Optic nerve sheath diameter measurement by ultrasound: Evaluation of a standardized protocol

Ultrasonographic Optic Nerve Sheath Diameter Technical Pitfalls and Imaging Artifacts

Ultrasonographic optic nerve sheath diameter (ONSD) is a non-invasive intracranial pressure (ICP) surrogate. This article discusses the effect of ultrasound settings and imaging artifacts on ONSD assessment. Ultrasound settings that may affect ONSD assessment include gain, dynamic range, frequency, harmonic imaging, and focal zones. Artifacts can be related to imaged structures (acoustic shadowing, enhancement, comet tail, and speckle artifacts) or to beam properties (partial volume and refraction artifacts). In addition, optic nerve sheath (ONS) properties such as echogenicity changes based on ICP or ONS kinking are discussed.

Advancements in Non-Invasive Intracranial Pressure Monitoring via Optic Nerve Sheath Diameter Measurement

Intracranial pressure (ICP) monitoring is the mainstay of treatment for patients with brain tumors, hydrocephalus, cerebral edema, and traumatic brain injury (TBI). At present, there are 2 main monitoring methods: non-invasive and invasive. Although invasive monitoring of ICP is the criterion standard, non-invasive approaches based on measurement of optic nerve sheath diameter (ONSD) are becoming increasingly popular because of their simplicity, low cost, and accuracy. Ultrasound (US) measurement of ONSD is especially useful because it allows dynamic evaluation of ICP over the hospital and treatment period in a real-time manner and can be performed bedside for better patient acceptance. This paper reviews the research progress, and highlights the advantages, performance, and results of various ONSD measurement approaches, including US-based ONSD measurement, with regard to its principles, operation method, and clinical applications, as well as ONSD measurement by other techniques such as computed tomography (CT) and magnetic resonance imaging (MRI). New developments, including use of the ONSD/ocular transverse diameter (ETD) index and possible future studies on ONSD-based/assisted therapy and treatment for patients with TBI, stroke, and other conditions that can increase ICP will also be discussed.

Intracranial pressure estimated non-invasively and postoperative outcomes in surgery in the Trendelenburg position with pneumoperitoneum

BACKGROUND

Surgery in the Trendelenburg position (TP) with pneumoperitoneum (PP) is beneficial in several aspects but is associated with postoperative complications, such as postoperative nausea and vomiting (PONV). The mechanism behind this is unknown, but an increase in intracranial pressure (ICP) has been suggested. There are several studies of non-invasively estimated ICP during surgery in TP with PP. The association between perioperative estimated ICP and postoperative complications has not yet been reviewed.

METHODS

We performed a scoping review of peer-reviewed clinical studies reporting on both perioperative estimation of ICP and postoperative complications in patients undergoing surgery in TP with PP. The literature search was performed in February 2025 on PubMed, CINAHL, and Web of Science.

RESULTS AND CONCLUSIONS

Ten of 12 included studies suggested associations between perioperative elevation of estimated ICP and postoperative complications, most notably PONV. This may have clinical implications since elevated ICP can be treated. Future research should focus on the association between perioperative ICP estimation and postoperative complications and the effects of ICP-lowering strategies on postoperative outcomes.

The impact of demographics and positioning on the imaging features of the optic nerve sheath and ophthalmic vessels

BACKGROUND

There are significant discrepancies in the optic nerve sheath diameter (ONSD) reported in the literature. We aimed to determine the ultrasonographic imaging features of ONSD and ophthalmic vessels in a healthy population, using a standardized protocol, and to estimate the effect of demographics and positioning changes on imaging measurements.

METHODS

We measured the mean values of the ONSD in supine and sitting position and the Doppler imaging parameters of the ophthalmic, central retinal and short posterior ciliary arteries. Inter-observer reliability was assessed using intraclass correlation coefficient (ICC). Linear regression models were fitted to predict the effect of demographic and clinical determinants on the imaging features.

