EEG

The test is done by an EEG technologist in your health care provider's office or at a hospital or lab. The test is done in the following way: You lie on your back on a bed or in a reclining chair. Flat metal disks called electrodes are placed on many spots on your scalp. The disks are held in place with a sticky…

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 provider for special instructions. Your provider may want you to stop taking certain medicines before the test. Do not change or stop taking any medicines without first talking to…

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.

Brain cells communicate with each other by producing tiny electrical signals, called impulses. An EEG measures this activity. It can be used to diagnose or monitor the following health conditions: Seizures and epilepsy Abnormal changes in body chemistry that affect the brain Brain diseases, such as Alzheimer disease…

Brain electrical activity has a certain number of waves per second (frequencies) that are normal for different levels of alertness. For example, brain waves are faster when you are awake and slower in certain stages of sleep. There are also normal patterns to these waves. Note: A normal EEG does not mean that a…

Abnormal results on an EEG test may be due to: Abnormal bleeding (hemorrhage) in the brain An abnormal structure in the brain (such as a brain tumor) Tissue death due to a blockage in blood flow (cerebral infarction, also called a stroke ) Medicine or illegal drug or alcohol abuse Head injury Migraines (in some cases)…

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 provider performing the EEG is trained to take care of you if this happens.

De Luca GC, Griggs RC, Johnston SC. Approach to the patient with neurologic disease. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine . 27th ed. Philadelphia, PA: Elsevier; 2024:chap 366. Hahn CD, Emerson RG. Electroencephalography and evoked potentials. In: Jankovic J, Mazziotta JC, Pomeroy SL, Newman NJ, eds.…