Ultrasound Measurement of Optic Nerve Sheath Diameter for Detection of Elevated Intracranial Pressure in Pediatric Encephalitis

Background and Objectives: Elevated intracranial pressure (ICP) is a critical and potentially life-threatening complication of pediatric encephalitis. Early detection is essential for improved outcomes. This study assessed the diagnostic utility of optic nerve sheath diameter (ONSD) ultrasound for identifying elevated ICP in children with encephalitis. Methods: A prospective descriptive case series was conducted at the Infectious Disease Intensive Care Unit (ID-ICU), Children’s Hospital 1, Ho Chi Minh City, from August 2023 to April 2025. Children with encephalitis underwent daily ONSD ultrasound during the first seven days of admission. Elevated ICP was defined based on clinical signs and neuroimaging findings. ONSD measurements were compared between patients with and without elevated ICP, and age-specific diagnostic cut-off values were determined. Results: Thirty-six patients were enrolled, with elevated ICP confirmed in 72.2% of cases. ONSD values were higher in patients with raised ICP than in those without at all time points. Receiver operating characteristic (ROC) analysis identified optimal ONSD thresholds for detecting elevated ICP of 5.2 mm in children younger than 60 months, 5.9 mm in those aged 60 months or older, and 5.6 mm in the overall cohort. Serial measurements showed a decline in ONSD over time. No significant difference was observed between right and left eye measurements, with strong inter-eye correlation. Conclusions: Ultrasound measurement of ONSD is a useful, noninvasive, repeatable bedside tool for early identification of elevated ICP in pediatric encephalitis. Incorporating age-specific ROC-derived ONSD thresholds may improve diagnostic accuracy and support bedside assessment in pediatric intensive care settings.