RESULTS

A total of 50 measurements were obtained for each observer. The mean ONSD was 5.9 mm and there was a mean reduction of 0.2 mm when assessed in sitting position (p < 0.001). Doppler analysis showed higher peak-systolic velocity and resistive index in the ophthalmic artery (35.6 cm/s vs. 12.0 cm/s; 0.78 vs. 0.70) compared to the central retinal artery (p < 0.001). Age, sex, heart rate and systolic blood pressure were significant determinants of the imaging features, with ONSD being larger in males (p < 0.001) and increasing with heart rate (p = 0.001). ICC estimates indicated 'good' inter-observer reliability of the ONSD and the ophthalmic and central retinal arteries velocities and resistance.

CONCLUSIONS

Our findings suggest a significant impact of patient demographics and positioning during ultrasonography on the normal imaging features of the ONSD and ophthalmic vessels. The heterogeneity in methodology and clinical cohorts may justify previous discrepancies in the literature. These findings can assist in the interpretation of imaging features in clinical settings and in the standardization of point of care ONSD ultrasonography.

Ultrasonic optic nerve sheath diameter as a new predictor for the mortality of patients with large hemispheric infarction

Large hemispheric infarction (LHI) is a severe form of stroke with high mortality and poor outcomes. Ultrasonic optic nerve sheath diameter (ONSD) is considered an effective indicator for intracranial hypertension. Our study aimed to validate the efficiency of ultrasonic ONSD and develop a nomogram to identify LHI patients who have 90-day mortality. We recruited 419 LHI patients (training cohort, n = 202; internal validation cohort, n = 86; and external validation cohort, n = 131) from six centers. Demographic, laboratory, computed tomography, and ultrasonic data were collected. At 90 days, 41.8% of patients died. Ultrasonic ONSD (odds ratio [OR], 7.026; 95% CI, 2.638-18.708; P < 0.001), male (OR, 8.620; 95% CI, 2.962-25.092; P < 0.001), midline shift (OR, 1.207; 95% CI, 1.085-1.342; P = 0.001), and infarction volume (OR, 1.020; 95% CI, 1.012-1.028; P < 0.001) were independent predictors. In identifying LHI patients prone to 90-day mortality, the nomogram developed using these predictors showed areas under the receiver operating characteristic curve (AUC) of 0.897, 0.824, 0.833 in the training cohort, internal and external validation cohorts, respectively. Ultrasonic ONSD complement the midline shift and infarction volume to create a reliable multimodal method for monitoring prognosis in patients with LHI.

The Approach to Altered Mental Status in the Intensive Care Unit

Altered mental status (AMS) is a syndrome posing substantial burden to patients in the intensive care unit (ICU) in both prevalence and intensity. Unfortunately, ICU patients are often diagnosed merely with syndromic labels, particularly the duo of toxic-metabolic encephalopathy (TME) and delirium. Before applying a nonspecific diagnostic label, every patient with AMS should be evaluated for specific, treatable diseases affecting the central nervous system. This review offers a structured approach to increase the probability of identifying specific causal etiologies of AMS in the critically ill. We provide tips for bedside assessment in the challenging ICU environment and review the role and yield of common neurodiagnostic procedures, including specialized bedside modalities of diagnostic utility in unstable patients. We briefly review two common etiologies of TME (uremic and septic encephalopathies), and then review a selection of high-yield toxicologic, neurologic, and infectious causes of AMS in the ICU, with an emphasis on those that require deliberate consideration as they elude routine screening. The final section lays out an approach to the various etiologies of AMS in the critically ill.

Pcv-aCO2/Ca-cvO2 Combined with Optic Nerve Sheath Diameter in Predicting Elevated Intracranial Pressure of Patients with Traumatic Brain Injury in Prehospital Setting

Purpose

To investigate a correlation between the central venous minus arterial CO2 pressure to arterial minus central venous O2 content ratio (Pcv-aCO2/Ca-cvO2) combined with optic nerve sheath diameter (ONSD) in predicting prehospital elevated intracranial pressure (ICP) in traumatic brain injury (TBI) patients.

