Acute pediatric encephalitis: etiology, course, and outcome of a 12-year single-center immunocompetent cohort

Background Encephalitis is an uncommon but severe disorder due to an inflammation of the brain parenchyma, usually diagnosed on clinical, laboratory, electroencephalographic, and neuroradiological features. New causes of encephalitis have been reported in recent years, so diagnostic criteria have changed over time. We report on a single-center experience of a pediatric Hospital, the hub of its region, over 12 years (2008–2021), with the evaluation of all children managed for acute encephalitis. Methods We retrospectively reviewed clinical, laboratory, neuroradiological, and EEG data from the acute phase and outcome of all immunocompetent patients diagnosed with acute encephalitis. According to the newly proposed criteria for pediatric autoimmune encephalitis, we divided patients into infectious, definite autoimmune, probable autoimmune, and possible autoimmune, and performed a comparison between the different groups. Results 48 patients (26 females, mean age 4.4 years), 19 with infections, and 29 with autoimmune encephalitis, were included. Herpes simplex virus 1 encephalitis was the most frequently identified etiology followed by anti-NMDA receptor encephalitis. Movement disorders at onset and a longer hospital stay were observed more frequently in autoimmune compared to infectious encephalitis ( p p < 0.001 and p = 0.001 , respectively). Among the autoimmune group, children who started immunomodulatory treatment earlier (within 7 days from onset) had more frequent complete functional recovery ( p = 0.002). Conclusions Herpes virus and anti-NMDAR encephalitis are the most frequent etiologies within our cohort. Clinical onset and course are extremely variable. Since early immunomodulatory treatment was associated with a better functional outcome, our data confirm that a timely diagnostic classification in definite, probable, or possible autoimmune encephalitis can help the clinician in a successful therapeutic approach.