Diagnostic evaluation of optic nerve sheath diameter in predicting elevated intracranial pressure among neurocritically ill patients: A prospective observational study

Background: Optic nerve sheath diameter (ONSD) is used as a surrogate for intracranial pressure (ICP) with a marked variation in its optimal cutoff in various subgroups of neurocritical illnesses. Real-world data on ultrasound (US)-ONSD performance among a diverse population and its trend corresponding with clinical deterioration are scarce. We aim to determine the diagnostic performance of ONSD compared to computed tomography (CT) in predicting elevated ICP in a mixed population of neurocritical patients.

Methods: Baseline ONSD measurements (T1) using B-mode US were recorded among eligible patients. Follow-up ONSD (T2) was recorded during clinical deterioration defined by ≥2 drops in Glasgow Coma Scale/Full Outline of UnResponsiveness (GCS/FOUR) scores. Its diagnostic performance in predicting elevated ICP was assessed by comparing it with the concurrently taken CT findings as a reference standard. The difference between the two ONSD measurements was termed delta ONSD.

Results: In the final analysis, 129 participants were included. The population comprised traumatic brain injury, stroke (hemorrhagic and ischemic), intracranial space-occupying lesions, and other medical conditions. The optimal ONSD (T2) cutoff of 5.23 mm had a diagnostic accuracy of 80.73% to predict elevated ICP (sensitivity: 82%; specificity: 78%; area under the curve: 0.88; and 95% confidence interval [CI]: 0.819-0.941). Each unit increase in delta ONSD was associated with increased odds of need for surgical intervention (odds ratio [OR]: 3.91; 95% CI: 1.31-12.6, P = 0.017) and death at intensive care unit discharge (OR: 8.24; 95% CI: 1.78-41.15, P = 0.007).

Conclusions: ONSD cutoff of 5.23 mm has a good diagnostic accuracy in predicting elevated ICP compared to CT during clinical deterioration. ONSD measurements correlate well with corresponding GCS/FOUR scores.