Correlation of optic nerve sheath diameter with direct measurement of intracranial pressure

Effect of Positive End-Expiratory Pressure on the Sonographic Optic Nerve Sheath Diameter as a Surrogate for Intracranial Pressure during Robot-Assisted Laparoscopic Prostatectomy: A Randomized Controlled Trial

Background

Positive end-expiratory pressure (PEEP) can increase intracranial pressure. Pneumoperitoneum and the Trendelenburg position are associated with an increased intracranial pressure. We investigated whether PEEP ventilation could additionally influence the sonographic optic nerve sheath diameter as a surrogate for intracranial pressure during pneumoperitoneum combined with the Trendelenburg position in patients undergoing robot-assisted laparoscopic prostatectomy.

Methods

After anesthetic induction, 38 patients were randomly allocated to a low tidal volume ventilation (8 ml/kg) without PEEP group (zero end-expiratory pressure [ZEEP] group, n = 19) or low tidal volume ventilation with 8 cmH₂O PEEP group (PEEP group, n = 19). The sonographic optic nerve sheath diameter was measured prior to skin incision, 5 min and 30 min after pneumoperitoneum and the Trendelenburg position, and at the end of surgery. The study endpoint was the difference in the sonographic optic nerve sheath diameter 5 min after pneumoperitoneum and the Trendelenburg position between the ZEEP and PEEP groups.

Results

Optic nerve sheath diameters 5 min after pneumoperitoneum and the Trendelenburg position did not significantly differ between the groups [least square mean (95% confidence interval); 4.8 (4.6–4.9) mm vs 4.8 (4.7–5.0) mm, P = 0.618]. Optic nerve sheath diameters 30 min after pneumoperitoneum and the Trendelenburg position also did not differ between the groups [least square mean (95% confidence interval); 4.5 (4.3–4.6) mm vs 4.5 (4.4–4.6) mm, P = 0.733].

Conclusions

An 8 cmH₂O PEEP application under low tidal volume ventilation does not induce an increase in the optic nerve sheath diameter during pneumoperitoneum combined with the steep Trendelenburg position, suggesting that there might be no detrimental effects of PEEP on the intracranial pressure during robot-assisted laparoscopic prostatectomy.

Trial Registration

ClinicalTrial.gov NCT02516566

Optic Nerve and Cerebral Edema in the Course of Diabetic Ketoacidosis

In the recent years we have been observing an increased incidence of type 1 diabetes in children and adolescents. This leads to a more frequent acute complication of type 1 diabetes among children with hyperglycemia. The most common of these is diabetic ketoacidosis (DKA), while cerebral edema is the most dangerous. In children with DKA, cerebral edema most often presents with clinical symptoms but may also appear in the so-called "subclinical" form. That is why the search continues for new methods of assessing and monitoring cerebral edema in the course of DKA treatment. Ultrasonographic optic nerve sheath diameter (US ONSD) assessment is performed in various clinical scenarios when cerebral edema is suspected. It is most often performed in adult patients but increasingly often in children. US ONSD assessment is useful in the treatment of DKA in children with type 1 diabetes. This manuscript provides an overview of research results available in PubMed and other available databases on the course of treatment of DKA in children with type 1 diabetes.

Diagnostic value of neuro-ophthalmological signs in cases of Chiari I malformation

INTRODUCTION

Our purpose was to evaluate the diagnostic value of measuring diameters of optic nerve sheath (ONSD), presence/absence of papilledema, tortuosity of the optic nerve, flattening of the posterior sclera, and intraocular protrusion of the prelaminar optic nerve for intracranial pressure assessment in cases of Chiari I malformation.

METHODS

In a retrospective study, MRI data of 37 consecutive pediatric patients with Chiari malformation and data of 400 patients without intracranial pathology were compared and analyzed. ONSDs were measured at the point where the ophthalmic artery crosses the optic nerve (anatomical landmark). The correlation analysis was performed with clinical findings, gender, age, papilledema, and other neuro-ophthalmological findings.

RESULTS

ONSD was enlarged in 38 % of cases of Chiari malformation. The enlargement was bilateral, no correlation with age or gender was found (p = 0.67 and p = 0.76, respectively). The presence of papilledema was detected in 19 % of cases presenting less valuable diagnostic sign if compared with ONSD. The tortuosity of the optic nerve was found in 22 % of cases, but in three patients, it was unilateral. All patients with enlarged ONSD and other neuro-ophthalmological signs present were treated surgically, while most of the patients without these signs (20/23) were treated conservatively.

CONCLUSION

In majority of pediatric cases of Chiari malformation, the ONSD is not enlarged and other neuro-ophthalmological signs are not present. Detecting the enlarged ONSD and other neuro-ophthalmological signs in cases of Chiari malformation may indicate the elevated intracranial pressure and necessity for urgent surgical intervention.

The incidence of increased ICP in ICU patients with non-traumatic coma as diagnosed by ONSD and CT: a prospective cohort study

BACKGROUND

Unexplained coma after critical illness can be multifactorial. We evaluated the diagnostic ability of bedside Optic Nerve Sheath Diameter [ONSD] as a screening test for non-traumatic radiographic cerebral edema.

METHODS

In a prospective study, mixed medical-surgical intensive care units [ICU] patients with non-traumatic coma [GCS < 9] underwent bedside ultrasonographic ONSD measurements. Non-traumatic radiographic cerebral edema [NTRCE] was defined as > 5 mm midline shift, cisternal, sulcal effacement, or hydrocephalus on CT.

RESULTS

NTRCE was identified in 31 of 102 patients [30.4 %]. The area under the ROC curve for detecting radiographic edema by ONSD was 0.785 [95 % CI 0.695-0.874, p <0.001]. ONSD diameter of 0.57 cm was found to be the best cutoff threshold with a sensitivity 84 % and specificity 71 %, AUC 0.785 [95 % CI 0.695-0.874, p <0.001]. Using ONSD as a bedside test increased the post-test odds ratio [OR] for NTRCE by 2.89 times [positive likelihood ratio], whereas post-test OR for NTRCE decreased markedly given a negative ONSD test [ONSD measurement less than 0.57 cm]; negative likelihood ratio 0.22.

CONCLUSIONS

The use of ONSD as a bedside test in patients with non-traumatic coma has diagnostic value in identifying patients with non-traumatic radiographic cerebral edema.

The relationship between transorbital ultrasound measurement of the optic nerve sheath diameter (ONSD) and invasively measured ICP in children : Part I: repeatability, observer variability and general analysis

PURPOSE

The aim of this study was to investigate the relationship between optic nerve sheath diameter (ONSD) measurement and invasively measured intracranial pressure (ICP) in children.

