# Prognostic Value of Optic Nerve Sheath Diameters after Acute Ischemic Stroke According to Slice Thickness on Computed Tomography

## TL;DR

This study examines whether optic nerve sheath diameter measurements on CT scans can predict outcomes in stroke patients, finding that thinner CT slices provide slightly better results.

## Contribution

The study demonstrates that thin-slice CT imaging improves the prognostic value of optic nerve sheath diameter measurements in acute ischemic stroke.

## Key findings

- Thin-slice ONSD measurements showed a marginal difference between good and poor stroke outcomes.
- Thin-slice ONSD/ETD ratio correlated with initial stroke severity (NIHSS scores).
- Adding ONSD-related variables to models with NIHSS and age did not improve outcome prediction.

## Abstract

The optic nerve sheath diameter (ONSD) can predict intracranial pressure and outcomes in neurological disease, but it remains unclear whether a small ONSD can be accurately measured on routine CT images with a slice thickness of approximately 4–5 mm. We measured the ONSD and ONSD/eyeball transverse diameter (ETD) ratio on routine-slice (4 mm) and thin-slice (0.6–0.75 mm) brain CT images from initial scans of acute ischemic stroke (AIS) patients. ONSD-related variables, National Institutes of Health Stroke Scale (NIHSS) scores, and age were compared between good (modified Rankin Scale [mRS] ≤ 2) and poor (mRS > 2) outcomes at discharge. Among 155 patients, 38 had poor outcomes. The thin-slice ONSD was different between outcome groups (p = 0.047), while the routine-slice ONSD showed no difference. The area under the curve (AUC) values for the ONSD and ONSD/ETD were 0.58 (95% CI, 0.49–0.66) and 0.58 (95% CI, 0.50–0.66) on the routine-slice CT, and 0.60 (95% CI, 0.52–0.68) and 0.62 (95% CI, 0.54–0.69) on the thin-slice CT. The thin-slice ONSD/ETD ratio correlated with initial NIHSS scores (r = 0.225, p = 0.005). After adjusting for NIHSS scores and age, ONSD-related variables were not associated with outcomes, and adding them to a model with NIHSS scores and age did not improve performance (all p-values > 0.05). Although ONSD measurements were not an independent outcome predictor, they correlated with stroke severity, and the thin-slice ONSD provided a slightly better prognostic performance than the routine-slice ONSD.