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

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.