Patients and Methods

This was a prospective observational study of all adult TBI patients from the surgical intensive care unit who underwent invasive ICP monitoring between January 2023 and December 2023. Using a Delica MVU-6300 machine with 14-5 MHz linear probe to measure ONSD. We drew blood samples for arterial and central venous blood gases to measure and calculate the following indicators such as Pcv-aCO2, Ca-cvO2, and Pcv-aCO2/Ca-cvO2 ratio. ONSD and Pcv-aCO2/Ca-cvO2 were recorded during the first 3 days after admission. Simultaneous ICP values were gained from the invasive monitoring. Associations between ONSD, Pcv-aCO2/Ca-cvO2 and simultaneous ICP were explored by Spearman correlation analysis. We constructed an ROC curve to identify the ONSD and Pcv-aCO2/Ca-cvO2 cutoff for the evaluation of elevated ICP.

Results

We included 54 patients aged mean 57.13 (standard deviation 4.02) years and 24 (44%) were male. A significant correlation was observed between ONSD and ICP (r = 0.74, P < 0.01). The AUC was 0.861 (95% CI: 0.727-0.951), with a best cutoff value of 5.62 mm. Using a cutoff of 5.62mm, ONSD had a sensitivity of 92.8%, specificity of 80.4%. The Pcv-aCO2/Ca-cvO2 ratio also significantly correlated with ICP (r = 0.70, P < 0.01). The AUC was 0.791 (95% CI: 0.673-0.889). The optimal Pcv-aCO2/Ca-cvO2 value for predicting elevated ICP was 1.98 mmHg/mL. Using a cutoff of 1.98 mmHg/mL, Pcv-aCO2/Ca-cvO2 had a sensitivity of 87.3%, specificity of 77.2%. The AUC for ONSD combined with Pcv-aCO2/Ca-cvO2 was 0.952 (95% CI: 0.869-0.971), which had a sensitivity of 95.1%, specificity of 93.9%.

Conclusion

Pcv-aCO2/Ca-cvO2 combined with ONSD performed best in predicting elevated intracranial pressure of patients with TBI in a prehospital setting. Our findings provide a crucial tool to improve earlier management of these patients in prehospital care, where the availability and utilization of invasive monitoring is limited. It could lead to significant changes in how TBI patients are monitored and treated before reaching a hospital.

Optic Nerve Sheath Diameter Point-of-Care Ultrasonography Quality Criteria Checklist: An International Consensus Statement on Optic Nerve Sheath Diameter Imaging and Measurement

OBJECTIVES

To standardize optic nerve sheath diameter (ONSD) point-of-care ultrasonography (POCUS) and improve its research and clinical utility by developing the ONSD POCUS Quality Criteria Checklist (ONSD POCUS QCC).

DESIGN

Three rounds of modified Delphi consensus process and three rounds of asynchronous discussions.

SETTING

Online surveys and anonymous asynchronous discussion.

SUBJECTS

Expert panelists were identified according to their expertise in ONSD research, publication records, education, and clinical use. A total of 52 panelists participated in the Delphi process.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Three Delphi rounds and three asynchronous discussion rounds generated consensus on quality criteria (QC). This started with 29 QC in addition to other QC proposed by expert panelists. The QC items were categorized into probe selection, safety, body position, imaging, measurement, and research considerations. At the conclusion of the study, 28 QC reached consensus to include in the final ONSD POCUS QCC. These QC were then reorganized, edited, and consolidated into 23 QC that were reviewed and approved by the panelists.

CONCLUSIONS

ONSD POCUS QCC standardizes ONSD ultrasound imaging and measurement based on international consensus. This can establish ONSD ultrasound in clinical research and improve its utility in clinical practice.

Which compartments of the optic nerve and its sheath are associated with intracranial pressure? An exploratory study

BACKGROUND AND PURPOSE

The optic nerve sheath diameter (ONSD) is a commonly used estimate of intracranial pressure (ICP). The rationale behind this is that pressure changes in the cerebrospinal fluid affect the optic nerve subarachnoid space (ONSAS) thickness. Still, possible effects on other compartments of the optic nerve sheath (ONS) have not been studied. This is the first study ever to analyze all measurable compartments of the ONS for associations with elevated ICP.

