What is an EEG?

An electroencephalogram (EEG) is a test that uses small, flat metal discs called electrodes to detect electrical activity in your brain. These electrodes are attached to your scalp in order to track electrical impulses, which then are translated as wavy lines on an EEG recording.

EEG is the primary diagnostic procedure for epilepsy but also may help identify other brain disorders.

What to Expect During an EEG

EEG is a non-invasive, safe, and painless procedure that may be conducted at your physician’s office, laboratory, or hospital. The typical EEG lasts between 30 and 60 minutes.

EEGs may be conducted while you are awake or asleep. When EEGs are performed on people with epilepsy, sometimes seizures are intentionally triggered; in such cases, medical assistance is always on hand if necessary.

Uses of EEG Imaging

EEG is an important tool for use in diagnosing and treating:

  • Epilepsy and other seizure disorders
  • Stroke
  • Brain dysfunction or inflammation (encephalitis)
  • Brain tumors
  • Head injuries
  • Dementia
  • Sleep disorders
  • Memory problems

Video EEG

Video EEG (electroencephalography) allows physicians to monitor patients using video and audio while recording the electrical activity in their brains. EEG is the cornerstone study to identify seizures and epilepsy. For some epilepsy patients, the monitoring study uses special intracranial electrodes that are temporarily implanted on the brain by a neurosurgeon.

How do I prepare for an EEG?

Wash your hair the night before or the day of the test, but don’t use any conditioners, hair creams, sprays or styling gels. Hair products can make it harder for the sticky patches that hold the electrodes to adhere to your scalp.

Avoid anything with caffeine on the day of the test, because caffeine can affect the test results.

Take your usual medications unless instructed otherwise.

If you’re supposed to sleep during your EEG, your doctor may ask you to sleep less or even avoid sleep entirely the night before your test.

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