An electroencephalogram (EEG) is a test that
measures and records the electrical activity of your brain. Special sensors
(electrodes ) are attached to your head and hooked by
wires to a computer. The computer records your brain's electrical activity on
the screen or on paper as wavy lines. Certain conditions, such as
seizures, can be seen by the changes in the normal
pattern of the brain's electrical activity.
Why It Is Done
electroencephalogram (EEG) may be done to:
epilepsy and see what type of seizures are occurring.
EEG is the most useful and important test in confirming a diagnosis of
- Check for problems with loss of consciousness or
- Help find out a person's chance of recovery after a change in
- Find out if a person who is in a coma is brain-dead.
- Study sleep disorders, such as
- Watch brain activity while a person is receiving general
anesthesia during brain surgery.
- Help find out if a person has a physical problem (problems in the
brain, spinal cord, or nervous system) or a mental health problem.
How To Prepare
Before the day of the
electroencephalogram (EEG) test, tell your doctor if you are taking any
medicines. Your doctor may ask you to stop taking certain medicines (such as
sedatives and tranquilizers, muscle relaxants,
sleeping aids, or medicines used to treat seizures) before the test. These
medicines can affect your brain's usual electrical activity and cause abnormal
Do not eat or drink foods that have caffeine (such
as coffee, tea, cola, and chocolate) for 12 hours before the test.
Since the electrodes are attached to your scalp, make sure
your hair is clean and free of sprays, oils, creams, and lotions. Shampoo your
hair and rinse with clear water the evening before or the morning of the test.
Do not put any hair conditioner or oil on after shampooing.
find certain types of abnormal electrical activity in the brain, you may have
to be asleep during the recording. You may be asked not to sleep at all the
night before the test or to sleep less (about 4 or 5 hours) by going to bed
later and getting up earlier than usual. If your child is going to be tested,
try to keep him or her from taking naps just before the test. If you know that
you are going to have a sleep-deprived EEG, plan to have someone drive you to
and from the test.