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We analyzed the prognostic performance of optic nerve sheath diameter (ONSD) on thin-slice (0.6 mm) brain computed tomography (CT) reconstruction images as compared to routine-slice (4 mm) images. We conducted a retrospective analysis of brain CT images taken within 2 h after cardiac arrest. The maximal ONSD (mONSD) and optic nerve sheath area (ONSA) were measured on thin-slice images, and the routine ONSD (rONSD) and gray-to-white matter ratio (GWR) were measured on routine-slice images. We analyzed their area under the receiver operator characteristic curve (AUC) and the cutoff values for predicting a poor 6-month neurological outcome (a cerebral performance category score of 3–5). Of the 159 patients analyzed, 113 patients had a poor outcome. There was no significant difference in rONSD between the outcome groups (p = 0.116). Compared to rONSD, mONSD (AUC 0.62, 95% CI: 0.54–0.70) and the ONSA (AUC 0.63, 95% CI: 0.55–0.70) showed better prognostic performance and had higher sensitivities to determine a poor outcome (mONSD, 20.4% [95% CI, 13.4–29.0]; ONSA, 16.8% [95% CI, 10.4–25.0]; rONSD, 7.1% [95% CI, 3.1–13.5]), with specificity of 95.7% (95% CI, 85.2–99.5). A combined cutoff value obtained by both the mONSD and GWR improved the sensitivity (31.0% [95% CI, 22.6–40.4]) of determining a poor outcome, while maintaining a high specificity. In conclusion, rONSD was clinically irrelevant, but the mONSD had an increased sensitivity in cutoff having acceptable specificity. Combination of the mONSD and GWR had an improved prognostic performance in these patients.

Background: Increased intracranial pressure (ICP) is a known complication of pre-eclampsia with severe features. The use of magnesium sulphate (MgSO4) is the standard treatment and is associated with marked reduction of cerebral perfusion pressure (CPP) and prevention of cerebral damage. Optic nerve sheath diameter (ONSD) ultrasonography is a bedside tool used to reflect changes in the ICP. The aim of this study is to detect the effect of MgSO4 administration on ICP in severe preeclampsia through measuring changes in the ONDS. Methods: Thirty pregnant female patients suffering from severe pre-eclampsia were enrolled in this prospective pilot study. Ultrasound measurement of ONSD was measured before the commencement of MgSO4 and after 1, 6, and 24 h after the administration. Results: There was a significant difference in ONSD measurements between that at baseline and post magnesium administration at 1, 6, and 24 h (P-value 0.001). Additionally, a significant difference in measurements between 1 and 6 and 6 and 24 h after magnesium initiation (P-value 0.001). Conclusions: Ultrasound ONSD measurement in patients with severe preeclampsia is a non-invasive easy tool to detect increased intracranial pressure and monitor the response to magnesium sulphate infusion.

SummaryPurposeAlthough invasive intracranial devices (IIDs) are the gold standard for intracranial pressure (ICP) measurement, ultrasonography of the optic nerve sheath diameter (ONSD) has been suggested as a potential non-invasive ICP estimator. We performed a meta-analysis to evaluate the diagnostic accuracy of sonographic ONSD measurement for assessment of intracranial hypertension (IH) in adult patients.MethodsWe searched on electronic databases (MEDLINE/PubMed®, Scopus®, Web of Science®, ScienceDirect®, Cochrane Library®) until 31 May 2018 for comparative studies that evaluated the efficacy of sonographic ONSD vs. ICP measurement with IID. Data were extracted independently by two authors. We used the QUADAS-2 tool for assessing the risk of bias (RB) of each study. A diagnostic meta-analysis following the bivariate approach and random-effects model was performed.ResultsSeven prospective studies (320 patients) were evaluated for IH detection (assumed with ICP > 20 mmHg or > 25 cmH2O). The accuracy of included studies ranged from 0.811 (95% CI 0.678‒0.847) to 0.954 (95% CI 0.853‒0.983). Three studies were at high RB. No significant heterogeneity was found for the diagnostic odds ratio (DOR), positive likelihood ratio (PLR) and negative likelihood ratio (NLR), with I2 < 50% for each parameter. The pooled DOR, PLR and NLR were 67.5 (95% CI 29‒135), 5.35 (95% CI 3.76‒7.53) and 0.088 (95% CI 0.046‒0.152), respectively. The area under the hierarchical summary receiver-operating characteristic curve (AUHSROC) was 0.938. In the subset of five studies (275 patients) with IH defined for ICP > 20 mmHg, the pooled DOR, PLR and NLR were 68.10 (95% CI 26.8‒144), 5.18 (95% CI 3.59‒7.37) and 0.087 (95% CI 0.041‒0.158), respectively, while the AUHSROC was 0.932.ConclusionsAlthough the wide 95% CI in our pooled DOR suggests caution, ultrasonographic ONSD may be a potentially useful approach for assessing IH when IIDs are not indicated or available (CRD42018089137, PROSPERO).