METHODS

We measured changes in ICP and changes in ONS compartments in 75 patients treated with invasive ICP monitoring at the Karolinska University Hospital. Associations between changes in ICP and changes in ONS compartments were estimated with generalized estimating equations. The potential to identify elevated ICP was assessed with the area under the receiver operating characteristic curve (AUROC) for ONS compartments associated with ICP changes.

RESULTS

Both ONSAS and perioptic dura mater thickness were significantly associated with changes in ICP in multivariable modeling. ONSAS was the only compartment that independently predicted changes in ICP, with an AUROC of 0.69 for predicting ICP increase. Still, both the perioptic dura mater thickness and the optic nerve diameter added value in predicting ICP changes in multivariable modeling.

CONCLUSIONS

The results from this study challenge the current understanding of the mechanism behind the association between ICP and ONSD. Contrary to the common opinion that ONSAS is the only affected compartment, this study shows a more complex picture. It suggests that all ONS compartments may add value in predicting changes in ICP.

Dimensions of Arachnoid Bulk Ratio: A Superior Optic Nerve Sheath Index for Intracranial Pressure

Background Discrepancies in the literature regarding optimal optic nerve sheath diameter (ONSD) cutoffs for intracranial pressure (ICP) necessitate alternative neuroimaging parameters to improve clinical management. Purpose To evaluate the diagnostic accuracy of the dimensions of the perineural subarachnoid space to the optic nerve sheath ratio, measured using US, in predicting increased ICP. Materials and Methods In a prospective cohort study from April 2022 to December 2023, patients with suspected increased ICP underwent optic nerve US to determine the dimensions of arachnoid bulk (DAB) ratio and ONSD before invasive ICP measurement. Correlation between the parameters and ICP, as well as diagnostic accuracy, was assessed using area under the receiver operating characteristic curve (AUC) analysis. Results A total of 30 participants were included (mean age, 39 years ± 14 [SD]; 24 female). The DAB ratio and ONSD were significantly larger in participants with increased ICP (38% [0.16 of 0.42] and 14% [0.82 of 6.04 mm], respectively; P < .001). The DAB ratio showed a stronger correlation with ICP than ONSD (rs = 0.87 [P < .001] vs rs = 0.61 [P < .001]). The DAB ratio and ONSD optimal cutoffs for increased ICP were 0.5 and 6.5 mm, respectively, and the ratio had higher sensitivity (100% vs 92%) and specificity (94% vs 83%) compared with ONSD. Moreover, the DAB ratio better predicted increased ICP than ONSD, with a higher AUC (0.98 [95% CI: 0.95, 1.00] vs 0.86 [95% CI: 0.71, 0.95], P = .047). Conclusion An imaging ratio was proposed to predict ICP based on the relative anatomy of the cerebrospinal fluid space, demonstrating more accurate diagnosis of increased ICP and a strong correlation with ICP values, suggesting its potential utility as a neuroimaging marker in clinical settings. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Shepherd in this issue.

Role of point-of-care ultrasound (POCUS) in clinical hepatology

Hospitalized patients with cirrhosis frequently require critical care management for sepsis, HE, respiratory failure, acute variceal bleeding, acute kidney injury (AKI), shock, and optimization for liver transplantation, while outpatients have unique care considerations. Point-of-care ultrasonography (POCUS) enhances bedside examination of the hepatobiliary system and relevant extrahepatic sites. POCUS includes cardiac US and is used to assess volume status and hemodynamic parameters like cardiac output, systemic vascular resistance, cardiac contractility, and pulmonary artery pressure, which aid in the early and accurate diagnosis of heart failure, cirrhotic cardiomyopathy, porto-pulmonary hypertension, hepatopulmonary syndrome, arrhythmia, and pulmonary embolism. This also helps in fluid management and vasopressor use in the resuscitation of patients with cirrhosis. Lung ultrasound (LUS) can help in differentiating pneumonia, effusion, and edema. Further, US guides interventions such as line placement, drainage of abdominal collections/abscesses, relief of tension pneumothorax, drainage of pleural and pericardial effusions, and biliary drainage in cholangitis. Additionally, its role is essential to assess liver masses foci of sepsis, for appropriate sites for paracentesis, and to assess for vascular disorders such as portal vein or hepatic vein thrombosis. Renal US can identify renal and postrenal causes of AKI and aid in diagnosis of prerenal AKI through volume assessment. In this review, we address the principles and methods of POCUS in hospitalized patients and in outpatients with cirrhosis and discuss the application of this diverse modality in clinical hepatology.

