Diagnosing Epilepsy: EEG's Limits

Topic Overview

Electroencephalography (EEG) is thought to be the most useful test in confirming a diagnosis of epilepsy, but it is not foolproof.

  • Some people with abnormal EEG results do not have epilepsy. This is not common.
  • About 50% of people with epilepsy will have normal results on their first EEG.1 If epilepsy is still suspected, a follow-up EEG may be done. This second test may be a sleep-deprived EEG, in which the test is done after you have been forced to stay awake for a longer period of time than usual. A sleep-deprived EEG can sometimes reveal abnormalities that did not show up on the regular EEG.
  • From 10% to 40% of people with epilepsy will have normal EEG results even after having several EEG tests done.1

Video and EEG monitoring records seizures on videotape and computer so that the doctor can see what happens just before, during, and right after a seizure occurs. The video records what you are doing while the EEG records the electrical activity occurring in your brain. This type of monitoring may be used:

  • When your medical history and repeated EEGs are not enough to figure out what kinds of seizures you are having. Simultaneous video and EEG recording can provide important clues about what type of seizure you have had.
  • To evaluate your condition before you have epilepsy surgery.
  • To diagnose seizures that are not from epilepsy, such as psychogenic seizures.

Related Information

References

Citations

  1. Bazil CW, Pedley TA (2010). Epilepsy. In LP Rowland, TA Pedley, eds., Merritt’s Neurology, 12th ed., pp. 927–948. Philadelphia: Lippincott Williams and Wilkins.

Credits

By Healthwise Staff
Primary Medical Reviewer John Pope, MD - Pediatrics
Specialist Medical Reviewer Steven C. Schachter, MD - Neurology
Last Revised August 28, 2013

Last Revised: August 28, 2013

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.

© 1995-2013 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.

First Nurse

First Nurse

Call First Nurse 24 Hours a Day for free health care advice, resources and referrals!

Ames: 515-239-6877
In Iowa: 800-524-6877 

Search health information online in our Mulimedia Health Library.

High Quality Care

Guardian of Excellence

Mary Greeley consistently delivers high quality patient care.

  • 2013 Guardian of Excellence Award for Clinical Quality
  • Grade 'A' Patient Safety from the Leapfrog Group
  • 2013 Top Performer on Key Quality Measures ranking from The Joint Commission
  • Highest percentage bonus of any Iowa hospital in Medicare's quality incentive program

Mary Greeley on Facebook

Like us on Facebook

Patient Privacy | Net Learning for Employees | MGMC PACS for Physicians
Emergency Preparedness

1111 Duff Avenue Ames, IA 50010 - 515-239-2011 - yourhealth.mgmc@mgmc.com

©2014 Mary Greeley Medical Center - All rights reserved.