Critical thresholds for intracranial pressure vary over time in non-craniectomised traumatic brain injury patients

Artifact identification and removal methodologies for intracranial pressure signals: a systematic scoping review

Objective. Intracranial pressure measurement (ICP) is an essential component of deriving of multivariate data metrics foundational to improving understanding of high temporal relationships in cerebral physiology. A significant barrier to this work is artifact ridden data. As such, the objective of this review was to examine the existing literature pertinent to ICP artifact management.Methods.A search of five databases (BIOSIS, SCOPUS, EMBASE, PubMed, and Cochrane Library) was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines with the PRISMA Extension for Scoping Review. The search question examined the methods for artifact management for ICP signals measured in human/animals.Results.The search yielded 5875 unique results. There were 19 articles included in this review based on inclusion/exclusion criteria and article references. Each method presented was categorized as: (1) valid ICP pulse detection algorithms and (2) ICP artifact identification and removal methods. Machine learning-based and filter-based methods indicated the best results for artifact management; however, it was not possible to elucidate a single most robust method.Conclusion.There is a significant lack of standardization in the metrics of effectiveness in artifact removal which makes comparison difficult across studies. Differences in artifacts observed on patient neuropathological health and recording methodologies have not been thoroughly examined and introduce additional uncertainty regarding effectiveness.Significance. This work provides critical insights into existing literature pertaining to ICP artifact management as it highlights holes in the literature that need to be adequately addressed in the establishment of robust artifact management methodologies.

Evaluation of Miethke M.scio Device Implantation for Intracranial Pressure Monitoring in Patients with Cerebrospinal Fluid Disorders

BACKGROUND

Patients with complex shunt-related problems and varying diagnoses of cerebrospinal fluid (CSF) disturbance can present with headache and clinical symptoms that may be difficult to relate to underdrainage or overdrainage. Telemetric intracranial pressure (ICP) monitoring may assist in evaluating individual patients and assessing shunt function and adjustment. We report a case series of patients receiving a Miethke M.scio sensor.

METHODS

Between June 2016 and August 2021, 14 patients older than 18 years with different diagnoses underwent ventriculoperitoneal shunt surgery and received a Miethke M.scio sensor.

RESULTS

Patients had idiopathic intracranial hypertension (n = 3), obstructive hydrocephalus caused by tumors (n = 4), and malformations (n = 5). Headaches (71%) and visual impairment (50%) were the most common symptoms before surgery and 65% of the symptoms were improved after surgery. In total, 25 measurements were made and 11 of these led to changes in the shunt settings. Postoperative measurements were taken in 8 patients and the most common indication of ICP measurement was headache and/or control of the shunt settings.

CONCLUSIONS

The Miethke M.scio is a safe and valuable device to use in shunt-treated patients, in particular those expected to need assessment of ICP monitoring postoperatively. Repeated ICP measurements can also assist in personalized adjustment of the shunt setting to optimize CSF flow in this diverse patient group. Future studies should include a standardized protocol with ICP measurements correlated to the symptoms and cause of CSF disturbances to provide better understanding of the dynamics of the ICP in each patient.

The intracranial compartmental syndrome: a proposed model for acute brain injury monitoring and management

For decades, one of the main targets in the management of severe acute brain injury (ABI) has been intracranial hypertension (IH) control. However, the determination of IH has suffered variations in its thresholds over time without clear evidence for it. Meanwhile, progress in the understanding of intracranial content (brain, blood and cerebrospinal fluid) dynamics and recent development in monitoring techniques suggest that targeting intracranial compliance (ICC) could be a more reliable approach rather than guiding actions by predetermined intracranial pressure values. It is known that ICC impairment forecasts IH, as intracranial volume may rapidly increase inside the skull, a closed bony box with derisory expansibility. Therefore, an intracranial compartmental syndrome (ICCS) can occur with deleterious brain effects, precipitating a reduction in brain perfusion, thereby inducing brain ischemia. The present perspective review aims to discuss the ICCS concept and suggest an integrative model for the combination of modern invasive and noninvasive techniques for IH and ICC assessment. The theory and logic suggest that the combination of multiple ancillary methods may enhance ICC impairment prediction, pointing proactive actions and improving patient outcomes.

