Optic nerve sheath diameter ultrasound: optic nerve growth curve and its application to detect intracranial hypertension in children

Purpose (1) To create an optic nerve growth curve from the optic nerve sheath diameter (ONSD) normal values ​​measured with B-scan ultrasound in subjects aged 0-18. (2) To identify age-appropriate cut-offs of ONSD to be used in the diagnosis of intracranial hypertension (IHT). Design Prospective cross-sectional study. Methods B-scan ocular ultrasound was performed on both eyes of 215 subjects aged 0-18, divided into 3 groups: 165 healthy children, 29 children with IHT (all >4 years of age) and 21 with optic disc drusen (ODD). Results There were no statistically significant differences in ONSDs between healthy children and subjects with ODD. We created an optic nerve growth curve using ONSDs measured in healthy subjects aged 0-18: ONSD = ln (33.15) – [–0.18 * ln (children’s age)].Our curve shows a progressive increase of ONSD up to 10 years and then it remains constant until the age of 18. For this reason, we calculated two different cut-offs for age groups 4-10 and 11-18. They are 4.10 mm and 4.4 mm respectively, with a 100.0% sensitivity and a specificity ranged from 83.9% to 98.8%. We reached a sensitivity of 28.6%, applying to our population aged 4-18 the 5 mm threshold used in literature. Conclusions The ONSD continues to enlarge gradually until the age of 10. Therefore we calculated two different cut-offs for the age groups 4-10 and 11-18, considering the ONSDs of subjects aged 11-18 overlapping with those of adults. As we had no patients with IHT