Electroencephalogram (EEG) is a test used to look at the electrical activity in the brain.

Placement of Sensors for an EEG

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Reasons for Test

An EEG may be done to:

  • Help diagnose seizures
  • Assess if brain function has been affected by certain conditions and diseases, such as:
Possible Complications

There are no major complications associated with this test.

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 you need to stop any medications, 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 hair styling products.
  • 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 bed. Electrodes will be placed on 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. Depending on the reason for the test, there may be other steps such as:

  • You may be asked to breathe deeply and rapidly.
  • A strobe light may be turned on. It sends fast pulses of light.

In some cases, a video recording of the test will be made.

After Test

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

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

How Long Will It Take?

The test may take about one hour. In some cases, an EEG is done overnight or over a number of days. The test may be done at home or in the hospital.

Will It Hurt?

No, an EEG is painless.

Results

Your test results will be reviewed. Your doctor will get a report within 1-2 weeks and will talk to you about the results.

Call Your Doctor

Call your doctor if you have a seizure disorder and your regular seizure pattern changes when you restart your anti-seizure medication.