Brain injury mobile diagnostic system: Applications in civilian medical service and on the battlefield-General concept and medical aspects

To present the concept of a portable ultrasound tomography device for diagnosing traumatic and vascular brain lesions. The device consisting of multiple transcranial ultrasound probes placed on the surface of the head, specifically but not exclusively in natural acoustic windows. An integral part of the mobile diagnostic system (MDS) is a decision support system based on artificial intelligence algorithms utilizing information from: head images, laboratory data, and assessment of the patient's clinical condition. The MDS can significantly reduce the time from stroke onset to rtPA therapy in civilian medical services and support therapeutic and evacuation strategies in instances of brain and skull trauma on the battlefield.

Dilatation of the bridging cerebral veins in multiple sclerosis correlates with fatigue and suggests an increase in pressure

BACKGROUND

There is a significant increase in the parenchymal microvessel blood volume in the earliest forms of multiple sclerosis (MS) which may be due to venular dilatation. Increased cortical venous pressure could account for this finding. Venous pressure is also implicated in the physiology of fatigue. The purpose of this study is to discover if there is dilatation of the veins within the subarachnoid space in multiple sclerosis and to estimate the pressures required to maintain any enlargement found. These findings will be correlated with the fatigue symptoms found in MS.

METHODS

103 patients with MS were compared with a control group of 50 patients. Post contrast 3DT1 images were used. The cross-sectional area of the bridging cortical veins and the vein of Galen were measured.

RESULTS

In MS, the superficial territory cortical veins were 29% larger and the veins of Galen were 25% larger than the controls.

CONCLUSION

There is evidence of a significant increase in the bridging vein transmural pressure in MS, estimated to be approximately 6.5 mmHg in the superficial cortical veins. MS patients with significant fatigue have larger cortical veins than those who are not significantly fatigued.

A prospective exploratory study to assess echocardiographic changes in patients with supratentorial tumors - Effect of craniotomy and tumor decompression

Background

Functional changes in the myocardium secondary to increased intracranial pressure (ICP) are studied sparingly. Direct echocardiographic changes in patients with supratentorial tumors have not been documented. The primary aim was to assess and compare the transthoracic echocardiography changes in patients with supratentorial tumors presenting with and without raised intracranial pressure for neurosurgery.

Methods

Patients were divided into two groups based on preoperative radiological and clinical evidence of midline shift of <6 mm without features of raised ICP (Group 1) or greater than 6mm with features of raised ICP (Group 2). Hemodynamic, echocardiographic, and optic nerve sheath diameter (ONSD) parameters were obtained during the preoperative period and 48 h after the surgery.

Results

Ninety patients were assessed, 88 were included for analysis. Two were excluded based on a poor echocardiographic window (1) and change in the operative plan (1). Demographic variables were comparable. About 27% of the patients in Group 2 had ejection fraction <55% and 21.2% had diastolic dysfunction in Group 2 in the preoperative period. There was a decrease in the number of patients with a left ventricular (LV) function <55% from 27% before surgery to 19% in the postoperative period in group 2. About 5.8% patients with moderate LV dysfunction in the preoperative period had normal LV function postoperatively. We found a positive correlation between ONSD parameters and radiological findings of raised intracranial pressure.

Conclusion

The study demonstrated that in patients with supratentorial tumors with ICP, cardiac dysfunction might be present in the preoperative period.

Non-Invasive Intracranial Pressure Monitoring

(1) Background: Intracranial pressure (ICP) monitoring plays a key role in the treatment of patients in intensive care units, as well as during long-term surgeries and interventions. The gold standard is invasive measurement and monitoring via ventricular drainage or a parenchymal probe. In recent decades, numerous methods for non-invasive measurement have been evaluated but none have become established in routine clinical practice. The aim of this study was to reflect on the current state of research and shed light on relevant techniques for future clinical application. (2) Methods: We performed a PubMed search for “non-invasive AND ICP AND (measurement OR monitoring)” and identified 306 results. On the basis of these search results, we conducted an in-depth source analysis to identify additional methods. Studies were analyzed for design, patient type (e.g., infants, adults, and shunt patients), statistical evaluation (correlation, accuracy, and reliability), number of included measurements, and statistical assessment of accuracy and reliability. (3) Results: MRI-ICP and two-depth Doppler showed the most potential (and were the most complex methods). Tympanic membrane temperature, diffuse correlation spectroscopy, natural resonance frequency, and retinal vein approaches were also promising. (4) Conclusions: To date, no convincing evidence supports the use of a particular method for non-invasive intracranial pressure measurement. However, many new approaches are under development.

Noninvasive intracranial pressure monitoring in central nervous system infections

Intracranial pressure (ICP) monitoring constitutes an important part of the management of traumatic brain injury. However, its application in other brain pathologies such as neuroinfections like acute bacterial meningitis is unclear. Despite focus on aggressive, prompt treatment, morbidity and mortality from acute bacterial meningitis remain high. Increased ICP is well-known to occur in severe neuroinfections. The increased ICP compromise cerebral perfusion pressure and may ultimately lead to brain stem herniation. Therefore, controlling the ICP could also be important in acute bacterial meningitis. However, risk factors for complications due to invasive monitoring among these patients may be significantly increased due to higher age and levels of comorbidity compared to the traumatic brain injury patient from which the ICP treatment algorithms are developed. This narrative review evaluates the different modalities of ICP monitoring with the aim to elucidate current status of non-invasive alternatives to invasive monitoring as a decision tool and eventually monitoring. Non-invasive screening using ultrasound of the optical nerve sheath, transcranial doppler, magnetic resonance imaging or preferably a combination of these modalities, provides measurements that can be used as a decision guidance for invasive ICP measurement. The available data do not support the replacement of invasive techniques for continuous ICP measurement in patients with increased ICP. Non-invasive modalities should be taken into consideration in patients with neuroinfections at low risk of increased ICP.

Modelling of the dilated sagittal sinuses found in multiple sclerosis suggests increased wall stiffness may be a contributing factor

The cross-sectional area of the superior sagittal sinus (SSS) is larger in multiple sclerosis than normal and correlates with disease severity and progression. The sinus could be enlarged due to a decrease in the pressure difference between the lumen and the subarachnoid space, an increase in wall thickness or increased wall stiffness. The cross-sectional area of the SSS and straight sinus (ST) were measured in 103 patients with multiple sclerosis and compared to 50 controls. The cross-sectional area of the SSS and ST were increased by 20% and 13% compared to the controls (p = 0.005 and 0.02 respectively). The deflection of the wall of the sinus was estimated. The change in pressure gradient, wall thickness or elastic modulus between groups was calculated by modelling the walls as simply supported beams. To account for these findings, the modelling suggests either a 70% reduction in transmural venous pressure or a 2.4 fold increase in SSS wall stiffness plus an 11% increase in wall thickness or a combination of changes. An increase in sinus pressure, although the most straight forward possibility to account for the change in sinus size may exist in only a minority of patients. An increase in sinus wall stiffness and thickness may need further investigation.

