Electroencephalography (EEG)

What is an electroencephalography (EEG)?

An EEG, which stands for electroencephalogram, is a test that measures electrical activity in the brain and can detect abnormalities in brain waves. The test involves placement of small electrode patches with thin wires attached to the scalp. The electrodes detect electrical charges in the brain, which translates to a graph on a computer screen. The technologist reading the graph will look for bursts of activity and brain wave patterns as well as responses to outside stimuli, such as flashing lights.

Your doctor may order an EEG to help diagnose a condition or disorder such as epilepsy, brain tumor, head injury, stroke or dementia. An EEG is often used to help detect sleep disorders as well.

How to prepare for EEG

An EEG is an outpatient test that takes up to about 60 minutes. The test may take longer if you are required to sleep during the test. To prepare for the test, you will be asked to:

  • Wash your hair with shampoo the night before. However, you should avoid using any hair care products, such as gel or conditioner, that may affect placement of the electrodes.
  • Avoid eating or drinking anything with caffeine for eight to 12 hours beforehand. Caffeine can affect brain activity and the results of the test.
  • Stop certain medications, if appropriate, as recommended by your doctor.

Depending on your health condition, your provider may have other specific requests to ensure the most accurate results from the test.

During the test you’ll be asked to lie on a bed or comfortable reclining chair while the electrodes are placed on your scalp. You will be asked to keep your eyes closed and be still throughout the test. Try to avoid any movement as this can influence the outcome of the test. The EEG is painless and you will not feel any electrical activity in your body.

After the test, the results will be given to your doctor who will go over the results with you in a separate appointment. Depending on the outcome of your EEG, additional testing or procedures may be recommended. Be sure to write down any questions you might have for your doctor.