Diagnostic Performance of the Electroencephalogram in the Elderly Manifesting With Episodes of Unresponsiveness

Abstract

This study aimed to determine diagnostic performance of the EEG in diagnosing seizures and to ascertain risk factors associated with seizures in the elderly presenting with episodes of unresponsiveness compared with younger patients. This is a cross-sectional study. Only EEGs requested with indication of transient unresponsiveness (TUR) were included. Patients were divided into 2 groups, younger (aged 18-49 years) and elderly (aged >60 years). The EEG was an index test. Reference standard, independently verified by 2 board-certified neurologists, was a clinical diagnosis of presence or absence of epilepsy/probable seizures. Univariate and multivariate analyses were performed to ascertain associated risk factors for epilepsy/probable seizures. Among 2187 total EEG recordings, 244 (11.16%) recordings were requested with indication of TUR. A total of 156 patients (50 younger and 106 elderly) were recruited for analysis. Prevalence of epilepsy/probable seizures in patients with TUR was 26.9%. Prevalence of interictal epileptiform discharges was 16% in the younger and 12.3% in the elderly. Overall diagnostic performance was poorer in the elderly. Associated risk factors for having seizures were presence of intermittent slow waves in the younger and presence of positive motor signs as well as presence of nonepileptiform abnormalities in the elderly. Prevalence of seizures and interictal epileptiform discharges was low in the elderly who manifests with TUR. Overall diagnostic performance of the EEG in diagnosing seizures was poorer in the elderly mainly due to low sensitivity. When we encounter patients with TUR, thorough and detailed history is still a mainstay of a diagnosis of seizures, not the EEG results.