METHODS

ONSD measurement was performed prior to invasive measurement of ICP. The mean binocular ONSD measurement was compared to the ICP reading. Physiological variables including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse rate, temperature, respiratory rate and end tidal carbon dioxide (ETCO2) level were recorded at the time of ONSD measurement. Diagnostic accuracy analysis was performed at various ICP thresholds and  repeatability, intra- and inter-observer variability, correlation between measurements in different imaging planes as well the relationship over the entire patient cohort were examined in part I of this study.

RESULTS

Data from 174 patients were analysed. Repeatability and intra-observer variability were excellent (α = 0.97-0.99). Testing for inter-observer variability revealed good correlation (r = 0.89, p < 0.001). Imaging in the sagittal plane demonstrated a slightly better correlation with ICP (r = 0.66, p < 0.001). The ONSD measurement with the best diagnostic accuracy for detecting an ICP ≥ 20 mmHg over the entire patient cohort was 5.5 mm, sensitivity 93.2 %, specificity 74 % and odds ratio (OR) of 39.3.

CONCLUSION

Transorbital ultrasound measurement of the OSND is a reliable and reproducible technique, demonstrating a good relationship with ICP and high diagnostic accuracy for detecting raised ICP.

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.

OBJECTIVES

The objective of the study is to find a correlation between sonographic measurements of ONSD value with ICP value measured via the gold standard invasive intracranial ICP catheter, and to find the cut-off value of ONSD measurement in predicting raised ICP, along with its sensitivity and specificity value.

METHODS

A prospective observational study was performed using convenience sample of 41 adult neurosurgical patients treated in neurosurgical intensive care unit with invasive intracranial pressure monitoring placed in-situ as part of their clinical care. Portable SonoSite ultrasound machine with 7 MHz linear probe were used to measure optic nerve sheath diameter using the standard technique. Simultaneous ICP readings were obtained directly from the invasive monitoring.

RESULTS

Seventy-five measurements were performed on 41 patients. The non-parametric Spearman correlation test revealed a significant correlation at the 0.01 level between the ICP and ONSD value, with correlation coefficient of 0.820. The receiver operating characteristic curve generated an area under the curve with the value of 0.964, and with standard error of 0.22. From the receiver operating characteristic curve, we found that the ONSD value of 5.205 mm is 95.8% sensitive and 80.4% specific in detecting raised ICP.

CONCLUSIONS

ONSD value of 5.205 is sensitive and specific in detecting raised ICP. Bedside ultrasound measurement of ONSD is readily learned, and is reproducible and reliable in predicting raised ICP. This non-invasive technique can be a useful adjunct to the current invasive intracranial catheter monitoring, and has wide potential clinical applications in district hospitals, emergency departments and intensive care units.

Noninvasive assessment of the intracranial pressure in non-traumatic intracranial hemorrhage

The article describes the modified technique of measuring the diameters of the optic nerve sheath (ONSD) for assessment of the intracranial pressure (ICP) in patients with intracerebral or subarachnoid hemorrhage (SAH). The CT scans of 443 patients were analyzed retrospectively. The ONSDs were measured at 3mm behind the globe and at the point where the ophthalmic artery crosses the optic nerve. The ONSD/eyeball transverse diameter (ETD) ratio was calculated. The correlation analysis was performed with the Glasgow Coma Scale score, Hemispheric Stroke Scale score, Glasgow Outcome Score, and invasive ICP readings. ONSD was enlarged in 95% of patients with intracerebral hemorrhage or SAH. Pathological ONSDs were 6.6±0.8mm (cut-off value >5.5mm; p<0.05). ONSD/ETD ratio was 0.29±0.05 against normative 0.19±0.02 (p<0.01) with no correlation with initial Glasgow Coma Scale score or Hemispheric Stroke Scale score. There was an inverse correlation between ONSD/ETD ratio and Glasgow Outcome Score (r=-0.7) and direct correlation with invasive ICP readings. This study provides further evidence that in patients with intracranial hemorrhage and SAH, the presence of ONSD greater than a threshold of 5.5mm is significantly predictive of invasively measured elevated ICP. The prediction of raised ICP can be further refined by measuring ONSD at the point where the optic nerve and the ophthalmic artery cross, and by determining the ratio between the ONSD and ETD.

Bedside ultrasound as a simple non-invasive method of assessing intracranial pressure in a limited resource setting

Introduction

Increased intracranial pressure is usually measured with invasive methods that are not practical in resource-limited countries. However, bedside ultrasound, a non-invasive method, measures the optic nerve sheath diameter and could be a safe and accurate alternative to measure intracranial pressure, even in children.

Case report

We report a case of a 15-year old patient who presented with severe headache, projectile vomiting, and neck pain for two months. The bedside ultrasound showed a 10 mm optic nerve sheath diameter and a Computed Tomography scan of her brain revealed obstructive hydrocephalus secondary to a mass in the fourth ventricle. After intervening, we were able to monitor the decrease in her optic nerve sheath diameter with ultrasound.

Conclusion

Performing invasive procedures continues to be a challenge in the resource limited setting. However, bedside ultrasound can be a useful tool in emergency centres for early detection and monitoring of intracranial pressure.

Non-invasive intracranial pressure assessment

Assessing intracranial pressure (ICP) remains a cornerstone in neurosurgical care. Invasive techniques for monitoring ICP remain the gold standard. The need for a reliable, safe and reproducible technique to non-invasively assess ICP in the context of early screening and in the neurocritical care environment is obvious. Numerous techniques have been described with several novel advances. While none of the currently available techniques appear independently accurate enough to quantify raised ICP, there is some promising work being undertaken.

Ultrasonography in the emergency department

Point-of-care ultrasonography (POCUS) is a useful imaging technique for the emergency medicine (EM) physician. Because of its growing use in EM, this article will summarize the historical development, the scope of practice, and some evidence supporting the current applications of POCUS in the adult emergency department. Bedside ultrasonography in the emergency department shares clinical applications with critical care ultrasonography, including goal-directed echocardiography, echocardiography during cardiac arrest, thoracic ultrasonography, evaluation for deep vein thrombosis and pulmonary embolism, screening abdominal ultrasonography, ultrasonography in trauma, and guidance of procedures with ultrasonography. Some applications of POCUS unique to the emergency department include abdominal ultrasonography of the right upper quadrant and appendix, obstetric, testicular, soft tissue/musculoskeletal, and ocular ultrasonography. Ultrasonography has become an integral part of EM over the past two decades, and it is an important skill which positively influences patient outcomes.