Modelling glioma progression, mass effect and intracranial pressure in patient anatomy

Increased intracranial pressure is the source of most critical symptoms in patients with glioma, and often the main cause of death. Clinical interventions could benefit from non-invasive estimates of the pressure distribution in the patient's parenchyma provided by computational models. However, existing glioma models do not simulate the pressure distribution and they rely on a large number of model parameters, which complicates their calibration from available patient data. Here we present a novel model for glioma growth, pressure distribution and corresponding brain deformation. The distinct feature of our approach is that the pressure is directly derived from tumour dynamics and patient-specific anatomy, providing non-invasive insights into the patient's state. The model predictions allow estimation of critical conditions such as intracranial hypertension, brain midline shift or neurological and cognitive impairments. A diffuse-domain formalism is employed to allow for efficient numerical implementation of the model in the patient-specific brain anatomy. The model is tested on synthetic and clinical cases. To facilitate clinical deployment, a high-performance computing implementation of the model has been publicly released.

Association of Age and Sex With Multi-Modal Cerebral Physiology in Adult Moderate/Severe Traumatic Brain Injury: A Narrative Overview and Future Avenues for Personalized Approaches

The impact of age and biological sex on outcome in moderate/severe traumatic brain injury (TBI) has been documented in large cohort studies, with advanced age and male sex linked to worse long-term outcomes. However, the association between age/biological sex and high-frequency continuous multi-modal monitoring (MMM) cerebral physiology is unclear, with only sparing reference made in guidelines and major literature in moderate/severe TBI. In this narrative review, we summarize some of the largest studies associating various high-frequency MMM parameters with age and biological sex in moderate/severe TBI. To start, we present this by highlighting the representative available literature on high-frequency data from Intracranial Pressure (ICP), Cerebral Perfusion Pressure (CPP), Extracellular Brain Tissue Oxygenation (PbtO₂), Regional Cerebral Oxygen Saturations (rSO₂), Cerebral Blood Flow (CBF), Cerebral Blood Flow Velocity (CBFV), Cerebrovascular Reactivity (CVR), Cerebral Compensatory Reserve, common Cerebral Microdialysis (CMD) Analytes and their correlation to age and sex in moderate/severe TBI cohorts. Then we present current knowledge gaps in the literature, discuss biological implications of age and sex on cerebrovascular monitoring in TBI and some future avenues for bedside research into the cerebrovascular physiome after TBI.

Failure of an effective physiologic threshold compliance tool to demonstrate benefit in a clinical trial of traumatic brain injury patients

BACKGROUND

Better physiologic threshold compliance holds promise for improving outcomes in neurocritical care patients.

METHODS

Our group developed a threshold compliance tool. This software computes and displays the proportion of values out of range in real time. We captured intracranial pressure (ICP) measures in our patients before and after implementation of this technology. Ten months after the threshold compliance tool was introduced we initiated a randomized controlled trial involving acute traumatic brain injury (TBI) patients to assess whether the tool was effective at reducing out-of-range ICP values.

RESULTS

A total of 54 patients with ICP monitors were included in our analysis, 42 of whom sustained a TBI. Implementation of the threshold compliance tool was associated with an 85.3% reduction in ICP values exceeding 22 mmHg in neurocritical care patients (p = 0.004) and a 76.8% reduction in patients with TBI (p = 0.043). Out-of-range values in an area-under-the-curve analysis were reduced by 78.8% in all patients (p = 0.009) and in TBI patients by 77.9% (p = 0.051). Out-of-range values were not further reduced during our randomized controlled trial examining the threshold compliance tool, and a difference between treatment groups was not suggested.

