Electroencephalogram (EEG)
What is it?
An electroencephalogram (EEG) is a painless procedure
used to measure the brain’s electrical activity.
Who needs this procedure?
An EEG may be used to diagnose conditions that affect
the brain, such as brain tumors, epilepsy, sleep apnea,
and encephalitis. It is used when the patient is
experiencing a decline in mental ability or problems with
impaired consciousness. This procedure is sometimes used
during surgery to detect tumors or to monitor the effects
of anesthesia. It may also be used to locate areas of
brain tissue death.
How do I prepare for this procedure?
Unless you receive special instructions from your
doctor, there are no preparations necessary for this
procedure.
How is this procedure performed?
Wires, called leads or electrodes, are attached to your
scalp with a special, easy to remove glue-like solution or
tape. The wires are connected to an instrument that
measures your brain’s activity and records the activity as
a pattern of wavy lines on a sheet of paper. These line
patterns indicate different types of brain waves. During
the procedure, you may be asked to remain still with your
eyes closed, remain still with your eyes opened, follow a
flashing light, or breathe rapidly. If you are being
tested for sleep apnea, you may be given medication to
make you sleep, or you may remain in the testing area
overnight so your brain activity can be tested as you
sleep. Because the occurrence of seizures is
unpredictable, the EEG may be administered over a 24-hour
period if you are being tested for epilepsy. When an EEG
is being used during neurosurgery to detect lesions or
tumors on the brain, the electrodes are applied directly
to the surface of the brain or within the brain tissue.
What can I expect after the procedure?
This procedure has no side effects. Your doctor will
notify you of the test results.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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