EEG (Electroencephalogram)
An electroencephalogram, or EEG, records the natural electrical activity of your brain through small sensors placed on the scalp. It is painless and uses no radiation. By capturing patterns of brain waves while you rest, the test helps doctors investigate seizures, episodes of altered awareness, and other conditions affecting the brain.
Overview
What is an EEG?
An EEG is a test that records the electrical activity produced by your brain cells as they communicate. Several small metal sensors, called electrodes, are attached to your scalp and connected to a recorder that displays the signals as wavy lines. The test simply listens to your brain's own activity and is completely painless.
Why is an EEG done?
An EEG is mainly used to help diagnose and monitor epilepsy and to find the cause of seizures or blackouts. It can also help investigate episodes of confusion, memory problems, fainting, or unusual movements, and assess brain activity in people who are seriously unwell. The pattern of brain waves gives doctors useful clues about how the brain is functioning.
Test Details
How do I prepare for an EEG?
Wash your hair the night before and avoid hair oils, gels, or sprays so the sensors attach well. Ask your care team whether to take your usual medicines as normal. You may be asked to limit caffeine, and for some tests to sleep less the night before so a drowsy recording can be made. Bring a list of your medicines.
What happens during an EEG?
You sit or lie down while a technologist measures your scalp and attaches the sensors with a mild paste. The room is kept quiet, and you simply relax with your eyes open or closed. You may be asked to breathe deeply for a short time or look at a flashing light, as these can reveal changes. A standard recording often takes about an hour.
Results and Follow-Up
What happens after the test, and what do the results show?
The sensors are removed and the paste washed out, after which you can usually go straight back to your normal day. A specialist examines the recording for unusual brain-wave patterns and prepares a report for the doctor who arranged the test. Results are not given immediately; your doctor will explain what the patterns mean and whether any further tests or treatment are needed.
Additional Common Questions
Does an EEG hurt or give electric shocks?
No. The sensors only record the brain's own activity and do not pass any current into your head, so the test is painless. The mild paste used to attach them washes out easily afterwards.
Will the flashing lights or deep breathing trigger a seizure?
These steps are done carefully to gather more information, and trained staff stay with you throughout. If anything unusual happens, the technologist responds immediately, which is part of why the test is helpful.
Can I drive home afterwards?
Most people feel completely normal after a routine EEG and can carry on as usual. If you were asked to stay awake the night before, arrange a lift home, as tiredness can affect concentration.
Sources
This health topic is for general information and is not a substitute for professional medical advice. Always consult a qualified clinician about your individual situation. See our medical disclaimer.