Correlation of the transorbital ultrasonographic optic nerve sheath diameter with intracranial pressure measured intraoperatively in infants with hydrocephalus

Abstract

Objective: Hydrocephalus is a highly significant global public health concern. In infants, it may be associated with a potentially deleterious increase in intracranial pressure (ICP). Currently, the gold standard for accurate monitoring of ICP is an intraventricular ICP monitor, but this method is invasive and expensive. Transorbital ultrasound measurement of the optic nerve sheath diameter (ONSD) may provide a noninvasive and cost-effective alternative method for monitoring ICP. The goal of the study was to determine the extent of the correlation between ultrasonographic ONSD and ICP in infants.

Methods: A prospective observational study of 47 children with hydrocephalus aged ≤ 18 months was performed. The ONSD was measured with a transorbital ultrasound scan, while the intraventricular CSF opening pressure was assessed using a manometer during ventriculoperitoneal shunt insertion. Data were analyzed using SPSS software. The ONSD and ICP measurements were correlated, the receiver operating characteristic (ROC) curve was evaluated, and a sensitivity analysis was performed. Inferences were made using the 0.05 alpha level of significance.

Results: The mean age of the study cohort was 4.8 ± 4.3 months, and 93.6% of patients were infants. The mean ONSD was 4.5 ± 0.7 mm (range 2.9-6.0 mm), and the mean ICP was 19.9 ± 6.5 mm Hg (range 5.2-32.4 mm Hg). Both ONSD and ICP increased with increasing age. The Pearson correlation coefficient revealed a strong positive correlation between ONSD and ICP (r = 0.77, p < 0.001). The ONSD cutoff points were 3.2 mm, 4.0 mm, and 4.6 mm for patients with ICPs of 10 mm Hg, 15 mm Hg, and ≥ 20 mm Hg, respectively. The sensitivity of ONSD was 97.7% (area under the ROC curve 0.99), and for every 14.3-mm Hg increase in ICP, the ONSD increased by 1.0 mm holding age constant.

Conclusions: ONSD has a strong positive correlation with ICP. Correspondingly, ONSD is highly sensitive in estimating ICP.

Keywords: hydrocephalus; intracranial pressure; optic nerve sheath diameter; transorbital ultrasound.