the brain are recorded. This electrical activity is detected by electrodes, or sensors, placed on the patient's scalp, and transmitted to an amplifier that records the activity.

How do I prepare for an EEG?

Discuss any medicines you are taking with your doctor prior to your procedure. Continue to take any anticonvulsant medications you have been prescribed (unless your doctor specifically tells you otherwise). Wash your hair the night before the test. Do not use hair cream, oils, or spray afterward.

What happens during the EEG?

You lie down on the examining table or bed while about 20 electrodes are attached to your scalp. You are asked to relax and lie first with your eyes open, then closed. You might be asked to breathe deeply and rapidly, or to stare at a flashing light. Both of these activities produce changes in the brain-wave patterns. If you are prone to seizures, it is rare that you might experience one during the test.

What happens after the test?

The electrodes are removed and the glue that held them in place is washed away with acetone. You may have to use additional acetone at home to completely remove the glue. Unless you are actively having seizures or are restricted by your physician, you may drive home. If the EEG was performed overnight, you should arrange to have someone drive you home. A neurologist/epileptologist examines the EEG recording for abnormalities in the brain-wave pattern, which might reflect diseases of the nervous system, including epilepsy.