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

The prespecified primary analysis found no significant association between ICP and bilateral mean inner-reflection ONSD (irONSD) at 3 mm.

• β = 0.004 mm per mmHg, 95% CI -0.003 to 0.011; p = 0.169.
• Marginal R² = 0.3%.
• This was a prospective longitudinal study with daily ONSD measurements compared with simultaneously recorded invasive ICP.

At 6 mm behind the optic disc, a small but statistically significant association between ICP and outer-reflection ONSD was detected for bilateral mean values.

• β = 0.010, 95% CI 0.002-0.019; p = 0.016.
• Marginal R² = 1.3%.
• The effect size was small, so ICP explained very little of ONSD variance.

Overall, the association between ICP and ONSD was weak, with ICP explaining less than 2% of ONSD variance in this cohort.

• 55 patients with intracranial hemorrhage were included.
• Repeated measurements were obtained over a mean of 5.47 ± 2.27 days.
• ONSD was measured by transorbital ultrasound at 3 mm and 6 mm posterior to the optic disc.

The cohort was treated neurocritical care patients with predominantly controlled ICP, which may have limited ONSD variation and the ability to detect association.

• The authors describe the cohort as 'treated cohort with predominantly controlled ICP'.
• The findings relate to the ability of ONSD to track dynamic ICP changes over time in treated patients.

The authors conclude that ONSD should not be interpreted as a direct substitute for invasive ICP or as a stand-alone measure of short-term ICP change.

• The findings question ONSD's reliability as a stand-alone tool for serial monitoring of dynamic ICP changes.
• Background concerns cited include substantial variability in measurement techniques and cut-off values.