Hyperammonemia is generally used in clinical practice for assessment of liver failure and hepatic encephalopathy. However, especially in the intensive care unit (ICU), many other conditions can increase the serum ammonia level (SAL). Also, high ammonia levels cause swelling in astrocytes located in the optic nerve sheath (ONS). In this prospective observational study, the relationship between SAL and mortality and ONS diameter (ONSD) values was investigated in ICU patients. All patients who older than 18 years of age and who were hospitalized in the tertiary ICU between September/2022 and February/2023 without intracranial acute and chronic pathology were included. Patients with a history of meningitis, encephalitis, cerebrovascular accident, intracranial mass, head trauma, as well as patients with acute or chronic pathology in their cranial imaging were excluded from the study. SAL, other laboratory tests, demographic information, ONSD measurements and other clinical information were obtained in the first 48 h of ICU admission. ONSD measurements were made using the linear probe of the standard USG device while the patients were lying in the 30-degree supine position. ONSD measurements were made on the transverse and sagittal axes of both eyes as external (eONSD, between both dura mater-subarachnoid junction), internal (iONSD, between both piamater-subarachnoid junction) and optic nerve fiber (OND) thickness (Fig. 1). Each measurement was repeated 3 times. The cut-off value for high SAL was determined as 60 μg /dL. A total of 49 patients were included in the study. The median age of the patients was 74 [62–81] years and 27 (55%) of them were female. The body mass index (BMI), APACHE II and SOFA score were found as respectively 25 [22–31], 18 [13–21] and 5 [4–8]. Twenty (40.8%) of the patients were intubated. SALs were determined as 28.6 [19–45.4] μg /dL. A total of 7 patients had high ammonia levels and 6 of them died during ICU follow-up (p = 0.036). According to binary logistic analysis, SAL (p = 0.027, Exp(B) = 1.065 [1.007–1.126]), APACHE II score and serum lactate level were determined as independent risk factors for mortality. The eONSD, iONSD and OND values were 0.55 [0.52–0.60], 0.45 [0.41–0.48], 0.32 [0.30–0.35], respectively. No correlation was detected between ONSD measurements and SAL. High serum ammonia level is a marker for mortality in the ICU patients.

Purpose To evaluate the diagnostic accuracy of ultrasonography of optic nerve sheath diameter (ONSD) for assessment of intracranial hypertension. Methods Systematic review without language restriction based on electronic databases, with manual review of literature and conference proceedings until July 2010. Studies were eligible if they compared ultrasonography of ONSD with intracranial pressure (ICP) monitoring. Data were extracted independently by three authors. Random-effects meta-analysis and meta-regression were performed. Results Six studies including 231 patients were reviewed. No significant heterogeneity was detected for sensitivity, specificity, positive and negative likelihood ratios or diagnostic odds ratio. For detection of raised intracranial pressure, pooled sensitivity was 0.90 [95% confidence interval (CI) 0.80–0.95; p for heterogeneity, p het  = 0.09], pooled specificity was 0.85 (95% CI 0.73–0.93, p het  = 0.13), and the pooled diagnostic odds ratio was 51 (95% CI 22–121). The area under the summary receiver-operating characteristic (SROC) curve was 0.94 (95% CI 0.91–0.96). Conclusions Ultrasonography of ONSD shows a good level of diagnostic accuracy for detecting intracranial hypertension. In clinical decision-making, this technique may help physicians decide to transfer patients to specialized centers or to place an invasive device when specific recommendations for this placement do not exist.

