Cost of waiting: association of EEG delay and poor functional outcome in adult status epilepticus

Abstract

Background Status epilepticus (SE) is associated with substantial mortality and morbidity that increase with seizure duration. Prompt diagnosis is essential, but access to electroencephalography (EEG) is often limited outside regular working hours. We examined whether EEG delay due to prolonged waiting times for EEG is associated with worse outcomes. Methods This retrospective cohort study comprised adults (≥18 years; n=163) with first-time, non-anoxic, EEG-verified non-convulsive SE treated at Odense University Hospital, Denmark (2008–2017). EEG delay was defined as the time from last antiseizure treatment or clinical suspicion of SE to EEG confirmation. Outcomes were new neurological deficit at discharge and 2-year all-cause mortality. External validation used two retrospective German cohorts (n=906) differing in weekend EEG availability. Results Median EEG delay was 11.7 hours (IQR 3.5–22.6) and correlated with SE duration (r=0.2, p<0.01). Longer delay was associated with new neurological deficits at discharge (p<0.001 across delay groups; ρ=0.152, p=0.03) and higher long-term mortality (log-rank p=0.007), driven mainly by delays>22.6 hours. Multivariable analyses for 1 year mortality adjusting for factors including aetiology and age supported an independent association between delay and higher mortality. Delays were longer for Friday/Saturday admissions when next-day EEG was unavailable, with lower survival. In validation, lack of weekend EEG access showed etiology-dependent weekend-weekday mortality differences (eg, +18.8% in remote symptomatic SE; p=0.01) not seen in centres with weekend EEG availability. Conclusion In this cohort, prolonged waiting times for EEG for the diagnosis of SE were associated with worse neurological outcomes at discharge and higher mortality. Improving timely EEG access, including weekends, may be a modifiable system-level target to improve SE outcomes.