An electroencephalogram (EEG) is a recording of brain activity.

During the test, small sensors are attached to the scalp to pick up the electrical signals produced when brain cells send messages to each other.

These signals are recorded by a machine and are looked at by a doctor later to see if they’re unusual.

The EEG procedure is usually carried out by a highly trained specialist called a clinical neuro physiologist during a short visit to hospital.

When an EEG is used

An EEG can be used to help diagnose and monitor a number of conditions affecting the brain.

It may help identify the cause of certain symptoms – such as seizures (fits) or memory problems – or find out more about a condition you’ve already been diagnosed with.

The main use of an EEG is to detect and investigate epilepsy, a condition that causes repeated seizures. An EEG will help your doctor identify the type of epilepsy you have, what may be triggering your seizures, and how best to treat you.

Less often, an EEG may be used to investigate other problems, such as dementia, head injuries, brain tumors, encephalitis (brain inflammation) and sleep disorders, such as obstructive sleep apnoea.