Electroencephalogram (EEG) | Diagnosing epilepsy | About epilepsy

Electroencephalogram (EEG)

An EEG or electroencephalogram records the electrical activity in the brain.

It is a non invasive, painless procedure where electrodes, about the size of shirt buttons, are placed on the head and the signals are recorded by a computer. It usually takes place in a hospital or clinic.

The results of the EEG only give information about the electrical activity of the brain during the period of recording, it does not prove diagnosis of epilepsy.

Many people with epilepsy will have a normal trace. Only if specific patterns or characteristics of epilepsy are seen during the routine recording, is the EEG of value.

There are lots of different types of EEG testing:

Routine EEG

A routine EEG can be useful for anyone with a diagnosis, or suspected diagnosis of epilepsy. A short recording (up to 45 minutes) is taken whilst the person is awake.

During a routine EEG activation procedures are often performed which are used to obtain more information which cannot always be seen on an EEG whilst just sitting quietly. These activation procedures can include; deep breathing, photic stimulation (where a flashing light is watched at different flash rates), exercise, sleep deprivation and drug reduction.

Ambulatory EEG

Once the electrodes are in place, the person may move around freely during an ambulatory EEG. The information that the electrodes is recording is stored on a small recorder and downloaded on to a computer at the end.

This type of EEG lets the person sleep in normal conditions, and allows day to day activities to continue. Sometimes a portable video camera can be used with the ambulatory EEG.

The recording may be performed for up to a week; however 24 to 48 hours are more usual.


Our dedicated Helpline can provide further information about EEGs. For a private, confidential chat, call us on 01342 831342 or email This email address is being protected from spambots. You need JavaScript enabled to view it..

Helpline: 01342 831342 (Mon-Fri, 9am-3pm)

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