Sex differences in the diagnostic value of optic nerve sheath diameter for assessing intracranial pressure

The optic nerve sheath diameter (ONSD) can predict elevated intracranial pressure (ICP) but it is not known whether diagnostic characteristics differ between men and women. This observational study was performed at the Karolinska University Hospital in Sweden to assess sex differences in diagnostic accuracy for ONSD. We included 139 patients (65 women), unconscious and/or sedated, with invasive ICP monitoring. Commonly used ONSD derived measurements and associated ICP measurements were collected. Linear regression analyses were performed with ICP as dependent variable and ONSD as independent variable. Area under the receiver operator characteristics curve (AUROC) analyses were performed with a threshold for elevated ICP ≥ 20 mmHg. Analyses were stratified by sex. Optimal cut-offs and diagnostic characteristics were estimated. The ONSD was associated with ICP in women. The AUROCs in women ranged from 0.70 to 0.83. In men, the ONSD was not associated with ICP and none of the AUROCs were significantly larger than 0.5. This study suggests that ONSD is a useful predictor of ICP in women but may not be so in men. If this finding is verified in further studies, this would call for a re-evaluation of the usage and interpretation of ONSD to estimate ICP.

Optic Nerve Sheath Diameter for Assessing Prognosis after Out-of-Hospital Cardiac Arrest

PURPOSE

Evaluate optic nerve sheath and pial diameters (ONSD, ONPD) via sonography and computed tomography (CT) after out-of-hospital cardiac arrest (CA) and to compare their prognostic significance with other imaging and laboratory biomarkers.

MATERIALS AND METHODS

A prospective observational study enrolling patients after successful resuscitation between December 2017 and August 2021. ONSD and ONPD were measured with sonography. Additionally, ONSD, and also grey-to-white ratio at basal ganglia (GWRBG) and cerebrum (GWRCBR), were assessed using CT. Lactate and neuron specific enolase (NSE) blood levels were measured.

RESULTS

Sonographically measured ONSD and ONPD yielded no significant difference between survival and non-survival (p values ≥0.4). Meanwhile, CT assessed ONSD, GWRBG, GWRCBR, and NSE levels significantly differed regarding both, survival (p values ≤0.005) and neurological outcome groups (p values ≤0.04). For survival prognosis, GWRBG, GWRCBR, and NSE levels appeared as excellent predictors; in predicting a good neurological outcome, NSE had the highest accuracy.

CONCLUSIONS

CT diagnostics, in particular GWRBG and GWRCBR, as well as NSE as laboratory biomarker, appear as excellent outcome predictors. Meanwhile, our data lead us to recommend caution in utilizing sonography assessed ONSD and ONPD for prognostic decision-making post-CA.

Transorbital sonography in idiopathic intracranial hypertension: Single-center study, systematic review and meta-analysis

BACKGROUND AND PURPOSE

Transorbital sonography (TOS) provides a noninvasive tool to detect intracranial pressure by assessing optic nerve sheath diameter (ONSD) and optic disc elevation (ODE). The utility of TOS in the diagnosis of idiopathic intracranial hypertension (IIH) has been increasingly recognized.

METHODS

A single-center case-control study sought to compare TOS-acquired ONSD and ODE among IIH-cases versus patients with other neurological diseases (controls). Furthermore, a systematic review and meta-analysis was conducted to present pooled mean differences and diagnostic measures of ONSD and ODE between IIH-cases and controls.

