Pediatric Infectious Encephalitis in Spain

BACKGROUND: Pediatric infectious encephalitis remains a significant cause of neurologic morbidity. Prompt antiviral treatment is recommended in patients with suspected herpes simplex virus (HSV) encephalitis. This study aimed to describe the epidemiology and outcomes of infectious encephalitis and to evaluate acyclovir use in children with suspected encephalitis presenting to the pediatric emergency department (PED). METHODS: We conducted a multicenter, retrospective, cross-sectional study involving 10 Spanish PEDs (2017-2023), including children ≤18 years who underwent cerebrospinal fluid polymerase chain reaction testing as part of the evaluation of a possible central nervous system infection. Patients meeting the International Encephalitis Consortium (IEC) criteria for infectious encephalitis were analyzed, and acyclovir prescription rates were assessed. RESULTS: We registered 446 episodes; 118 patients (26.5%) met the IEC criteria, and 88 (74.6%) had microbiologic confirmation. The most common pathogens were enterovirus (43.2%), influenza virus (18.2%) and HSV (9.0%). Thirty-seven patients (31.4%) had an adverse outcome, including 75% of those with HSV infection. Acyclovir was administered to 56.9% and 53.1% of patients with and without an altered mental status, respectively. All patients meeting IEC criteria presented with altered mental status and ≥1 minor criterion at evaluation in the PED. CONCLUSIONS: Enteroviruses were the leading cause of pediatric infectious encephalitis, whereas HSV infection was associated with the highest risk of adverse outcomes. Acyclovir use in the PED was suboptimal and poorly aligned with clinical criteria. Our findings suggest that empirical acyclovir should be considered in patients with altered mental status and at least one minor criterion, whereas it may be unnecessary in the absence of these features.