Initial evaluation of the intracranial pressure in cases of traumatic brain injury without hemorrhage

Our objective was to apply the technique of measuring diameters of optic nerve sheath (ONSD) for the intracranial pressure assessment for the cases with traumatic head injury without hemorrhage. In a retrospective study, CT data of 720 adult patients were collected and analyzed. ONSDs were measured at the point where the ophthalmic artery crosses the optic nerve (anatomical landmark) together with the eyeball transverse diameter (ETD). The ONSD/ETD index was calculated. The correlation analysis was performed with gender, age, the Glasgow Coma Scale score, and the Glasgow Outcome Score. ONSD was enlarged in 82% cases (n=591). Enlarged right/left ONSDs were 6.7±1.0/6.7±0.9mm (cut-off value˃5.5mm). ONSD/ETD ratio was 0.28±0.05 against 0.19±0.02 in healthy adults (p=0.02). We did not find correlation between ONSD/ETD ratio with initial Glasgow Coma Scale score but there was an inverse correlation between ONSD/ETD ratio and the Glasgow Outcome Score (r=-0.64). We conclude that in majority of cases with traumatic head injury without hemorrhage the ONSD is significantly enlarged indicating elevated intracranial pressure even if CT scans are negative.

Non-invasive assessment of intracranial pressure

Monitoring of intracranial pressure (ICP) is invaluable in the management of neurosurgical and neurological critically ill patients. Invasive measurement of ventricular or parenchymal pressure is considered the gold standard for accurate measurement of ICP but is not always possible due to certain risks. Therefore, the availability of accurate methods to non-invasively estimate ICP has the potential to improve the management of these vulnerable patients. This review provides a comparative description of different methods for non-invasive ICP measurement. Current methods are based on changes associated with increased ICP, both morphological (assessed with magnetic resonance, computed tomography, ultrasound, and fundoscopy) and physiological (assessed with transcranial and ophthalmic Doppler, tympanometry, near-infrared spectroscopy, electroencephalography, visual-evoked potentials, and otoacoustic emissions assessment). At present, none of the non-invasive techniques alone seem suitable as a substitute for invasive monitoring. However, following the present analysis and considerations upon each technique, we propose a possible flowchart based on the combination of non-invasive techniques including those characterizing morphologic changes (e.g., repetitive US measurements of ONSD) and those characterizing physiological changes (e.g., continuous TCD). Such an integrated approach, which still needs to be validated in clinical practice, could aid in deciding whether to place an invasive monitor, or how to titrate therapy when invasive ICP measurement is contraindicated or unavailable.

A Unique Model for ONSD Part II: Inter/Intra-operator Variability

OBJECTIVE

To evauluate our novel ultrasound model for measurement of optic nerve sheath diameter (ONSD) and determine the intra- and inter-operator variability associated with this technique.

METHODS

We conducted ten measurements of ONSD per model amongst eight different models with a single experienced operator to examine intra-operator variability. Similarly, we had seven different operators measure the OSND twice in eight different models, in order to determine inter-operator variability analyzed with a three level linear statistical model.

RESULTS

For intra-operator variability, the intra-cluster correlation coefficients for the experienced and novice operators were 0.643 and 0.453 respectively. This displayed improvement in intra-operator variability with experience. The inter-cluster correlation coefficient was 0 for the group of novice operators, indicating negligible difference amongst multiple operators in measuring any given model of ONSD. A strong, statistically significant, linear relationship between the actual model disc size and the ultrasound ONSD measures was identified, implying the reliability of the images produced by our novel model.

CONCLUSIONS

Utilizing a novel model for ONSD ultrasonography, we have determined the intraoperator reliability of ONSD measurement to be moderate, with no appreciable difference amongst multiple operators. Improvement in measurement reliability has been demonstrated between expert and novice operators with our model, indicating the potential benefit of simulation platforms for teaching the technique of ONSD ultrasound.

Morbid obesity increases risk of morbidity and reoperation in resection of benign cranial nerve neoplasms

OBJECTIVE

Obesity has been associated with increased risk for postoperative CSF leak in patients with benign cranial nerve tumors. Other measures of postoperative morbidity associated with obesity have not been well characterized.

METHODS

Patients enrolled in the American College of Surgeons' National Surgical Quality Improvement Program (ACS-NSQIP) from 2007 to 2013 with a diagnosis code of a benign neoplasm of a cranial nerve were included. The primary outcome of postoperative morbidity was analyzed as well as secondary outcomes of readmission and reoperation. The main covariate of interest was body mass index (BMI).

RESULTS

A total of 561 patients underwent surgery for a benign cranial nerve neoplasm between 2007 and 2013. Readmission data, available for 2012-2013(n=353), revealed hydrocephalus, facial nerve injury, or CSF leak requiring readmission or reoperation occurred in 0.85%, 1.42%, and 3.12%, respectively. Composite morbidity included wound complications, infection, respiratory insufficiency, transfusion requirement, stroke, venous thromboembolism, coma and cardiac arrest. On multivariable analysis patients with class I (BMI 30-34.9) and II (BMI 35-39.9) obesity showed trends towards increasing return to operating room, though not significant, but there was no trend for composite complications in class I and II obesity patients. However, class III obesity, BMI≥40, was associated with increased odds of composite morbidity (OR 4.40, 95% CI 1.24-15.88) and return to the operating room (OR 5.97, 95% CI 1.20-29.6) relative to patients with a normal BMI, 18.5-25.

CONCLUSIONS

Obesity is an independent and important risk factor for composite morbidity in resection of benign cranial nerve neoplasms, and as such, merits discussion during preoperative counseling.

Intracranial Pressure Assessment in Traumatic Head Injury with Hemorrhage Via Optic Nerve Sheath Diameter

Our purpose was to improve the technique of measuring optic nerve sheath diameter (ONSD) for intracranial pressure (ICP) monitoring in cases of traumatic head injury with hemorrhage. In a retrospective study, computed tomography (CT) data of 312 adult patients were collected and analyzed. ONSDs were measured at 3 mm and 8-10 mm distance from the globe together with the eyeball transverse diameter (ETD). The ONSD/ETD ratio was calculated. The correlation analysis was performed with gender, age, Glasgow Coma Scale score, and Glasgow Outcome Score. ONSD was enlarged in all cases when CT scans indicated hematoma. Enlarged right/left ONSDs were 6.5 ± 1.5/6.4 ± 1.3 mm at 3 mm and 6.6 ± 0.8/6.6 ± 0.6 mm at 8-10 mm from the globe (cut-off value > 5.5 mm). ONSD/ETD ratio was 0.29 ± 0.05, compared with 0.19 ± 0.02 in healthy adults (p < 0.01). We did not find a correlation between ONSD/ETD ratio and initial Glasgow Coma Scale score, but there was an inverse correlation between ONSD/ETD ratio and Glasgow Outcome Score (r = -0.83). We conclude that in cases with a traumatic head injury with hemorrhage, the ONSD is significantly enlarged, indicating elevated ICP. In ICP assessment, the most accurate results can be obtained if the ONSD is measured 8-10 mm from the globe and the ONSD/ETD ratio is calculated.

