This painless, risk-free test can be performed in a doctor’s office or at a hospital or testing facility.
Prior to taking an EEG, the person must avoid caffeine intake and prescription drugs that affect the nervous system.
A series of cup-like electrodes are attached to the patient’s scalp,
either with a special conducting paste or with extremely fine needles.
electrodes (also called leads) are small devices that are attached to
wires and carry the electrical energy of the brain to a machine for
reading. A very low electrical current is sent through the electrodes
and the baseline brain energy is recorded. Patients are then exposed to
a variety of external stimuli—including bright or flashing light, noise
or certain drugs—or are asked to open and close the eyes, or to change
The electrodes transmit the resulting changes in brain wave patterns.
Since movement and nervousness can change brain wave patterns, patients
usually recline in a chair or on a bed during the test, which takes up
to an hour. Testing for certain disorders requires performing an EEG
during sleep, which takes at least 3 hours.
In order to learn more about brain wave activity, electrodes may be
inserted through a surgical opening in the skull and into the brain to
reduce signal interference from the skull.