Medical Q&As

EEG abnormal - proof of epilepsy?

Can the EEG determine that a person has epilepsy or not? Is it a definitive way of proving epilepsy?

The EEG (electroencephalogram) is a very useful tool in the investigation of seizures. However, it has its limitations. It is estimated that the EEG can be abnormal in 5% of people who donít have epilepsy and it can also be normal in 20% of people who do have epilepsy. That latter statistic includes cases where the person was observed having a grand mal fit. Sometimes the test may need to be performed over an extended period of time because the electrical abnormality may be intermittent and consequently may not be picked up during the more usual shorter duration test. In summary a normal EEG does not prove or disprove a diagnosis of epilepsy.