RESULTS

In the single-center study, consisting of 31 IIH-cases and 34 sex- and age-matched controls, ONSD values were higher among IIH-cases than controls (p<.001), while ODE was more prevalent in cases (65% vs. 15%; p<.001). The receiver-operating characteristic (ROC)-curve analysis revealed that the optimal cutoff value of ONSD for predicting IIH was 5.15 mm, with an area under the curve (AUC) of 0.914 (95% confidence interval [CI]: 0.861-0.967) and sensitivity and specificity values of 85% and 90%, respectively. In a meta-analysis of 14 included studies with 415 IIH-cases, ONSD and ODE values were higher in IIH-cases than controls (mean difference in ONSD 1.20 mm; 95% CI: 0.96-1.44 mm and in ODE 0.3 mm; 95% CI: 0.33-0.67 mm). With regard to ONSD, pooled sensitivity, specificity, and diagnostic odds ratio were calculated at 85.5% (95% CI: 77.9-90.8%), 90.7% (95% CI: 84.6-94.5%), and 57.394 (95% CI: 24.597-133.924), respectively. The AUC in summary ROC-curve analysis was 0.878 (95% CI: 0.858-0.899) with an optimal cutoff point of 5.0 mm.

CONCLUSIONS

TOS has a high diagnostic utility for the noninvasive diagnosis of IIH and may deserve wider implementation in everyday clinical practice.

Transorbital sonography and MRI reliability to assess optic nerve sheath diameter in idiopathic intracranial hypertension

BACKGROUND AND PURPOSE

The purpose of this study was to evaluate the performance of magnetic resonance imaging (MRI) in measuring the optic nerve sheath diameter (ONSD) compared to the established method transorbital sonography (TOS) in patients with idiopathic intracranial hypertension (IIH).

METHODS

Twenty-three patients with IIH were prospectively included applying IIH diagnostic criteria. All patients received a lumbar puncture with assessment of the cerebrospinal fluid (CSF) opening pressure to assure the IIH diagnosis. Measurement of ONSD was performed 3 mm posterior to inner sclera surface in B-TOS by an expert examiner, while three independent neuroradiologists took measurements in axial T-weighted MRI examinations. The sella turcica with the pituitary gland (and potential presence of an empty sella) and the trigeminal cavity were also assessed on sagittal and transversal T1-weighted MRI images by one independent neuroradiologist.

RESULTS

The means of ONSD between ultrasound and MRI measurements were 6.3 mm (standard deviation [SD] = 0.6 mm) and 6.2 mm (SD = 0.8 mm). The interrater reliability between three neuroradiologists showed a high interclass correlation coefficient (ICC) (confidence interval: .573 < ICC < .8; p < .001). In patients with an empty sella, the ONSD evaluated by MRI was 6.6 mm, while measuring 6.1 mm in patients without empty sella. No correlation between CSF opening pressure and ONSD was found.

CONCLUSIONS

MRI can reliably measure ONSD and yields similar results compared to TOS in patients with IIH. Moreover, patients with empty sella showed significantly larger ONSD than patients without empty sella.

A Narrative Review of Point of Care Ultrasound Assessment of the Optic Nerve in Emergency Medicine

Point of care ultrasound (POCUS) of the optic nerve is easy to learn and has great diagnostic potential. Within emergency medicine, research has primarily focused on its use for the assessment of increased intracranial pressure, but many other applications exist, though the literature is heterogeneous and largely observational. This narrative review describes the principles of POCUS of the optic nerve including anatomy and scanning technique, as well as a summary of its best studied clinical applications of relevance in emergency medicine: increased intracranial pressure, idiopathic intracranial hypertension, optic neuritis, acute mountain sickness, and pediatric intracranial pressure assessment. In many of these applications, sonographic optic nerve sheath diameter (ONSD) has moderately high sensitivity and specificity, but the supporting studies are heterogeneous. Further studies should focus on standardization of the measurement of ONSD, establishment of consistent diagnostic thresholds for elevated intracranial pressure, and automation of ONSD measurement.

Optic nerve sheath diameter in intracranial hypertension: Measurement external or internal of the dura mater?

BACKGROUND AND PURPOSE

Optic nerve sheath diameter (ONSD) is a promising metric to estimate intracranial pressure (ICP). There is no consensus whether ONSD should be measured external (ONSDext) or internal (ONSDint) of the dura mater. Expert opinion favors ONSDint, though without clear evidence to support this. Adjustments of ONSD for eye diameter (ED) and optic nerve diameter (OND) have been suggested to improve precision. We examined the diagnostic accuracy of ONSDext and ONSDint for estimating ICP, unadjusted as well as adjusted for ED and OND.

