# Optic nerve sheath diameter for prediction of intracranial hypertension after ischemic sTrokE – The ONSITE study

## TL;DR

This study shows that measuring the optic nerve sheath diameter with ultrasound can help predict dangerous brain swelling after stroke, offering a non-invasive and repeatable method for monitoring patients.

## Contribution

The study introduces a sonographic optic nerve sheath diameter cut-off (≥5.51 mm) as a reliable early predictor of intracranial hypertension after stroke.

## Key findings

- A sonographic ONSDint of ≥5.51 mm predicted intracranial hypertension with 85.7% sensitivity and 94.8% specificity.
- Neuroimaging-derived ONSD showed higher predictive accuracy (AUC 0.905) compared to sonography (AUC 0.687).
- Sonography allows for dynamic, bedside monitoring of intracranial pressure changes in stroke patients.

## Abstract

Intracranial hypertension (IH) from brain edema is a life-threatening complication of large vessel occlusion (LVO) stroke, yet clinical monitoring is often unreliable. Non-invasive methods for early IH prediction are needed. This study assessed whether sonographic measurement of the optic nerve sheath diameter (ONSD) could improve the prediction of IH after stroke.

We prospectively measured the internal optic nerve sheath diameter (ONSDint) via transorbital ultrasound in 65 stroke patients and 30 controls. ONSD was also measured on the initial CT or MRI. The primary endpoint of IH was a composite of clinical and radiological signs of brain swelling. A predictive ONSD cut-off was determined from a multivariable logistic regression model, adjusted for age and infarct volume. Predictive performance was assessed using leave-one-out cross-validation.

Seven of 65 stroke patients (11%) developed IH. The initial sonographic ONSDint was significantly increased in patients who developed IH. The multivariable model identified an optimal predictive cut-off of ⩾5.51 mm, which predicted IH with a sensitivity of 85.7% and a specificity of 94.8%. In comparison, ONSD derived from initial neuroimaging was also a strong predictor, with an optimal cut-off of 6.80 mm yielding a sensitivity of 100% and a specificity of 91.1%, and showed superior predictive accuracy in the cross-validation (AUC 0.905 vs 0.687).

Our sonographic ONSDint cut-off of ≥5.51 mm aligns well with recent stroke literature that used similar standardized measurement techniques. Our findings also highlight the distinct roles of different imaging modalities. While the initial CT/MRI provides a static measurement with high predictive power, the unique advantage of sonography is its bedside applicability, allowing for the crucial, non-invasive serial monitoring of ONSD as a dynamic marker of intracranial pressure changes.

Early ONSD assessment is a valuable predictor of IH after severe stroke. A sonographic ONSDint of ⩾5.51 mm identifies patients at high risk with excellent accuracy. While initial neuroimaging may offer superior predictive power, bedside sonography remains a crucial, repeatable tool for monitoring these critically ill patients.

Graphical abstract