The Impact of 24-Hour Ambulatory EEG in the Clinical Approach to Patients with Suspected Epilepsy

Background: The Electroencephalogram (EEG) is the gold standard technique to assess the epileptogenic cortical activity. However, due to the neurophysiology of the bioelectrical signal and the short duration of the routine EEG (rEEG) and sleepdeprived EEG (sEEG) registers, the sensitivity is low. The 24-hour Ambulatory EEG (aEEG), being a prolonged recording, could significantly improve the diagnostic capability, in an attractive cost-effective way. In this study, we analyzed the aEEG of patients with suspected epilepsy, addressing its specificity and sensitivity for the clinical diagnosis of epilepsy. Additionally, we endeavour to ascertain any other possible predictive factors of diagnosis. Methods and Findings: Retrospective observational study enrolling consecutive patients with suspected epilepsy who underwent aEEG between May 2011 and May 2018 at the Neurophysiology Laboratory from Local Health Unit of Matosinhos – Pedro Hispano Hospital. A sample of 83 individuals was obtained, with a mean age of 44.5 years (79 adults and 4 paediatric). aEEG showed a good diagnostic capacity for the clinical diagnosis of epilepsy with a specificity of 97% and sensitivity of 68%. The rate of false-negatives and false-positives was 7% and 5%, respectively. It’s expected that patients with an indication of syncope or loss of consciousness will not have epilepsy diagnosis. Conclusion: The aEEG can be a useful tool to assess patients with suspected epilepsy and unremarkable routine and sleep-deprived EEGs, or in cases of suspected non-epileptic seizures, particularly to exclude the epilepsy diagnosis given its high specificity. This approach can lessen the time required to identify the diagnosis.