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Epilepsy Health Center

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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:

Recommended Related to Epilepsy

Understanding Temporal Lobe Seizure -- the Basics

Temporal lobe, or psychomotor, seizures are caused by abnormal electrical activity in an area of the brain known as the temporal lobe, which sits just above your ear. This abnormal activity results in temporary changes in movement, sensation, or autonomic function (such as heart rate and salivation). A person experiencing a seizure may remain alert (simple seizure) or lose consciousness (complex seizure). These seizures may be brought on by any number of factors, from head trauma to high...

Read the Understanding Temporal Lobe Seizure -- the Basics article > >

  • 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.

    WebMD Medical Reference from Healthwise

    Last Updated: March 12, 2014
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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    Diagnosing Epilepsy: EEG's Limits Topics

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