Electroencephalograph (EEG)
What is an EEG?
EEG stands for electroencephalograph. The brain produces tiny electrical signals that come from the brain cells and nerves that send messages to each other. These electrical signals can be detected and recorded by the EEG machine. The EEG test is painless and harmless because the machine records electrical signals coming from the brain - it does not put any electricity into the brain or body.
What is done.
The EEG technician will attach several small patches (electrodes) to the scalp. Wires from the electrodes are connected to the EEG machine. The machine detects and amplifies the electrical signals and records them onto paper or a computer. The test takes approximately 30 minutes. The electrodes are usually removed at the end of the test.
Why is it done?
The test is used to look at the patterns of electrical activity in the brain at the time the test is done. If somebody is having a seizure at the time the test is done, this will produce a specific pattern of abnormal electrical activity. If the seizure occurred in the past, sometimes the pattern will be normal. Sometimes the electrical pattern remains abnormal for a while after the seizure and shows where in the brain the seizure began.
Some people
with certain types of epilepsy have abnormal electrical patterns all
the time, not just when they have seizures. For example, children with
‘absence seizures’ often have a characteristic EEG pattern that helps
identify the type of epilepsy. A small number of people have some
abnormal patterns in the EEG but have never suffered seizures, and
never had epilepsy.
So, if someone has symptoms that are thought to be due to seizures, an abnormal EEG generally indicates that the person has suffered a seizure. This does not mean that the person has epilepsy as seizures can occur for many reasons. However, if the EEG is normal the person may still need more tests to rule out epilepsy as a possible cause.
The EEG will be reviewed by a neurologist and the results usually available within a short period of time.
What are the risks?
There are minimal risks associated with this test. Please discuss these issues with the medical and nursing staff who are caring for the patient and of course, if you have any questions or concerns, please ask the ICU nurses and doctors.
EEG Version 1 April 2006 (Dr L Cole Intensive Care Specialist) First posted July 2006, revised July 2009
The information contained on this page is general in nature and therefore cannot reflect individual patient variation. In addition it reflects Australian intensive care practice which may differ from other countries. It is meant as a back up to specific information which will be discussed with you by the Doctors and Nurses caring for your loved one. ICCMU attests to the accuracy of the information contained here BUT takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.
