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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 -- Symptoms

A seizure originating in the temporal lobe of the brain may be preceded by an aura or warning symptom, such as: Abnormal sensations (which may include a rising or "funny" feeling under your breast bone or in the area of your stomach) Hallucinations (including sights, smells, tastes) Vivid deja vu (a sense of familiarity) or recalled memories or emotions A sudden, intense emotion not related to anything happening at the time During the seizure, a person may experience motor disturbances,...

Read the Understanding Temporal Lobe Seizure -- Symptoms 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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