An EEG detects electrical activity in the brain. This non-invasive procedure is used to help diagnose a wide array of disorders, including seizure disorders, head injuries, brain tumors, infections, degenerative diseases and metabolic disturbances.
The test involves recording and evaluating electrical activity of the brain, detected through electrodes attached to your scalp that are connected by wires to a computer. The computer will record your brain’s electrical activity represented as wavy lines. During the test, you will lie in a prone position in a relaxed and quiet atmosphere. While in the recording phase of your test, you may be asked to complete simple tasks, such as opening and closing your eyes.
To help in finding certain types of electrical activity in the brain, you may have to be asleep during the recording – this is called a sleep-deprived EEG. You may be asked not to sleep at all the night before the test or to sleep less by going to bed later and getting up earlier than usual.
A routine procedure for an adult takes approximately 60 minutes. For children, the test will last approximately 90 minutes. Sleep-deprived testing also lasts approximately 90 minutes.
Preparing for your EEG
Preparation may vary according to the type of EEG testing or physician’s orders. In general:
- Since the electrodes are attached to your head, your hair should be clean, free of oil or hairspray, and dry.
- Meals and medication may be taken unless your physician advises otherwise.
- Sleep-deprived testing normally requires a special sleeping schedule the night before the test. Your physician will order the sleep schedule. After the test, it is recommended that you be accompanied and do not drive.
- Children being tested should be kept awake later than normal the night before and awakened a few hours earlier than usual. This unusual sleep schedule, along with keeping the child from napping, often helps the child lie still or fall asleep during testing.