Authored by Revere Health

How EEGs are Used to Diagnose Neurological Disorders

June 6, 2017 | NeurologySleep Medicine

Your brain cells communicate via electrical impulses, even while you sleep. Interruptions to these impulses can cause several problems in the brain. In order to diagnose the condition caused by these interruptions, your doctor will perform a test that detects electrical activity in the brain. This test is called an electroencephalogram, or an EEG.


How It’s Done


During an EEG, electrodes made up of small discs and thin wires are attached to your scalp. These electrodes are able to detect tiny electrical charges that result from brain cell activity—these charges are amplified and projected as a graph on a computer screen or piece of paper. Your doctor will typically evaluate about 100 pages or computer screens of brain activity, looking for basic waveform, bursts of energy and responses to stimuli like flashing lights.


Why It’s Done


EEGs are used to evaluate several different types of brain disorders. These include:


EEGs may also be used to confirm brain death in someone in a persistent coma, or to help monitor blood flow in the brain during surgery.


Risks and Interfering Factors


The EEG is considered safe and has been used for many years, and it causes no noticeable discomfort. There’s no risk of electrical shock. An EEG can cause seizures in people with seizure disorders, but in some cases of epilepsy, a seizure is intentionally triggered. If there are any other risks in your individual case, your doctor will discuss these with you.


A few factors or prior conditions can interfere with EEG readings, however. These factors include:

  • Low blood sugar (hypoglycemia) caused by fasting
  • Body or eye movements during the test (rarely an interfering factor)
  • Lights, particularly bright or flashing ones
  • Certain medications, including sedatives
  • Drinks containing caffeine
  • Oily hair or hair spray in hair


Preparation, Expectations and Results


Preparing for an EEG may require a few different steps, which can include:

  • Initial doctor visit: Your doctor will explain the procedure to you and you can ask any questions you may have. You’ll also need to inform your doctor of any medications or supplements you’re taking. • They may direct you to stop taking certain medications.
  • Signing a consent form.
  • Washing your hair the night before the test (do not use any conditioners, creams, gels or sprays)
  • Abstaining from eating and drinking anything that contains caffeine 8 to 12 hours before the test.
  • Not fasting the night before or the day of the procedure (this can lower blood sugar levels and influence results)


If your doctor gives you directions about reducing sleep the night before the test, follow them. During the test itself, a few things to expect include:

  • Your scalp will be measured and marked for the place where electrodes will be attached. (This may involve a scrub with a gritty cream to improve recording quality)
  • Flat discs (electrodes) will be attached to your scalp using an adhesive.
  • You will relax in a comfortable position, with your eyes closed.
  • Video is often recorded during the test as the EEG simultaneously records your brain waves. (Your doctor can use the combination to help diagnose any conditions you may have)


From here, a specialist will interpret the results send them back to the doctor who ordered the EEG (if that’s not the same doctor who administered it). Your doctor may schedule an appointment to discuss the results. In these cases, try to bring along a friend or loved one—EEG results can be detailed, and absorbing all the information you’re given can be tough. Write down any questions you may have, and don’t be afraid to ask them.


Our neurologists are trained specialists and work with your primary care physicians to develop a treatment plan personalized for you. We have access to the latest in imaging technology and our specialists are up to date on the most recent treatment options.




“Electroencephalogram (EEG).” Johns Hopkins Medicine.,P07655/

“EEG (electroencephalogram).” The Mayo Clinic.


The Live Better Team

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This information is not intended to replace the advice of a medical professional. You should always consult your doctor before making decisions about your health.