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.
References
Citations
- 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 | Susan C. Kim, MD - Pediatrics |
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| Specialist Medical Reviewer | Steven C. Schachter, MD - Neurology |
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| Last Revised | August 26, 2011 |
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Last Revised:
August 26, 2011
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.
