Measurement of optic nerve sheath diameter by ultrasound in healthy term neonates

Optic nerve sheath diameter (ONSD) ultrasound is a noninvasive and repeatable tool to dynamically evaluate intracranial pressure with high diagnostic accuracy; however, data in neonates are scarce. The aim of this study was to determine the reference value of ONSD and potential influencing factors in healthy term neonates.

We retrospectively reviewed 250 full-term neonates who underwent cranial ultrasound as part of selective newborn screening over a 2-year period. Neonates with any of the following conditions were excluded: using mechanical ventilation, sedatives and/or vasopressors, or signs of infection which needed cerebrospinal fluid analysis and/or intracranial pathologies. Data on sex, gestational age, birth body weight, birth body height, birth head circumference, Apgar score and types of delivery were collected. The neurodevelopmental outcomes were reviewed.

A total of 234 neonates (123 girls and 111 boys) were included. The mean ONSD value was 3.30 ± 0.27 mm in the right eye and 3.30 ± 0.23 mm in the left eye, with no significant difference between both eyes (p = 0.797). Male neonates had a larger ONSD than female neonates (3.34 ± 0.22 mm versus 3.26 ± 0.20 mm, p = 0.007), and ONSD was correlated with birth weight in the males. Otherwise, there were no statistically significant associations between ONSD and other birth characteristics in both sexes. Most (63%) cases were followed for at least 12 months, and 98% had normal neurodevelopment.

The reference value reported in this study may be used to evaluate the ONSD in healthy term neonates. Sex differences should be considered in this age group.