Optic nerve sheath diameter on initial brain CT,raised intracranial pressure and mortality after severe TBI: an interesting link needing confirmation

Optic nerve sheath diameter (ONSD) enlargement on initial computed tomography (CT) scan has been found to be associated with increased mortality after severe traumatic brain injury. This could offer the possibility to detect patients with raised intracranial pressure requiring urgent therapeutic interventions and/or invasive intracranial monitoring to guide the treatment. The method to measure ONSD using CT scan, however, needs further confirmation. Moreover, the link between ONSD enlargement on initial CT scan and raised intracranial pressure also needs to be confirmed by further studies.In a very interesting study performed on 77 severe traumatic brain injury patients, Legrand and colleagues found that the optic nerve sheath diameter (ONSD) measured on the initial brain computed tomography(CT) scan (performed within the first 3 hours of injury) was a very good predictor of ICU mortality [1]. In the multivariate analysis, ONSD >7.3 mm was independently associated with ICU mortality, and performed better than age >32 years, anisocoria at admission, and basal cistern compression on initial CT scan.The optic nerve is surrounded by a dural sheath that can inflate in cases of raised pressure in the cerebrospinal fluid. An enlarged ONSD, measured using ocular sonography, has been found in patients with raised intracranial pressure (ICP) [2]. Even if in Legrand and colleagues'' study the ICP was measured in only 9% of the patients, we can assume that the strong association between ONSD enlargement of initial CT and mortality was related to raised ICP occurring very early after trauma, as suggested by the fact that ONSD enlargement was also associated with other signs of raised ICP in the first CT scan as basal cistern effacement and midline shift. This is probably the major interest of this study: ONSD measurement on initial CT scan could offer the possibility to detect patients with raised ICP needing urgent therapeutic interventions and/or invasive intracranial monitoring to guide the treatment.Our enthusiasm must be tempered, however, as the method to measure ONSD using CT scan needs clarification and confirmation. ONSD has been measured 3 mm behind the globe - where the dural sheath is distensible, as has previously been determined using sonography [2-4] and magnetic resonance imaging [5]. In Legrand and colleagues'' study, ONSD has been measured on a millimetric slice brain CT scan but only in one plane. As suggested by Unsold and colleagues [6], since the optic nerve has a sinuous course in the horizontal and the vertical plane, a section of the nerve in a single plane can conduce one to overestimate ONSD. Actually, the values of ONSD in Legrand and colleagues'' study are larger than values obtained with ultrasound or magnetic resonance imaging or even with CT [7]. Moreover, the precise limits of the sheath and the orbital fat surrounding the sheath can be very difficult to determine. This study probably needs further confirmation of the reliability of the ONSD measurement, after realignment in the optic nerve plane and measurement in several axes.     

Use of T2-weighted magnetic resonance imaging of the optic nerve sheath to detect raised intracranial pressure

Introduction  

The dural sheath surrounding the optic nerve communicates with the subarachnoid space, and distends when intracranial pressure is elevated. Magnetic resonance imaging (MRI) is often performed in patients at risk for raised intracranial pressure (ICP) and can be used to measure precisely the diameter of optic nerve and its sheath. The objective of this study was to assess the relationship between optic nerve sheath diameter (ONSD), as measured using MRI, and ICP.     

Optic nerve sonography in the diagnostic evaluation of adult brain injury

Introduction  

The optic nerve sheath diameter (ONSD) may be increased in brain-injured patients, especially children, with intracranial hypertension. We investigated whether measurements of ONSD correlated with simultaneous noninvasive and invasive measurements of the intracranial pressure (ICP) in brain-injured adults.     

