An electroencephalogram records spontaneous electrical activity generated in the brain. This activity reflects the electrical currents of flow in the brain. The spontaneous activity of the brain nerve cells is influenced by multiple structures in the brain.
An electroencephalogram is an essential part of the study of patients with seizures, those suspected of having seizures, and those having spells or episodes of undefined cause. It is also used to evaluate the cerebral effects of systemic diseases and in the study of sleep. In some diseases, it can be the defining laboratory test.
To perform an electroencephalogram, approximately 21 disc electrodes are placed onto the scalp with a sticky, conductive paste. Two EKG electrodes are placed on the chest to record heart rate simultaneously with the EEG. Two activation procedures are performed. The first activation is a strobe light, which is placed in front of the face over closed eyes with flashes of light for approximately three minutes in increasing frequencies every 10 seconds. The second activation is to perform three minutes of deep breathing (unless you are unable to perform this test due to health reasons). The remainder of the test is performed resting and, hopefully, sleeping.