Electroencephalogram (EEG)

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

During this painless test, small sensors are attached to the scalp to pick up the electrical signals produced by the brain.

These signals are recorded by a machine and are looked at by a doctor.
The EEG procedure is usually carried out by a highly trained specialist, called a clinical neurophysiologist, 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 injury and concussion
  • brain tumours
  • encephalitis (brain inflammation)
  • sleep disorders, such as sleep apnoea.

Preparing for an EEG

Your appointment letter will mention anything you need to do to prepare for the test.

Unless told otherwise, you can usually eat and drink beforehand and continue to take all your normal medication.

To help the sensors stick to your scalp more easily, you should make sure your hair is clean and dry before arriving for your appointment, and avoid using products such as hair gel and wax.

You might want to bring a hairbrush or comb with you, as your hair may be a bit messy when the test is finished. Some people bring a hat to cover their hair until they can wash it at home afterwards.

Types of EEG

  • Routine EEG
  • Sleep EEG or sleep-deprived EEG
  • Ambulatory EEG

Are there any risks or side effects?

The EEG procedure is painless, comfortable and generally very safe. No electricity is put into your body while it’s carried out. Apart from having messy hair and possibly feeling a bit tired, you normally will not experience any side effects.