Objective:To determine annual incidence, etiology, severity, and short-and long-term mortality of first-time, nonanoxic status epilepticus (SE) in adults in a population-based retrospective cohort study. Methods: We systematically identified all episodes of SE in the year 2014 on the island of Funen. Patients with SE due to anoxia, patients with recurrent SE, and patients <18 years old were excluded. Nonconvulsive SE in coma was diagnosed according to the Salzburg criteria. Etiology, semiology, modified Rankin Scale (mRS) at discharge, survival, and the Status Epilepticus Severity Score were retrospectively determined from patients' records. Patients with first-time nonanoxic SE diagnosed during 2008-2013 from our database (n = 88) were used to confirm the results. Results: The incidence of first-time, nonanoxic SE in 2014 was 10.7/100 000 persons at risk (n = 41). Median Status Epilepticus Severity Score was 3; in-hospital mortality was 24.4%. After median follow-up of 39.2 months, 53.7% of the patients had died (age-and gender-adjusted mortality rate of 5.2/100 000). Mortality stabilized 2 years after diagnosis. Analysis of the cohort from 2008-2013 confirmed stabilization of survival after 2-3 years and the high mortality 2 years after discharge. When correcting for acute symptomatic causes, the in-hospital mortality was 16.7% and 46.7% at follow-up (crude mortality rate of nonhypoxic and nonacute symptomatic SE = 3.5/100 000). An exploratory multivariate analysis of pooled patients with SE from 2008 to 2014 revealed mRS ≥ 2 at discharge as a prognostic factor for long-term mortality. Significance: In this cohort, the overall mortality of first-time nonhypoxic SE was >50%. Mortality of SE after discharge was substantially higher than in-house mortality and stabilized after 2 years. The degree of disability as indicated by mRS at discharge was associated with long-term mortality after discharge. K E Y W O R D Slong-term outcome, long-term survival, population-based, prognosis, status epilepticus, STESS

Purpose: Rapid and correct diagnosis of nonconvulsive status epilepticus (NCSE) is crucial for optimal treatment. However, electroencephalographic diagnosis can be challenging. Salzburg Consensus Criteria (SCC) have been proposed to facilitate correct diagnosis, but their validity needs to be further established. Methods: We retrospectively reanalyzed the first EEG in adult patients (n = 284) referred under the suspicion of NCSE at our institution in 2014. Nonconvulsive status epilepticus or possible NCSE was diagnosed according to the SCC by an examiner specifically trained in SCC and was compared with the original diagnosis made by an expert EEG examiner, which in this context served as the reference standard, to assess the validity of the criteria. Furthermore, the clinical outcome for patients not diagnosed using SCC (false-negatives) was examined. Results: Nonconvulsive status epilepticus or possible NCSE was diagnosed in 40 patients by the inexperienced reader using the SCC, blinded to other clinical data, and in 47 patients by the experienced reader, not blinded to the clinical data, who did not use SCC. There were eight false-negatives, one false-positive, 39 true-positives, and 236 true-negatives. Concordance between SCC and the reference standard was high (k = 0.88 [95% confidence interval, 0.80 to 0.96]). Four of the eight false-negatives suffered from anoxic encephalopathy. The remainder had a history of epilepsy and returned to preictal functional state. Conclusions: The SCC for NCSE implemented by an inexperienced EEG reader, blinded to all other data, yielded results highly concordant with the evaluation of EEG by an experienced reader. False-negative diagnoses were associated with postictal states or anoxic encephalopathy.