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Background: Spontaneous intracranial hypotension (SIH) is a debilitating disorder, with an estimated annual incidence of 3.7 per 100,000. Diagnosing SIH can be challenging for clinicians, as patients frequently present with normal investigation findings. Intracranial pressure (ICP) monitoring has been proposed as a valuable tool for patients with orthostatic headaches that are highly suggestive of SIH but have inconclusive investigation results. The primary objective of this study was to determine the proportion of patients with spontaneous orthostatic headaches and normal diagnostic work-up who exhibited abnormal ICP monitoring results., Methods: This single-centre, retrospective observational study was conducted at a tertiary referral centre specialising in SIH and CSF dynamics disorders. Consecutive patients with spontaneous orthostatic headaches and inconclusive diagnostic work-up who underwent 24-hour ICP monitoring were considered eligible. The 24-hour ICP monitoring followed a standardised protocol, measuring median ICP and pulse amplitude (a marker of brain compliance) during the daytime, nighttime, and over the entire 24-hour period. Specific cut-offs for low and high ICP states were predetermined based on the best available current evidence., Results: Thirty-eight patients (23 females, mean age 41 years ± 14SD) were identified. All patients had orthostatic headaches with a spontaneous onset. The mean duration of symptoms was 46 months ± 36SD. ICP monitoring identified 3 patients (7.9%) with low ICP (mean of the median 24-hour ICP - 2 mmHg ± 2SD) and 6 patients (15.8%) with high ICP (mean of the median 24-hour ICP 9 mmHg ± 3SD). Obvious CSF dynamics disturbances were excluded in the remaining 29 patients (76.3%, mean of the median 24-hour ICP 3 mmHg ± 3SD). The only clinical feature that was more common in patients with abnormal ICP compared to patients with normal ICP results was audiovestibular disturbance, namely aural fullness or muffled hearing (67% versus 17%, p = 0.015). There were no complications from the ICP monitoring procedure for any patient., Conclusions: When appropriately selected, patients with a clinical picture highly suggestive of SIH, who have a negative diagnostic work-up, may benefit from consideration of invasive ICP monitoring. Moreover, a significant minority of patients with orthostatic headache may paradoxically have a high CSF pressure state, which can be detected using ICP monitoring., Meeting Presentations: Portions of this work were presented in abstract and oral presentation form at the Twenty-eighth Anglo-Dutch Migraine Association meeting (08/06/2018), the Tenth Meeting of the International Society for Hydrocephalus and Cerebrospinal Fluid Disorders (20/10/2018; Bologna, Italy), the Society of British Neurological Surgeons 2018 Autumn Meeting (19/09/2018; London, United Kingdom), and the European Association of Neurosurgical Societies 2023 congress (27/09/2023; Barcelona, Spain). This work is also part of the doctoral thesis of one of the authors (LD)., Competing Interests: Declarations. Ethics approval and consent to participate: This study has been approved by the North-East Newcastle and North Tyneside 2 Research Ethics Committee and the Health Research Authority (20/NE/0127). Due to its retrospective nature, written consent to take part in this study was waived. All patients provided written consent to undergo the ICP monitoring procedure as part of their standard clinical care. Consent for publication: Not applicable. Competing interests: LD is supported by an Academic Clinical Fellowship from the National Institute for Health Research and was the recipient of a research fellowship sponsored by B.Braun. LDW has received honoraria from and served on advisory boards for Medtronic, B.Braun and Codman. AKT research time was supported by the National Institute for Health Research University College London Hospitals Biomedical Research Centre. MSM serves on the advisory board for AbbVie, Pfizer, Eli Lilly, Lundbeck and TEVA and has received payment for the development of educational presentations from AbbVie, Eli Lilly, Lundbeck and TEVA. SC, DM and FB report no disclosures., (© 2024. The Author(s).)

