Comparison of ultrasonography and computed tomography for measuring optic nerve sheath diameter for the detection of elevated intracranial pressure

Objective: The main aim of this study was to compare optic nerve sheath diameter (ONSD) measured using ultrasonography (USG) and computed tomography (CT) almost simultaneously in the same patients with suspected elevated intracranial pressure. The other aim of this study was to evaluate the diagnostic ability for detecting elevated intracranial pressure using ONSD measured by USG (USG-ONSD) and by CT (CT-ONSD).

Patients and methods: This prospective, observational study was undertaken from June to October 2020 in the emergency department (ED) of a tertiary medical center in Seoul. ONSD was measured by USG and CT at 3 mm behind the posterior aspect of the globe.

Result: A total of 199 patients were enrolled. The median USG-ONSD and CT-ONSD were significantly higher in patients with elevated intracranial pressure than in patients with normal intracranial pressure. The interclass correlation coefficient between USG-ONSD and CT-ONSD was 0.785 (95% CI 0.715-0.837). A Bland-Altman plot showed significant agreement between USG and CT measurements. The optimal cutoff for detecting elevated intracranial pressure was >5.3 mm (sensitivity of 75.4% and specificity of 90.8%) for USG and >5.0 mm (sensitivity of 68.4% and specificity of 85.2%) for CT.

Conclusion: The ONSD measured using USG and CT were increased in patients with elevated intracranial pressure. Measurement of ONSD by USG and CT showed very high agreement.