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

BackgroundThe “Status Epilepticus Severity Score” (STESS) is the most important clinical score to predict in-hospital mortality of patients with status epilepticus (SE), but its prognostic relevance for long-term survival is unknown. This study therefore examined if STESS and its components retain their prognostic relevance beyond acute treatment.MethodsOne hundred twenty-five non-anoxic patients with SE were retrospectively identified in two hospitals between 2008 and 2014 (39.2 % refractory SE). Patients’ treatment, demographic data, date of death, aetiology of SE, and the components of the STESS (age, history of seizures, level of consciousness and worst seizure type) were determined based on the patients’ records.ResultsIn 94.4 % of patients, SE was treated successfully; in-hospital mortality rate was 12 %. The overall mortality was 42 % after median follow-up of 28.1 months. The survival plateaued after about 3 years, all patients with progressive brain diseases (n = 4) died within one year. In-hospital mortality correlated highly significantly with STESS, the optimal cut-off was 4. With respect to long-term outcome, STESS correlated significantly with overall mortality though with lower odds ratios. When looking only at patients that survived the acute phase of treatment, only the STESS components “level of consciousness” (at admission), “coma” as worst seizure type, and “age” reached a statistical significant association with mortality. In these patients, STESS with a cut-off of 4 was not significantly associated with survival/mortality. Aetiology of SE was insufficient to explain the weak association and the high mortality after discharge alone.ConclusionSTESS at onset of SE reliably assessed in-hospital mortality, and was indicative for overall survival. However, STESS did not allow correct estimation of mortality after discharge. The high mortality after discharge and high overall mortality of patients diagnosed with SE was not explained by progressive brain disorders alone. Further research is needed to understand the causes for high overall mortality after SE and putative prognostic factors.Electronic supplementary materialThe online version of this article (doi:10.1186/s12883-016-0730-0) contains supplementary material, which is available to authorized users.

The authors' contributions are given below. All meet the requirement for authorship. The manuscript has not been submitted elsewhere or is under consideration by another journal. Financial support: This study was supported by a grant of the Region of Southern Denmark to CPB (17/18517). This study adheres to the relevant ethical guidelines and was evaluated and approved by the local authorities as described in the Methods section of the manuscript.