Is Bigger Always Bad ? Evaluating Effect of Sedation on MRI-Based Optic Nerve Sheath Diameter Measurements in Children

Objectives To assess the impact of sedation on optic nerve sheath diameter (ONSD) as measured by MRI in pediatric patients. ONSD is a widely accepted non-invasive marker for estimating raised intracranial pressure (ICP), but potential effects of sedation on its accuracy remain understudied in children. Materials and Methods A retrospective observational study was conducted on brain MRI scans from pediatric patients aged 0–18 years. Patients were divided into two groups: those who received sedation and those who underwent MRI without sedation. Bilateral ONSD was measured at a standardized point 3 mm posterior to the globe on axial T2-weighted images. Inter-observer agreement was analyzed, and group comparisons used non-parametric statistical methods. Results Out of 78 pediatric patients, 38 received mild sedation and 40 were imaged without sedation. The mean ONSD in the non-sedated group was 4.8 ± 0.3 mm compared to 5.7 ± 0.4 mm in the non-sedated group (p = 0.02). This difference was statistically significant(t(68.5) = -11.2, p < <0.01, Cohen’s d = 2.53). Age-stratified data affirmed a normal increase in ONSD across early childhood with stabilization during adolescence. Conclusion Sedation significantly influences ONSD measurements on MRI in pediatric patients. These findings highlight the need for careful consideration of sedation status when using ONSD as a surrogate for ICP. Age-related trends further highlight the importance of using adjusted reference values.