Epileptiform abnormalities discovered on electroencephalographic screening of psychiatric inpatients.

The results of electroencephalographic screening of 3225 inpatients from a community general hospital psychiatric service were reviewed. When patients with a prior diagnosis of epilepsy were excluded, epileptiform abnormalities were discovered in 2.6% of patients. Patients younger than age 25 years and patients with a diagnostic impression of anorexia nervosa, recent barbiturate abuse, or nonpsychotic explosive behavior were significantly more likely to have epileptiform abnormalities. The use of certain therapeutic agents was associated with a significant excess of epileptiform abnormalities in patients aged 25 years and older. The most frequently encountered epileptiform abnormalities were photoconvulsive responses. Focal temporal epileptiform abnormalities were detected in only four patients without a prior diagnosis of epilepsy. The diagnosis of epilepsy on the basis of a primarily psychiatric presentation and the discovery of epileptiform abnormalities on electroencephalographic screening should be approached with caution.