CONCLUSIONS

Implementation of a threshold compliance tool was associated with a marked and significant reduction in out-of-range ICP values. Benefit was, however, not evident in a randomized controlled trial. Our analysis provides a unique perspective on our failure to detect an apparent true difference and may provide insights into other neurotrauma trial failures.

Ten physiological commandments for severe head injury

Advances in multiparametric brain monitoring have allowed us to deepen our knowledge of the physiopathology of head injury and how it can be treated using the therapies available today. It is essential to understand and interpret a series of basic physiological and physiopathological principles that, on the one hand, provide an adequate metabolic environment to prevent worsening of the primary brain injury and favour its recovery, and on the other hand, allow therapeutic resources to be individually adapted to the specific needs of the patient. Based on these notions, this article presents a decalogue of the physiological objectives to be achieved in brain injury, together with a series of diagnostic and therapeutic recommendations for achieving these goals. We emphasise the importance of considering and analysing the physiological variables involved in the transport of oxygen to the brain, such as cardiac output and arterial oxygen content, together with their conditioning factors and possible alterations. Special attention is paid to the basic elements of physiological neuroprotection, and we describe the multiple causes of cerebral hypoxia, how to approach them, and how to correct them. We also examine the increase in intracranial pressure as a physiopathological element, focussing on the significance of thoracic and abdominal pressure in the interpretation of intracranial pressure. Treatment of intracranial pressure should be based on a step-wise model, the first stage of which should be based on a physiopathological reflection combined with information on the tomographic lesions rather than on rigid numerical values.

Ten physiological commandments for severe head injury

Advances in multiparametric brain monitoring have allowed us to deepen our knowledge of the physiopathology of head injury and how it can be treated using the therapies available today. It is essential to understand and interpret a series of basic physiological and physiopathological principles that, on the one hand, provide an adequate metabolic environment to prevent worsening of the primary brain injury and favour its recovery, and on the other hand, allow therapeutic resources to be individually adapted to the specific needs of the patient. Based on these notions, this article presents a decalogue of the physiological objectives to be achieved in brain injury, together with a series of diagnostic and therapeutic recommendations for achieving these goals. We emphasise the importance of considering and analysing the physiological variables involved in the transport of oxygen to the brain, such as cardiac output and arterial oxygen content, together with their conditioning factors and possible alterations. Special attention is paid to the basic elements of physiological neuroprotection, and we describe the multiple causes of cerebral hypoxia, how to approach them, and how to correct them. We also examine the increase in intracranial pressure as a physiopathological element, focussing on the significance of thoracic and abdominal pressure in the interpretation of intracranial pressure. Treatment of intracranial pressure should be based on a step-wise model, the first stage of which should be based on a physiopathological reflection combined with information on the tomographic lesions rather than on rigid numerical values.

Impact of duration and magnitude of raised intracranial pressure on outcome after severe traumatic brain injury: A CENTER-TBI high-resolution group study

Magnitude of intracranial pressure (ICP) elevations and their duration have been associated with worse outcomes in patients with traumatic brain injuries (TBI), however published thresholds for injury vary and uncertainty about these levels has received relatively little attention. In this study, we have analyzed high-resolution ICP monitoring data in 227 adult patients in the CENTER-TBI dataset. Our aim was to identify thresholds of ICP intensity and duration associated with worse outcome, and to evaluate the uncertainty in any such thresholds. We present ICP intensity and duration plots to visualize the relationship between ICP events and outcome. We also introduced a novel bootstrap technique to evaluate uncertainty of the equipoise line. We found that an intensity threshold of 18 ± 4 mmHg (2 standard deviations) was associated with worse outcomes in this cohort. In contrast, the uncertainty in what duration is associated with harm was larger, and safe durations were found to be population dependent. The pressure and time dose (PTD) was also calculated as area under the curve above thresholds of ICP. A relationship between PTD and mortality could be established, as well as for unfavourable outcome. This relationship remained valid for mortality but not unfavourable outcome after adjusting for IMPACT core variables and maximum therapy intensity level. Importantly, during periods of impaired autoregulation (defined as pressure reactivity index (PRx)>0.3) ICP events were associated with worse outcomes for nearly all durations and ICP levels in this cohort and there was a stronger relationship between outcome and PTD. Whilst caution should be exercised in ascribing causation in observational analyses, these results suggest intracranial hypertension is poorly tolerated in the presence of impaired autoregulation. ICP level guidelines may need to be revised in the future taking into account cerebrovascular autoregulation status considered jointly with ICP levels.

