An EEG detects electrical charges from your brain cells

An electroencephalography, or EEG, is a test that detects abnormalities in your brain waves, or in the electrical activity of your brain. During the procedure, electrodes consisting of small metal discs with thin wires are pasted onto your scalp. The electrodes detect tiny electrical charges that result from the activity of your brain cells. The charges are amplified and appear as a graph on a computer screen, or as a recording that may be printed out on paper. Your health care provider then interprets the reading.

During an EEG, your health care provider typically evaluates about 100 pages, or computer screens, of activity. He or she pays special attention to the basic wave form, but also examines brief bursts of energy and responses to stimuli, such as flashing lights.

Evoked potential studies are related procedures that also may be done. These studies measure electrical activity in your brain in response to stimulation of sight, sound or touch.

Why you might need an EEG

The EEG is used to evaluate several types of brain disorders. When epilepsy is present, seizure activity will appear as rapid spiking waves on the EEG.

People with lesions of their brain, which can result from tumors or stroke, may have unusually slow EEG waves, depending on the size and the location of the lesion.

The test can also be used to diagnose other disorders that influence brain activity, such as Alzheimer disease, certain psychoses, and a sleep disorder called narcolepsy.

The EEG may also be used to determine the overall electrical activity of the brain (for example, to evaluate trauma, drug intoxication, or extent of brain damage in comatose patients). The EEG may also be used to monitor blood flow in the brain during surgical procedures.

There may be other reasons for your health care provider to recommend an EEG.

Getting an EEG is safe and painless

The EEG has been used for many years and is considered a safe procedure. The test causes no discomfort. The electrodes record activity. They do not produce any sensation. In addition, there is no risk of getting an electric shock.

In rare instances, an EEG can cause seizures in a person with a seizure disorder. This is due to the flashing lights or the deep breathing that may be involved during the test. If you do get a seizure, your health care provider will treat it immediately.

Other risks may be present, depending on your specific medical condition. Be sure to discuss any concerns with your health care provider before the procedure.

To schedule an appointment with a specialist at Main Line Health, call 1.866.CALL.MLH (1.866.225.5654) or use our secure online appointment request form.