Correlation of Optic Nerve Sheath Diameter with Direct Measurement of Intracranial Pressure

Background: Measurements of the optic nerve sheath diameter (ONSD) using bedside ultrasound (US) have been shown to correlate with clinical and radiologic signs and symptoms of increased intracranial pressure (ICP). Objectives: Previous literature has identified 5 mm as the ONSD measurement above which patients exhibit either clinical or radiologic signs of elevated ICP. The goals of this study were to evaluate the association between ONSD and ICP and to validate the commonly used ONSD threshold of 5 mm using direct measurements of ICP as measured by ventriculostomy. Methods: A prospective blinded observational study was performed using a convenience sample of adult patients in both the emergency department (ED) and the neurologic intensive care unit (ICU) who had invasive intracranial monitors placed as part of their clinical care. Ocular USs were performed with a 10–5 MHz linear probe. Emergency physicians (EPs) with previous ocular US experience performed ONSD measurements while blinded to the contemporaneous ICP reading obtained directly from invasive monitoring. The association between ONSD and ICP was assessed with the Spearman rank correlation coefficient, and a receiver operator characteristic (ROC) curve was created to determine the optimal ONSD cutoff to detect ICP > 20 cm H₂O. Results: Thirty‐eight ocular USs were performed on 15 individual patients. Spearman rank correlation coefficient of ONSD and ICP was 0.59 (p < 0.0005) demonstrating a significant positive correlation. An ROC curve was created to assess the ability of ONSD to distinguish an abnormal ICP greater than 20 cm H₂O. The area under the ROC curve was 0.93 (95% confidence interval [CI] = 0.84 to 0.99). Based on inspection of the ROC curve, ONSD > 5 mm performed well to detect ICP > 20 cm H₂O with a sensitivity of 88% (95% CI = 47% to 99%) and specificity of 93% (95% CI = 78% to 99%). Conclusions: Using an ROC curve the authors systematically confirmed the commonly used threshold of ONSD > 5 mm to detect ICP > 20 cm H₂O. This study directly correlates ventriculostomy measurements of ICP with US ONSD measurements and provides further support for the use of ONSD measurements as a noninvasive test for elevated ICP.     

肢体的外周神经鞘类肿瘤的高频超声表现

目的：探讨肢体的外周神经鞘类肿瘤的高频超声图像特征。方法：用高频超声检查了肢体的外周神经鞘类肿瘤6例，其中4例为神经鞘瘤，2例为神经纤维瘤。结果：神经鞘瘤和神经纤维瘤的超声表现是：两者都为实性低回声肿物，卵圆形，边界清楚，并可见肿物与神经纤维相连。高频超声还可发现神经纤维瘤的中心部有神经出入，而神经鞘瘤则无此现象。结论：高频超声很容易观察到肢体较大的神经干与神经类肿物相连，根据肿瘤与神经不同的连接方式帮助鉴别神经纤维瘤和神经鞘瘤。     

The Impact of Head of Bed Elevation on Optic Nerve Sheath Diameter in Cervical Collar Applied Healthy Volunteers

Background

Guidelines recommend placing a cervical collar (c-collar) until spinal injury is excluded. Previous studies have shown that c-collar placement increases intracranial pressure (ICP), which can worsen outcomes for trauma patients who are at risk of increased ICP. Head of bed elevation (HBE) has been found to decrease ICP. However, there is no consensus in the literature for the optimal degree of HBE to decrease ICP.

Normal Age- and Sex-Related Values of the Optic Nerve Sheath Diameter and Its Dependency on Position and Positive End-Expiratory Pressure

Optic nerve sheath diameter (ONSD) sonography is a reliable method for evaluation of intracranial pressure, yet there is a lack of reliable normal values. In the study described here, we established normal ONSD values in three different age groups and both sexes. One hundred eighty-seven volunteers without central nervous system disease were enrolled in this prospective study. ONSD measurements were taken in volunteers in the supine and upright positions and after application of positive end-expiratory pressure (PEEP). Normal ONSD values were 4.9–5.3 mm (patient age range: 20–85), with significant differences between men and women (p < 0.001). ONSD values increased with age (∆ = 0.34 mm, p < 0.001). There were no differences compared with the upright position but application of PEEP led to significantly increased ONSD values (∆ = 0.21 mm, p = 0.008). ONSD values increased with age, correlated well with the width of the third ventricle, were significantly lower in the female cohort and quickly responded to PEEP, especially in women.     

床旁超声测量视神经鞘直径对颅脑损伤患者颅内压增高的诊断价值

[目的]探讨利用床旁超声测量视神经鞘直径在颅脑损伤患者中检出颅内压（ICP）增高者的应用价值.[方法]35例颅脑损伤（ICP正常22例,ICP增高13例）患者及10名健康志愿者行床旁超声检查测量视神经鞘直径,并对颅脑损伤患者进行ICP测定.比较三组之间视神经鞘直径,计算视神经鞘直径与ICP的相关性,利用ROC曲线探究预测ICP增高的最佳阈值及准确性.[结果]ICP增高组视神经鞘直径显著高于ICP正常组及对照组（P〈0.05）,ICP正常组视神经鞘直径与对照组差异无统计学意义（P〉0.05）,视神经鞘直径与ICP之间存在正相关关系（r=0.733,P〈0.01）.ROC曲线显示视神经鞘直径≥5.0 mm作为判断标准效果最佳,此时敏感度86.4%（19/22）、特异度84.6%（11/13）、准确度85.7%（30/35）、阳性预测值90.5%（19/21）、阴性预测值78.9%（11/14）.[结论]床旁超声测量视神经鞘直径能够较好预测ICP水平,当视神经鞘直径≥5.0mm提示ICP增高.     

