Serial Optic Nerve Sheath Diameter via Radiographic Imaging: Correlation with ICP and Outcomes

Background: Evaluation of optic nerve sheath diameter (ONSD) is a suggested correlate of intracranial pressure (ICP) and potential predictor of outcome after neurological injury. Studies have evaluated sonographic measurement of ONSD, yet clinical limitations to this approach persist. Evaluation of ONSD measurements via routine brain computed tomography (CT) imaging is less studied but offers potential for detection of increased ICP in the absence of invasive monitoring. Previous studies have employed cross-sectional approaches to ONSD measurements via CT scan among traumatic brain injury (TBI) patients. No studies have evaluated serial correlations between CT ONSD measurements and ICP throughout hospitalization and across diagnosis types. The objective of this study was to investigate correlations between ONSD via serial CT imaging, ICP, and outcome at discharge among patients with neurological injury.

Methods: Retrospective cohort study of all adult patients admitted during a 12 month period with acute neurological injury requiring ICP monitoring and critical care admission.

Results: N=48. There was a strong, positive correlation between right/left ONSD across time points (r=0.7-9, p<0.001), suggesting a consistent bilateral response. Correlations were strongest between initial inpatient CT scan ONSD readings and ICP (r=0.5, p<0.05), but decreased over time. Patients with increased ICP across all diagnosis types experienced higher ONSD values upon presentation to the emergency department (ED) and throughout hospitalization (range 5.7mm-6.4mm, p<0.05).

Conclusions: Findings contribute to the utility of CT ONSD measurements as a potential indicator of increased ICP. Measurement of ONSD during serial CT brain imaging may inform clinical decisions regarding need for more invasive monitoring after neurological injury.