Optic nerve sheath diameter measurement for predicting raised intracranial pressure in adult patients with severe traumatic brain injury: A meta-analysis

ObjectiveTo evaluate and compare the diagnostic feasibility of measuring the optic nerve sheath diameter (ONSD), via brain computed tomography (CT) and ocular ultrasonography (US) for prediction of raised intracranial pressure (ICP) in severe traumatic brain injury (TBI) patients.MethodsThe PubMed and EMBASE databases were searched for studies assessing the diagnostic accuracy of brain CT or ocular US for predicting raised ICP. Bivariate and hierarchical summary receiver operating characteristic modeling were performed to evaluate and compare the diagnostic feasibility of measuring the ONSD in adult patients with severe TBI according to modality (ocular US vs. brain CT).ResultsFive studies (four with ocular US and one with brain CT) were included. The ONSD had a pooled sensitivity of 0.91, pooled specificity of 0.77, and area under the HSROC curve of 0.92 for predicting raised ICP. More importantly, studies using ocular US found an almost equal sensitivity (0.91 vs. 0.90; p = .35) and higher specificity (0.82 vs. 0.58; p = .01) than those using brain CT.ConclusionsMeasurement of the ONSD may be a useful method for predicting raised ICP in adult patients with severe TBI.     

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.     

The effects of spinal immobilization at 20° on intracranial pressure

ObjectiveIn this study, it was aimed to evaluate whether spinal immobilization at 20°, instead of the traditional 0°, affects intracranial pressure (ICP) via the ultrasonographic (USG) measurement of optic nerve sheath diameter (ONSD).Methods140 healthy, adult, non-smoking volunteers who had no acute or chronic diseases were included this study. Volunteers were randomly divided into two groups; performed spinal immobilization at 0° (Group 1) and at 20° (Group 2). After spinal immobilization (at 0 or 20°), measurements of ONSD were performed at 0, 30, and 60 min in an immobilized position.ResultsWhen evaluating the change in ONSD over time (at 30 and 60 min) as compared to basal measurements at 0 min, it was found that the ONSD values of both sides (the right and left eyes) were significantly increased in Group 1 and Group 2. For Groups 1 and 2, these differences existed both between 0 and 30 min and between 30 and 60 min.In addition, in this study, the amounts of increase in the ONSD measurements from 0 to 30 min and from 30 to 60 min (ΔONSD0–30 min and ΔONSD30–60 min) in both groups were compared. The results showed that there was no significant difference between Group 1 and Group 2 in terms of ΔONSD measurements.ConclusionsSpinal immobilization at 0° as a part of routine trauma management increased ONSD and thus ICP. Secondly, we found that similar to immobilization at 0°, spinal immobilization at 20° increased ONSD.     

Alterations in optic nerve sheath diameter according to cerebrovascular disease sub-groups

Background

ONSD (optic nerve sheath diameter) is a method used for indirect measurement of the increased intracranial pressure. In previous studies, the relation between the increased intracranial pressure and ONSD was analyzed in the patients suffering from cerebrovascular diseases (CVD). In our study, the patients suffering from ischemic CVD were categorized into 4 subgroups according to Oxfordshire Community Stroke Project classification (OCSP); the relationship between each group and ONSD, and the influence on each eye were analyzed.

Using MRI of the optic nerve sheath to detect elevated intracranial pressure

The current gold standard for the diagnosis of elevated intracranial pressure (ICP) remains invasive monitoring. Given that invasive monitoring is not always available or clinically feasible, there is growing interest in non-invasive methods of assessing ICP using diagnostic modalities such as ultrasound or magnetic resonance imaging (MRI). Increased ICP is transmitted through the cerebrospinal fluid surrounding the optic nerve, causing distention of the optic nerve sheath diameter (ONSD). In this issue of Critical Care, Geeraerts and colleagues describe a non-invasive method of diagnosing elevated ICP using MRI to measure the ONSD. They report a positive correlation between measurements of the ONSD on MRI and invasive ICP measurements. If the findings of this study can be replicated in larger populations, this technique may be a useful non-invasive screening test for elevated ICP in select populations.     

