Optic Nerve Sheath Diameter on Computed Tomography Scans Reflects Elevated Intracranial Pressure in Patients with Craniosynostosis.

Introduction: Assessment for elevated intracranial pressure (ICP) helps guide interventional decision-making to treat craniosynostosis. However, non-invasive techniques for measuring ICP are limited. This study assesses whether optic nerve sheath diameter (ONSD) on low-dose computed tomography (CT) scans is associated with ICP in patients with craniosynostosis.

Methods: Pediatric patients treated between 2014 and 2023 with craniosynostosis, intraoperative ICP measurements by direct subdural catheterization, and spectral domain-optical coherent tomography (SD-OCT) data were included. ONSD was retrospectively assessed on pre-operative CT scans by a masked neuroradiologist and compared to measures and proxies of ICP.

Results: Among 132 patients included, median age was 6.9 years (IQR 4.7-9.5) and 41 (31.1%) had a syndromic diagnosis. Maximum ONSD (ONSDmax) was increased in patients with ICP≥15mmHg (6.1mm vs. 5.5mm, p<0.01) and ICP≥20mmHg (6.3mm vs. 5.6mm, p<0.01). Maximum (r=0.32, p<0.001), minimum (r=0.26, p=0.003), and average (r=0.29, p<0.001) ONSD correlated with direct ICP measurements. ONSD and SD-OCT measurements were also correlated (RNFLmax: r=0.21, p=0.04; RTmax: r=0.24, p=0.02). An ONSDmax threshold of 5.75mm demonstrated 65% sensitivity and 64% specificity for detecting ICP≥15mmHg on optimized receiver operating characteristic curve analysis. Multivariable logistic regression generated an algorithm incorporating ONSDmax and age to detect ICP≥20mmHg with 64% sensitivity and 80% specificity.

Conclusion: Optic nerve sheath diameter measured in low-dose CT scans detects elevated intracranial pressure with moderate accuracy, and precision increases when patient age is taken into consideration. Given the ease of accessing CT scan data, this may be a helpful ICP proxy for clinical decision-making.