Background Although placement of an intra-cerebral catheter remains the gold standard method for measuring intracranial pressure (ICP), several non-invasive techniques can provide useful estimates. The aim of this study was to compare the accuracy of four non-invasive methods to assess intracranial hypertension. Methods We reviewed prospectively collected data on adult intensive care unit (ICU) patients with traumatic brain injury (TBI), subarachnoid hemorrhage (SAH), or intracerebral hemorrhage (ICH) in whom invasive ICP monitoring had been initiated and estimates had been simultaneously collected from the following non-invasive indices: optic nerve sheath diameter (ONSD), pulsatility index (PI), estimated ICP (eICP) using transcranial Doppler, and the neurological pupil index (NPI) measured using automated pupillometry. Intracranial hypertension was defined as an invasively measured ICP > 20 mmHg. Results We studied 100 patients (TBI = 30; SAH = 47; ICH = 23) with a median age of 52 years. The median invasively measured ICP was 17 [12–25] mmHg and intracranial hypertension was present in 37 patients. Median values from the non-invasive techniques were ONSD 5.2 [4.8–5.8] mm, PI 1.1 [0.9–1.4], eICP 21 [14–29] mmHg, and NPI 4.2 [3.8–4.6]. There was a significant correlation between all the non-invasive techniques and invasive ICP (ONSD, r  = 0.54; PI, r  = 0.50; eICP, r  = 0.61; NPI, r  = − 0.41— p  < 0.001 for all). The area under the curve (AUC) to estimate intracranial hypertension was 0.78 [CIs = 0.68–0.88] for ONSD, 0.85 [95% CIs 0.77–0.93] for PI, 0.86 [95% CIs 0.77–0.93] for eICP, and 0.71 [95% CIs 0.60–0.82] for NPI. When the various techniques were combined, the highest AUC (0.91 [0.84–0.97]) was obtained with the combination of ONSD with eICP. Conclusions Non-invasive techniques are correlated with ICP and have an acceptable accuracy to estimate intracranial hypertension. The multimodal combination of ONSD and eICP may increase the accuracy to estimate the occurrence of intracranial hypertension.

The measurement of optic nerve sheath diameter (ONSD) is a rapid, safe, and non-invasive method for assessing increased intracranial pressure (ICP). This study aimed to determine the mean ONSD in a healthy Iranian adult population and its correlation with demographic and anthropometric factors. Given that normal ONSD values can vary based on sex, age, ethnicity, and ultrasound techniques, establishing a local reference can enhance clinical assessment. In this cross-sectional study, 100 healthy Iranian adults (mean age 38.7 ± 9.8 years; 60 females) underwent ultrasonographic examination of the left optic nerve sheath. ONSD was measured 3 mm behind the globe in two planes, and the average of these measurements was calculated. The mean axial length (AL) was 23.53 mm (SD ± 0.94), and the mean ONSD was noted at 6.3 mm (SD ± 0.42). Statistical analysis did not reveal significant correlations between ONSD and various demographic or anthropometric factors (P:0.236). This study contributes to the literature by providing local reference values for ONSD in a healthy Iranian adult population, establishing an upper limit of 6.3 mm, and highlighting the consistency of these values with international norms, thereby improving the assessment of ICP in diverse populations.

BackgroundEstimation of intracranial pressure (ICP) may be helpful in the management of neurological critically ill patients. It has been shown that ultrasonography of the optic nerve sheath diameter (ONSD) is a reliable tool for non-invasive estimation of increased intracranial pressure (ICP) at hospital admission or in intensive care. Less is known about the estimation of increased ICP and usefulness of ONSD in the prehospital setting. The aim of this review was to elucidate both prevailing and novel applications of ONSD for neurologists and critical care physicians.MethodsIn this review, we discuss the technique and the novel approach of ONSD measurement, the clinical applications of ONSD in neurology and critical care patients.ResultsONSD measurement is simple, easy to learn, and has diverse applications. ONSD has utility for ICP measurement in intracranial hemorrhage and ischemic stroke, meningitis and encephalitis, and idiopathic intracranial hypertension (IIH). It is also valuable for lesser known syndromes, where an increase of ICP is postulated, such as acute mountain sickness and posterior reversible encephalopathy syndrome. ONSD changes develop in inflammatory or ischemic optic neuropathies. Some papers demonstrate the usefulness of ONSD studies in symptomatic intracranial hypotension.ConclusionsONSD is a safe and low-cost bedside tool with the potential of screening patients who need other neuroimaging and those who may need an invasive measurement of ICP.

Brain ultrasonography can be used to evaluate cerebral anatomy and pathology, as well as cerebral circulation through analysis of blood flow velocities. Transcranial colour-coded duplex sonography is a generally safe, repeatable, non-invasive, bedside technique that has a strong potential in neurocritical care patients in many clinical scenarios, including traumatic brain injury, aneurysmal subarachnoid haemorrhage, hydrocephalus, and the diagnosis of cerebral circulatory arrest. Furthermore, the clinical applications of this technique may extend to different settings, including the general intensive care unit and the emergency department. Its increasing use reflects a growing interest in non-invasive cerebral and systemic assessment. The aim of this manuscript is to provide an overview of the basic and advanced principles underlying brain ultrasonography, and to review the different techniques and different clinical applications of this approach in the monitoring and treatment of critically ill patients.

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.