Diagnostic yield of electroencephalography in a general inpatient population

Abstract

Objective: To determine the frequency and clinical predictors of seizures and markers of epileptiform activity in a non-critically ill general inpatient population.

Patients and methods: We performed a retrospective cohort study of patients 18 years and older who underwent inpatient electroencephalography (EEG) between January 1, 2005, and December 31, 2010, for an indication of spells or altered mental status. The EEGs and reports were reviewed for ictal activity, interictal epileptiform abnormalities, and nonepileptiform abnormalities. Demographic and clinical data were gathered from the electronic medical record to determine seizure predictors.

Results: Of 2235 patients screened, 1048 met the inclusion criteria, of which 825 (78.7%) had an abnormal EEG finding. Seizures occurred in 78 of 1048 patients (7.4%), and interictal epileptiform discharges were noted in 194 of 1048 patients (18.5%). An intracranial mass and spells as the indication for the EEG were independently associated with the group of patients experiencing seizures in a multivariate logistic regression model (adjusted for age, sex, EEG indication, intracranial mass, stroke, and history of epilepsy). Ninety-seven percent of patients (69 of 71) experienced their first seizure within 24 hours of monitoring, and the presence of seizures was associated with a lower likelihood of being discharged (odds ratio, 0.45; 95% CI, 0.27-0.76).

Conclusion: Seizures occurred at a high frequency in hospitalized patients with spells and altered mental status. The EEG may be an underused investigative tool in the hospital with the potential to identify treatable causes of these common disorders.