Electroencephalogram

(EEG)

Definition

The electroencephalogram (EEG) is a noninvasive test used to evaluate brain function or disorders or to confirm brain death.

Placement of Sensors for an EEG

Parts of the Body Involved

Scalp

Reasons for Procedure

An EEG may be done for the following reasons:

To diagnose seizures
To assess conditions and diseases that affect the brain, such as trauma , coma , encephalitis , cognitive impairment, brain tumors , or certain psychological disorders

Risk Factors for Complications During the Procedure

There are very few risks associated with this procedure. If you are prone to seizures and need to discontinue medication for the test, you may be more likely to have a seizure.

What to Expect

Prior to Procedure

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

Stop taking medications, such as antidepressants, stimulants, or seizure medicines, at least 1-2 days before the test.
Avoid caffeine the day before and the day of the test.
Shampoo hair and do not use hairspray or gel the day of the test.
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.

Anesthesia

None

Description of the Procedure

You sit or lie in a chair or cot. Electrodes are attached to your scalp with a special gel or paste. These electrodes record the brain's electrical activity and transmit impulses to an electroencephalograph, which magnifies them and records them as brain waves on moving strips of paper. You will be asked to close your eyes and be still for most of the test. However, depending on the reason for the test, you may also be asked to breathe deeply and rapidly for three minutes. A strobe light may also used for a portion of the test.

After Procedure

The technician removes the electrodes. You will be advised about restarting any medications you may have stopped.

How Long Will It Take?

A standard EEG takes about one hour.

Will It Hurt?

No, an EEG is painless.

Possible Complications

None

Average Hospital Stay

None

Postoperative Care

None

Outcome

Your test results will be interpreted by a neurologist and forwarded to your doctor. Within one to two weeks of your test, your doctor will discuss the results with you.

Call Your Doctor If Any of the Following Occurs

Change in your regular seizure pattern once restarting your anti-seizure medication

RESOURCES:

Epilepsy Foundation
http://www.epilepsyfoundation.org/

National Institutes of Health
http://www.nih.gov

CANADIAN RESOURCES:

Epilepsy Canada
http://www.epilepsy.ca/

Epilepsy Ontario
http://www.epilepsyontario.org/

References:

Harrison's Principles of Internal Medicine . 14th ed. McGraw-Hill Company; 1998.

Shevell M, Ashwal S, Donley D, et al. Practice parameter: Evaluation of the child with global developmental delay: Report of the Quality Standards Subcommittee of the American Academy of Neurology and The Practice Committee of the Child Neurology Society. Neurology. 2003;60:367-380.

Last reviewed November 2007 by J.L. Chang, MD, FAASM

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.