Diagnostic Ophthalmic Ultrasound for Radiologists

Ophthalmic ultrasound is an invaluable tool that provides quick and noninvasive evaluation of the eye and the orbit. It not only allows the clinicians to view structures that may not be visible with routine ophthalmic equipment or neuroimaging techniques but also provides unique diagnostic information in various ophthalmic conditions. In this article, the basic principles of ophthalmic ultrasound and examination techniques are discussed. Its clinical application is illustrated through a variety of ocular pathologic abnormalities (eg, narrow angles, ciliary body tumor, detached retina, choroidal melanoma, and papilledema).

High resolution transbulbar sonography in children with suspicion of increased intracranial pressure

PURPOSE

To evaluate the accuracy of high resolution transbulbar sonography for the estimation of intracranial pressure (ICP) in children.

METHODS

In children and adolescents with acute neurologic symptoms of various origin, transbulbar sonography was performed. Besides measurement of the optic nerve sheath diameter (ONSD), the ultrastructure of the subarachnoid space of the optic nerve sheath was evaluated. The results of transbulbar sonography were correlated with clinical data based on cross-sectional imaging, ICP measurement, and ophthalmologic examination.

RESULTS

Eighty-one patients (age 3-17.8 years, mean 11.7 years) were included. In 25 children, cross-sectional imaging and ICP measurement revealed increased intracranial pressure. The mean ONSD was 6.85 ± 0.81 mm. Twenty patients (20/25, 80 %) had a microcystic appearance of the subarachnoid space of the optic nerve. In 56 children without evidence of increased intracranial pressure, the mean ONSD was 5.77 ± 0.48 mm. Forty-nine patients (49/56, 87.5 %) had a normal homogenous appearance of the subarachnoid space. The ONSD in children with increased intracranial pressure was significantly higher than in patients without (p < 0.001).

CONCLUSION

High resolution transbulbar sonography of the optic nerve is a useful technique for the rapid and non-invasive estimation of intracranial pressure in children. Besides measurement of the optic nerve sheath diameter, evaluation of the ultrastructure of the subarachnoid space of the optic nerve is a helpful parameter.

Evidence for cerebral edema, cerebral perfusion, and intracranial pressure elevations in acute mountain sickness

INTRODUCTION

We hypothesized that cerebral alterations in edema, perfusion, and/or intracranial pressure (ICP) are related to the development of acute mountain sickness (AMS).

METHODS

To vary AMS, we manipulated ambient oxygen, barometric pressure, and exercise duration. Thirty-six subjects were tested before, during and after 8 h exposures in (1) normobaric normoxia (NN; 300 m elevation equivalent); (2) normobaric hypoxia (NH; 4400 m equivalent); and (3) hypobaric hypoxia (HH; 4400 m equivalent). After a passive 15 min ascent, each subject participated in either 10 or 60 min of cycling exercise at 50% of heart rate reserve. We measured tissue absorption and scattering via radio-frequency near-infrared spectroscopy (NIRS), optic nerve sheath diameter (ONSD) via ultrasound, and AMS symptoms before, during, and after environmental exposures.

RESULTS

We observed significant increases in NIRS tissue scattering of 0.35 ± 0.11 cm(-1) (P = 0.001) in subjects with AMS (i.e., AMS+), consistent with mildly increased cerebral edema. We also noted a small, but significant increase in total hemoglobin concentrations with AMS+, 3.2 ± 0.8 μmolL(-1) (P < 0.0005), consistent with increased cerebral perfusion. No effect of exercise duration was found, nor did we detect differences between NH and HH. ONSD assays documented a small but significant increase in ONSD (0.11 ± 0.02 mm; P < 0.0005) with AMS+, suggesting mildly elevated ICP, as well as further increased ONSD with longer exercise duration (P = 0.005).

CONCLUSION

In AMS+, we found evidence of cerebral edema, elevated cerebral perfusion, and elevated ICP. The observed changes were small but consistent with the reversible nature of AMS.

Ultrasonographic Evaluation of Optic Nerve Sheath Diameter among Healthy Chinese Adults

The aim of the work described here was to establish the range for optic nerve sheath diameter (ONSD) and potential factors influencing ONSD in healthy Chinese adults. Both ONSDs were measured twice in the sagittal and transversal planes by two observers. The final ONSD value for each participant was the average of 16 measurements of both eyes. The ONSD range (N = 3680) among 230 participants was 2.65-4.30 mm. The upper ONSD limit was lower than those in previous studies in Caucasian and African samples. Simple linear regression analyses revealed that the ONSD was correlated with sex, body mass index and waistline and head circumference. After adjustment for potential confounds between these factors, sex (coefficient = 0.225, p < 0.001) and body mass index (coefficient = 0.042, p < 0.001) were independently associated with ONSD. Underweight women had the smallest ONSD. These results suggest that racial, sex, and body mass index differences should be noted when assessing ultrasonographic criteria.

Idiopathic intracranial hypertension: ongoing clinical challenges and future prospects

Idiopathic intracranial hypertension (IIH) is an uncommon disorder characterized by increased intracranial pressure without radiological or laboratory evidence of intracranial pathology except empty sella turcica, optic nerve sheath with filled out cerebrospinal fluid spaces, and smooth-walled nonflow-related venous sinus stenosis or collapse. This condition typically affects obese women. The incidence of IIH is increasing with the rising prevalence of obesity. Persistent headache is the most common symptom. Visual impairment is a serious complication that may not be recognized by the patients. This paper reviews clinical manifestations, diagnostic challenges, and current treatments of IIH in adults. Various imaging modalities have been studied on their validity for detection of IIH and papilledema. This review also includes new studies on medical, surgical, and interventional management of this condition. Acetazolamide and topiramate are the only two medications that have been studied in randomized controlled trials about their efficacy in treatment of IIH. In patients who have severe visual impairment or progressive visual deterioration despite medical management, surgical or interventional treatment may be considered. The efficacy and complications of cerebrospinal fluid diversion, optic nerve sheath fenestration, and endovascular venous stenting reported in the last 3 decades have been summarized in this review. Finally, the prospective aspects of biomarkers and treatments are proposed for future research.

Bedside sonographic measurement of optic nerve sheath diameter as a predictor of intracranial pressure in ED

BACKGROUND

Ocular ultrasonography of optic nerve sheath diameter (ONSD) to determine intracranial pressure (ICP) has become favorable in recent years.

OBJECTIVE

To demonstrate the efficacy of ONSD measurement in determining the ICP increase due to nontraumatic events in the emergency department.