Dysfunctional lymphatic drainage from the central nervous system (CNS) has been linked to neuroinflammatory and neurodegenerative disorders, but our understanding of the lymphatic contribution to CNS fluid autoregulation remains limited. Here, we studied forces that drive the outflow of the cerebrospinal fluid (CSF) into the deep and superficial cervical lymph nodes (dcLN and scLN) and tested how the blockade of lymphatic networks affects CNS fluid homeostasis. Outflow to the dcLN occurred spontaneously in the absence of lymphatic pumping and was coupled to intracranial pressure (ICP), whereas scLN drainage was driven by pumping. Impaired dcLN drainage led to elevated CSF outflow resistance and delayed CSF-to-blood efflux despite the recruitment of the nasal-to-scLN pathway. Fluid regulation was better compensated after scLN obstruction. The dcLN pathway exhibited steady, consistent drainage across conditions, while the nasal-to-scLN pathway was dynamically activated to mitigate perturbances. These findings highlight the complex physiology of CSF homeostasis and lay the groundwork for future studies aimed at assessing and modulating CNS lymphatic function., (© 2025 Papadopoulos et al.)

Background: Brain energy metabolism is often disturbed after acute brain injuries. Current neuromonitoring methods with cerebral microdialysis (CMD) are based on intermittent measurements (1-4 times/h), but such a low frequency could miss transient but important events. The solution may be the recently developed Loke microdialysis (MD), which provides high-frequency data of glucose and lactate. Before clinical implementation, the reliability and stability of Loke remain to be determined in vivo. The purpose of this study was to validate Loke MD in relation to the standard intermittent CMD method., Methods: Four pigs aged 2-3 months were included. They received two adjacent CMD catheters, one for standard intermittent assessments and one for continuous (Loke MD) assessments of glucose and lactate. The standard CMD was measured every 15 min. Continuous Loke MD was sampled every 2-3 s and was averaged over corresponding 15-min intervals for the statistical comparisons with standard CMD. Intravenous glucose injections and intracranial hypertension by inflation of an intracranial epidural balloon were performed to induce variations in intracranial pressure, cerebral perfusion pressure, and systemic and cerebral glucose and lactate levels., Results: In a linear mixed-effect model of standard CMD glucose (mM), there was a fixed effect value (± standard error [SE]) at 0.94 ± 0.07 (p < 0.001) for Loke MD glucose (mM), with an intercept at - 0.19 ± 0.15 (p = 0.20). The model showed a conditional R 2 at 0.81 and a marginal R 2 at 0.72. In a linear mixed-effect model of standard CMD lactate (mM), there was a fixed effect value (± SE) at 0.41 ± 0.16 (p = 0.01) for Loke MD lactate (mM), with an intercept at 0.33 ± 0.21 (p = 0.25). The model showed a conditional R 2 at 0.47 and marginal R 2 at 0.17., Conclusions: The established standard CMD glucose thresholds may be used as for Loke MD with some caution, but this should be avoided for lactate., Competing Interests: Conflict of interest: The authors have no conflicts of interest. Human and Animal Rights: The study was approved by the Animal Ethics Committee in Uppsala, Sweden (Dnr 5.8.18-21799/2022). All applicable institutional and/or national guidelines for the care and use of animals were followed., (© 2024. The Author(s).)

Objective: To gain initial insight into the efficacy to lower intracranial pressure (ICP), side effects, and effects on cognition of five drugs commonly used to treat idiopathic intracranial hypertension (IIH)., Background: Limited clinical data exist for the treatment for IIH. Impaired cognition is recognized in IIH and can be exacerbated by medications., Methods: This human experimental medicine study was a secondary analysis that focused on an unblinded randomized, sequential, cross-over extension of a previously completed randomized controlled trial. This study evaluated females with active IIH, recruited from University Hospital Birmingham, UK. Participants were treated, in randomized order, for 2 weeks with acetazolamide, amiloride, furosemide, spironolactone, and topiramate; assessment was at baseline and 2 weeks with a minimum 1-week drug washout between drugs. The primary outcome was change in ICP at 2 weeks post-drug administration. The cognitive evaluation was an exploratory study of the trial. ICP was recorded with telemetric, intraparenchymal ICP monitors (Raumedic, Hembrechts, Germany). Adverse events were recorded, and cognition was assessed utilizing the National Institutes of Health Toolbox Cognitive Battery., Results: Fourteen participants were recruited and evaluated by