120 Change in Optic Nerve Sheath Parameters Are a Sensitive Radiological Marker of ETV Outcome in Children

Abstract

INTRODUCTION: The clinical response of pediatric patients after an ETV remains quite varied. Numerous radiological features correlating with ETV outcome have been described, but there still remains a distinct group of patients in which the outcome of the procedure remains uncertain. METHODS: We reviewed magnetic resonance imaging (MRI) for all ETVs performed between 2008 and 2012 to identify whether a change in the optic nerve sheath diameter (ONSD), as well as the optic nerve to sheath ratio (ONSR), as measured on T2 axial MRI provided a useful radiological marker of ETV outcome. Suitable preoperative and postoperative imaging (acquired within 3 months of the procedure) was necessary for inclusion into the study. The ONSD, as well as the ONSR in both eyes were calculated, and the average change in these parameters was compared to conventional imaging features associated with ETV outcome. These findings were then also correlated with the clinical assessment of ETV outcome. RESULTS: MRI in 21 patients was adequate to measure and calculate the change in ONSD and ONSR, respectively. In successful ETVs (n = 17), the mean change in ONSD was a decrease of 0.9 ± 0.13 mm, whereas in failed ETVs (n = 4), the mean change was an increase of 0.14 ± 0.12 mm (P < .02). The ONSR increased from 0.48 to 0.66 (change of 0.22) in successful ETVs and decreased from 0.44 to 0.43 (change of 0.01) in failed ETVs. Change in ONSD of more than 6.1% has a sensitivity of 96% and a specificity of 75% (receiver operating characteristic = 0.75) for ETV outcome. CONCLUSION: Change in optic nerve sheath parameters, specifically ONSD and ONSR, are good independent radiological markers of ETV outcome, but are probably most useful when combined with the historical radiological features of ETV outcome.