METHODS

A total of 100 patients with suspected nontraumatic intracranial event were enrolled in this prospective study. Patients were divided equally into 2 groups including 50 patients as group I with pathology on cranial computed tomography (CT) and group II with normal cranial CT. Prior to CT scans, patients underwent ONSD measurement by a radiologist using 11- and 14-MHz transducers.

RESULTS

The ONSD values of groups I and II were 5.4±1.1and 4.1±0.5mm, respectively. Optic nerve sheath diameter was found to be larger on the side of lesion in patients with a lesion (P<.05). The cutoff value of the difference between ONSD values of both eyes in the presence of pathology was determined as 0.45 (sensitivity, 80%; specificity, 60%; the area under the curve, 0.794; 95% confidence interval, 0.705-0.883). The between-ONSD and midline shift size was statistically significant (r=0.366, P=.009). The cutoff value of ONSD for the detection of midline shift was determined as 5.3mm (sensitivity, 70%; specificity, 74%; the area under the curve, 0.728; 95% confidence interval, 0.585-0.871).

CONCLUSION

Optic nerve sheath diameter measurement via bedside ocular ultrasonography in patients with suspected intracranial event in the emergency department is a useful method to determine ICP increase and its severity.

Optic nerve sonography: A noninvasive means of detecting raised intracranial pressure in a resource-limited setting

Objective:

The aim was to assess the use of optic nerve sonography (ONS) as a quick, noninvasive diagnostic test tool for detecting raised the intracranial pressure (ICP).

Materials and Methods:

A prospective blinded observational study was conducted at Obafemi Awolowo University Teaching Hospitals Complex (OAUTHC), Ile-Ife, Nigeria. The study population consisted of 160 adult patients referred to the radiology department for cranial computed tomography (CT) scan. There were 80 subjects and 80 controls. Optic nerve sheath diameter (ONSD) was measured by a radiologist using a 7.5 Megahertz ultrasound probe while cranial CT was reviewed by other radiologists blinded to the ONSD.

Results:

Sixty-nine subjects (86.3%) had intracranial space occupying lesions (SOL) with cranial CT confirmed features of increased ICP, mean binocular ONSD of 5.7 ± 0.59 mm while 11 (13.7%) had intracranial SOL without any cranial CT evidence of increased ICP, mean binocular ONSD of 4.8 ± 0.39 mm. The difference of mean ONSD of the two groups was statistically significant (P = 0.0001). The controls had a mean binocular ONSD of 4.5 ± 0.22 mm and the difference in mean binocular ONSD for subjects with raised ICP and the controls were also statistically significant (P = 0.0001). A cut-off value of 5.2 mm (sensitivity 81.2% [95% confidence interval (CI): 69.9–89.6], specificity 100% [95% CI: 71.5–100]) was obtained from the receiver operator characteristics curve as the mean binocular ONSD that best predicts raised ICP confirmed by at least a sign on cranial CT.

Conclusions:

Optic nerve sonography can differentiate between normal and elevated ICP and may serve as a useful screening tool in resource-limited practice.

The relationship between intracranial pressure and obesity: an ultrasonographic evaluation of the optic nerve

BACKGROUND

Measurements of optic nerve sheath diameter (ONSD) with noninvasive ocular ultrasonography have been shown to be accurate in determining increased intracranial pressure. Obesity is associated with chronic increases in intraabdominal pressure that could consequently result in intracranial hypertension. By utilizing ONSD ultrasonographic measurements, we compare the difference that may exist between obese and non-obese patients.

STUDY DESIGN

We prospectively collected data from patients who underwent laparoscopic procedures in the supine position between July 2013 and March 2014. Ophthalmic pathology was not present in any patient. Ultrasonographic measurement of the ONSD was obtained sagittally with a 12-MHz transducer 3 mm from its origin. The measurements were taken at 0, 15, and 30 min, and at the end of surgery.

RESULTS

There were 62 subjects, 28 females (45.2 %) and 34 males (54.8 %), with a mean age of 44.22 ± 10.44 years (range 23-66). Forty-eight percent of patients were non-obese, and 52 % of patients were obese. The mean body mass index was 30.70 ± 7.61 kg/m(2) (range 20.0-59.5). The mean ONSD of non-obese and obese patients was 4.7 and 5.5 mm at baseline (p = 0.01), 5.4 and 6.2 mm at 15 min (p = 0.01), 5.8 and 6.6 mm at 30 min (p = 0.01), and 5.1 and 5.7 mm after deflation of pneumoperitoneum (p = 0.03), respectively.

CONCLUSIONS

Utilizing a noninvasive method to measure the ONSD, a chronic increase in intracranial pressure in obese patients was demonstrated. The increase in the ONSD during laparoscopic procedures reflects a temporary increase in the intracranial pressure from baseline.

Accuracy, Precision, Sensitivity, and Specificity of Noninvasive ICP Absolute Value Measurements

An innovative absolute intracranial pressure (ICP) value measurement method has been validated by multicenter comparative clinical studies. The method is based on two-depth transcranial Doppler (TCD) technology and uses intracranial and extracranial segments of the ophthalmic artery as pressure sensors. The ophthalmic artery is used as a natural pair of "scales" that compares ICP with controlled pressure Pe, which is externally applied to the orbit. To balance the scales, ICP = Pe a special two-depth TCD device was used as a pressure balance indicator. The proposed method is the only noninvasive ICP measurement method that does not need patient-specific calibration.

Monitoring of Intracranial Pressure by CT-Defined Optic Nerve Sheath Diameter

BACKGROUND AND PURPOSE

Intracranial pressure (ICP) can be monitored by the optic nerve sheath diameter (ONSD) technique. We hypothesized that diameter of the optic canal (OC) can be a limiting factor for this technique.

METHODS

In the prospective cohort study, we analyzed CT scans of 600 OCs of healthy adults and 54 canals of patients with ICP monitoring. The diameters were measured through its length and the narrowest one was chosen for further analysis. ONSD was measured at 3 and 10 mm from the anterior opening of the canal. The correlation analysis was performed between invasive and ONSD methods of ICP monitoring and OC diameters in pathological cases.

RESULTS

The narrowest cross-sectional area of the normal OC was 13.85±2.89 mm² and varied from 25.5 to 6.6 mm². Apparently 9.17% OCs were narrow (˂10.9 mm²). Correlations exist between the optic nerve sheath area at the 3-mm distance from the anterior opening of the canal and the area of the anterior opening itself (P = .012), and the sheath area 10 mm from the anterior opening and the narrowest part of the canal (P = .015). Cases with narrow canals provided false-negative readings via ONSD method if compared with invasive monitoring.

CONCLUSION

In its narrowest part, the average OC is 11 to 16.75 mm² wide. We suggest measuring this area simultaneously with the ONSD during ICP monitoring. If the area of the narrowest lumen of the canal is less than 10 mm², ONSD technique for ICP monitoring should not be used.

