The CLOSED protocol to assess optic nerve sheath diameter using color-Doppler: a comparison study in a cohort of idiopathic normal pressure hydrocephalus patients

Abstract

Background Sonographic assessment of the optic nerve sheath diameter represents a promising non-invasive technique for estimation of the intracranial pressure. A wide inter-observer variability, along with a lack of a standardized protocol for the optic nerve sheath diameter measurements, could lead to over- or under-estimation. The present study was aimed at evaluating feasibility of color-Doppler for better delineating optic nerve sheath borders, comparing it to B-mode imaging, using the magnetic resonance measurements as a comparison. Methods Optic nerve sheath diameters were evaluated using magnetic resonance by an expert radiologist in a cohort of patients with suspected idiopathic normal pressure hydrocephalus. Magnetic resonance findings were evaluated twice. In the first half of this cohort, optic nerve sheath diameters were measured using B-mode only, in the second half applying color-Doppler. Measurements obtained using these two techniques were compared to magnetic resonance imaging measurements. The Bland–Altman analysis and concordance correlation coefficient were computed to quantify the strength of agreement between the two magnetic resonance assessments. Box plots and average (± SD) were used to compare assessments by sonographic and magnetic resonance methods. Results Fifty patients were included. MRI assessment showed a moderate concordance correlation coefficient. Optic nerve sheath diameters measured applying color-Doppler were lower (p < 0.001) and less scattered compared to B-mode assessment, which approached more to magnetic resonance measurements. Conclusions In this cohort of patients, magnetic resonance showed high intra-rater variability in optic nerve sheath diameter assessments. Optic nerve sheath diameter assessments using color-Doppler yielded lower and less scattered diameters compared to B-mode only.

Magnetic Resonance-Based Assessment of Optic Nerve Sheath Diameter: A Prospective Observational Cohort Study on Inter- and Intra-Rater Agreement

“…The great diffusion in recent years of the ultrasound (US) method for the measurement of ONSD, repeatable, non-invasive, inexpensive and available bedside, still denotes many limitations due to the operator-dependent method and there is little agreement on the cut-off values compared to invasive measurement of ICP. In the same authors’ work, which compares measurements of ONSD performed with US and MRI, the data contradict the idea that measurement with US is absolutely imprecise and too operator-dependent [ 25 ]. This team of authors is working on implementing a “bundle” capable of reducing the measurement error of ONSD with US [ 26 ].…”

Non-Invasive Intracranial Pressure Monitoring

“…A study from China found a cutoff of 4.1 mm for an increased ICP, with a sensitivity of 95% and a specificity of 92% [ 204 ]. In a study comparing only color Doppler and B-mode, the first measurement method indicated significantly lower diameters [ 205 ]. This finding, along with the use of different ultrasound devices, may explain the differences between studies.…”

Ultrasonographic measurement of the optic nerve sheath diameter to detect intracranial hypertension: an observational study

“…Recently, Aspide et al studied the feasibility of using color Doppler to measure the ONSD as compared to 2D ultrasonography, having magnetic resonance imaging as the gold standard, and found that ONSD assessments using color Doppler yielded lower and less scattered measurements compared to 2D ultrasonography [8].…”