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

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A Letters to the editor to this article was published on 28 September 2023

A Response to Letter To The Editor to this article was published on 28 September 2023


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.

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As low as reasonably achievable


Central retinal artery


Central retinal vein


Intracranial pressure


Intensive care unit


Idiopathic intracranial hypertension


Idiopathic normal pressure hydrocephalus

I SPTA.3 :

Spatial-peak temporal-average intensity


Mechanical index




Optic nerve


Optic nerve sheath diameter


Pulse repetition frequency


Subarachnoid hemorrhage


Thermal index


Thermal index cranium


Soft tissue thermal index at surface




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We thank Dr. Monica Ferri for color Doppler learning skills, Dr. Veronica Salvatore for assistance with US settings support, and Dr. Franziska Lohmeyer for the revision of our manuscript.


The author(s) received no financial support for the research, authorship, and/or publication of this article.

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Authors and Affiliations



Aspide, Bertolini was involved in conception and design. Aspide, Bertolini, Albini was involved in acquisition of data. Aspide, Bertolini, Biasucci contributed in drafting the article. All authors critically revised the article and reviewed the submitted version of manuscript. Albini was also involved in Technical/material support. Mazzatenta, Palandri, and Biasucci contributed in study supervision.

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Correspondence to Raffaele Aspide.

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The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Ethical approval

The local Institutional Review Board approved the present study. CLOSED protocol adhered to ethical standards and Helsinki Declaration.

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Aspide, R., Bertolini, G., Albini Riccioli, L. et al. A Proposal for a New Protocol for Sonographic Assessment of the Optic Nerve Sheath Diameter: The CLOSED Protocol. Neurocrit Care 32, 327–332 (2020).

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