A machine learning approach in the non-invasive prediction of intracranial pressure using Modified Photoplethysmography

The ideal Intracranial pressure (ICP) estimation method should be accurate, reliable, cost-effective, compact, and associated with minimal morbidity/mortality. To this end several described non-invasive methods in ICP estimation have yielded promising results, however the reliability of these techniques have yet to supersede invasive methods of ICP measurement. Over several publications, we described a novel imaging method of Modified Photoplethysmography in the evaluation of the retinal vascular pulse parameters decomposed in the Fourier domain, which enables computationally efficient information filtering of the retinal vascular pulse wave. We applied this method in a population of 21 subjects undergoing lumbar puncture manometry. A regression model was derived by applying an Extreme Gradient Boost (XGB) machine learning algorithm using retinal vascular pulse harmonic regression waveform amplitude (HRWa), first and second harmonic cosine and sine coefficients (an1,2, bn1,2) among other features. Gain and SHapley Additive exPlanation (SHAP) values ranked feature importance in the model. Agreement between the predicted ICP mean, median and peak density with measured ICP was assessed using Bland-Altman bias±standard error. Feature gain of intraocular pressure (IOPi) (arterial = 0.6092, venous = 0.5476), and of the Fourier coefficients, an1 (arterial = 0.1000, venous = 0.1024) ranked highest in the XGB model for both vascular systems. The arterial model SHAP values demonstrated the importance of the laterality of the tested eye (1.2477), which was less prominent in the venous model (0.8710). External validation was achieved using seven hold-out test cases, where the median venous predicted ICP showed better agreement with measured ICP. Although the Bland-Altman bias from the venous model (0.034±1.8013 cm water (p<0.99)) was lower compared to that of the arterial model (0.139±1.6545 cm water (p<0.94)), the arterial model provided a potential avenue for internal validation of the prediction. This approach can potentially be integrated into a neurological clinical decision algorithm to evaluate the indication for lumbar puncture.

Zero retinal vein pulsation amplitude extrapolated model in non-invasive intracranial pressure estimation

Intracranial pressure (ICP) includes the brain, optic nerve, and spinal cord pressures; it influences blood flow to those structures. Pathological elevation in ICP results in structural damage through various mechanisms, which adversely affects outcomes in traumatic brain injury and stroke. Currently, invasive procedures which tap directly into the cerebrospinal fluid are required to measure this pressure. Recent fluidic engineering modelling analogous to the ocular vascular flow suggests that retinal venous pulse amplitudes are predictably influenced by downstream pressures, suggesting that ICP could be estimated by analysing this pulse signal. We used this modelling theory and our photoplethysmographic (PPG) retinal venous pulse amplitude measurement system to measure amplitudes in 30 subjects undergoing invasive ICP measurements by lumbar puncture (LP) or external ventricular drain (EVD). We estimated ICP from these amplitudes using this modelling and found it to be accurate with a mean absolute error of 3.0 mmHg and a slope of 1.00 (r = 0.91). Ninety-four percent of differences between the PPG and invasive method were between − 5.5 and + 4.0 mmHg, which compares favourably to comparisons between LP and EVD. This type of modelling may be useful for understanding retinal vessel pulsatile fluid dynamics and may provide a method for non-invasive ICP measurement.

Non-invasive detection of intracranial pressure related to the optic nerve

Intracranial pressure (ICP) is associated with a variety of diseases. Early diagnosis and the timely intervention of elevated ICP are effective means to clinically reduce the morbidity and mortality of some diseases. The detection and judgment of reduced ICP are beneficial to glaucoma doctor and neuro ophthalmologist to diagnose optic nerve disease earlier. It is important to evaluate and monitor ICP clinically. Although invasive ICP detection is the gold standard, it can have complications. Most non-invasive ICP tests are related to the optic nerve and surrounding tissues due to their anatomical characteristics. Ultrasound, magnetic resonance imaging, transcranial Doppler, papilledema on optical coherence tomography, visual evoked potential, ophthalmodynamometry, the assessment of spontaneous retinal venous pulsations, and eye-tracking have potential for application. Although none of these methods can completely replace invasive technology; however, its repeatable, low risk, high accuracy, gradually attracted people's attention. This review summarizes the non-invasive ICP detection methods related to the optic nerve and the role of the diagnosis and prognosis of neurological disorders and glaucoma. We discuss the advantages and challenges and predict possible areas of development in the future.

Can the Treatment of Normal-Pressure Hydrocephalus Induce Normal-Tension Glaucoma? A Narrative Review of a Current Knowledge

Ventriculoperitoneal shunt placement is the most commonly used treatment of normal-pressure hydrocephalus (NPH). It has been hypothesized that normal-tension glaucoma (NTG) is caused by the treatment of NPH by using the shunt to reduce intracranial pressure (ICP). The aim of this study is to review the literature published regarding this hypothesis and to emphasize the need for neuro-ophthalmic follow-up for the concerned patients. The source literature was selected from the results of an online PubMed search, using the keywords "hydrocephalus glaucoma" and "normal-tension glaucoma shunt". One prospective study on adults, one prospective study on children, two retrospective studies on adults and children, two case reports, three review papers including medical hypotheses, and one prospective study on monkeys were identified. Hypothesis about the association between the treatment of NPH using the shunt to reduce ICP and the development of NTG were supported in all reviewed papers. This suggests that a safe lower limit of ICP for neurological patients, especially shunt-treated NPH patients, should be kept. Thus, we proposed to modify the paradigm of safe upper ICP threshold recommended in neurosurgery and neurology into the paradigm of safe ICP corridor applicable in neurology and ophthalmology, especially for shunt-treated hydrocephalic and glaucoma patients.

