Diagnosing Migraines and Headaches With an EEG

An EEG, or electroencephalogram, is a test in which the electrical signals of the brain are recorded. The electrical activity is detected by electrodes, or sensors, placed on a person's scalp and is transmitted to a polygraph that records the activity.

Why Is an EEG Performed to Evaluate Headaches?

EEGs are not a standard part of a headache evaluation. However, an EEG may be done to look for evidence of seizures, which can cause symptoms similar to those in people with migraines or other types of headaches. Some people also have seizures with their headaches. An EEG can indicate a malfunction of the brain, but it does not necessarily pinpoint the exact problem that might be causing a headache.

How Does an EEG Work?

Electrical signals produced by the brain cells or neurons are picked up by the electrodes and transmitted to a polygraph, where they produce separate graphs on moving paper using an ink writing pen or on a computer screen.

How Do I Prepare for an EEG?

Discuss any medications that you are taking with your doctor prior to your procedure.
Wash your hair the night before the test. Do not use hair cream, oils, or spray afterward.

What Happens During an EEG?

You will be asked to lie down on the examining table or bed while about 20 electrodes are attached to your scalp.
You will be asked to relax and lie first with your eyes open, and then closed.
You may 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.

What Happens After an EEG?

The electrodes are removed and the glue that held them in place is washed away with acetone. You may have to use additional acetone (nail polish remover) at home to completely remove the glue.
Unless you are actively having seizures or are restricted by your doctor, you may drive home. If the EEG was performed overnight, you should arrange to have someone drive you home.
If you stopped taking anti-convulsant (anti-seizure) medication for the EEG, you can usually start taking it again. Talk to your doctor.
A neurologist (a doctor who specializes in brain diseases) will examine the EEG recording for abnormalities in the brain-wave pattern, which may reflect a disease of the nerves or brain.

Reviewed by Department of Neurology, Department of Pediatric Neurology, The Cleveland Clinic.

WebMD Medical Reference provided in collaboration with the Cleveland Clinic