Infectious encephalitis in elderly patients: a prospective multicentre observational study in France 2016–2019

Purpose Data on encephalitis in elderly patients are scarce. We aimed to describe the characteristics, aetiologies, management, and outcome of encephalitis in patients older than 65 years. Methods We performed an ancillary study of ENCEIF, a prospective cohort that enrolled all cases of encephalitis managed in 46 clinical sites in France during years 2016–2019. Cases were categorized in three age groups: (1) 18–64; (2) 65–79; (3) ≥ 80 years. Results Of the 494 adults with encephalitis enrolled, 258 (52%) were ≥ 65 years, including 74 (15%) ≥ 80 years. Patients ≥ 65 years were more likely to present with coma, impaired consciousness, confusion, aphasia, and rash, but less likely to present with fever, and headache ( P