Clinical Epidemiology, Risk Factors, and Outcomes of Encephalitis in Older Adults

Encephalitis is associated with significant morbidity and mortality, with unknown etiologies in the majority of patients. Large prognostic studies evaluating elderly patients are currently lacking.

We performed a retrospective cohort of encephalitis cases in 19 hospitals from New Orleans, Louisiana, and Houston, Texas, between the years 2000 and 2017.

A total of 340 adult (aged ≥17 years) patients with confirmed encephalitis were enrolled, and 194 (57%) had unknown etiologies. A cerebrospinal fluid polymerase chain reaction (PCR) for herpes simplex virus (HSV) and varicella zoster virus was done in 237 (69%) and 82 (24%) patients, respectively. Furthermore, an arboviral serology was done in 169 (49%) patients and measurements of anti-N-methyl-D-aspartate receptor antibodies were taken in 49 (14%) patients. A total of 172 out of 323 patients (53%) had adverse clinical outcomes (ACOs) at discharge. Older individuals (>65 years of age) had a lower prevalence of human immunodeficiency virus, had a higher number of comorbidities, were less likely to receive adjuvant steroids, were more likely to have a positive arbovirus serology, were more likely to have a positive HSV PCR, were more likely to have abnormal computerized tomography findings, and were more likely to have to have an ACO (all P values < .05). Prognostic factors independently associated with an ACO were age ≥65, fever, Glasgow Coma Scale (GCS) score <13, and seizures (all P values ≤0.01).

Encephalitis in adults remain with unknown etiologies and adverse clinical outcomes in the majority of patients. Independent prognostic factors include age ≥65 years, fever, GCS score <13, and seizures.