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Neurocrit Care. 2019 Oct 3. doi: 10.1007/s12028-019-00853-x. [Epub ahead of print]

A Proposal for a New Protocol for Sonographic Assessment of the Optic Nerve Sheath Diameter: The CLOSED Protocol.

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Anesthesia and Neurointensive Care Unit, IRCCS Istituto delle Scienze Neurologiche di Bologna, Via Altura, 3, 40139, Bologna, Italy.
Department of Biomedical and Neuromotor Sciences, University of Bologna, Bologna, Italy.
Neuroradiology Unit, IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy.
Department of Neurosurgery, IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy.
Neurointensive Care Unit, Department of Emergency, Anesthesiology and Intensive Care Medicine, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy.


Measuring and monitoring of intracranial pressure is considered standard of care in patients with suspected intracranial hypertension. Sonographic assessment of the optic nerve sheath diameter (ONSD) has been promising and potentially useful for noninvasive intracranial hypertension screening. ONSD measurements are easy to perform, repeatable at bedside, fast, low cost, and radiation-free. However, they are still burdened by inter-rater variability, lack of ultrasound (US) setting standardization (e.g., US frequency, focus depth, etc.), and possible artifacts. To overcome this problem, we propose the CLOSED protocol associated with equipment specifications, as a guide to minimize the occurrence of such artifacts enabling a more reliable and accurate measurement. We suggest that color Doppler could be used as a new standard evaluation for the ONSD.


CLOSED protocol; Central retinal artery; Optic nerve sheath diameter; Point-of-care ultrasound; Ultrasound color Doppler


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