• Jakob Pansell, Max Bell, Peter Rudberg, Ola Friman, and Charith Cooray.
• Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
• J Neuroimaging. 2022 Jan 1; 32 (1): 104-110.

Background And PurposeTreatment of elevated intracranial pressure (ICP) is central to neurocritical care, but not all patients are eligible for invasive ICP-monitoring. A promising noninvasive option is ultrasound measurement of the optic nerve sheath diameter (ONSD). However, meta-analyses of ONSD for elevated ICP show wide confidence intervals. This might be due to baseline variations, inter-rater variability, and varying measurement methods. No standardized protocol has been validated. Corrections for eyeball diameter (ED) and optic nerve diameter (OND) may compensate for baseline variations. We evaluated a protocol and compared two different measurement methods for ONSD ultrasound.MethodsTwo operators, blinded to each other's measurements, measured ONSD, ED, and OND twice in 20 patients. ONSD was measured with two different methods in use: internal (ONSDint) or external (ONSDext) of the dura mater. Intra-class correlation (ICC) was calculated for inter-rater and intra-rater reliability.ResultsICCs for inter-rater reliability of ONSDext and ONSDint (95% confidence interval) were 0.96 (0.93, 0.98) and 0.88 (0.79, 0.94), respectively. ICCs for intra-rater reliability of ONSDext and ONSDint were 0.97 (0.94, 0.99) and 0.93 (0.87, 0.96), respectively. There was no significant bias or difference in intra-rater reliability between operators.ConclusionsONSD can be measured with an excellent inter- and intra-rater reliability and low risk of inter-rater bias, when using this protocol. ONSDext yields a higher inter- and intra-rater reliability than ONSDint. Corrections for ED and OND can be performed reliably.© 2021 The Authors. Journal of Neuroimaging published by Wiley Periodicals LLC on behalf of American Society of Neuroimaging.

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