METHODS

We performed an observational cohort study, measuring ONSDext and ONSDint in patients with invasive ICP monitoring at Karolinska University Hospital in Stockholm, Sweden. We used ONSDext and ONSDint unadjusted as well as adjusted for ED and for OND. We compared the area under the receiver operator characteristics curve (AUROC) for these methods. Thresholds for elevated ICP were set at ≥20 and ≥22 mmHg, respectively.

RESULTS

We included 220 measurements from 100 patients. Median ONSDext and ONSDint were significantly different at 6.7 and 5.2 mm (p = .00). There was no significant difference in AUROC for predicting elevated ICP between ONSDext and ONSDint (.67 vs. .64, p = .31). Adjustment for ED yielded better diagnostic accuracy (AUROC, cutoff, sensitivity, specificity) for ONSDext/ED (.76, .29, .81, .62) and ONSDint/ED (.71, .24, .5, .89).

CONCLUSIONS

ONSDext and ONSDint differ significantly and are not interchangeable. However, there were no significant differences in diagnostic accuracy between ONSDext and ONSDint. Adjustment for ED may improve diagnostic accuracy of ONSD.

POCUS, how can we include the brain? An overview

Point-of-care ultrasound (POCUS) is an essential tool to assess and manage different pathologies in the intensive care unit, and many protocols have been proposed for its application in critical care literature. However, the brain has been overlooked in these protocols.

Brain ultrasonography (BU) is easily available, and it allows a goal-directed approach thanks to its repeatability and immediate interpretation and provides a quick management and real time assessment of patients’ conditions. Based on recent studies, the increasing interest from intensivists, and the undeniable benefits of ultrasound, the main goal of this overview is to describe the main evidence and progresses in the incorporation of BU into the POCUS approach in the daily practice, and thus becoming POCUS-BU. This integration would allow a noninvasive global assessment to entail an integrated analysis of the critical care patients.

Echographic criteria for the assessment of the optic nerve condition in intracranial hypertension

Purpose: to develop objective acoustic criteria of the condition of the optic nerve and its sheaths for an early diagnosis of intracranial hypertension (IH). Material and methods. The research involved 24 patients (average age 35.8 ± 8.5 years) with suspected IH. The control group consisted of 48 healthy subjects (average age 28.5 ± 9.5 years). Ultrasound examination of the retrobulbar part of the optic nerve (ON) included the measurement of the ON thickness with sheaths (ONSD) and without sheaths (OND) and the calculation of the ratio K = ONSD/ OND. Echodensitometry was used to evaluate the echographic density of the parenchyma and the sheaths of the optic nerve. All patients were tested with magnetic resonance imaging (MRI) to analyse brain images. Results. The biometrical parameters of ON in healthy subjects were as follows: ONS 2.64 ± 0.21 mm and ONSD — 4.60 ± 0.34 mm. In patients with suspected IH the average parameters of the ON diameter were as follows: ONS — 2.57 ± 0.25 mm and ONSD — 5.81 ± 0.42 mm. A comparative assessment of the ON thickness with and without sheaths showed that in the control group the values of ONS did not exceed 3.5 mm and ONSD did not exceed 5.0 mm. In patients with IH, the values of ONSD were significantly higher than those in the control group (p < 0.05). The ratio coefficient (K)=ONSD/ONS in the group of healthy subjects ranged from 1.53 to 2.0 and averaged 1.75 ± 0.14. In patients with IH the values of K exceeded 2.0 (2,40 ± 0.18). The analysis of acoustic density data showed a significant variability in the parameters of the ON sheaths echodensitometry in IH patients as compared to the norm. Conclusion. The echography of the ON makes it possible to determine the acoustic and biometric parameters of the ON with high accuracy, to assess its structure and relationship with the surrounding tissues. The ratio coefficient (K) of ONSD/ONS makes it possible to determine IH in the early stages of the disease, even in the absence of objective clinical criteria.

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

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.

