EEG or Electroencephalogram; Brain wave test

An electroencephalogram (EEG) is a test to detect abnormalities in the electrical activity of the brain.

How the test is performed:

Brain cells communicate by producing tiny electrical impulses. In an EEG, electrodes are placed on the scalp over multiple areas of the brain to detect and record patterns of electrical activity and check for abnormalities.

The test is performed by an EEG technician in a specially designed room. You will be asked to lie on your back on a table.

The technician will apply between 16 and 25 flat metal discs (electrodes) in different positions on your scalp. The discs are held in place with a sticky paste. The electrodes are connected by wires to an amplifier and a computerized recording machine.

The recording machine converts the electrical signals into a series of wavy lines that are digitally recorded on the computer. You will need to lie still with your eyes closed because any movement can alter the results.

You may be asked to do certain things during the recording, if indicated, such as breathe deeply and rapidly for several minutes, or look at a bright flickering light through closed eyes.

How to prepare for the test:

• You will need to wash your hair the night before the test. Do not use any oils, sprays, or conditioner on your hair before this test.
• You should take all medications regularly, unless given other instructions by your physician.
• Sometimes it is necessary to sleep during the test, so you may be asked to reduce your sleep time the night before

How the test will feel:

This test causes no discomfort. Although having electrodes pasted onto your skin may feel strange, they only record activity and do not produce any sensation.

Why the test is performed:

EEG is used to help diagnose the presence and type of seizure disorders, to look for causes of confusion, and to evaluate head injuries, tumors, infections, degenerative diseases, and metabolic disturbances that affect the brain.

It is also used to evaluate sleep disorders and to investigate periods of unconsciousness. EEG cannot be used to "read the mind", measure intelligence, or diagnose mental illness.

Return to Diagnostic Testing Main Page