Intracranial Pressure Monitoring Signals After Traumatic Brain Injury: A Narrative Overview and Conceptual Data Science Framework

Continuous intracranial pressure (ICP) monitoring is a cornerstone of neurocritical care after severe brain injuries such as traumatic brain injury and acts as a biomarker of secondary brain injury. With the rapid development of artificial intelligent (AI) approaches to data analysis, the acquisition, storage, real-time analysis, and interpretation of physiological signal data can bring insights to the field of neurocritical care bioinformatics. We review the existing literature on the quantification and analysis of the ICP waveform and present an integrated framework to incorporate signal processing tools, advanced statistical methods, and machine learning techniques in order to comprehensively understand the ICP signal and its clinical importance. Our goals were to identify the strengths and pitfalls of existing methods for data cleaning, information extraction, and application. In particular, we describe the use of ICP signal analytics to detect intracranial hypertension and to predict both short-term intracranial hypertension and long-term clinical outcome. We provide a well-organized roadmap for future researchers based on existing literature and a computational approach to clinically-relevant biomedical signal data.

Extreme intracranial pressure elevation > 90 mmHg in an awake patient with primary CNS lymphoma-case report

We describe a patient with primary CNS lymphomas, awake despite an extreme ICP elevation. A 48-year-old woman presented with headache since 1 month, and bilateral papillary edema was observed. Magnetic resonance imaging revealed diffuse infiltration around the petrous bone. Following external ventricular drainage (EVD) placement, ICP levels of > 90 mmHg were recorded while the patient was fully awake. Cytology revealed an aggressive primary CNS lymphoma. Cerebrospinal fluid (CSF) drainage at high opening pressure levels was required. We conclude that extreme ICP elevations, treatable by CSF drainage, can be observed without a reduced level of consciousness.

Association between Cerebrovascular Reactivity Monitoring and Mortality Is Preserved When Adjusting for Baseline Admission Characteristics in Adult Traumatic Brain Injury: A CENTER-TBI Study

Cerebral autoregulation, as measured using the pressure reactivity index (PRx), has been related to global patient outcome in adult patients with traumatic brain injury (TBI). To date, this has been documented without accounting for standard baseline admission characteristics and intracranial pressure (ICP). We evaluated this association, adjusting for baseline admission characteristics and ICP, in a multi-center, prospective cohort. We derived PRx as the correlation between ICP and mean arterial pressure in prospectively collected multi-center data from the High-Resolution Intensive Care Unit (ICU) cohort of the Collaborative European NeuroTrauma Effectiveness Research in TBI (CENTER-TBI) study. Multi-variable logistic regression models were analyzed to assess the association between global outcome (measured as either mortality or dichotomized Glasgow Outcome Score-Extended [GOSE]) and a range of covariates (IMPACT [International Mission for Prognosis and Analysis of Clinical Trials] Core and computed tomography [CT] variables, ICP, and PRx). Performance of these models in outcome association was compared using area under the receiver operating curve (AUC) and Nagelkerke's pseudo-R2. One hundred ninety-three patients had a complete data set for analysis. The addition of percent time above threshold for PRx improved AUC and displayed statistically significant increases in Nagelkerke's pseudo-R2 over the IMPACT Core and IMPACT Core + CT models for mortality. The addition of PRx monitoring to IMPACT Core ± CT + ICP models accounted for additional variance in mortality, when compared to models with IMPACT Core ± CT + ICP alone. The addition of cerebrovascular reactivity monitoring, through PRx, provides a statistically significant increase in association with mortality at 6 months. Our data suggest that cerebrovascular reactivity monitoring may provide complementary information regarding outcomes in TBI.