Pediatric point-of-care ultrasound of optic disc elevation for increased intracranial pressure: A pilot study

ObjectivePapilledema is often difficult to detect in children. Ocular point-of-care ultrasound (POCUS) measurement of the optic nerve sheath diameter (ONSD) is a non-invasive test for increased intracranial pressure (ICP), but no consensus exists on normal pediatric ONSD values. Detection of optic disc elevation (ODE, a component of papilledema) using POCUS has recently been qualitatively described. We sought to establish the diagnostic accuracy of different ODE cutoffs to detect increased ICP in children who underwent ocular POCUS in our pediatric emergency department (PED).MethodsWe retrospectively reviewed charts of patients ages 0–18 years who received ocular POCUS in our tertiary PED between 2011 and 2016. Patients were included if their archived POCUS examinations were deemed high-quality by a POCUS expert and they underwent ICP determination within 48 h after ocular POCUS. A blinded POCUS expert measured ODE, optic disc width at mid-height (ODWAMH), and ONSD. Receiver-operator curve analysis was performed for various cutoffs for these measurements in detecting increased ICP.Results76 eyes from 40 patients met study criteria. 26 patients had increased ICP. The mean ODE of both eyes (ODE-B) generated the largest area under the curve (0.962, 95% CI 0.890–1). The optimal ODE-B cutoff was 0.66 mm, with a sensitivity of 96% (95% CI 79–100%) and a specificity of 93% (95% CI 79–100%). 1/40 (2.5%) of patients with ODE-B < 0.66 had increased ICP.ConclusionsODE-B may represent the optimal ocular POCUS measurement for detecting increased ICP in children, and future prospective studies could more accurately describe the diagnostic performance of different pediatric ODE-B cutoffs.     

Optic nerve sheath diameter and lumbar puncture opening pressure in nontrauma patients suspected of elevated intracranial pressure

ObjectiveThe purpose of this study was to determine if patients with nontraumatic causes of elevated intracranial pressure (ICP) could be identified by ultrasound measurement of optic nerve sheath diameter (ONSD). It was hypothesized that an ONSD greater than or equal to 5 mm would identify patients with elevated ICP.MethodThis was a prospective observational trial comparing ONSD with ICP measured by opening pressure manometry on lumbar puncture (LP). The cohort consisted of a convenience sample of adult patients presenting to the emergency department, requiring LP. The ONSD measurement was performed before computed tomography and LP. The physician performing the LP was blinded to the result of the ONSD measurement. An opening pressure on manometry of greater than or equal to 20 cm H₂O and an ONSD greater than or equal to 5 mm were considered elevated.ResultsFifty-one patients were included in our study, 24 (47%) with ICP greater than or equal to 20 cm H₂O and 27 (53%) with ICP less than 20 cm H₂O. The sensitivity of ONSD greater than or equal to 5 for identifying elevated ICP was 75% (95% confidence interval, 53%-90%) with specificity of 44% (25%-65%). The area under the receiver operator characteristic curve was 0.69 (0.54-0.84), suggesting a relationship between ONSD and ICP.ConclusionAn ONSD greater than or equal to 5 mm was associated with elevated ICP in nontraumatic causes of elevated ICP. Although a relationship exists, a sensitivity of 75% does not make ONSD measurement an adequate screening examination for elevated ICP in this patient population.     

Diagnostic modalities to determine ventriculoperitoneal shunt malfunction: A systematic review and meta-analysis

BackgroundVentriculoperitoneal (VP) shunt malfunction is an emergency. Timely diagnosis can be challenging because shunt malfunction often presents with symptoms mimicking other common pediatric conditions.MethodsWe performed a systematic review and meta-analysis to determine which commonly used imaging modalities; Magnetic resonance imaging (MRI), Computed Tomography (CT), X-ray Shunt series or Optic Nerve Sheath Diameter (ONSD) ultrasound, are superior in evaluating shunt malfunction. Inclusion Criteria: patients less than 21 years old with symptoms of shunt malfunction. We calculated the pooled sensitivity, specificity, Likelihood Ratios (LR+, LR-) using a random-effects model.ResultsEight studies were included encompassing 1906 patients with a prevalence of VP shunt malfunction of (29.3%). Shunt series: sensitivity (14%–53%), specificity (99%), LR+ (23.2), and LR- (0.47–0.87). CT scan: sensitivity (53%–100%), specificity (27%–98%), LR+ (1.34–22.87), LR- (0.37). MRI: sensitivity (57%), specificity (93%), LR+ (7.66), and LR- (0.49). ONSD: sensitivity (64%), specificity (22%–68%), LR+ (4.4–8.7), LR- (0.93). A positive shunt series, CT scan, MRI, or ONSD has a post-test probability of (23%–84%). A normal shunt series, CT scan, MRI, or ONSD results in a post-test probability of (7%–31%). A positive shunt series results in a post-test probability of 80%, which is equivalent to the post-test probability of CT scan (23–84%) and MRI (83%).ConclusionDespite the low sensitivity, a positive shunt series obviates the need for further imaging studies. Prompt referral for neurosurgical intervention is recommended. A negative shunt series or any result (positive or negative) from CT, MRI, or ONSD will still require an emergent neurosurgical referral.     

