Electroencephalogram (EEG) Test

ByJanis Updated

Overview

An electroencephalogram (EEG) is a test that records electrical activity in the brain. Small metal discs, called electrodes, are placed on the scalp to pick up brain signals. EEG patterns appear as wavy lines that show how the brain is functioning.

Doctors use EEGs to help diagnose epilepsy, sleep disorders, and other conditions that affect the brain. EEGs can be done while a person is awake or asleep.

Reasons for the Test

Doctors recommend an EEG to check for unusual brain wave patterns, especially in people with seizures, epilepsy, or other neurological conditions. It also helps diagnose sleep disorders, brain infections, and certain diseases. Some common reasons include:

  • Epilepsy and Seizure Disorders: Changes in brain activity can signal seizure activity.
  • Sleep Disorders: Issues with sleeping may be related to abnormal brain waves.
  • Stroke or Brain Injury: EEGs can detect damage from head injuries or strokes.
  • Encephalopathy and Brain Infections: This test can help find diseases or swelling in the brain.
  • Brain Tumors and Dementia: EEGs may help spot tumors or signs of dementia.

Doctors also use the test in critical care settings, such as to monitor brain function in people in comas or to track anesthesia levels in certain situations.

Common Uses Related Conditions
Epilepsy Check Frontal lobe seizures
Sleep Problem Chronic daily headaches
Brain Injury Creutzfeldt-Jakob disease
Coma Assessment Huntington’s disease

Possible Side Effects

EEGs are generally safe and do not apply electricity to the body. Mild dizziness or discomfort can occur. People with epilepsy may have a seizure during the test if flashing lights or breathing exercises are used, but medical staff are prepared for this.

Getting Ready for the Test

Steps to Consider

Step What To Do
Hair Care Wash hair and skip styling products.
Sleep Adjustments Follow sleep instructions, if given.
Transportation Have a driver if using a sedative.
Caffeine Do not have caffeine before the EEG.
  • Hair Care: Wash hair either the night before or the morning of the test. Avoid using hair products such as conditioners, sprays, gels, or creams. These products can stop the electrodes from sticking properly.
  • Sleep Changes: If a sleep study is part of the EEG, sometimes less sleep or missing sleep is needed before the test.
  • After the Test: If a sedative is planned, arrange a ride home.
  • Caffeine: Avoid any drinks or foods with caffeine during the hours leading up to the test, since caffeine can affect the results.

What You Can Expect

During the Procedure

An EEG technician attaches electrodes to the scalp. They use a special pencil to mark the electrode spots and may clean these areas with a slightly grainy cream for better contact. Sticky paste or an elastic cap may hold the electrodes in place.

Wires from the electrodes connect to a recording machine that tracks and amplifies brain signals. Most EEGs take 20 to 40 minutes after setup. If brain activity during sleep is needed, the test may take longer. The person usually relaxes in a seated or lying position.

The technician may ask the person to open and close their eyes, breathe deeply, read, solve simple problems, or respond to flashing lights. These tasks help measure how brain waves respond to different actions.

Modern EEGs often include video monitoring. A camera records the person’s movements to help doctors link physical actions with brain wave changes. In some cases, an ambulatory EEG is used.

The person wears electrodes and a recording device at home or during daily routines, usually for a few days. This method helps capture less frequent events but may not provide as much detail as hospital-based tests.

Step What Happens
Mark spots on scalp Technician marks and prepares scalp.
Attach electrodes Discs or caps are fixed on the scalp.
Connect to machine Wires go to an EEG device.
Record activity Person stays relaxed; sometimes does tasks.
Video monitoring Camera captures movements.

What Happens When the Test Is Over

At the end of the test, the technician removes the electrodes or cap. You can wash off the leftover paste or gel with soap and water. If you didn’t have a sedative, you can return to your normal activities right away.

If a sedative was used, a friend or family member should drive you home. The sedative may cause drowsiness, so it’s best to rest and avoid driving or making important decisions for the rest of the day.

Findings

After the test, a specialist reviews the EEG recordings and looks for unusual electrical patterns. The results are sent to the healthcare provider who ordered the test. Key points to consider after the test:

  • Write down questions for the follow-up visit.
  • Bring a friend or family member to help remember information.
  • Ask whether any unusual patterns were found and what they might mean.
  • Discuss whether any factors may have affected your results.
Key Areas to Discuss Notes
Next Steps Clarify recommended actions.
Need for Retesting Find out if another EEG is needed.
Follow-up Understand any further checks required.
Possible Influencing Factors Review anything that may affect results.

EEG Summary

An EEG measures the brain’s electrical signals using sensors placed on the scalp. It helps doctors detect unusual activity, monitor brain function, and assess conditions like epilepsy and sleep disorders.

Purpose What EEG Shows
Study brain waves Electrical signals
Find issues Unusual patterns
Monitor changes Shifts in wave activity

Related Questions

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Health Writer

Janis's areas of expertise include nutrition, exercise, stress management, and mental health. She is passionate about educating and empowering people to take control of their health and make positive changes that can last a lifetime. Janis believes that small, sustainable changes are the key to long-term success, and she works with her clients to develop personalized plans that fit their individual needs and lifestyles.