Ambulatory cassette EEG in clinical practice.

We reviewed ambulatory cassette EEG (A/EEG) records of 500 patients. Epileptiform abnormalities, seizures, or both were detected in 87 patients (17.4%), including 22 who were not taking anticonvulsant drugs. Epileptiform abnormalities were found in 1.5% of patients with syncope and in none without a clear history of episodic complaints. Abnormalities were found in 5.1% of patients referred by nonneurologic physicians. Some clinical seizures were not accompanied by A/EEG change and some episodes were not seizures, despite detection of epileptiform abnormalities.