EEG (Electroencephalogram)

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What is an EEG (electroencephalogram)?

An EEG (electroencephalogram) is a noninvasive, painless test that detects abnormal electrical activity in the brain. An EEG involves attaching electrodes to your scalp to record electrical impulses in the form of waves. Brain activity results from an EEG test help doctors diagnose or evaluate brain disorders and conditions, such as seizures, head injury, behavior changes, and sleep disorders. 

An EEG is only one method your doctor can use to diagnose or evaluate brain disorders and conditions. Discuss all your testing options with your doctor to understand which tests are right for you.  

Why is an EEG (electroencephalogram) performed?

Your doctor may recommend an EEG (electroencephalogram) to diagnose or evaluate neurological disorders and conditions of the brain and nervous system. These include:

  • Attention disorders such as attention deficit hyperactivity disorder (ADHD) and hyperkinesis

  • Behavior and conduct problems such as oppositional defiant disorder and school conduct challenges

  • Brain damage including that caused by trauma, substance abuse, tumors, or stroke

  • Brain tumors including cancer and benign (noncancerous) tumors

  • Developmental delays including those involving motor skills, communication, and thinking skills

  • Growth abnormalities in the brain and nervous system including abnormalities in infants, children and adults

  • Headaches and fainting of unknown cause

  • Learning disorders including dyslexia, dyscalculia, dyspraxia, and auditory and visual processing disorders

  • Seizure disorders including epilepsy

  • Sleep disorders including narcolepsy

Who performs an EEG (electroencephalogram)?

A specially trained technician performs an EEG. Doctors who order EEGs include neurologists and neurosurgeons. Neurologists and pediatric neurologists are doctors who specialize in the diagnosis and medical treatment of diseases of the brain and spinal cord. A neurologist will study the recordings for any irregularities. Neurosurgeons specialize in the diagnosis and surgical treatment of diseases of the brain and spinal cord. 

How is an EEG (electroencephalogram) performed?

Your EEG will be performed in a hospital or outpatient setting. The procedure is noninvasive and takes one to two hours. It generally includes these steps:

  1. You dress in a patient gown.

  2. You lie on your back on a procedure table or sit in a chair.

  3. Your technician attaches electrodes to your scalp, or places a cap filled with electrodes on top of your head. The electrodes are similar to those used for other tests, such as an EKG (electrocardiogram). The electrodes measure electrical signals coming from your brain. They send the signals to a computer that records the signals as a graph. The test and electrodes are painless.

  4. Your technician records a test while you recline and rest. You need to stay very still during the recording. Your technician may also record a second test using different stimuli, such as flashing lights or by asking you to take deep breaths.

  5. The technician removes the electrodes.

  6. You may wait a short period while your technician verifies that the recording is complete. Patients usually go home right after the test.

Will I feel pain?

Your comfort and relaxation is important to you and your care team. An EEG is a painless, non-invasive procedure. Tell your care team if you have any discomfort.

What are the risks and potential complications of an EEG (electroencephalogram)?

Complications of an EEG are not common, but any medical procedure involves risk and potential complications. If you have a seizure disorder, an EEG may cause you to have a seizure. Your care team will treat any seizure activity immediately.

How do I prepare for an EEG (electroencephalogram)?

You are an important member of your own healthcare team. The steps you take before an EEG can improve your comfort and help obtain the most accurate test results. 

You can prepare for an EEG by:

  • Not applying conditions, gels, hairspray or other hair products. It is fine to wash your hair with shampoo and rinse it well.

  • Not eating or drinking anything for 8-12 hours before the EEG

  • Reducing sleep the night before your EEG, as directed by your doctor

  • Stopping medication as directed by your doctor

Questions to ask your doctor

Having an EEG can be stressful. It is common for patients to forget some of their questions during a brief doctor’s office visit. You may also think of other questions after your appointment. Contact your doctor with concerns and questions before the EEG and between appointments. 

It is also a good idea to bring a list of questions to your appointments. Questions can include:

  • Why do I need an EEG? Are there any other options for diagnosing my condition?

  • How long will the procedure take?

  • When and how will I receive the results of my test?

  • What other tests or treatments might I need?

  • Is this procedure covered by my insurance? Do I need pre-authorization? If it is not covered, how much does it cost? Is there financial assistance available to cover the cost?

  • When should I follow up with you?

  • How should I contact you? Ask for numbers to call during and after regular hours.

What can I expect after my EEG (electroencephalogram)?

Knowing what to expect after an EEG can help you get back to your everyday life as soon as possible.

How will I feel after an EEG?

Diagnostic EEG is a painless, noninvasive testing procedure. Tell your doctor or care team right away if you have any pain or discomfort during or after the procedure. Most patients return to normal activities immediately after an EEG.

When can I go home?

You will likely go home right after all testing is complete.

When should I call my doctor?

It is important to keep your follow-up appointments after an EEG. Call your doctor if you have concerns, new or worsening symptoms, or questions between appointments. 

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2020 Nov 22
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
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  5. Electroencephalograms (EEG). Children’s Hospital of Boston. http://www.childrenshospital.org/az/Site829/mainpageS829P0.html.