In recent years, ultrasonographic measurement of the optic nerve sheath diameter (ONSD) has been widely used to identify the presence of increased intracranial pressure (ICP). Intracranial hypertension is a life-threatening condition that can be caused by various neurological and non-neurological disorders, and it is associated to poor clinical results. Ultrasonography could be used to qualitatively and efficiently detect ICP increases, but to reach this purpose, clear cut-off values are mandatory. The aim of this review is to provide a wide overview of the most important scientific publications on optic nerve ultrasound normal values assessment published in the last 30 years. A total of 42 articles selected from PubMed medical database was included in this review. Our analysis showed that ocular ultrasonography is considered to be a valuable diagnostic tool, especially when intracranial hypertension is suspected, but unfortunately this research provided conflicting results that could be due to the different ultrasound protocols. This is mainly caused by the use of B scan alone, which presents several limitations. The use of B-scan coupled with the standardized A-scan approach could give more accurate, and reliable ultrasound evaluation, assuring higher data objectivity.

/pdf/optic-nerve-ultrasound-evaluation-in-animals-and-normal-1fmn8lyo.pdf

Optic Nerve Ultrasound Evaluation in Animals and Normal Subjects

Background Measurement of the optic nerve sheath diameter (ONSD) with ultrasound enables non-invasive and indirect assessment of increased intracranial pressure (ICP). Although most of the studies were employed with traumatic brain injury patients, it's increasingly popular in acute ischemic stroke (AIS) studies. Objectives Evaluating whether using ONSD as a follow-up measurement would help monitor the thrombolytic therapy (TT) effectiveness and determine the high-risk patients for malignant middle cerebral artery (MCA) syndrome. Methods This prospective observational study was conducted between August 1, 2019, and February 1, 2020, in a tertiary hospital. Forty-four patients were eligible. We determined the TT moment as the time when the first ocular ultrasound measurement would be made (time 0). Also, we decided on the 24th h after the treatment as the time to perform the second ocular ultrasound measurement (time 24). The National Institute of Health Stroke Scale (NIHSS), the Glasgow Coma Scale (GCS), and the Alberta Stroke Program Early Computed Tomography (ASPECT) scores were evaluated blindly at the time-0 and the time-24. The cut-off value of ONSD was 0.55 mm. Results There was no difference in ONSD results before and after the TT (p = 0.414). But, patients with an equal or higher value than cut-off had an increased risk for complications such as malignant-MCA, bleeding, seizure, etc. (p = 0.05). Malignant-MCA was observed in four patients with higher ONSD values. At the time-24, NIHSS decreased, GCS and ASPECT scores increased. Finally, ONSD was positively correlated with the NIHSS and negatively correlated with the GCS at the time-24. Conclusions Monitoring ONSD values in both the emergency department and the intensive care unit may be useful in the early diagnosis of MCA stroke complications and the follow-up of TT's effectiveness.

Measuring the Optic Nerve Sheath Diameter with Ultrasound in Acute Middle Cerebral Artery Stroke Patients.

The monitoring of intracranial pressure (ICP) is essential for the detection and treatment of most craniocerebral diseases. Invasive methods are the most accurate approach to measure ICP; however, these methods are prone to complications and have a limited range of applications. Therefore, non-invasive ICP measurement is preferable in a range of scenarios. The current non-invasive ICP measurement methods comprise fluid dynamics, and ophthalmic, otic, electrophysiological, and other methods. This article reviews eight methods of non-invasive estimation of ICP from ocular measurements, namely optic nerve sheath diameter, flash visual evoked potentials, two-depth transorbital Doppler ultrasonography, central retinal venous pressure, optical coherence tomography, pupillometry, intraocular pressure measurement, and retinal arteriole and venule diameter ratio. We evaluated and presented the indications and main advantages and disadvantages of these methods. Although these methods cannot completely replace invasive measurement, for some specific situations and patients, non-invasive measurement of ICP still has great potential.

/pdf/a-review-of-the-methods-of-non-invasive-assessment-of-dkclihd7.pdf

A Review of the Methods of Non-Invasive Assessment of Intracranial Pressure through Ocular Measurement

