Vital Prognosis and Causes of Death in Adults with Encephalitis

Background: Encephalitis in adults is associated with inpatient mortality in approximately 10% of patients, but the cause and timing of death are unknown. Methods: We conducted a retrospective study across two tertiary healthcare systems in Texas and Maryland between 2002 and 2023. Adults hospitalized with all-cause encephalitis were included. Our primary outcome was inpatient death. We investigated the association of various factors with mortality. The causes of death were categorized into three groups: category 1, where encephalitis was the direct cause of death; category 2, the underlying cause contributing to mortality but not directly responsible; or category 3, unrelated to the cause of death, acting independently. We subsequently examined the timing of death from initial presentation. Results: A total of 629 adults with encephalitis were enrolled, 45 (7.15%) of whom died inpatient. In the cohort of 243 patients admitted to the intensive care unit (ICU), 41 deaths occurred, corresponding to a mortality rate of 16.87%. Logistic regression analysis identified body mass index (BMI), presence of comorbidities [Charlson Comorbidity Index (CCI] score], immunocompromise, memory deficits, elevated Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation II (APACHE II) scores, altered mental status [Glasgow Coma Scale (GCS) score < 8], thrombocytopenia, hypoglycorrhachia, arrythmias, and ICU admission as significant predictors of mortality (p < 0.001 after Bonferroni correction). When restricting the analysis to patients admitted to the ICU, CCI score, psychiatric manifestations, memory deficits, and GCS retained statistical significance (p < 0.05). Encephalitis was the direct cause of death (category I) in 66% of cases with a median time to death of 12 days, the underlying cause (category 2) in 27% with a median of 14 days, and unrelated (category 3) in 7% within a median of 43 days. As for timing of death, 22% and 53% died in the first 7 and 14 days, respectively. Conclusion: All-cause encephalitis is associated with a low mortality rate of 7.15%, but higher among patients requiring ICU admission (16.87%). Among fatal cases, encephalitis was the direct or underlying cause of death in more than 90% of cases, with the majority of deaths occurring in the first 2 weeks.