What is Electroencephalography (EEG)?

Did you know that your brain cells communicate with each other through electricity? An electroencephalogram (EEG) evaluates your brain activity by recording the electrical signals that your brain cells, or neurons, send to each other. 

Hence, it can be used to detect any abnormalities in your brain waves, which can help to diagnose and monitor many brain conditions.

When might you need an EEG?

An EEG is used to detect problems in your brain activity, which may be associated with certain brain disorders. These disorders include:

  • Epilepsy — when one has epilepsy, seizures lead to abnormal impulses and will appear as rapid spikes on the EEG.
  • Trauma or head injury leading to brain lesions or damage — which will appear as abnormally slow waves on the EEG.
  • Brain Tumor
  • Neuroinfections such as encephalitis
  • Memory problems such as dementia
  • Stroke
  • Sleep disorders such as narcolepsy
  • Certain neurodegenerative disorders

An EEG may also be used to guide certain brain surgery and monitor blood flow in your brain. When someone is in a coma, an EEG may also help to measure the brain activity or to confirm brain death.

How to prepare for an EEG?

Your doctor or nurse should inform you on things that you need to do before the EEG procedure. Some preparation steps include:

  • You may eat and drink normally before the EEG procedure, but do avoid anything with caffeine as it may interfere with the results
  • Take your usual medications as prescribed but do let your doctor know which medications or supplements you are taking
  • Wash your hair the night before your EEG procedure to keep your hair clean and dry. Avoid using conditioners, hair gels, or hair spray as oily hair may make it harder for the electrodes to adhere to your scalp during the EEG.

How is an EEG performed?

During an EEG procedure, a technician attaches small flat metal discs called electrodes on your scalp. Sometimes, you may be asked to wear an elastic cap attached with the electrodes instead. These electrodes detect the electrical activity in your brain when your neurons transmit electrical signals to each other. They then transmit these data into a machine or a computer that measures and record the data.

An EEG procedure usually takes around 20 to 40 minutes, but can last as long as an hour. You may relax in a comfortable position and close your eyes during the EEG. The technician may present you with various stimuli so as to measure and activate your brain wave activities. For example, you may be asked to breathe rapidly for a few minutes, perform simple calculations or be exposed to a bright flashing light. If you are being evaluated for a sleep disorder, you may be asked to sleep during the EEG.

What happens after an EEG?

After your EEG, the technician removes the electrodes and washes off the glue or adhesive that was used to attach the electrodes on your scalp.

You can usually go home and resume your normal activities on the same day after the EEG test. You may feel tired after the procedure and can arrange for someone to fetch you home if needed.

A neurologist, a doctor who specialises in brain issues, will analyse your results. They will then discuss the results with you a few days or a week later.

Are there any risks involved in EEG?

Typically, EEG is a safe and painless procedure. The electrodes only measure the electrical signals produced from your brain and do not emit any electricity into your body. There is no risk of an electric shock.

Occasionally, there is a small risk of an EEG leading to seizures if you have epilepsy. If it happens that you have a seizure during the procedure, you will be closely monitored by your healthcare provider, who will be there to help and treat it immediately.

Should you have further concerns, discuss them with your doctor before you go for your EEG test.