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Electroencephalography (EEG)

An Electroencephalogram (EEG) records the electrical activity of the brain. Highly sensitive monitoring equipment records the activity through electrodes that are placed at measured positions on the patient’s scalp. An EEG is not painful. The test usually takes about 90 minutes and the principal role of the patient is simply to remain still, relaxed, and comfortable. During the test, the patient may be asked to take repeated deep breaths (hyperventilate) and/or be shown a strobe light that flashes at different speeds. Both activities can help reveal different brain patterns useful for diagnosis.

How can EEG contribute to clinical diagnosis and patient management?

In some cases, physicians also want to observe brain patterns that occur during sleep. For sleep EEGs, the patient may be asked to stay awake most of the night prior to the EEG appointment, or in some cases, may need a mild sedative. EEGs assist physicians in the diagnosis of a variety of neurological problems—from common headaches and dizziness to seizure disorders, strokes, and degenerative brain disease. The EEG is also used to determine organic causes of psychiatric symptoms and disabilities in adults and children. EEGs also assist physicians in determining irreversible brain death.

24-hour Ambulatory EEG monitoring

An Ambulatory EEG records brain activity for 24 or more hours on a small lightweight recorder that is either worn around the waist or over the shoulder. Electrodes are applied to the patient’s scalp, and the head is gently wrapped to secure the electrodes. The patient is sent home with a diary to record activities and any symptoms during a 24-hour period.

Monitoring is valuable in evaluating and quantifying:

  • Episodic altered behavior
  • Episodic altered consciousness
  • Dizzy spells
  • Seizures versus pseudo or hysterical seizures
  • Syncope