Dynamic optic nerve sheath diameter changes upon moderate hyperventilation in patients with traumatic brain injury

BackgroundSonographic assessment of optical nerve sheath diameter (ONSD) has the potential for non-invasive monitoring of intracranial pressure (ICP). Hyperventilation (HV) -induced hypocapnia is used in the management of patients with traumatic brain injury (TBI) to reduce ICP. This study investigates, whether sonography is a reliable tool to detect dynamic changes in ONSD.MethodsThis prospective single center trial included patients with TBI and neuromonitoring within 36 h after injury. Data collection and ONSD measurements were performed at baseline and during moderate HV for 50 min. Patients not suffering from TBI were recruited as control group.ResultsTen patients with TBI (70% males, mean age 35 ± 14 years) with a median of first GCS of 5.9 and ten control patients (40% males, mean age 45 ± 16 years) without presumed intracranial hypertension were included. During HV, ICP decreased significantly (p < .0001) in the TBI group. An ONSD response was found for HV (p = .05).ConclusionWe observed a dynamic decrease of ONSD during moderate HV. This suggests a potential use of serial ONSD measurements when applying HV in cases of suspected intracranial hypertension.     

Utility of Point-of-Care Ultrasound in the Diagnosis of Idiopathic Intracranial Hypertension in the Emergency Department

BackgroundEmergency physicians are frequently required to identify and triage patients with increased intracranial pressure (ICP). Idiopathic intracranial hypertension (IIH) is a possible cause that must be considered. Its prognosis depends on prompt recognition and treatment, and progression of the disease can lead to permanent vision loss and considerable morbidity. Point-of-care ultrasound can rapidly identify elevated ICP. Measurements of the optic nerve sheath diameter (ONSD) and optic disc elevation (ODE) can act as surrogates for ICP.Case SeriesWe describe five cases in which ultrasound was used to identify increased ICP and aid clinical decision-making. In several of the cases, ultrasound was used to confirm a suspicion for IIH and initiate therapy while awaiting the results of a more time-consuming and technically challenging test, such as lumbar puncture or optical coherence tomography. One of the patients was pregnant, and sonographic evidence of elevated ICP helped avoid exposing the patient to unnecessary radiation.Why Should an Emergency Physician Be Aware of This?Ultrasound is a quick and versatile tool for screening patients with neurologic symptoms, and when integrated into the proper clinical context, can reduce the use of more invasive tests. It can be particularly useful in patients with pathology that may not show abnormalities on computed tomography scan or in whom lumbar puncture is technically difficult, making patients at risk for IIH well-suited to examination by ultrasound. We use a cutoff of 5 mm for ONSD and 0.6 mm for ODE, though there are no universally agreed on cutoff values.     

Optic nerve sheath diameter on computed tomography is correlated with simultaneously measured intracranial pressure in patients with severe traumatic brain injury

Purpose

Assess the relationship between optic nerve sheath diameter (ONSD) measured on bedside portable computed tomography (CT) scans and simultaneously measured intracranial pressure (ICP) in patients with severe traumatic brain injury.

Methods

Retrospective cohort study of 57 patients admitted between 2009 and 2013. Linear and logistic regression were used to model the correlation and discrimination between ONSD and ICP or intracranial hypertension, respectively.