Optic nerve sheath diameters in healthy adults measured by computer tomography

AIM

To measure optic nerve sheath diameters (ONSD) in different locations by computer tomography (CT) and to recommend the best location for cases when ONSD is used for intracranial pressure monitoring.

METHODS

In a prospective cohort study, CT data of 300 healthy adults were analyzed (600 eyes). In all cases, the CT investigation was performed at the Emergency Department because of the various conditions that proved not to be connected with ophthalmological or neurological pathology. The ONSD were measured at 3 mm and 8 mm distance from the globe, and 3 mm from the anterior opening of the optic canal. The correlation analysis was performed with gender, age, and ethnic background.

RESULTS

The right/left ONSD are 4.94±1.51/5.17±1.34 mm at 3 mm, 4.35±0.76/4.45±0.62 mm at 8 mm from the globe, and 3.55±0.82/3.65±0.7 mm at 3 mm from the optic canal. No significant differences correlated with gender of the patients, their age, and ethnic background were found.

CONCLUSION

In healthy persons, the ONSD varies from 5.17±1.34 mm to 3.55±0.82 mm in different locations within the intraorbital space. The most stable results with lesser standard deviation can be obtained if it is measured 8-10 mm from the globe.

The diagnostic performance of ultrasonographic optic nerve sheath diameter and color Doppler indices of the ophthalmic arteries in detecting elevated intracranial pressure

OBJECTIVES

To assess the diagnostic accuracy of ultrasonographic optic nerve sheath diameter (ONSD) measurement and color Doppler indices of the ophthalmic arteries in detecting elevated intracranial pressure (ICP).

PATIENTS AND METHODS

A total 60 patients with (cases, n=30) and without (controls, n=30) acute clinical and computed tomographic findings of elevated ICP due to intracranial mass/hemorrhage were recruited from a teaching hospital. The mean binocular and maximum ultrasonographic ONSDs, as well as the mean binocular Doppler ultrasound waveform indices of the ophthalmic arteries including pulsatility index (PI), resistive index (RI), end-systolic velocity (ESV), peak systolic velocity (PSV) and end-diastolic velocity (EDV) were compared between the two groups.

RESULTS

Compared to controls, the case group had significantly higher mean binocular ONSD (5.48 ± 0.52 mm vs. 4.09 ± 0.22 mm, p<0.001), maximum ONSD (5.63 ± 0.55 mm vs. 4.16 ± 0.23 mm, p<0.001), mean PI (1.53 ± 0.16 vs. 1.45 ± 0.20, p=0.01), and mean RI (0.76 ± 0.07 vs. 0.73 ± 0.04, p=0.01). The mean EDV, in contrast, was significantly higher in controls (8.55 ± 3.09 m/s vs. 7.17 ± 2.61 m/s, p=0.01). The two groups were comparable for the mean PSV (30.73 ± 7.93 m/s in cases vs. 32.27 ± 10.39 m/s in controls, p=0.36). Among the mentioned variables, the mean binocular ONSD was the most accurate parameter in detecting elevated ICP (sensitivity and specificity of 100%, cut-off point=4.53 mm). The Doppler indices were only moderately accurate (sensitivity: 56.7-60%, specificity: 63.3-76.7%).

CONCLUSION

While the ultrasonographic mean binocular ONSD (>4.53 mm) was completely accurate in detecting elevated ICP, color Doppler indices of the ophthalmic arteries were of limited value.

Intracranial pressure and cerebral perfusion pressure monitoring in non-TBI patients: special considerations

The effect of intracranial pressure (ICP) and the role of ICP monitoring are best studied in traumatic brain injury (TBI). However, a variety of acute neurologic illnesses e.g., subarachnoid hemorrhage, intracerebral hemorrhage, ischemic stroke, meningitis/encephalitis, and select metabolic disorders, e.g., liver failure and malignant, brain tumors can affect ICP. The purpose of this paper is to review the literature about ICP monitoring in conditions other than TBI and to provide recommendations how the technique may be used in patient management. A PubMed search between 1980 and September 2013 identified 989 articles; 225 of which were reviewed in detail. The technique used to monitor ICP in non-TBI conditions is similar to that used in TBI; however, indications for ICP monitoring often are intertwined with the presence of obstructive hydrocephalus and hence the use of ventricular catheters is more frequent. Increased ICP can adversely affect outcome, particularly when it fails to respond to treatment. However, patients with elevated ICP can still have favorable outcomes. Although the influence of ICP-based care on outcome in non-TBI conditions appears less robust than in TBI, monitoring ICP and cerebral perfusion pressure can play a role in guiding therapy in select patients.

Prospective analysis of single operator sonographic optic nerve sheath diameter measurement for diagnosis of elevated intracranial pressure

Introduction

The accurate diagnosis of elevated intracranial pressure (eICP) in the emergent setting is a critical determination that presents significant challenges. Several studies show correlation of sonographic optic nerve sheath diameter (ONSD) to eICP, while others show high inter-observer variability or marginal performance with less experienced sonographers. The objective of our study is to assess the ability of bedside ultrasound measurement of ONSD to identify the presence of eICP when performed by a single experienced sonographer. We hypothesize that ONSD measurement is sensitive and specific for detecting eICP and can be correlated with values obtained by external ventricular device (EVD).

Methods

This was a prospective blinded observational study conducted in a neurocritical care unit of a level 1 trauma center. ONSD measurement was performed on a convenience sample of 27 adult patients who required placement of an invasive intracranial monitor as part of their clinical care. One certified sonographer/physician performed all ultrasounds within 24 hours of placement of EVD. The sonographer was blinded to the ICP recorded by invasive monitor at the time of the scan. A mean ONSD value of ≥5.2 mm was taken as positive.

Results

The sonographer performed 27 ocular ultrasounds on individual patients. Six (22%) of these patients had eICP (EVD measurement of >20 mmHg). Spearman rank correlation coefficient of ONSD and ICP was 0.408 (p=0.03), demonstrating a moderate positive correlation. A ROC curve was created to determine the optimal cut off value to distinguish an eICP greater than 20 mmHg. The area under the receiver operator characteristic curve was 0.8712 (95% confidence interval [CI]=0.67 to 0.96). ONSD ≥5.2 mm was a good predictor of eICP (>20 mmHg) with a sensitivity of 83.3% (95% CI=35.9% to 99.6%) and specificity of 100% (95% CI=84.6% to 100%).

Conclusion

While the study suggests ONSD measurements performed by a single skilled operator may be both sensitive and specific for detecting eICP, confirmation in a much larger sample is needed. Ocular ultrasound may provide additional non-invasive means of assessing eICP.

