Abstracts

Rationale: Inpatient video EEG telemetry monitoring is the gold standard to accurately diagnose epileptic versus non epileptic events and for the localization of epileptogenic areas in the assessment of patients for surgical treatment. This technique is expensive and requires specialized technical and human resource. Ambulatory EEG is a technique that allow to record EEG continuous activity when patients are at home without the necessity of admission to the hospital for prolonged video EEG monitoring Methods: This is a prospective cohort study performed in a Canadian teaching center in order to assess the yield and tolerability of ambulatory electroencephalogram. In a period of three years forty nine patients were included. The yield was assessed taking into account the question performed before and after the investigation. Results: Forty nine patients, aged 13-73 years, undergoing ambulatory electroencephalography (EEG) were prospectively recruited during a 36 months in Royal University Hospital, Saskatchewan. Our population consisted of fifteen males (30%) and thirty four females (70%).The age of onset of the events was 30.2 18.98 years with 7.42 10.36 years of evolution. Most of the patients had had previous routine EEG (98%) and 74% (37 EEGs) were normal. The most frequent reason (53% of the times) for ordered an ambulatory EEG was for the characterization of the spells (query non epileptic events), in 31% (15 patients) of the cases the ambulatory was order for the characterization of the spells with potential epileptic diagnosis. In 4 patients (8%) the ambulatory was order for work up in candidates for epilepsy surgery. Finally in 4% of patients (2) the indication of ambulatory was the characterization of the spells in patients with epilepsy (possible non epileptic events) and the quantification of spikes and seizures in two cases (4%). The minimum days with the ambulatory EEG was one day with a maximum of 3 days, the mean days of recording was 1.22 0.55 days. No complications were seen in the 49 included patients. The ambulatory EEG answered the clinical question in 70% (35) of cases. Of these, only in 22 (45%) of the patients was possible to recorded events, of these events 10 % (5) were seizures and the 90% were non epileptic. The most frequent reasons why the initial question was not answered were: the lack of recorded events (64 %) and the lack of epileptic activity in the recording (36%) Conclusions: In this study, we found that ambulatory electroencephalography has a high diagnostic yield (70%), this is comparable with our Video-EEG rate (80%). We believed that a careful selection of patients is the most important factor to have a high diagnostic yield. The main utility of the ambulatory EEG is the characterization of patients with non epileptic events, in patients where the diagnosis of epilepsy is not clear and in the quantification of spikes and seizure to improve the medical management of patients. The ambulatory EEG is a cost effective solution for increasing necessities of Video-EEG