Diagnostic yield of ambulatory EEGs in the elderly

Abstract

Objective: The diagnostic yield of ambulatory EEG in the elderly is not known. We sought to determine diagnostic yield and identify factors predicting diagnostic findings in this elderly population.

Methods: We reviewed 156 consecutive 24-72h ambulatory EEGs performed on patients aged 60 or older.

Results: Of the 156 studies, 58 studies (37%) revealed potentially diagnostic findings: either epileptiform discharges, an epileptic seizure, or a typical nonepileptic event. Focal slowing on routine EEG predicted epileptiform abnormalities on ambulatory EEG with an odds ratio of 4.0 (95% CI 1.7-9.7, p=0.002). Age, the presence of a focal lesion on MRI, and duration of ambulatory EEG failed to predict epileptiform abnormalities on ambulatory EEG. Duration of ambulatory EEG predicted capture of a typical nonepileptic event with an odds ratio of 2.7 (95% CI 1.3-5.7, p=0.009) for every additional day of study duration.

Conclusions: Focal slowing on routine EEGs may warrant an ambulatory EEG in the setting of diagnostic uncertainty. Longer ambulatory EEGs have a higher yield in capturing patients' typical non-epileptic events, and should be considered in patients where nonepileptic events are a likely diagnostic possibility.

Significance: These findings offer guidance in the use of ambulatory EEGs in the elderly.

Keywords: Diagnosis; EEG monitoring; Epilepsy; Epileptiform discharges; Geriatric; Seizure.