Human ophthalmic artery as a sensor for non-invasive intracranial pressure monitoring: numerical modeling and in vivo pilot study

Intracranial pressure (ICP) monitoring is important in managing neurosurgical, neurological, and ophthalmological patients with open-angle glaucoma. Non-invasive two-depth transcranial Doppler (TCD) technique is used in a novel method for ICP snapshot measurement that has been previously investigated prospectively, and the results showed clinically acceptable accuracy and precision. The aim of this study was to investigate possibility of using the ophthalmic artery (OA) as a pressure sensor for continuous ICP monitoring. First, numerical modeling was done to investigate the possibility, and then a pilot clinical study was conducted to compare two-depth TCD-based non-invasive ICP monitoring data with readings from an invasive Codman ICP microsensor from patients with severe traumatic brain injury. The numerical modeling showed that the systematic error of non-invasive ICP monitoring was < 1.0 mmHg after eliminating the intraorbital and blood pressure gradient. In a clinical study, a total of 1928 paired data points were collected, and the extreme data points of measured differences between invasive and non-invasive ICP were - 3.94 and 4.68 mmHg (95% CI - 2.55 to 2.72). The total mean and SD were 0.086 ± 1.34 mmHg, and the correlation coefficient was 0.94. The results show that the OA can be used as a linear natural pressure sensor and that it could potentially be possible to monitor the ICP for up to 1 h without recalibration.

Prospective Clinical Study of Non-Invasive Intracranial Pressure Measurements in Open-Angle Glaucoma Patients and Healthy Subjects

Background and Objective: Glaucoma is a progressive optic neuropathy in which the optic nerve is damaged. The optic nerve is exposed not only to intraocular pressure (IOP) in the eye, but also to intracranial pressure (ICP), as it is surrounded by cerebrospinal fluid in the subarachnoid space. Here, we analyse ICP differences between patients with glaucoma and healthy subjects (HSs). Materials and Methods: Ninety-five patients with normal-tension glaucoma (NTG), 60 patients with high-tension glaucoma (HTG), and 62 HSs were included in the prospective clinical study, and ICP was measured non-invasively by two-depth transcranial Doppler (TCD). Results: The mean ICP of NTG patients (9.42 ± 2.83 mmHg) was significantly lower than that of HSs (10.73 ± 2.16 mmHg) (p = 0.007). The mean ICP of HTG patients (8.11 ± 2.68 mmHg) was significantly lower than that of NTG patients (9.42 ± 2.83 mmHg) (p = 0.008) and significantly lower than that of HSs (10.73 ± 2.16 mmHg) (p < 0.001). Conclusions: An abnormal ICP value could be one of the many influential factors in the optic nerve degeneration of NTG patients and should be considered as such instead of just being regarded as a "low ICP".

Evaluation of Optic Nerve Sheath Diameter and Transcranial Doppler As Noninvasive Tools to Detect Raised Intracranial Pressure in Children

OBJECTIVES

To compare the diagnostic accuracy of the ultrasonography-guided optic nerve sheath diameter with transcranial Doppler-guided middle cerebral artery flow indices against the gold standard invasive intraparenchymal intracranial pressure values in children.

DESIGN

A single-center prospective cohort study.

SETTING

PICU of a tertiary care teaching hospital in North India.

PATIENTS

Eligible children (2-12 yr) are admitted to ICU and are undergoing intracranial pressure monitoring using an intraparenchymal catheter. Observations with a parallel measured intracranial pressure greater than or equal to 20 mm Hg were included as case-observations. Children with an invasive intracranial pressure of less than or equal to 15 mm Hg were taken as neurologic-control-observations and healthy children served as healthy-control-observations.

INTERVENTIONS

The horizontal and vertical diameters of the optic nerves were measured, and averages were calculated and compared. Middle cerebral artery flow indices (pulsatility index and resistive index) were measured bilaterally and averages were calculated and compared in the three groups. Twenty-two measurements of optic nerve sheath diameter were assessed by two different observers in quick succession for interrater reliability.

MEASUREMENTS AND MAIN RESULTS

A total of 148 observations were performed in 30 children. Four observations were excluded (intracranial pressure between 16 and 19 mm Hg). Of the 144 observations, 106 were case-observations and 38 were neurologic-control-observations. Additional 66 observations were healthy-control-observations. The mean optic nerve sheath diameter was 5.71 ± 0.57 mm in the case-observations group, 4.21 ± 0.66 mm in the neurologic-control-observations group, and 3.71 ± 0.27 mm in the healthy-control-observations group (p < 0.001 for case-observations vs neurologic-control-observations/healthy-control-observations). The mean pulsatility index in case-observations was 0.92 ± 0.41 compared with controls 0.79 ± 0.22 (p = 0.005) and the mean resistive index was 0.56 ± 0.13 in case-observations compared with 0.51 ± 0.09 (p = 0.007) in controls (neurologic-control-observations and healthy-control-observations). For the raised intracranial pressure defined by intracranial pressure greater than or equal to 20 mm Hg, the area under the curve for optic nerve sheath diameter was 0.976, while it was 0.571 for pulsatility index and 0.579 for resistive index. Furthermore, the optic nerve sheath diameter cutoff of 4.0 mm had 98% sensitivity and 75% specificity for raised intracranial pressure, while the pulsatility index value of 0.51 had 89% sensitivity and 10% specificity by middle cerebral artery flow studies. The sensitivity and specificity of 0.40 resistive index value in the raised intracranial pressure were 88% and 11%, respectively. Kendall correlation coefficient between intracranial pressure and optic nerve sheath diameter, pulsatility index, and resistive index was 0.461, 0.148, and 0.148, respectively. The Pearson correlation coefficient between two observers for optic nerve sheath diameter, pulsatility index, and resistive index was 0.98, 0.914, and 0.833, respectively.

CONCLUSIONS

Unlike transcranial Doppler-guided middle cerebral artery flow indices, ultrasonography-guided optic nerve sheath diameter was observed to have a good diagnostic accuracy in identifying children with an intracranial pressure of greater than or equal to 20 mm Hg.

Prehospital Detection of Life-Threatening Intracranial Pathology: An Unmet Need for Severe TBI in Austere, Rural, and Remote Areas

Severe traumatic brain injury (TBI) is a leading cause of death and disability worldwide, especially in low- and middle-income countries, and in austere, rural, and remote settings. The purpose of this Perspective is to challenge the notion that accurate and actionable diagnosis of the most severe brain injuries should be limited to physicians and other highly-trained specialists located at hospitals. Further, we aim to demonstrate that the great opportunity to improve severe TBI care is in the prehospital setting. Here, we discuss potential applications of prehospital diagnostics, including ultrasound and near-infrared spectroscopy (NIRS) for detection of life-threatening subdural and epidural hemorrhage, as well as monitoring of cerebral hemodynamics following severe TBI. Ultrasound-based methods for assessment of cerebrovascular hemodynamics, vasospasm, and intracranial pressure have substantial promise, but have been mainly used in hospital settings; substantial development will be required for prehospital optimization. Compared to ultrasound, NIRS is better suited to assess certain aspects of intracranial pathology and has a smaller form factor. Thus, NIRS is potentially closer to becoming a reliable method for non-invasive intracranial assessment and cerebral monitoring in the prehospital setting. While one current continuous wave NIRS-based device has been FDA-approved for detection of subdural and epidural hemorrhage, NIRS methods using frequency domain technology have greater potential to improve diagnosis and monitoring in the prehospital setting. In addition to better technology, advances in large animal models, provider training, and implementation science represent opportunities to accelerate progress in prehospital care for severe TBI in austere, rural, and remote areas.

