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

Abstract

Background: 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.

Patients and methods: 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.

Results: 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).

Discussion: 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.

Conclusion: 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.

Keywords: Ischemic stroke; intracranial hypertension; intracranial pressure; large vessel occlusion stroke; malignant media infarction; optic nerve sheath; optic nerve sheath diameter; ultrasound.

Graphical abstract

Figure 1.

Standardized Measurement of the Optic Nerve Sheath Diameter (ONSD): (a) application of the high-frequency linear probe for transorbital sonography, (b) ultrasound image demonstrating the measurement of the internal ONSD (ONSDint, light blue dashed line) 3 mm posterior to the globe. The white calipers indicate the measurement of the external ONSD, and (c) corresponding ONSD measurement on an axial CT scan.

Figure 2.

Flow chart of included and excluded patients.

Figure 3.

Longitudinal ONSDint measurements after stroke. Mean ONSDint is plotted for the ipsilateral and contralateral eye at six time points after stroke onset. Error bars represent the standard error of the mean. The dashed horizontal line indicates the mean ONSDint of the non-stroke control group (4.66 mm).

Figure 4.

Longitudinal ONSDint by grade of cerebral edema: (a) mean ONSDint at six time points after stroke onset for patients with no edema (white bars), mild-to-moderate edema (gray bars), and severe edema (dark gray bars). Error bars represent the standard error of the mean, (b–d) representative MRI FLAIR images of a patient with no edema (b), mild-to-moderate edema (c), and severe edema with midline shift (d).

Figure 5.

Predictive performance of ONSD for intracranial hypertension. Receiver Operating Characteristic (ROC) curves from the leave-one-out cross-validation. (a) The model including sonography-derived ONSDint (red line) compared to the baseline model without ONSD (blue line). (b) The model including CT/MRI-derived ONSD (red line) showed a substantial improvement in predictive performance compared to the baseline model. AUC values are provided with 95% confidence intervals.