Optic nerve sheath diameter is associated with outcome in severe Covid-19

Neurological symptoms are common in Covid-19 and cerebral edema has been shown post-mortem. The mechanism behind this is unclear. Elevated intracranial pressure (ICP) has not been extensively studied in Covid-19. ICP can be estimated noninvasively with measurements of the optic nerve sheath diameter (ONSD). We performed a cohort study with ONSD ultrasound measurements in severe cases of Covid-19 at an intensive care unit (ICU). We measured ONSD with ultrasound in adults with severe Covid-19 in the ICU at Karolinska University Hospital in Sweden. Patients were classified as either having normal or elevated ONSD. We compared ICU length of stay (ICU-LOS) and 90 day mortality between the groups. 54 patients were included. 11 of these (20.4%) had elevated ONSD. Patients with elevated ONSD had 12 days longer ICU-LOS (95% CI 2 to 23 p = 0.03) and a risk ratio of 2.3 for ICU-LOS ≥ 30 days. There were no significant differences in baseline data or 90 day mortality between the groups. Elevated ONSD is common in severe Covid-19 and is associated with adverse outcome. This may be caused by elevated ICP. This is a clinically important finding that needs to be considered when deciding upon various treatment strategies.

Quality assessment of optic nerve sheath diameter ultrasonography: Scoping literature review and Delphi protocol

BACKGROUND AND PURPOSE

The optic nerve is surrounded by the extension of meningeal coverings of the brain. When the pressure in the cerebrospinal fluid increases, it causes a distention of the optic nerve sheath diameter (ONSD), which allows the use of this measurement by ultrasonography (US) as a noninvasive surrogate of elevated intracranial pressure. However, ONSD measurements in the literature have exhibited significant heterogeneity, suggesting a need for consensus on ONSD image acquisition and measurement. We aim to establish a consensus for an ONSD US Quality Criteria Checklist (ONSD US QCC).

METHODS

A scoping systematic review of published ultrasound ONSD imaging and measurement criteria was performed to guide the development of a preliminary ONSD US QCC that will undergo a modified Delphi study to reach expert consensus on ONSD quality criteria. The protocol of this modified Delphi study is presented in this manuscript.

RESULTS

A total of 357 ultrasound studies were included in the review. Quality criteria were evaluated under five categories: probe selection, safety, positioning, image acquisition, and measurement.

CONCLUSIONS

This review and Delphi protocol aim to establish ONSD US QCC. A broad consensus from this process may reduce the variability of ONSD measurements in future studies, which would ultimately translate into improved ONSD clinical applications. This protocol was reviewed and endorsed by the German Society of Ultrasound in Medicine.

Ultrasound Detection of Intracranial Hypertension in Brain Injuries

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.

Optic Nerve Sheath Diameter Ultrasound: A Non-Invasive Approach to Evaluate Increased Intracranial Pressure in Critically Ill Pediatric Patients

Early diagnosis of increased intracranial pressure (ICP) is crucial for prompt diagnosis and treatment of intracranial hypertension in critically ill pediatric patients, preventing secondary brain damage and mortality. Although the placement of an external ventricular drain coupled to an external fluid-filled transducer remains the gold standard for continuous ICP monitoring, other non-invasive approaches are constantly being improved and can provide reliable estimates. The use of point-of-care ultrasound (POCUS) for the assessment of ICP has recently become widespread in pediatric emergency and critical care settings, representing a valuable extension of the physical examination. The aim of this manuscript is to review and discuss the basic principles of ultra-sound measurement of the optic nerve sheath diameter (ONSD) and summarize current evidence on its diagnostic value in pediatric patients with ICP. There is increasing evidence that POCUS measurement of the ONSD correlates with ICP, thus appearing as a useful extension of the physical examination in pediatrics, especially in emergency medicine and critical care settings for the initial non-invasive assessment of patients with suspected raised ICP. Its role could be of value even to assess the response to therapy and in the follow-up of patients with diagnosed intracranial hypertension if invasive ICP monitoring is not available. Further studies on more homogeneous and extensive study populations should be performed to establish ONSD reference ranges in the different pediatric ages and to define cut-off values in predicting elevated ICP compared to invasive ICP measurement.