Validation of Noninvasive Absolute Intracranial Pressure Measurements in Traumatic Brain Injury and Intracranial Hemorrhage

BACKGROUND

Increased intracranial pressure (ICP) causes secondary damage in traumatic brain injury (TBI), and intracranial hemorrhage (ICH). Current methods of ICP monitoring require surgery and carry risks of complications.

OBJECTIVE

To validate a new instrument for noninvasive ICP measurement by comparing values obtained from noninvasive measurements to those from commercial implantable devices through this pilot study.

METHODS

The ophthalmic artery (OA) served as a natural ICP sensor. ICP measurements obtained using noninvasive, self-calibrating device utilizing Doppler ultrasound to evaluate OA flow were compared to standard implantable ICP measurement probes.

RESULTS

A total of 78 simultaneous, paired, invasive, and noninvasive ICP measurements were obtained in 11 ICU patients over a 17-mo period with the diagnosis of TBI, SAH, or ICH. A total of 24 paired data points were initially excluded because of questions about data independence. Analysis of variance was performed first on the 54 remaining data points and then on the entire set of 78 data points. There was no difference between the 2 groups nor was there any correlation between type of sensor and the patient (F[10, 43] = 1.516, P = .167), or the accuracy and precision of noninvasive ICP measurements (F[1, 43] = 0.511, P = .479). Accuracy was [-1.130; 0.539] mm Hg (CL = 95%). Patient-specific calibration was not needed. Standard deviation (precision) was [1.632; 2.396] mm Hg (CL = 95%). No adverse events were encountered.

CONCLUSION

This pilot study revealed no significant differences between invasive and noninvasive ICP measurements (P < .05), suggesting that noninvasive ICP measurements obtained by this method are comparable and reliable.

Review: pathophysiology of intracranial hypertension and noninvasive intracranial pressure monitoring

Measurement of intracranial pressure (ICP) is crucial in the management of many neurological conditions. However, due to the invasiveness, high cost, and required expertise of available ICP monitoring techniques, many patients who could benefit from ICP monitoring do not receive it. As a result, there has been a substantial effort to explore and develop novel noninvasive ICP monitoring techniques to improve the overall clinical care of patients who may be suffering from ICP disorders. This review attempts to summarize the general pathophysiology of ICP, discuss the importance and current state of ICP monitoring, and describe the many methods that have been proposed for noninvasive ICP monitoring. These noninvasive methods can be broken down into four major categories: fluid dynamic, otic, ophthalmic, and electrophysiologic. Each category is discussed in detail along with its associated techniques and their advantages, disadvantages, and reported accuracy. A particular emphasis in this review will be dedicated to methods based on the use of transcranial Doppler ultrasound. At present, it appears that the available noninvasive methods are either not sufficiently accurate, reliable, or robust enough for widespread clinical adoption or require additional independent validation. However, several methods appear promising and through additional study and clinical validation, could eventually make their way into clinical practice.

Review of non-invasive intracranial pressure measurement techniques for ophthalmology applications

Assessment and monitoring of intracranial pressure (ICP) are important in the management of traumatic brain injury and other cerebral pathologies. In the eye, ICP elevation and depression both correlate with optic neuropathies, the former because of papilledema and the latter related to glaucoma. While the relationship between ICP elevation and papilledema is well established, the relationship between low ICP and glaucoma is still poorly understood. So far, ICP monitoring is performed invasively, but this entails risks including infection, spurring the study of non-invasive alternatives. We review 11 methods of non-invasive estimation of ICP including correlation to optic nerve sheath diameter, intraocular pressure, ophthalmodynamometry and two-depth transcranial Doppler of the ophthalmic artery. While none of these methods can fully replace invasive techniques, certain measures show great potential for specific applications. Although only used in small studies to date, a MRI based method known as MR-ICP, appears to be the best non-invasive technique for estimating ICP, with two-depth transcranial ultrasound and ophthalmodynamometry showing potential as well.

Ultrasound measurements versus invasive intracranial pressure measurement method in patients with brain injury: a retrospective study

BACKGROUND

The invasive method for intracranial pressure measurement is 'gold standard' but not always feasible because the intraventricular catheter/ intraparenchymal micro transducer used in the measurement of intracranial pressure measurement may cause complications. Imaging modalities with clinical examination protocol have a lack of specificity and accuracy. The objective of the study was to compare the accuracy of diagnostic parameters of ultrasound measurements in patients with brain injury underwent invasive intracranial pressure measurement method.

METHODS

Data of invasive intracranial pressure measurement method and ultrasound measurements of 185 patients with brain injury who required admission diagnosis were included in the analysis. Pearson correlation was tested for diagnostic parameters. Logistical regression analysis was performed for diagnostic parameters of death patients to evaluate independent parameter of mortality.

RESULTS

Straight sinus flow velocities, middle cerebral artery flow velocities, and optic nerve sheath diameter were correlated with intracranial pressure (p < 0.0001 for all). Arterial blood pressure (p = 0.127) and middle cerebral artery pulsatility index (p = 0.06) were not correlated with intracranial pressure. A total of 47 patients died during the study period. Intracranial pressure (p = 0.015) and optic nerve sheath diameter (p = 0.035) were found to be independent predictor of mortality.

CONCLUSIONS

Ultrasound measurement especially optic nerve sheath diameter can be successfully used instead of invasive intracranial pressure measurement method in patients with brain injury.

LEVEL OF EVIDENCE

III.

