CT-derived optic nerve sheath diameter as a noninvasive proxy for intracranial pressure in traumatic brain injury patients undergoing preoperative ICP monitoring: An institutional analysis and scoping review.

BACKGROUND

Severe traumatic brain injury (TBI) often requires urgent assessment of intracranial pressure (ICP). While invasive ICP monitoring remains the gold standard, it requires neurosurgical expertise, which is not universally available. CT-derived optic nerve sheath diameter (ONSD) has been proposed as a non-invasive proxy for elevated ICP. We conducted a scoping review and single-institution retrospective cohort study to evaluate the relationship between CT-derived ONSD and elevated ICP, neurosurgical intervention, and mortality in patients with severe TBI.

METHODS

We conducted a scoping review for studies of CT-derived ONSD in adult TBI patients. We performed a retrospective cohort study including 94 consecutive patients (age ≥ 18 years) with severe TBI (GCS ≤ 8) who underwent invasive ICP monitoring at our institution (2012-2023). ONSD was measured bilaterally 3 mm posterior to the globe on initial CT. Primary outcomes were opening pressure, development of intracranial hypertension (ICP > 20 mmHg), need for neurosurgical intervention, and mortality. Statistical analysis used pre-specified multivariable linear regression for continuous ICP outcomes, with logistic regression for dichotomous outcomes as secondary analyses. Established CT markers (basal cistern effacement, Rotterdam score) served as comparators.

RESULTS

The review identified 22 studies (2013-2025). Correlation coefficients between ONSD and ICP ranged from non-significant (r = 0.115) to strong (r = 0.74). In our institutional cohort of 94 adult severe TBI patients, ONSD showed no significant associations with continuous ICP outcomes (ICPmax: β = +1.5 mmHg, p = 0.60; opening pressure: β = +2.3 mmHg, p = 0.19) when added to CT severity models. Basal cistern effacement was independently associated with higher ICP (ICPmax: β = +10.8 mmHg, p = 0.002).

CONCLUSIONS

CT-derived ONSD was not associated with elevated ICP, surgical intervention, or mortality in this cohort of severe TBI patients. In contrast, established CT markers (Rotterdam score, midline shift, basal cistern effacement) demonstrated consistent associations with clinical outcomes. These findings do not support routine clinical reliance on CT-ONSD for ICP estimation in severe TBI.