A Guide to an Electroencephalogram Procedure


An electroencephalogram or EEG is a test that detects the electrical activity of your brain. It uses a few electrodes (metal strips) attached to your scalp to measure electrical activity. Your brain is the control centre of your body which has an extensive communication network. All this communication is done in the form of electrical impulses sent from one cell to the other. 

The computer connected to the electrodes gathers up these impulses and shows them in the form of waves.  

EEG is used primarily to detect and diagnose different brain abnormalities. One of the most common uses of EEG in the diagnosis and management of a disabling disease – epilepsy.  

In this article, we will learn some basic principles about EEG and its clinical use.  

Baburov, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons


EEG can be used as a rule-in or rule-out test for various diseases related to your brain. They are also useful in measuring brain activity in order to study brain activity in various conditions. Some of the common indications of getting an EEG test are: 

  • Seizures – such as epileptic seizures or other non-epileptic seizures  
  • To confirm the diagnosis of epilepsy and to confirm the type of epilepsy  
  • Assessment of frequency of seizures  
  • Brain tumours 
  • Encephalopathy 
  • Memory disorders  
  • Sleep problems i.e., insomnia  
  • Stroke  
  • Trauma or head injury  

Risks of the Procedure  

An electroencephalograph is considered a safe and painless test. You might have little to no discomfort during the process and while taking your electrodes off.  


EEGs are rather simples tests and require a few preparations only. Some of the precautions you should take care of are: 

  • Avoid the intake of caffeine and any other stimulants, e.g., tea, coffee, or energy drinks on the day of your test. These compounds can stimulate brain activity and alter the results of your test. 
  • You can take your medications unless instructed otherwise 
  • You would need to wash your hair thoroughly the night before and the day of the test in order to ensure that electrodes stick properly. Be sure to avoid using any kinds of conditioners, hair creams, or hair gels. These products can reduce the adhesion of electrodes and alter the results.  
  • Your doctor might ask you to have a sedative in certain cases.  


As mentioned above EEG would not feel uncomfortable. The electrodes, place on your scalp, are just placed to record the brain’s electrical impulses and not to transmit any sensations. The procedure will go as follows: 

  • Marking your head – the technician will measure and mark your scalp for the placement of electrodes. These marks are placed using a special marking pencil that won’t interfere with the test. Usually, a conducting lube or cream is put on these marks to enhance the conduction through the skin.  
  • Attaching electrodes to your scalp – the technician will attach the electrodes to your scalp using special adhesives. The electrodes are attached to computers through some wires and an amplifier. This can also be done by placing a head cap attached to electrodes 
  • The test takes around 60 minutes to complete – during the test you can relax in a comfortable position with your eyes closed.  
  • During the test, your technician may ask you to perform a few simple calculations, open and close your eyes, look at a picture, and breathe in and out a couple of times during the test. 
  • A video camera will record your body movements simultaneously to compare your movements with your brain activity.  
Image by Tim Sheerman-Case

Ambulatory EEGs 

Ambulatory EEGs (aEEGs), are a special form of EEG which allows for recording of your brain activity over the course of several days. This test increases the chances of learning your seizures in a better way. However, this test is in limited use and doesn’t allow you to video record your movements. Another downside of aEEGs is that it doesn’t help differentiate between epileptic and non-epileptic seizures due to lack of the video recording.  

Patient Recovery  

The technician will remove your electrodes from your scalp or the head cap. In most cases, no sedatives are administered and you can return to your normal routine without any side effects.  

If you were administered a sedative, it will take some time for the medication to ward off. In this case, you would need someone to accompany you back home safely. You should drink plenty of water and relax for the rest of the day. You will be able to get back to your normal routine by the next day.  


Doctors, especially neurologists, who have specialised in interpreting the EEGs will analyse your EEG recording along with your video recording and then send the results to your doctor or the doctor who ordered the EEG. Your physician might ask you to visit in order to discuss the results and findings with you.  

Normal results appear as a pattern of waves. Different waves show different stages of brain arousal and activity. For instance, the waves produced while sleeping is different from the waves produced while you’re actively solving a maths problem. A normal pattern of waves means that your brain is working fine and you don’t have any abnormalities.  

moep, Public domain, via Wikimedia Commons

Abnormal EEGs results may be due to certain brain problems: 

  • Epilepsy or other seizures disorders  
  • Abnormal bleeding or intracranial haemorrhage  
  • Recent or past head injury  
  • Any sleeping disorders 
  • Tumours of the brain, especially growing tumours which may compress other parts of the brain  
  • Persistent migraines 
  • Chronic drug use or abuse  

You should discuss your results in detail with your doctor in order to get treated better and avoid future complications. You can also take someone with you on your visit in order to remember the details your doctor will tell you.  

  1. Moeller J, et al. Electroencephalography (EEG) in the diagnosis of seizures and epilepsy. https://www.uptodate.com/contents/search. Accessed Feb. 12, 2018. 
  1. Neurological diagnostic tests and procedures fact sheet. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Neurological-Diagnostic-Tests-and-Procedures-Fact. Accessed Feb. 13, 2018. 
  1. Hirsch LJ, et al. Video and ambulatory EEG monitoring in the diagnosis of seizures and epilepsy. https://www.uptodate.com/contents/search. Accessed Feb. 12, 2018. 
  1. EEG. The Epilepsy Foundation. https://www.epilepsy.com/learn/diagnosis/eeg. Accessed Feb. 12, 2018. 
  1. Swanson JW (expert opinion). Mayo Clinic, Rochester, Minn. Feb. 27, 2018. 
  1. https://www.mayoclinic.org/tests-procedures/eeg/about/pac-20393875 

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