Automated Optic Nerve Sheath Diameter Measurement Using Super-pixel Analysis

The optic nerve is a part of the central nervous system surrounded by cerebrospinal fluid and is encased in a sheath. Changes to the cerebrospinal fluid due to injury, tumor rupture and so on can increase intracranial pressure (ICP) and can result in changes in the sheath diameter. Measuring the changes in the sheath can be done through ultrasound imaging with which the optic nerve sheath diameter can be measured. Since this approach is non-invasive, it would reduce the cost for patients and healthcare if sheath diameter could be used as a predictor of increase in ICP. However, the manual measurement of the nerve sheath diameter is very time consuming and could be affected by human errors. In this paper we propose an image processing approach in which the optic nerve sheath diameter is measured automatically. In our proposed method, we first denoise images and then detect the region of interest using a simple line integral method. After that by analyzing super-pixels we measure the diameter. We compared the results of the proposed method with manual measurements from two experts. The average percentage of error between the proposed method and the experts' measurements did not substantially differ from the error between the two experts.

Incorporation of Transcranial Doppler into the ED for the neurocritical care patient

INTRODUCTION

In the catastrophic neurologic emergency, a complete neurological exam is not always possible or feasible given the time-sensitive nature of the underlying disease process, or if emergent airway management is indicated. As the neurologic exam may be limited in some patients, the emergency physician is reliant on the assessment of brainstem structures to determine neurological function. Physicians thus routinely depend on advanced imaging modalities to further investigate for potential catastrophic diagnoses. Acquiring these tests introduces the risks of transport as well as delays in managing time-sensitive neurologic processes. A more immediate, non-invasive bedside approach complementing these modalities has evolved: Transcranial Doppler (TCD).

OBJECTIVE

This narrative review will provide a description of scenarios in which TCD may be applicable. It will summarize the sonographic findings and associated underlying pathophysiology in such neurocritical care patients. An illustrated tutorial, along with pearls and pitfalls, is provided.

DISCUSSION

Although there are numerous formalized TCD protocols utilizing four views (transtemporal, submandibular, suboccipital, and transorbital), point-of-care TCD is best accomplished through the transtemporal window. The core applications include the evaluation of midline shift, vasospasm after subarachnoid hemorrhage, acute ischemic stroke, and elevated intracranial pressure. An illustrative tutorial is provided.

CONCLUSIONS

With the wide dissemination of bedside ultrasound within the emergency department, there is a unique opportunity for the emergency physician to utilize TCD for a variety of conditions. While barriers to training exist, emergency physician performance of limited point-of-care TCD is feasible and may provide rapid and reliable clinical information with high temporal resolution.

Location of the internal carotid artery and ophthalmic artery segments for non-invasive intracranial pressure measurement by multi-depth TCD

The aim of the present study was to locate the ophthalmic artery by using the edge of the internal carotid artery (ICA) as the reference depth to perform a reliable non-invasive intracranial pressure measurement via a multi-depth transcranial Doppler device and to then determine the positions and angles of an ultrasonic transducer (UT) on the closed eyelid in the case of located segments. High tension glaucoma (HTG) patients and healthy volunteers (HVs) undergoing non-invasive intracranial pressure measurement were selected for this prospective study. The depth of the edge of the ICA was identified, followed by a selection of the depths of the IOA and EOA segments. The positions and angles of the UT on the closed eyelid were measured. The mean depth of the identified ICA edge for HTG patients was 64.3 mm and was 63.0 mm for HVs (p = 0.21). The mean depth of the selected IOA segment for HTG patients was 59.2 mm and 59.3 mm for HVs (p = 0.91). The mean depth of the selected EOA segment for HTG patients was 48.5 mm and 49.8 mm for HVs (p = 0.14). The difference in the located depths of the segments between groups was not statistically significant. The results showed a significant difference in the measured UT angles in the case of the identified edge of the ICA and selected ophthalmic artery segments (p = 0.0002). We demonstrated that locating the IOA and EOA segments can be achieved using the edge of the ICA as a reference point.

Abbreviations: OA: ophthalmic artery; IOA: intracranial segments of the ophthalmic artery; EOA: extracranial segments of the ophthalmic artery; ICA: internal carotid artery; UT: ultrasonic transducer; HTG: high tension glaucoma; SD: standard deviation; ICP: intracranial pressure; TCD: transcranial Doppler

Graphical and statistical analyses of the oculocardiac reflex during a non-invasive intracranial pressure measurement

PURPOSE

This study aimed to examine the incidence of the oculocardiac reflex during a non-invasive intracranial pressure measurement when gradual external pressure was applied to the orbital tissues and eye.

METHODS

Patients (n = 101) and healthy volunteers (n = 56) aged 20-75 years who underwent a non-invasive intracranial pressure measurement were included in this retrospective oculocardiac reflex analysis. Prespecified thresholds greater than a 10% or 20% decrease in the heart rate from baseline were used to determine the incidence of the oculocardiac reflex.

RESULTS

None of the subjects had a greater than 20% decrease in heart rate from baseline. Four subjects had a greater than 10% decrease in heart rate from baseline, representing 0.9% of the total pressure steps. Three of these subjects were healthy volunteers, and one was a glaucoma patient.

CONCLUSION

The incidence of the oculocardiac reflex during a non-invasive intracranial pressure measurement procedure was very low and not associated with any clinically relevant effects.

Noninvasive Assessment of Intracranial Pressure Status in Idiopathic Intracranial Hypertension Using Displacement Encoding with Stimulated Echoes (DENSE) MRI: A Prospective Patient Study with Contemporaneous CSF Pressure Correlation

BACKGROUND AND PURPOSE

Intracranial pressure is estimated invasively by using lumbar puncture with CSF opening pressure measurement. This study evaluated displacement encoding with stimulated echoes (DENSE), an MR imaging technique highly sensitive to brain motion, as a noninvasive means of assessing intracranial pressure status.

MATERIALS AND METHODS

Nine patients with suspected elevated intracranial pressure and 9 healthy control subjects were included in this prospective study. Controls underwent DENSE MR imaging through the midsagittal brain. Patients underwent DENSE MR imaging followed immediately by lumbar puncture with opening pressure measurement, CSF removal, closing pressure measurement, and immediate repeat DENSE MR imaging. Phase-reconstructed images were processed producing displacement maps, and pontine displacement was calculated. Patient data were analyzed to determine the effects of measured pressure on pontine displacement. Patient and control data were analyzed to assess the effects of clinical status (pre-lumbar puncture, post-lumbar puncture, or control) on pontine displacement.

RESULTS

Patients demonstrated imaging findings suggesting chronically elevated intracranial pressure, whereas healthy control volunteers demonstrated no imaging abnormalities. All patients had elevated opening pressure (median, 36.0 cm water), decreased by the removal of CSF to a median closing pressure of 17.0 cm water. Patients pre-lumbar puncture had significantly smaller pontine displacement than they did post-lumbar puncture after CSF pressure reduction (P = .001) and compared with controls (P = .01). Post-lumbar puncture patients had statistically similar pontine displacements to controls. Measured CSF pressure in patients pre- and post-lumbar puncture correlated significantly with pontine displacement (r = 0.49; P = .04).