Traumatic brain injury among female veterans: a review of sex differences in military neurosurgery

The impact of traumatic brain injury (TBI) has been demonstrated in various studies with respect to prevalence, morbidity, and mortality data. Many of the patients burdened with long-term sequelae of TBI are veterans. Although fewer in number, female veterans with TBI have been suggested to suffer from unique physical, mental, and social challenges. However, there remains a significant knowledge gap in the sex differences in TBI. Increased female representation in the military heralds an increased risk of TBI for female soldiers, and medical professionals must be prepared to address the unique health challenges in the face of changing demographics among the veteran TBI population. In this review, the authors aimed to present the current understanding of sex differences in TBI in the veteran population and suggest directions for future investigations.

Why Does Brain Trauma Research Fail?

Traumatic brain injury (TBI) represents a major health care problem and a significant social and economic issue worldwide. Considering the generalized failure in introducing effective drugs and clinical protocols, there is an urgent need for efficient treatment modalities, able to improve devastating posttraumatic morbidity and mortality. In this work, the status of brain trauma research is analyzed in all its aspects, including basic and translational science and clinical trials. Implicit and explicit challenges to different lines of research are discussed and clinical trial structures and outcomes are scrutinized, along with possible explanations for systematic therapeutic failures and their implications for future development of drug and clinical trials. Despite significant advances in basic and clinical research in recent years, no specific therapeutic protocols for TBI have been shown to be effective. New potential therapeutic targets have been identified, following a better understanding of pathophysiologic mechanisms underlying TBI, although with disappointing results. Several reasons can be pinpointed at different levels, from inaccurate animal models of disease to faulty preclinical and clinical trials, with poor design and subjective outcome measures. Distinct strategies can be delineated to overcome specific shortcomings of research studies. Identifying and contextualizing the failures that have dominated TBI research is mandatory. This review analyzes current approaches and discusses possible strategies for improving outcomes.

Univariate comparison of performance of different cerebrovascular reactivity indices for outcome association in adult TBI: a CENTER-TBI study

BACKGROUND

Monitoring cerebrovascular reactivity in adult traumatic brain injury (TBI) has been linked to global patient outcome. Three intra-cranial pressure (ICP)-derived indices have been described. It is unknown which index is superior for outcome association in TBI outside previous single-center evaluations. The goal of this study is to evaluate indices for 6- to 12-month outcome association using uniform data harvested in multiple centers.

METHODS

Using the prospectively collected data from the Collaborative European NeuroTrauma Effectiveness Research in TBI (CENTER-TBI) study, the following indices of cerebrovascular reactivity were derived: PRx (correlation between ICP and mean arterial pressure (MAP)), PAx (correlation between pulse amplitude of ICP (AMP) and MAP), and RAC (correlation between AMP and cerebral perfusion pressure (CPP)). Univariate logistic regression models were created to assess the association between vascular reactivity indices with global dichotomized outcome at 6 to 12 months, as assessed by Glasgow Outcome Score-Extended (GOSE). Models were compared via area under the receiver operating curve (AUC) and Delong's test.

RESULTS

Two separate patient groups from this cohort were assessed: the total population with available data (n = 204) and only those without decompressive craniectomy (n = 159), with identical results. PRx, PAx, and RAC perform similar in outcome association for both dichotomized outcomes, alive/dead and favorable/unfavorable, with RAC trending towards higher AUC values. There were statistically higher mean values for the index, % time above threshold, and hourly dose above threshold for each of PRx, PAx, and RAC in those patients with poor outcomes.

CONCLUSIONS

PRx, PAx, and RAC appear similar in their associations with 6- to 12-month outcome in moderate/severe adult TBI, with RAC showing tendency to achieve stronger associations. Further work is required to determine the role for each of these cerebrovascular indices in monitoring of TBI patients.