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

Abstract

Background: 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. Methods: Retrospective cohort of encephalitis cases in 19 hospitals from New Orleans, Louisiana and Houston, Texas between the years 2000 and 2017. Findings: A total of 340 adult (age >17 years) patients with confirmed encephalitis were enrolled, 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 in 82 (24%) of patients, respectively. Furthermore, an arboviral serology was done in 169 (49%) and measurements of anti-N-methyl-D-aspartate receptor antibodies in 49 (14%) of patients. A total of 172 out of 323 (53%) had adverse clinical outcomes (ACO) at discharge. Older individuals (>65 years of age) had a lower prevalence of HIV, higher number of comorbidities, were less likely to receive adjuvant steroids, and more likely to have a positive arbovirus serology, a positive HSV PCR, an abnormal computerized tomography findings and to have ACO (all P values < 0.05). Prognostic factors independently associated with an ACO were age ≥ 65, fever, Glasgow coma scale (GCS) < 13, and seizures (all P values < 0.01). Interpretation: Encephalitis remains with adverse clinical outcomes and unknown etiologies in the majority of patients in the molecular diagnostic era. Independent prognostic factors include age >65 years, fever, GCS <13 and seizures. Funding Statement:.Grant A Starr Foundation. Declaration of Interests: RH is a speaker for Merck, and Biofire, and consultant to Gilead. Ethics Approval Statement: The UT Health Committee for the Protection of Human Subjects, the Memorial Hermann Hospital Research Review Committee, and the Harris Health Research Committee approved the study.