intention-to-treat analysis. Mean (standard deviation) body mass index was 37.3 (7.0) kg/m 2 and ICP was 33.2 (7.1) cm cerebrospinal fluid (CSF) at baseline. ICP fell with four drugs (mean [standard error (SE)]), acetazolamide -3.3 (1.0) mmHg, p = 0.001, furosemide -3.0 (0.9) mmHg, p = 0.001, spironolactone -2.7 (0.9) mmHg, p = 0.003, and topiramate -2.3 (0.9) mmHg, p = 0.010. There was no significant difference between drugs. Side effects were common with acetazolamide (100%, 11/11) and topiramate (93%, 13/14). Baseline cognitive performance was impaired, T-score (mean [SE]) 37.2 (2.6). After treatment, there was a further significant reduction in the fluid cognition domain (ability to process and integrate) with acetazolamide (mean T-score [SE]), -5.0 (2.6), p = 0.057 and topiramate -4.1 (2.0), p = 0.061., Conclusions: Acetazolamide, furosemide, spironolactone, and topiramate marginally reduced ICP. While their effects were not significant, this study was not powered to detect a difference between drugs. Participants reported significant side effects with acetazolamide and topiramate including cognitive decline. Cognitive measures were impaired by acetazolamide and topiramate. Therapeutics with greater efficacy and a favorable side effect profile are an unmet need in the treatment of IIH., (© 2025 The Author(s). Headache: The Journal of Head and Face Pain published by Wiley Periodicals LLC on behalf of American Headache Society.)

Introduction: Traumatic brain injury (TBI) is a prevalent type of disabling and fatal injury in infants/toddlers, which is usually caused by falls or traffic accidents. Considering that it is difficult to collect realistic material properties and validation data of child heads due to ethical reasons, experiments on the piglet heads and the finite element (FE) models are generally used as a substitute for the investigations of child TBI., Methods: In this study, first, a high-quality FE model of a 4-week-old piglet head, including brain (cerebrum, cerebellum, brainstem), skull, soft tissue, cerebrospinal fluid, dura matter, pia matter and mandible, is developed. Then, test for the material properties of the piglet head and that for the global validation data are conducted. For the former, the mechanical properties of the brain, overlying soft tissue and skull of the 4-week-old piglet head are tested, and the constitutive models and corresponding parameters are further defined. For the latter, the quasi-static compression test and dynamic impact test (free-fall drop impact test, drop-hammer impact test) are performed on the piglet head. Finally, the piglet head FE model was validated against tests in terms of the contact force and intracranial pressure (ICP) under eight conditions (one for the compression condition, four for the free-fall impact condition, and three for the drop-hammer impact condition)., Results: The trends of simulated curves are consistent with the experimental results under all conditions. For the contact force, the average error of the peak values between simulations and tests is about 12.9 %, and the average error of time durations is about 6.8 %. For the ICP, the average errors of peak values and time durations between simulations and tests are about 8.9 % and 9.9 %., Conclusions: The results show that the piglet head model has high bio-fidelity, which can be used to predict the head global response and the ICP, and further to assist the investigation of child TBI. The model provides another effective way to evaluate the modeling strategies and material constitute models suitable for child head FE model, and can better to understand the inducement and mechanism of child TBI under different external loading conditions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Importance: Invasive intracranial pressure (ICP) is the standard of care in patients with acute brain injury (ABI) with impaired consciousness. The Neurological Pupil Index (NPi) obtained by automated pupillometry is promising for noninvasively estimating ICP., Objectives: To evaluate the association between repeated NPi and invasive ICP values., Design, Setting, and Participants: This study is a secondary analysis of the Outcome Prognostication of Acute Brain Injury With the Neurological Pupil Index (ORANGE), a multicenter, prospective, observational study of patients with ABI performed from October 1, 2020, to May 31, 2022, with follow-up at 6 months after ABI. The ORANGE study was performed at neurologic intensive care units of tertiary hospitals in Europe and North America. In ORANGE, 514 adult patients receiving mechanical ventilatory support were admitted to the intensive care unit after ABI., Exposure: Invasive ICP monitoring and automated pupillometry assessment every 4 hours during the first 7 days, considered as a standard