The electroencephalogram (EEG) is a test that uses sensors to evaluate electrical brain activity.

Placement of Sensors for an EEG

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Reasons for Test

An EEG may be done for the following reasons:

  • To help diagnose seizures]]>
  • To assess brain function affected by certain conditions and diseases, such as:


What to Expect

Prior to Test

Depending on the reason for your EEG, you may be given some of the following instructions:

  • Ask your doctor whether to stop any medicines, such as stimulants, prior to the test.
  • Avoid caffeine]]> for eight hours before the test.
  • Shampoo your hair the day of the test. Do not use hairspray or gel that day.
  • If you are having a sleep-deprived EEG, you may need to stay awake the night before the test. You should also arrange for a ride to and from the test.
  • If you are prone to seizures, arrange for a ride to and from the test.

Description of Test

You will sit in a chair or lie on a cot. Electrodes will be attached to your scalp with special gel or paste. The electrodes will record the brain's electrical activity. You will be asked to close your eyes and be still for most of the test. You may be asked to breathe deeply and rapidly. A strobe light may also be used for a portion of the test. In some cases, the doctor will make a video recording of the test.

After Test

The technician will remove the electrodes, and you will be able to go home.

Talk to your doctor about restarting any medicines you may have stopped.

How Long Will It Take?

About one hour.

Will It Hurt?

No, an EEG is painless.


Your test results will be interpreted by a neurologist. Your doctor will receive a report within 1-2 weeks of your test. Discuss the results with your doctor.

Call Your Doctor

After the test, call your doctor if any of the following occurs:

If you have a seizure disorder and you have a change in your regular seizure pattern once you have restarted your anti-seizure medicine