Limited utility of optic nerve sheath diameter for monitoring intracranial pressure in patients with intracranial hemorrhage

Introduction Monitoring intracranial pressure (ICP) is a key component in the management of patients with intracranial hemorrhage. Transorbital ultrasound (toUS)- based measurement of the optic nerve sheath diameter (ONSD) - has been proposed as a non-invasive surrogate for ICP assessment. However, substantial variability in measurement techniques and cut-off values has raised concerns regarding its reliability. This study aimed to evaluate the association between repeatedly measured ONSD and invasively measured ICP in patients with intracranial hemorrhage and to assess the ability of ONSD to reflect changes in ICP over time. Methods In this prospective longitudinal study ONSD was measured daily using ultrasound at 3- and 6 mm posterior to the optic disc and compared with simultaneously recorded invasive ICP measurements. A total of 55 patients with intracranial hemorrhage were included, contributing repeated measurements over a mean of 5.47 ± 2.27 days. Results Overall, the association between ICP and ONSD was weak. In the prespecified primary analysis, ICP was not associated with bilateral mean irONSD at 3 mm ( β = 0.004 mm per mmHg, 95% CI − 0.003 to 0.011; p = 0.169; marginal R2 = 0.3%). At 6 mm, a small but statistically significant relationship was detectable at bilateral ICP mean values for outer-reflection ONSD [ β = 0.010, 95% CI (0.002–0.019), p = 0.016; marginal r2 = 1.3%]. Conclusion ICP explains less than 2% of the variance in ONSD in this treated cohort with predominantly controlled ICP. These findings question its reliability as a stand-alone tool for serial monitoring of dynamic ICP changes in treated neurocritical care patients and therefore should not be interpreted as a direct substitute for invasive ICP or as a stand-alone measure of short-term ICP change.