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An electroencephalogram (EEG) or brain wave test is a noninvasive procedure which is used to record the brain’s electrical activity. Because normal brain waves have recognizable patterns, variations or abnormalities in these patterns seen on EEG may help in the diagnosis of conditions such as seizure disorders (e.g. epilepsy), brain infections, head injury and sleep disorders. An EEG tracing is depicted below.
To perform an EEG, 16 to 25 small metal disks (called electrodes) are attached to the scalp using a sticky paste. These electrodes are in turn attached by wires to a machine that records the brain's electrical signals through the scalp. These signals are then converted into wavy lines that are printed on a moving sheet of graph paper or displayed on a monitor. In some cases, the patient is asked to perform tasks, such as breathing deeply or looking at a blinking light. Generally, this test takes one to two hours and there is no discomfort associated with it.
In general, there are no risks associated with an EEG. However, in patients who have seizure disorders, a seizure may be triggered by the use of flashing lights or by hyperventilation.