CONCLUSIONS

This study establishes a relationship between pontine displacement from DENSE MR imaging and measured pressure obtained contemporaneously by lumbar puncture, providing a method to noninvasively assess intracranial pressure status in idiopathic intracranial hypertension.

Spaceflight-Induced Intracranial Hypertension and Visual Impairment: Pathophysiology and Countermeasures

Visual impairment intracranial pressure (VIIP) syndrome is considered an unexplained major risk for future long-duration spaceflight. NASA recently redefined this syndrome as Spaceflight-Associated Neuro-ocular Syndrome (SANS). Evidence thus reviewed supports that chronic, mildly elevated intracranial pressure (ICP) in space (as opposed to more variable ICP with posture and activity on Earth) is largely accounted for by loss of hydrostatic pressures and altered hemodynamics in the intracranial circulation and the cerebrospinal fluid system. In space, an elevated pressure gradient across the lamina cribrosa, caused by a chronic but mildly elevated ICP, likely elicits adaptations of multiple structures and fluid systems in the eye which manifest themselves as the VIIP syndrome. A chronic mismatch between ICP and intraocular pressure (IOP) in space may acclimate the optic nerve head, lamina cribrosa, and optic nerve subarachnoid space to a condition that is maladaptive to Earth, all contributing to the pathogenesis of space VIIP syndrome. Relevant findings help to evaluate whether artificial gravity is an appropriate countermeasure to prevent this seemingly adverse effect of long-duration spaceflight.

Invasive and noninvasive means of measuring intracranial pressure: a review

Measurement of intracranial pressure (ICP) can be invaluable in the management of critically ill patients. Cerebrospinal fluid is produced by the choroid plexus in the brain ventricles (a set of communicating chambers), after which it circulates through the different ventricles and exits into the subarachnoid space around the brain, where it is reabsorbed into the venous system. If the fluid does not drain out of the brain or get reabsorbed, the ICP increases, which may lead to brain damage or death. ICP elevation accompanied by dilatation of the cerebral ventricles is termed hydrocephalus, whereas ICP elevation accompanied by normal or small ventricles is termed idiopathic intracranial hypertension.

OBJECTIVE

We performed a comprehensive literature review on how to measure ICP invasively and noninvasively.

APPROACH

This review discusses the advantages and disadvantages of current invasive and noninvasive approaches.

MAIN RESULTS

Invasive methods remain the most accurate at measuring ICP, but they are prone to a variety of complications including infection, hemorrhage and neurological deficits. Ventricular catheters remain the gold standard but also carry the highest risk of complications, including difficult or incorrect placement. Direct telemetric intraparenchymal ICP monitoring devices are a good alternative. Noninvasive methods for measuring and evaluating ICP have been developed and classified in five broad categories, but have not been reliable enough to use on a routine basis. These methods include the fluid dynamic, ophthalmic, otic, and electrophysiologic methods, as well as magnetic resonance imaging, transcranial Doppler ultrasonography (TCD), cerebral blood flow velocity, near-infrared spectroscopy, transcranial time-of-flight, spontaneous venous pulsations, venous ophthalmodynamometry, optical coherence tomography of retina, optic nerve sheath diameter (ONSD) assessment, pupillometry constriction, sensing tympanic membrane displacement, analyzing otoacoustic emissions/acoustic measure, transcranial acoustic signals, visual-evoked potentials, electroencephalography, skull vibrations, brain tissue resonance and the jugular vein.

SIGNIFICANCE

This review provides a current perspective of invasive and noninvasive ICP measurements, along with a sense of their relative strengths, drawbacks and areas for further improvement. At present, none of the noninvasive methods demonstrates sufficient accuracy and ease of use while allowing continuous monitoring in routine clinical use. However, they provide a realizable ICP measurement in specific patients especially when invasive monitoring is contraindicated or unavailable. Among all noninvasive ICP measurement methods, ONSD and TCD are attractive and may be useful in selected settings though they cannot be used as invasive ICP measurement substitutes. For a sufficiently accurate and universal continuous ICP monitoring method/device, future research and developments are needed to integrate further refinements of the existing methods, combine telemetric sensors and/or technologies, and validate large numbers of clinical studies on relevant patient populations.

Ultrasound non-invasive measurement of intracranial pressure in neurointensive care: A prospective observational study

BACKGROUND

The invasive nature of the current methods for monitoring of intracranial pressure (ICP) has prevented their use in many clinical situations. Several attempts have been made to develop methods to monitor ICP non-invasively. The aim of this study is to assess the relationship between ultrasound-based non-invasive ICP (nICP) and invasive ICP measurement in neurocritical care patients.

METHODS AND FINDINGS

This was a prospective, single-cohort observational study of patients admitted to a tertiary neurocritical care unit. Patients with brain injury requiring invasive ICP monitoring were considered for inclusion. nICP was assessed using optic nerve sheath diameter (ONSD), venous transcranial Doppler (vTCD) of straight sinus systolic flow velocity (FVsv), and methods derived from arterial transcranial Doppler (aTCD) on the middle cerebral artery (MCA): MCA pulsatility index (PIa) and an estimator based on diastolic flow velocity (FVd). A total of 445 ultrasound examinations from 64 patients performed from 1 January to 1 November 2016 were included. The median age of the patients was 53 years (range 37-64). Median Glasgow Coma Scale at admission was 7 (range 3-14), and median Glasgow Outcome Scale was 3 (range 1-5). The mortality rate was 20%. ONSD and FVsv demonstrated the strongest correlation with ICP (R = 0.76 for ONSD versus ICP; R = 0.72 for FVsv versus ICP), whereas PIa and the estimator based on FVd did not correlate with ICP significantly. Combining the 2 strongest nICP predictors (ONSD and FVsv) resulted in an even stronger correlation with ICP (R = 0.80). The ability to detect intracranial hypertension (ICP ≥ 20 mm Hg) was highest for ONSD (area under the curve [AUC] 0.91, 95% CI 0.88-0.95). The combination of ONSD and FVsv methods showed a statistically significant improvement of AUC values compared with the ONSD method alone (0.93, 95% CI 0.90-0.97, p = 0.01). Major limitations are the heterogeneity and small number of patients included in this study, the need for specialised training to perform and interpret the ultrasound tests, and the variability in performance among different ultrasound operators.