Elevated Intracranial Pressure Diagnosis with Emergency Department Bedside Ocular Ultrasound

Bedside sonographic measurement of optic nerve sheath diameter can aid in the diagnosis of elevated intracranial pressure in the emergency department. This case report describes a 21-year-old female presenting with 4 months of mild headache and 2 weeks of recurrent, transient binocular vision loss. Though limited by patient discomfort, fundoscopic examination suggested the presence of blurred optic disc margins. Bedside ocular ultrasound (BOUS) revealed wide optic nerve sheath diameters and bulging optic discs bilaterally. Lumbar puncture demonstrated a cerebrospinal fluid (CSF) opening pressure of 54 cm H2O supporting the suspected diagnosis of idiopathic intracranial hypertension. Accurate fundoscopy can be vital to the appropriate diagnosis and treatment of patients with suspected elevated intracranial pressure, but it is often technically difficult or poorly tolerated by the photophobic patient. BOUS is a quick and easily learned tool to supplement the emergency physician's fundoscopic examination and help identify patients with elevated intracranial pressure.

Transocular Doppler and optic nerve sheath diameter monitoring to detect intracranial hypertension

Background:

Increases in intracranial pressure (ICP) require a rapid recognition to allow for adequate treatments. The aim of this study was to determine whether transocular Doppler and optic nerve sheath diameter (ONSD) monitoring could reliably identify increases in ICP.

Materials and Methods:

This is a cross-sectional case-control study, which was carried out on 2013. Subjects were chosen from patients who admitted to the neurology and neurosurgery departments and the intensive care unit of Alzahra Hospital (Isfahan, Iran). To measure the ICP, the authors used ultrasound to measure the diameter of the optic nerve sheath and transocular Doppler (TOD) to measure blood flew velocity in ophthalmic artery (OA) and ophthalmic vein (OV) in both groups.

Results:

The mean of ONSD was 4.8 mm (SD 0.77) in patients with raised ICP and 3.2 mm (SD 0.3) in healthy volunteers which was significant (P < 0.001). The mean (SD) of TOD parameters were also significantly more in OA and OV of patients with raised ICP.

Conclusion:

Ultrasound methods has been proposed as an alternative safe technique for invasive ICP measuring methods.

Intraoperative non invasive intracranial pressure monitoring during pneumoperitoneum: a case report and a review of the published cases and case report series

Non-invasive measurement of ICP (nICP) can be warranted in patients at risk for developing increased ICP during pneumoperitoneum (PP). Our aim was to assess available data on the application of nICP monitoring during these procedures and to present a patient assessed with an innovative combination of noninvasive tools. Literature review of nICP assessment during PP did not find any studies comparing different methods intraprocedurally and only few studies of any nICP monitoring were available: transcranial Doppler (TCD) studies used the pulsatility index (PI) as an estimator of ICP and failed to detect a significant ICP increase during PP, whereas two out of three optic nerve sheath diameter (ONSD) studies detected a statistically significant ICP increase. In the case study, we describe a 52 year old man with a high grade thalamic glioma who underwent urgent laparoscopic cholecystectomy. Considering the high intraoperative risk of developing intracranial hypertension, he was monitored through parallel ONSD ultrasound measurement and TCD derived formulae (flow velocity diastolic formula, FVdnICP, and PI). ONSD and FVdnICP methods indicated a significant ICP increase during PP, whereas PI was not significantly increased. Our experience, combined with the literature review, seems to suggest that PI might not detect ICP changes in this context, however we indicate a possible interest of nICP monitoring during PP by means of ONSD and of TCD derived FVdNICP, especially for patients at risk for increased ICP.

Optic Nerve Sheath Diameter Increase on Ascent to High Altitude: Correlation With Acute Mountain Sickness

OBJECTIVES

Elevated optic nerve sheath diameter on sonography is known to correlate with increased intracranial pressure and is observed in acute mountain sickness. This study aimed to determine whether optic nerve sheath diameter changes on ascent to high altitude are associated with acute mountain sickness incidence.

METHODS

Eighty-six healthy adults enrolled at 1240 m (4100 ft), drove to 3545 m (11,700 ft) and then hiked to and slept at 3810 m (12,500 ft). Lake Louise Questionnaire scores and optic nerve sheath diameter measurements were taken before, the evening of, and the morning after ascent.

RESULTS

The incidence of acute mountain sickness was 55.8%, with a mean Lake Louise Questionnaire score ± SD of 3.81 ± 2.5. The mean maximum optic nerve sheath diameter increased on ascent from 5.58 ± 0.79 to 6.13 ± 0.73 mm, a difference of 0.91 ± 0.55 mm (P = .09). Optic nerve sheath diameter increased at high altitude regardless of acute mountain sickness diagnosis; however, compared to baseline values, we observed a significant increase in diameter only in those with a diagnosis of acute mountain sickness (0.57 ± 0.77 versus 0.21 ± 0.76 mm; P = .04). This change from baseline, or Δ optic nerve sheath diameter, was associated with twice the odds of developing acute mountain sickness (95% confidence interval, 1.08-3.93).

CONCLUSIONS

The mean optic nerve sheath diameter increased on ascent to high altitude compared to baseline values, but not to a statistically significant degree. The magnitude of the observed Δ optic nerve sheath diameter was positively associated with acute mountain sickness diagnosis. No such significant association was found between acute mountain sickness and diameter elevation above standard cutoff values, limiting the utility of sonography as a diagnostic tool.

Correlation of measurement of optic nerve sheath diameter using ultrasound with magnetic resonance imaging

Background and Aims:

Analysis to correlate the measurements of optic nerve sheath diameter (ONSD) obtained by using ultrasound to magnetic resonance imaging (MRI) techniques in order to establish the accuracy of ocular sonography as a noninvasive modality for detecting raised intracranial pressure (ICP).

Materials and Methods:

A prospective, observational study was performed in 100 cases of adult meningoencephalitis patients admitted to Intensive Care Unit in whom MRI was performed for neurodiagnosis. ONSD was measured in such patients, 3 mm behind the globe in each eye. A mean binocular ONSD >4.6 mm in female and 4.8 mm in male was taken as cut-off values for diagnosing raised ICP. This was compared with ONSD measured on T2-weighted MRI image measured 3 mm behind the globe. The reading obtained from both the methods were compared with Bland–Altman analysis for correlation and the findings were tabulated.

Results:

The mean ONSD values measured with ultrasonography (USG) and MRI for female were 5.48 ± 0.43 mm and 5.68 ± 0.44 mm and for male were 5.40 ± 0.37 mm and 5.56 ± 0.38 mm, respectively. The mean age of the female and male was 53.90 ± 17.84 and 56.06 ± 15.67 years, respectively. On comparing ultrasound with MRI-derived ONSD values, we found acceptable agreement between both methods for measurements at a depth of 3 mm (r = 0.02, P < 0.001).