Elevated Intracranial Pressure Detected by Bedside Emergency Ultrasonography of the Optic Nerve Sheath

Patients with altered level of consciousness may be suffering from elevated intracranial pressure (EICP) from a variety of causes. A rapid, portable, and noninvasive means of detecting EICP is desirable when conventional imaging methods are unavailable. OBJECTIVES: The hypothesis of this study was that ultrasound (US) measurement of the optic nerve sheath diameter (ONSD) could accurately predict the presence of EICP. METHODS: The authors performed a prospective, blinded observational study on emergency department (ED) patients with a suspicion of EICP due to possible focal intracranial pathology. The study was conducted at a large community ED with an emergency medicine residency program and took place over a six-month period. Patients suspected of having EICP by an ED attending were enrolled when study physicians were available. Unstable patients were excluded. ONSD was measured 3 mm behind the globe using a 10-MHz linear probe on the closed eyelids of supine patients, bilaterally. Based on prior literature, an ONSD above 5 mm on ultrasound was considered abnormal. Computed tomography (CT) findings defined as indicative of EICP were the presence of mass effect with a midline shift 3 mm or more, a collapsed third ventricle, hydrocephalus, the effacement of sulci with evidence of significant edema, and abnormal mesencephalic cisterns. For each patient, the average of the two ONSD measurements was calculated and his or her head CT scans were evaluated for signs of EICP. Student's t-test was used to compare ONSDs in the normal and EICP groups. Sensitivity, specificity, and positive and negative predictive values were calculated. RESULTS: Thirty-five patients were enrolled; 14 had CT results consistent with EICP. All cases of CT-determined EICP were correctly predicted by ONSD over 5 mm on US. One patient with ONSD of 5.7 mm in one eye and 3.7 mm in the other on US had a mass abutting the ipsilateral optic nerve; no shift was seen on CT. He was placed in the EICP category on his data collection sheet. The mean ONSD for the 14 patients with CT evidence of EICP was 6.27 mm (95% CI = 5.6 to 6.89); the mean ONSD for the others was 4.42 mm (95% CI = 4.15 to 4.72). The difference of 1.85 mm (95% CI = 1.23 to 2.39 mm) yielded a p = 0.001. The sensitivity and specificity for ONSD, when compared with CT results, were 100% and 95%, respectively. The positive and negative predictive values were 93% and 100%, respectively. CONCLUSIONS: Despite small numbers and selection bias, this study suggests that bedside ED US may be useful in the diagnosis of EICP.     

视神经鞘超声评估颅内高压的研究进展

颅内高压是临床常见的危重急症之一,严重影响患者脑功能甚至危及患者生命。故需迅速、准确的颅内压评估方法以及时采取临床干预和对后续治疗效果的评估。有创监测仍然是评估颅内压的金标准,然而,该方法存在如感染和出血等潜在风险。以往文献报道视神经鞘超声检查可以无创评估颅内高压。本文就此综述如下。     

Quality And Feasibility of Sonographic Measurement of the Optic Nerve Sheath Diameter to Estimate the Risk of Raised Intracranial Pressure After Traumatic Brain Injury in Prehospital Setting

Objective: In patients with traumatic brain injury (TBI), early detection and subsequent prompt treatment of elevated intracranial pressure (ICP) is a challenge in the prehospital setting, because physical examination is limited in comatose patients and invasive device placement is not possible. The aim of this study was to evaluate the quality and feasibility of optic nerve sheath diameter (ONSD) measurements obtained during the prehospital management of patients with TBI. Methods: This study was a prospective, observational study of 23 patients with moderate and severe TBI during prehospital medical care. The primary endpoint was the quality of ONSD measurements expressed as the percentage of ONSD validated by the experts. Secondary endpoints included the feasibility of ONSD measurements as the percentage of ONSD performed and assessment by operators of ease and duration to perform. Results: Ultrasound ONSD was performed in 19 (82%) patients and 80% of ONSD measurements were validated by the experts. The ONSD measurements were possible in 15 (79%) cases. The physicians have assessed the ease of use at 8 (interquartile range [IQR]?=?2.5–8) on 10 for and the median time to obtain ONSD measurement was 4?min (IQR?=?3–5). ONSD measurement was performed in 12 (63%) cases during the transport and in 7 (37%) cases on scene, with 58% (n?=?7) and 71% (n?=?5) validated ONSD, respectively. The success rate in the helicopter was 43% compared to 80% in the ambulance. Conclusion: This study shows that it is feasible to obtain high-quality ONSD measurements in the management of patients with TBI in a prehospital setting. A randomized study evaluating the usefulness of ONSD to guide management of TBI in the prehospital phase may be of great interest.     

Acute Vascular Insufficiency of the Optic Nerve

Sudden, temporary loss of vision in one or both eyes is often the first sign of a diffuse vascular disorder that may affect other organ systems in a short time. Persistent visual loss in a patient who has had episodes of temporary loss of vision is almost diagnostic of ischemic optic nerve disease and calls for urgent measures (within the first two hours). While arteriosclerosis is the most common underlying process, giant- cell arteritis may be responsible. The diagnosis is confirmed by biopsy of a temporal artery. Steroid therapy is given in an effort to halt progression.