Abstracts

Rationale: The electroencephalogram (EEG) is underused or not available in the Emergency Department (ED). Criteria for EEG in the ED have not been established. This study sought to determine whether EEG performed within 30 minutes of referral by an ED physician helps establish diagnosis and/or changes management, and which clinical features/diagnoses are useful in selecting patients for ED EEG. The reliability of an abbreviated 5 min EEG was explored.Methods: Single-center prospective cohort intervention study one day/week, of sequentially referred adult patients presenting with clinical seizure activity or altered mental status (AMS). Standard EEGs (20 minute 16-channel) were performed by an EEG technician using a commercially available cap. EEGs were graded for quality and interpreted by an epileptologist, immediately reported to the ED physician and a utility survey completed. The inter-EEG reliability of quality and interpretation of the 20 min EEG vs. a pre-specified 5 min segment of each EEG was measured using the Kappa Coefficient.Results: Over 1 year, 82 patients (mean age 58.1 2.0 years) underwent ED EEG. Tonic clonic seizure activity had occurred in 33%. Mean time for EEG setup was 13.1 6.2 min. Time from start of EEG setup to arrival of the epileptologist was 55.0 25.7 min. The EEG result was reported to ED staff in 4.3 2.7 min. EEGs were categorized as normal (39.0%), showing diffuse abnormalities ( epileptiform discharges)((31.7%), focal abnormalities ( epileptiform discharges)(17.1%), electrographic seizures (1.2%) or uninterpretable (11.0%). EEG assisted the diagnosis in 51%, changed ED management in 4% and would be ordered again if EEG was available in 46%. Positive utility of EEG was significantly associated with etiology of AMS (toxicologic, psychiatric and endocrine/metabolic causes vs. other causes) (P=0.001) and sudden onset of AMS (P=0.04). Independent predictors of whether ED EEG would be ordered if available were witnessed seizure activity (P=0.01), absent prior head trauma (P=0.001) and survey respondent being a physician assistant (vs. MD) (p=0.008). The 5 min EEG (vs. 20 min EEG) presented substantial agreements on waveform shape/amplitude (Kappa=0.78), presence of artifact (Kappa=0.75) and on interpretation categories (diffuse or focal abnormalities, normal, seizure and uninterpretable) (all Kappa levels > 0.70).Conclusions: Rapid availability of standard 20 min full-montage EEG in the ED is feasible and helps establish a diagnosis in about half of patients with AMS, but rarely changes management. While witnessed seizure activity and absence of head trauma are most likely to prompt a request for ED EEG, non-neurologic causes of AMS and sudden onset are more likely to be associated with positive benefit. Our results suggest that an abbreviated 5 min full-montage EEG presents adequate reliability which may improve acceptance and use of EEG in the ED.