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What is an electroencephalogram (EEG)?

At Northwell Health, we provide you with the most advanced technology for measuring and recording the electrical activity of your brain, including electroencephalogram. EEG is a safe and painless test used to measure and record the electrical activity of your brain. With special sensors attached to your head, a computer records your brain’s electrical activity.

Why it's done

Changes from a normal pattern of electrical activity can indicate certain conditions, such as:

  • Epilepsy, including type of seizure occurring
  • Sleep disorders, such as narcolepsy
  • Dementia
  • Brain damage


There are multiple types of EEG tests, including:

  • Routine EEGs
  • Sleep deprived EEGs
  • Ambulatory EEG monitoring
  • Intracranial EEGs
  • Inpatient video EEG monitoring during medication changes, refractory epilepsy or for initial diagnosis and classification of epilepsy

What to expect

If you require an EEG, it may be performed either in a hospital or in your doctor’s office. An EEG technologist will perform the test. During the test, you will be asked to sit in a chair with your eyes closed or to lie on your back on a table or bed. The technologist will use electrodes that are hooked by wires to a computer that record the electrical activity in your brain. An EEG test can take one to two hours. Your doctor will follow up with you regarding the results of your EEG test.


You can return to normal activities immediately after the test. However, if you were given a sleep medication, you will need someone to drive you home following the test.

Potential side effects

Some of the adhesive used to hold electrodes to your head may stick in your hair and can be easily washed out. If needle electrodes were used, you may have some soreness or bleeding for one to two days after the test. Although rare, you may experience some skin irritation or even ulceration.

Our Epilepsy Center offers comprehensive inpatient and outpatient epilepsy services designed to improve the lives of patients and their families dealing with epilepsy and related disorders.

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