TOP 47 - Early Clinical and Laboratory Indicators for Differentiating Infectious from Autoimmune Encephalitis in Pediatric Patients: A Single-Center Retrospective Cohort Study

Publication Number: 2799.TOP 47

Ruth N. Vela Sosa, The Children's Hospital at Montefiore, NYC, NY, United States; Audrey Uong, The Children's Hospital at Montefiore, New York, NY, United States; Alvaro J. Coronado Munoz, The Children's Hospital at Montefiore, NEW York, NY, United States

Background: Encephalitis is an inflammation of the brain parenchyma that may present with fever, new focal neurologic findings, or seizures. Multiple etiologies have been described. In children, viral causes predominate, with an estimated incidence of 7 per 100,000 annually in the United States. Autoimmune encephalitis (AE) is less common but highly morbid. Treatment differs between infectious and autoimmune causes, yet many pediatric AE cases lack identifiable biomarkers, making diagnosis difficult and often delayed. Differentiating infectious from autoimmune etiologies remains a major challenge because early presentations often overlap, and misclassification can delay appropriate therapy and increase the risk of long-term neurologic sequelae.

Objective: Evaluate the performance of an adult encephalitis model in a pediatric population, assessing the significance of fever, CSF white blood cell count, and CSF protein levels as early indicators of infectious versus autoimmune encephalitis. We also aim to identify additional pediatric-specific clinical and laboratory predictors for pediatric AE.

Design/Methods: This retrospective cohort study was conducted at the Children’s Hospital at Montefiore. Data was obtained from the electronic health record system. Inclusion criteria were patients aged 90 days–24 years diagnosed with encephalitis between January 2016 and September 2025. Encephalitis was defined by ICD-10 codes or, if uncertain, by the 2013 International Encephalitis Consortium criteria (altered mental status ≥24 h plus ≥2 supportive features). Autoimmune encephalitis followed the 2019 Cellucci criteria, requiring subacute neurologic or psychiatric symptoms, supportive MRI, CSF, or EEG findings, exclusion of infectious/metabolic causes, and antibody detection. Infectious cases were defined by pathogen detection. Exclusion criteria included oncologic or structural CNS disease, multiple sclerosis, prior epilepsy, toxic-metabolic, traumatic, or vascular etiologies, and incomplete records.

Collected variables included demographics, clinical factors (e.g., fever), CSF (WBC, protein, glucose), inflammatory markers (ESR, CRP, autoantibodies), neuroimaging, EEG, and treatments (steroids, IVIG). Multivariable logistic regression will identify predictors of infectious and autoimmune encephalitis. Based on fever prevalence differences reported by Hoang et al. (2022), a target sample of 134 achieves 80% power. To date, 220 cases have been identified; chart review is ongoing, with analysis planned for November and results expected by December 2025. Analysis will be performed using Stata/BE 18.0.