Abstract Background: Idiopathic intracranial hypertension (IIH) is primarily a disorder of obese young women characterized by symptoms associated with raised intracranial pressure in the absence of a space-occupying lesion. Objective: To compare the mean optic nerve sheath diameter (ONSD) measured using ultrasonography (USG) in patients with idiopathic intracranial hypertension (IIH) and normal healthy individuals. Methods: A prospective study. Ninety-seven participants aged 18-80 years were divided into two groups as patients with IIH (n=47) and the control group (n=50). The ONSD was measured using ultrasound with a 10-MHz probe. ONSD was measured 3 mm behind the optic disc. Receiver operating characteristic (ROC) curve analysis was performed to determine patients with IIH using ONSD. Results: Body mass index was higher in the IIH group compared with the control group (p=0.001). The mean ONSD was statistically significantly thicker in the IIH group (6.4 mm) than in the control group (4.90 mm). The cut-off value of ONSD in patients with IIH was measured as 5.70 mm. There was a significant negative correlation between ONSD and age (r:-0.416 and p&lt;0.001). There was a positive correlation between BMI and ONSD (r: 0.437 and p&lt;0.001). Conclusions: Ultrasound can be a reliable, non-invasive and rapid tool to measure ONSD in monitoring patients with IIH. After the first diagnosis of IIH, based on neuroimaging and measuring intracranial pressure using invasive methods, ONSD can be used in treatment and follow-up. 

/pdf/measuring-optic-nerve-sheath-diameter-using-ultrasonography-1cdtncd2.pdf

Measuring optic nerve sheath diameter using ultrasonography in patients with idiopathic intracranial hypertension

In recent years, the measurement of optic nerve sheath diameter with ultrasound to detect the presence of increased intracranial pressure has widely spread. It can be qualitatively and effectively used to identify intracranial hypertension. Intracranial pressure can rise due to acute injury, cerebral bleeding, hydrocephalus, brain tumors and other space-occupying abnormalities, and it is linked to a high death rate. The purpose of this review is to give a general overview of the most relevant scientific publications on ultrasonographic evaluation of the optic nerve in case of brain injuries published in the last 30 years, as well as to analyze the limits of the most extensively used B-scan approach. Fifty-two papers chosen from the PubMed medical database were analyzed in this review. Our findings revealed that ocular ultrasound is an useful diagnostic tool in the management of intracranial hypertension when it exceeds a certain value or after head trauma. As a result, an ultrasound of the optic nerve can be extremely helpful in guiding diagnosis and treatment. The blooming effect is one of the most critical restrictions to consider when using B-scan ultrasonography. Since amplitude-scan ultrasound, also known as A-scan, does not have this limit, these two diagnostic techniques should always be used together for a more full, accurate, and trustworthy ultrasound examination, ensuring more data objectivity.

https://www.frontiersin.org/articles/10.3389/fmed.2022.870808/pdf

Ultrasound Detection of Intracranial Hypertension in Brain Injuries

The measurement of optic nerve sheath diameter (ONSD) has been reported as a non-invasive marker for intracranial pressure (ICP). Nevertheless, it is uncertain whether possible ONSD differences occur with age and sex in healthy and brain-injured populations. The aim of this study was to investigate the effects of sex and age on ONSD in healthy volunteers and patients with traumatic brain injury. We prospectively included 122 healthy adult volunteers (Galliera Hospital, Genova, Italy), and compared age/sex dependence of ONSD to 95 adult patients (Addenbrooke's Hospital, Cambridge, UK) with severe traumatic brain injury (TBI) requiring intubation and invasive ICP monitoring. The two groups were stratified for sex and age. Age was divided into 3 subgroups: (1) young adults: 18-44 years; (2) middle-aged adults: 45-64 years; (3) old adults: >65 years. In healthy volunteers, ONSD was significantly different between males and females [median (interquartile range): 4.2 (3.9-4.6) mm vs. 4.1 (3.6-4.2) mm (p = 0.01), respectively] and was correlated with age (R = 0.50, p < 0.0001). ONSD was significantly increased in group 3 compared to groups 2 and 1, indicating that ONSD values are higher in elderly subjects. In TBI patients, no differences in ONSD were found for sex and the correlation between ONSD and age was non-significant (R = 0.13, p = 0.20). ONSD increases with age and is significantly larger for males in healthy volunteers but not in TBI patients. Different ONSD cut-off values need not be age- or sex-adjusted for the assessment of increased ICP in TBI patients.

/pdf/effects-of-age-and-sex-on-optic-nerve-sheath-diameter-in-4rv19wd1vn.pdf

Effects of Age and Sex on Optic Nerve Sheath Diameter in Healthy Volunteers and Patients With Traumatic Brain Injury

Many studies have demonstrated that the optic nerve sheath diameter (ONSD) is a good indicator of intracranial pressure (ICP). There are uncertainties regarding the optimal ONSD threshold, considering age and sex differences in the healthy population, and these differences could lead to uncertainties in evaluation of ONSD in pathological conditions.

Variability of the Optic Nerve Sheath Diameter on the Basis of Sex and Age in a Cohort of Healthy Volunteers.

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Effects of Age and Sex on Optic Nerve Sheath Diameter in Healthy Volunteers and Patients With Traumatic Brain Injury

Variability of the Optic Nerve Sheath Diameter on the Basis of Sex and Age in a Cohort of Healthy Volunteers.