Conclusion:

In our study, we have found a good correlation between ocular USG and MRI of ONSD. The study has shown agreement with the fact that ocular sonography can be used as a noninvasive tool for detecting raised ICP with accuracy.

How accurate is ultrasound of the optic nerve sheath diameter performed by inexperienced operators to exclude raised intracranial pressure?

Background: It has been well documented that ultrasound measurement of the optic nerve sheath diameter performed by an experienced operator shows good correlation with raised intracranial pressure, irrespective of the cause. Objective: To establish the accuracy of this technique performed by inexperienced operators.Method: A prospective analytical cross-sectional study was conducted. All patients ≥18 years of age who presented at our medical casualty and emergency departments with suspected meningitis were enrolled in the study. All patients were evaluated with the use of optic nerve sheath diameter ultrasound with or without computed tomography brain scan prior to lumbar puncture. Lumbar puncture opening pressure measurements were compared with the ultrasound measurements.Results: A total of 73 patients were enrolled in the study, of whom 14 had raised intracranial pressure. The study had a sensitivity of 50% (95% confidence interval (CI) 26.8%–73.2%) and specificity of 89.8% (95% CI 79.5%–95.3%) with a positive predictive value of 54.8% (95% CI 29.1%–76.8%) and negative predictive value of 88.3% (95% CI 77.8%–94.2%). The likelihood ratio of a positive test was 4.92 (95% CI 1.95–11.89) and that of a negative test 0.56 (95% CI 0.29–0.83). Cohen’s kappa value was 0.41 which indicates a moderate agreement. The receiver operating characteristic (ROC) curve had an area under the curve (AUC) of 0.73 (95% CI 0.51–0.95). Conclusion: Ultrasound measurement of the optic nerve sheath diameter can be used to exclude raised intracranial pressure, even in the hands of inexperienced operators.

Noninvasive intracranial pressure monitoring via optic nerve sheath diameter for robotic surgery in steep Trendelenburg position

Background:

Recent reports of increased intracranial pressure (ICP) due to steep Trendelenburg (ST) position causing neurological deterioration, decreased regional cerebral oxygen saturation and postoperative visual loss after robotic urological and gynecological surgeries led us to consider a simple technique of ICP monitoring. Ours is one of the first instances reported of quantitative noninvasive measurement of increase in ICP with ST position by serial measurement of binocular optic nerve sheath diameter (ONSD) in patients undergoing robot assisted urological and gynecological oncosurgery. We tested whether ONSD values rose to above the upper limits of normal and for what length of time they remained elevated.

Materials and Methods:

Prospective, randomized, interventional, parallel group, active control study conducted on 252 American Society of Anesthesiologists I and II patients. ONSD was measured using 7.5 MHz linear ultrasound probe in supine and Trendelenburg positions.

Statistics:

Student's t-test to compare the inter-group mean ONSD and the repetitive t-test for intra-group analysis.

Result:

Comparison of the mean ONSD values of both groups yielded a 2-tailed significance P <0.01 at all compared time points intra- and post-operatively. In Group-O (open surgery; supine position), the baseline mean bilateral ONSD was 4.36 mm, which did not show any statistically significant change throughout open surgery and postoperative period. On de-docking the robot, 6.2 mm was the mean ONSD value in Group-R (robotic group) while 4.3 mm was the corresponding value in control Group-O.

Conclusion:

ONSD evaluation is a simple, quick, safe, readily available, reliable, cost effective, noninvasive, potential standard of care for screening and monitoring of patients undergoing robotic surgery in ST position.

Position does not affect the optic nerve sheath diameter during laparoscopy

Background

Increase in intracranial pressure (ICP) is one of the physiologic changes during laparoscopic surgery, which is known to be associated with positional changes. Changes of ICP can be measured directly by invasive method, but ultrasonographic measurement of optic nerve sheath diameter (ONSD) is known to be a rapidly applicable technique for evaluating ICP. The aim of this study is to investigate the change of ONSD according to the positional change during laparoscopic surgery.

Methods

Female patients scheduled to undergo laparoscopic surgery were enrolled. Fifty-seven patients were assigned according to the position during surgery (Group T: gynecological surgery, Trendelenburg position, n = 27 vs. Group RT: laparoscopic cholecystectomy, Reverse trendelenburg position, n = 30). After induction of anesthesia, ONSD, PaCO₂, end-tidal carbon dioxide (ETCO₂), and mean arterial pressure (MAP) were measured. Parameters were measured at 6 time points during surgery.

Results

There were no significant differences in the demographic data of patients, procedure time, and anesthesia. After pneumoperitoneum and positional change, ONSD, ETCO₂, and MAP increased in both groups until 15 min and returned to the baseline. However, no significant differences in changes of ONSD, PaCO₂, ETCO₂, and MAP were observed between two groups.

Conclusions

ONSD during laparoscopic surgery with pneumoperitoneum increased slightly until 15 minutes, but there were no significant differences according to the position. Increases in ICP during laparoscopic surgery with short period of pneumoperitoneum would be small in disregard of position in patients without intracranial pathology.

Ultrasound measurement of optic nerve diameter and optic nerve sheath diameter in healthy Chinese adults

BACKGROUND

Measurement of optic nerve sheath diameter (ONSD) is a fast and non-invasive method in detecting elevated intracranial pressure. However, the reported normal range of ONSD was inconsistent. The objective of the study was to determine the normal range of ONSD in healthy Chinese adults.

METHODS

Eyeball transverse diameter (ETD), optic nerve diameter (OND), and ONSD were measured by ultrasound examination in healthy adult volunteers. The OND and ONSD were assessed 3 mm behind the globe. The section showing maximal transverse diameter of the eyeball was frozen and the diameter was measured. Each ETD, OND and ONSD was examined twice and the mean value was calculated.

RESULTS

A total of 519 healthy volunteers were included in the study. The median (interquartile range) of ETD, OND and ONSD were 22.3 (21.6 to 23.1) mm, 3.2 (2.9 to 3.4) mm, and 5.1 (4.7 to 5.4) mm, respectively. The 95% percentile of ONSD was 5.9 mm. There was no significant difference in ETD, OND or ONSD between male and female, or between left and right eye. ONSD was significantly correlated with OND (r = 0.62, P < 0.001), and the median OND/ONSD ratio (interquartile range) was 0.63 (0.59 to 0.67).

CONCLUSIONS

The median and the 95% percentile of sonographic measurement of ONSD are 5.1 mm and 5.9 mm in healthy Chinese adults. The ONSD is correlated with OND, while independent of gender, age, height, weight and ETD. The median OND/ONSD ratio is 0.63 and this parameter warrants further investigation in patients with brain injury.