CONCLUSIONS

Of the studied ultrasound nICP methods, ONSD is the best estimator of ICP. The novel combination of ONSD ultrasonography and vTCD of the straight sinus is a promising and easily available technique for identifying critically ill patients with intracranial hypertension.

Through the looking glass: early non-invasive imaging in TBI predicts the need for interventions

Background

Early diagnosis and treatment of traumatic brain injury (TBI) lead to better outcomes. It is difficult to predict which patients benefit from specialised centres, leading to over triage or delay in definitive care. We propose that a non-invasive test comprising optic nerve sheath ultrasound, transcranial Doppler and quantitative papillary reactivity is feasible, correlates with CT findings and may allow for accurate early identification of TBI.

Methods

A 1-year, prospective observation study evaluated a low-risk, non-invasive method of assessing brain injury. Patients underwent a non-invasive neurological examination for trauma, including the above assessments. Data from the three examinations were collected within 6 hours of injury and at 24 hours, and were analysed. Demographics, haemodynamic data, imaging results and short-term outcomes/interventions were recorded.

Results

Trauma patients over the age of 18 years, with a Glascow coma scale (GCS) of <12 or CT evidence of TBI, and intubated were included (N=100). These were divided into +CT (n=49) and −CT groups (n=51) according to the Marshall CT classification of TBI. The +CT group was older, with worse GCS and higher lactate (p=0.008, p=0.001 and p=0.01) but were otherwise well matched. The +CT group included all TBI types, with 96% of the patients having more than one type of TBI. Pulsatility index and neurologic pupillary index were predictive of a +CT (p=0.04, p=0.02). Area under the receiver-operating curve for the logistic regression model for the prediction of positive radiographic findings was r=0.718. Finally, we suggest a preliminary scoring heuristic for predicting a positive radiological finding in a patient with TBI.

Conclusions

The proposed examination is a feasible, non-invasive tool that may have clinical utility in the early prediction of TBI. If validated, it may improve trauma triage for the brain-injured patient. Further studies are warranted to validate this model.

Noninvasive methods of detecting increased intracranial pressure

The detection of elevated intracranial pressure (ICP) is of paramount importance in the diagnosis and management of a number of neurologic pathologies. The current gold standard is the use of intraventricular or intraparenchymal catheters; however, this is invasive, expensive, and requires anesthesia. On the other hand, diagnosing intracranial hypertension based on clinical symptoms such as headaches, vomiting, and visual changes lacks sensitivity. As such, there exists a need for a noninvasive yet accurate and reliable method for detecting elevated ICP. In this review, we aim to cover both structural modalities such as computed tomography (CT), magnetic resonance imaging (MRI), ocular ultrasound, fundoscopy, and optical coherence tomography (OCT) as well as functional modalities such as transcranial Doppler ultrasound (TCD), visual evoked potentials (VEPs), and near-infrared spectroscopy (NIRS).

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.

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.

Neuroretinal rim area and ocular haemodynamic parameters in patients with normal-tension glaucoma with differing intracranial pressures

PURPOSE

To assess the differences in the neuroretinal rim area (NRA) and ocular haemodynamic parameters in patients with normal-tension glaucoma (NTG) with differing intracranial pressure (ICP) values.

METHODS

40 patients (11 males) with NTG (age 61.1 (11.5)) were included in the prospective study. Intraocular pressure (IOP), non-invasive ICP, retrobulbar blood flow (RBF) and confocal laser scanning tomography for optic nerve disc (OND) structural parameters were assessed. Non-invasive ICP was measured using a novel two-depth Transcranial Doppler device. RBF was measured using colour Doppler imaging in the ophthalmic artery (OA). The patients were divided into two groups, ICP ≥ and <8.3 mm Hg, based on the statistical median of ICP. p Values <0.05 were considered statistically significant.

RESULTS

Patients with NTG had mean ICP 8.8 (2.5) mm Hg, IOP 13.6 (2.1) mm Hg, OND size 2.3 (0.6) mm(2), NRA 1.2 (0.4) mm(2). Lower ICP was correlated with decreased NRA (r=0.51, p=0.001). Patients with NTG having lower ICP (N=20) had significantly lower NRA 1.0 (0.3) mm(2), than patients with NTG having higher ICP (N=20) 1.3 (0.3) mm(2), p=0.002, although there were no significant differences in OND size (accordingly, 2.2 (0.5) and 2.3 (0.6) mm(2), p=0.55) and IOP (accordingly, 13.5 (2.4) and 13.7 (1.8) mm Hg, p=0.58). Patients with NTG having lower ICP had significantly lower OA blood flow velocities (peak systolic volume (PSV) 28.7 (8.0), end-diastolic volume (EDV) 6.9 (3.0) cm/s), compared with patients with NTG having higher ICP (PSV 35.5 (10.2), EDV 9.4 (4.1) cm/s), p<0.04.

CONCLUSIONS

Patients with NTG having lower ICP have decreased neuroretinal rim area and OA blood flow parameters compared with patients having higher ICP. Further longitudinal studies are needed to analyse the involvement of ICP in NTG management.

The International Multi-disciplinary Consensus Conference on Multimodality Monitoring: future directions and emerging technologies

Neuromonitoring has evolved rapidly in recent years and there now are many new monitors that have revealed a great deal about the ongoing pathophysiology of brain injury and coma. Further evolution will include the consolidation of multi-modality monitoring (MMM), the development of next-generation informatics tools to identify complex physiologic events and decision support tools to permit targeted individualized care. In this review, we examine future directions and emerging technologies in neuromonitoring including: (1) device development, (2) what is the current limitation(s) of MMM in its present format(s), (3) what would improve the ability of MMM to enhance neurocritical care, and (4) how do we develop evidence for use of MMM?

Literature review and meta-analysis of translaminar pressure difference in open-angle glaucoma

There is increasing evidence in the literature regarding translaminar pressure difference's (TPD) role in the pathophysiology of glaucoma. The optic nerve is exposed not only to intraocular pressure in the eye, but also to intracranial pressure (ICP), as it is surrounded by cerebrospinal fluid in the subarachnoid space. Although pilot studies have identified the potential importance of TPD in glaucoma, limited available data currently prevent a comprehensive description of the role that TPD may have in glaucomatous pathophysiology. In this review, we present all available qualified data from a systematic review of the literature of the role of TPD in open-angle glaucoma (OAG). PubMed (Medline), OVID Medline, ScienceDirect, SpringerLink, and all available library databases were reviewed and subsequent meta-analysis of pooled mean differences are presented where appropriate. Five papers including 396 patients met criteria for inclusion to the analysis. Importantly, we included all observational studies despite differences in ICP measurement methods, as there is no consensus regarding best-practice ICP measurements in glaucoma. Our results show that not only TPD is higher in glaucoma patients compared with healthy subjects, it is related to structural glaucomatous changes of the optic disc. Our analysis suggests further longitudinal prospective studies are needed to investigate the influence of TPD in OAG, with a goal of overcoming methodological weaknesses of previous studies.

