Brief Description – An electroencephalogram (EEG) is a test to measure the electrical activity of the brain.
Why the Test is Performed
EEG can be used to diagnose or monitor the following health conditions:
- Abnormal changes in body chemistry that affect the brain
- Brain diseases, such as Migraines, Alzheimer disease
- Fainting spells or periods of memory loss that cannot be explained otherwise
- Head injuries
- Brain infections
- Sleep disorders
- Monitor the brain during brain surgeryAn EEG may be done to show that the brain has no activity, in the case of someone who is in a deep coma or when trying to decide if a person is brain dead. EEG cannot be used to measure intelligence.
How the Test is Performed
- Brain cells communicate with each other by producing tiny electrical signals, called impulses. An EEG measures this activity.
- The test is done by an EEG technologist in your doctor’s office or at a hospital or laboratory. You lie on your back on a bed or in a reclining chair.
- Flat metal disks called electrodes are placed all over your scalp. The disks are held in place with a sticky paste. The electrodes are connected by wires to a recording machine. The machine changes the electrical signals into patterns that can be seen on a monitor or drawn on paper. It looks like wavy lines.
- You need to lie still during the test with your eyes closed. This is because movement can change the results. You may be asked to do certain things during the test, such as breathe fast and deeply for several minutes or look at a bright flashing light.
• If your doctor needs to monitor your brain activity for a longer period, an ambulatory EEG will be ordered. In addition to the electrodes, you will wear or carry a special recorder for up to three days. You will be able to go about your normal routine as the EEG is being recorded.
How to Prepare For the Test
- Wash your hair the night before the test.
- Do not use conditioner, oils, sprays, or gel on your hair.
- If you have a hair weave, ask your doctor for special instructions.
- Your doctor may want you to stop taking certain medicines before the test. Do not change or stop taking any medicines without first talking to your doctor. Bring a list of your medications with you.
- Avoid all food and drinks containing caffeine for 8 hours before the test.
- You may need to sleep during the test. If so, you may be asked to reduce your sleep time the night before. If you are asked to sleep as little as possible before the test, do not eat or drink any caffeine, energy drinks, or other products that help you stay awake. Follow any other specific instructions you are given.During the Test
The electrodes may feel sticky and strange on your scalp, but should not cause any other discomfort. You should not feel any discomfort during the test.
After the Test
You can go on with your normal routine and resume any medication you may have stopped because of the test. Your doctor will discuss the test result at a later appointment.
An EEG test is very safe. The flashing lights or fast breathing (hyperventilation) required during the test may trigger seizures in those with seizure disorders. The doctor performing the EEG is trained to take care of you if this happens.