Results

The cohort had a mean age of 40 years (SD 16) and a median admission Glasgow coma score of 7 (IQR 4–10). The between-rater agreement by intraclass coefficient was 0.89 (95 % CI 0.83–0.93, P < 0.001). The mean ONSD was 6.7 mm (SD 0.75) and the mean ICP during CT was 21.3 mmHg (SD 8.4). Using linear regression, there was a strong correlation between ICP and ONSD (r = 0.74, P < 0.001). ONSD had an area under the curve to discriminate elevated ICP (≥20 mmHg vs. <20 mmHg) of 0.83 (95 % CI 0.73–0.94). Using a cutoff of 6.0 mm, ONSD had a sensitivity of 97 %, specificity of 42 %, positive predictive value of 67 %, and a negative predictive value of 92 %. Comparing linear regression models, ONSD was a much stronger predictor of ICP (R ² of 0.56) compared to other CT features (R ² of 0.21).

Conclusions

Simultaneous measurement of ONSD on CT and ICP were strongly correlated and ONSD was discriminative for intracranial hypertension. ONSD was much more predictive of ICP than other CT features. There was excellent agreement between raters in measuring ONSD.     

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.     

超声测量视神经鞘直径预测颅内压增高的围手术期应用进展

视神经鞘(ONS)是颅内硬脑膜的直接延续,内有横梁式的蛛网膜下腔。当患者颅内压(ICP)升高时,脑脊液会经蛛网膜滤出使视神经鞘增宽,因此可以用视神经鞘直径(ONSD)预测ICP增高。目前,围手术期ICP监测手段较少,超声测量ONSD预测ICP的技术因具有无创、床旁、快速等优势在临床上被广泛应用,将该技术应用于围术期患者中可以提供术中ICP监测。本文就ICP监测现状、ONSD与ICP的关系、ONSD预测ICP增高的临界值及ONSD预测围术期ICP增高的应用前景作一综述,以期为围手术期应用超声测量ONSD预测ICP增高提供支持。     

Real time optic nerve sheath diameter measurement during lumbar puncture

Measurement of optic nerve sheath diameter (ONSD) using point of care ultrasound has been used to indirectly assess the intracranial pressure (ICP) particularly in conditions where it is raised. Direct pressure measurements using probes reaching the ventricle system correlated with ONSD using ultrasound. Attempts were made to measure the ONSD pre and post lumbar puncture (LP) after draining cerebrospinal fluid (CSF) as well as post ventricular shunt placement. We report ONSD measurement and demonstrate dynamic changes during LP in a patient with known idiopathic intracranial hypertension (IIH).     

Optic nerve sheath diameter measurement: a means of detecting raised ICP in adult traumatic and non-traumatic neurosurgical patients

Introduction

Bedside ultrasound measurement of optic nerve sheath diameter (ONSD) is emerging as a non-invasive technique to evaluate and predict raised intracranial pressure (ICP). It has been shown in previous literature that ONSD measurement has good correlation with surrogate findings of raised ICP such as clinical and radiological findings suggestive of raised ICP.

Non-invasive assessment of intracranial pressure using ocular sonography in neurocritical care patients

Objective  To assess the relationship between optic nerve sheath diameter (ONSD) and intracranial pressure (ICP) in neurocritical care patients. Design  Prospective, observational study. Setting  Surgical critical care unit, level 1 trauma center. Patients  A total number of 37 adult patients requiring sedation and ICP monitoring after severe traumatic brain injury, subarachnoid hemorrhage, intracranial hematoma, or stroke. Measurements and main results  Optic nerve sheath diameter was measured with a 7.5 MHz linear ultrasound probe. ICP was measured invasively via a parenchymal device. Simultaneous measurements were performed atleast once a day during the first 2 days after ICP insertion and in cases of acute changes. There was a significant relationship between ONSD and ICP (78 simultaneous measures, r = 0.71, P < 0.0001). Changes in ICP were strongly correlated with changes in ONSD (39 measures, r = 0.73, P < 0.0001). Enlarged ONSD was a suitable predictor of elevated ICP (>20 mmHg) (area under ROC curve = 0.91). When ONSD was less than 5.86 mm, the negative likehood ratio for raised ICP was 0.06. Conclusion  In sedated neurocritical care patients, non-invasive sonographic measurements of ONSD are correlated with invasive ICP, and the probability to have raised ICP if ONSD is less than 5.86 mm is very low. This method could be used as a screening test when raised ICP is suspected. The authors received no financial support for this work.