Diagnostic yield of ambulatory EEGs in the elderly

- 37% of studies reveal diagnostic findings and 21% result in change in management.
- Focal slowing on routine EEG predicts epileptiform abnormalities on ambulatory EEG.
- Ambulatory EEG duration correlates with capture of typical nonepileptic events.

ObjectiveThe 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.MethodsWe reviewed 156 consecutive 24-72 h ambulatory EEGs performed on patients aged 60 or older.ResultsOf 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.ConclusionsFocal 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.SignificanceThese findings offer guidance in the use of ambulatory EEGs in the elderly.