Determination of normal values of optic nerve sheath diameter in newborns with bedside ultrasonography

Bedside sonographic opthalmic ultrasound measurement of optic nerve sheath diameter (ONSD) is an easy, portabl, noninvasive and a radiation free technique to determine increased intracranial pressure. This prospective, multicenter study was aimed to establish the range of normal values for ONSD in preterm and term newborns with a large study population.

Newborns without intracranial pathology in the Newborn Intensive Care Units and in Obstetrics and Gynecology Departments were enrolled in the study. ONSD was measured at 3 mm distance behind of the right optic nerve head. As 3 mm distance was beyond the optic nerve head in some of the premature newborns, we had also measurements at 2 and 2.5 mm.

ONSD was measured in 554 newborns. Mean ONSD of preterm babies at 2, 2.5 and 3 mm distances were 3.2 ± 0.3 mm (range 2.0-4.2 mm), 3.3 ± 0.3 mm (range 2.2-4.5 mm) and 3.6 ± 0.2 mm (range 2.9-4.5 mm), (p_{2.0-2.5 mm} < 0.001, p _2.5-3.0mm < 0.001, p_{2.0-3.0 mm} < 0.001) respectively. Mean ONSD of term babies at 3 mm was higher than the mean ONSD of preterm babies in 33 weeks 0 day- 37 weeks 0 days group (p < 0.001). In correlation analysis, a significant, strong and positive correlation was found between ONSD measurements and gestational age, weight, height and head circumference at 2, 2.5 and 3 mm distances.

The normal values reported by the present study may be used for evaluating the ONSD of newborns with different conditions with increased incracranial pressure.