Ambulatory cassette electroencephalography of psychiatric patients.

Indications and results of ambulatory cassette electroencephalography obtained on 133 hospitalized psychiatric patients were reviewed. Interictal epileptiform abnormalities were detected in 15 patients (11%), of whom six had an established diagnosis of epilepsy. Actual seizures were recorded in two patients, of whom one had an established diagnosis of epilepsy. Subclinical seizure activity was detected in only one patient, who also experienced overt seizures. Routine screening of psychiatric patients with ambulatory cassette electroencephalography does not seem to be justified, although the test can provide useful adjunctive evidence to support the diagnosis of epilepsy and clarify the nature of suspicious clinical episodes in selected patients.