Update in intracranial pressure evaluation methods and translaminar pressure gradient role in glaucoma

Glaucoma is one of the leading causes of blindness worldwide. Historically, it has been considered an ocular disease primary caused by pathological intraocular pressure (IOP). Recently, researchers have emphasized intracranial pressure (ICP), as translaminar counter pressure against IOP may play a role in glaucoma development and progression. It remains controversial what is the best way to measure ICP in glaucoma. Currently, the 'gold standard' for ICP measurement is invasive measurement of the pressure in the cerebrospinal fluid via lumbar puncture or via implantation of the pressure sensor into the brains ventricle. However, the direct measurements of ICP are not without risk due to its invasiveness and potential risk of intracranial haemorrhage and infection. Therefore, invasive ICP measurements are prohibitive due to safety needs, especially in glaucoma patients. Several approaches have been proposed to estimate ICP non-invasively, including transcranial Doppler ultrasonography, tympanic membrane displacement, ophthalmodynamometry, measurement of optic nerve sheath diameter and two-depth transcranial Doppler technology. Special emphasis is put on the two-depth transcranial Doppler technology, which uses an ophthalmic artery as a natural ICP sensor. It is the only method which accurately and precisely measures absolute ICP values and may provide valuable information in glaucoma.

Consensus summary statement of the International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care: a statement for healthcare professionals from the Neurocritical Care Society and the European Society of Intensive Care Medicine

Neurocritical care depends, in part, on careful patient monitoring but as yet there are little data on what processes are the most important to monitor, how these should be monitored, and whether monitoring these processes is cost-effective and impacts outcome. At the same time, bioinformatics is a rapidly emerging field in critical care but as yet there is little agreement or standardization on what information is important and how it should be displayed and analyzed. The Neurocritical Care Society in collaboration with the European Society of Intensive Care Medicine, the Society for Critical Care Medicine, and the Latin America Brain Injury Consortium organized an international, multidisciplinary consensus conference to begin to address these needs. International experts from neurosurgery, neurocritical care, neurology, critical care, neuroanesthesiology, nursing, pharmacy, and informatics were recruited on the basis of their research, publication record, and expertise. They undertook a systematic literature review to develop recommendations about specific topics on physiologic processes important to the care of patients with disorders that require neurocritical care. This review does not make recommendations about treatment, imaging, and intraoperative monitoring. A multidisciplinary jury, selected for their expertise in clinical investigation and development of practice guidelines, guided this process. The GRADE system was used to develop recommendations based on literature review, discussion, integrating the literature with the participants' collective experience, and critical review by an impartial jury. Emphasis was placed on the principle that recommendations should be based on both data quality and on trade-offs and translation into clinical practice. Strong consideration was given to providing pragmatic guidance and recommendations for bedside neuromonitoring, even in the absence of high quality data.

Noninvasive assessment of cerebrospinal fluid pressure

Measurement of intracranial pressure (ICP) is critical for the evaluation and management of many neurological and neurosurgical conditions. The invasiveness of ICP measurement limits the frequency with which ICP can be evaluated, hampering the clinical care of patients with ICP disorders. Thus, there has been substantial interest in developing noninvasive methods for the assessment of ICP. Numerous approaches have been applied to the problem, although none seems to represent a complete solution. The goal of this review is to familiarize the reader with the currently available methods to noninvasively evaluate ICP.

Consensus summary statement of the International Multidisciplinary Consensus Conference on Multimodality Monitoring in Neurocritical Care : a statement for healthcare professionals from the Neurocritical Care Society and the European Society of Intensive Care Medicine

Neurocritical care depends, in part, on careful patient monitoring but as yet there are little data on what processes are the most important to monitor, how these should be monitored, and whether monitoring these processes is cost-effective and impacts outcome. At the same time, bioinformatics is a rapidly emerging field in critical care but as yet there is little agreement or standardization on what information is important and how it should be displayed and analyzed. The Neurocritical Care Society in collaboration with the European Society of Intensive Care Medicine, the Society for Critical Care Medicine, and the Latin America Brain Injury Consortium organized an international, multidisciplinary consensus conference to begin to address these needs. International experts from neurosurgery, neurocritical care, neurology, critical care, neuroanesthesiology, nursing, pharmacy, and informatics were recruited on the basis of their research, publication record, and expertise. They undertook a systematic literature review to develop recommendations about specific topics on physiologic processes important to the care of patients with disorders that require neurocritical care. This review does not make recommendations about treatment, imaging, and intraoperative monitoring. A multidisciplinary jury, selected for their expertise in clinical investigation and development of practice guidelines, guided this process. The GRADE system was used to develop recommendations based on literature review, discussion, integrating the literature with the participants' collective experience, and critical review by an impartial jury. Emphasis was placed on the principle that recommendations should be based on both data quality and on trade-offs and translation into clinical practice. Strong consideration was given to providing pragmatic guidance and recommendations for bedside neuromonitoring, even in the absence of high quality data.

Monitoring of intracranial pressure in patients with traumatic brain injury

Since Monro published his observations on the nature of the contents of the intracranial space in 1783, there has been investigation of the unique relationship between the contents of the skull and the intracranial pressure (ICP). This is particularly true following traumatic brain injury (TBI), where it is clear that elevated ICP due to the underlying pathological processes is associated with a poorer clinical outcome. Consequently, there is considerable interest in monitoring and manipulating ICP in patients with TBI. The two techniques most commonly used in clinical practice to monitor ICP are via an intraventricular or intraparenchymal catheter with a microtransducer system. Both of these techniques are invasive and are thus associated with complications such as hemorrhage and infection. For this reason, significant research effort has been directed toward development of a non-invasive method to measure ICP. The principle aims of ICP monitoring in TBI are to allow early detection of secondary hemorrhage and to guide therapies that limit intracranial hypertension (ICH) and optimize cerebral perfusion. However, information from the ICP value and the ICP waveform can also be used to assess the intracranial volume-pressure relationship, estimate cerebrovascular pressure reactivity, and attempt to forecast future episodes of ICH.