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Northland DHB Neurology

Public Service, Neurology

Electroencephalogram (EEG)

An EEG is a test to detect abnormalities in the electrical activity of the brain.
Cells in the brain communicate with each other via electrical activity. In an EEG, electrodes are placed on the scalp over multiple areas of the brain to detect and record the patterns of electrical activity.
An EEG technician performs the test. You will be asked to lie on your back on a table or in a reclining chair. The technician will apply between 16 and 25 flat metal discs (electrodes) in different positions on your scalp. The discs are held in place with a sticky paste. The electrodes are connected to a recording machine which converts the electrical signals into a series of wavy lines that are recorded on a computer. You will need to lie still with your eyes closed because any movement can alter the results. Although having electrodes pasted onto your skin may feel strange, they only record activity and do not produce any sensation. There are no risks from this test.

You should avoid all foods containing caffeine for 8 hours before the test.
Sometimes it is necessary to sleep during the test, so you may be asked to reduce your sleep time the night before, and you may be given a mild sedative.

EEGs are used to help diagnose the presence and type of epilepsy (fits/seizures), to look for causes of confusion and to assess various diseases that affect the brain.

They are also used to evaluate sleep disorders and to investigate periods of unconsciousness.

The test will need to be interpreted afterwards, so the results will not be available at the time of the test but will be sent to the referring doctor or discussed with you at a subsequent clinic.

This page was last updated at 2:14PM on May 10, 2021.