The electroencephalogram in patients with epilepsy.

The EEG is useful in evaluating seizure disorders by establishing or confirming the diagnosis of a seizure disorder, determining the type and focus of origin of the seizure, and helping make the distinction between an epileptic attack and a nonepileptic condition. The EEG also may show other abnormalities, such as focal slowing, that give a clue about the underlying disease process. A negative EEG does not exclude the diagnosis of epilepsy. Activating procedures such as hyperventilation, photic stimulation, and recording during sleep may help bring out epileptiform activity. Occasionally, repeated or more prolonged recordings are necessary to demonstrate the epileptiform abnormalities. On the other hand, epileptiform-like activity may be present in the EEG without being associated with a seizure disorder. As the diagnosis of epilepsy is a clinical one, the EEG, like any test, should not be used independently in making the diagnosis of epilepsy but should be interpreted in the context of the whole clinical setting.