of care., Main Outcomes and Measures: Association between ICP and NPi values over time, using bayesian joint models, with linear and logistic mixed-effects longitudinal submodels., Results: The study included 318 adult patients (median [IQR] age, 58 [43-69] years; 187 [58.8%] male) who required intensive care unit admission, intubation, and mechanical ventilatory support due to acute traumatic brain injury (n = 133 [41.8%]), intracerebral hemorrhage (n = 104 [32.7%]), or aneurysmal subarachnoid hemorrhage (n = 81 [25.5%]) and had automatic infrared pupillometry used as part of the standard evaluation practice and ICP monitoring. A total of 8692 ICP measurements were collected, with a median (IQR) of 31 (18-37) evaluations per patient. The median (IQR) NPi and ICP for the study population were 4.1 (3.5-4.5) and 10 (5-14) mm Hg, respectively. In a linear mixed model, the mean change in the NPi value, as a continuous variable, was -0.003 (95% credible interval [CrI], -0.006 to 0.000) for each 1-mm Hg ICP increase. No significant association between ICP and abnormal NPi (<3; odds ratio, 1.01; 95% CrI, 0.99-1.03) or absent NPi (0; odds ratio, 1.03; 95% CrI, 0.99-1.06) was observed., Conclusions and Relevance: Although an abnormal NPi could indicate brainstem dysfunction, in this large and heterogeneous population of patients, NPi values were not significantly associated overall with ICP values. Repeated NPi measurements may not be a sufficient replacement for invasive monitoring., Trial Registration: ClinicalTrials.gov Identifier: NCT04490005.

Background: The study investigated the effectiveness of low-frequency sampling in detecting alterations in cerebrovascular reactivity (CVR) associated with changes in intracranial pressure (ICP) in patients with traumatic brain injury (TBI) across different age groups. The primary objective was to investigate an ICP threshold that indicates a decrease in CVR as evidenced by a significant increase in the ultra-low-frequency pressure reactivity index (UL-PRx). Additionally, the study aimed to develop an age-based categorization method for patients with TBI to investigate the differences between these ICP thresholds in different age groups., Methods: In this retrospective analysis, data from 263 patients with TBI were prospectively collected. ICP and mean arterial pressure were extracted from the hospital database at 5-min intervals. Demographic details, clinical presentation, computed tomography scans, neurosurgical interventions, and 12-months outcome were recorded. ICP versus UL-PRx values were categorized into ICP bins and graphically represented with boxplots for each age group, illustrating how as ICP values rise, there is a bin (age-tailored ICP [AT-ICP]) beyond which UL-PRx shows a sudden increase, indicating CVR loss. Homogeneous age groups were established to obtain a consistent AT-ICP threshold. The discriminatory ability of the AT-ICP thresholds was compared with the guideline-recommended thresholds by calculating the area under the Receiver Operating Characteristic curve of the ICP-derived indices (dose above threshold, and the hourly dosage above threshold)., Results: Age groups 0-5, 6-20, 21-60, 61-70, and 71-85 years were the best age subdivisions, corresponding to AT-ICP thresholds of 20, 30, 35, 25, and 30 mmHg, respectively. The AT-ICP thresholds exhibited better discriminative ability compared with the guideline-recommended thresholds., Conclusions: The AT-ICP thresholds offer a novel approach for estimating CVR impairment and the developed method represents an alternative solution to address the age stratification issue in patients with TBI., Competing Interests: Conflicts of Interest: The authors declare that they have no conflicts of interest. Ethical Approval/Informed Consent: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. This study was approved by the Bergamo’s ethics committee (February 22, 2021, amendment December 27, 2021; reference number 303/20). Researchers had access only to the anonymized data and for this type of study formal consent is not required., (© 2024. Springer Science+Business Media, LLC, part of Springer Nature and Neurocritical Care Society.)

Background and Objectives: Endoscopic endonasal surgery is a well-established surgical approach to the skull base. Surgeons need a reusable long-lasting tool to acquire the skills needed for skull base reconstruction. The aim of this study was to elaborate and validate a human formalin-fixed cadaveric model that reproduces a realistic cerebrospinal fluid (CSF) circulation and that adequately renders a CSF leak., Methods: An external ventricular drain that connects with a peristaltic pump is placed in the subarachnoid space, which allows a water circulation that reproduces CSF circulation. Intracranial pressure is measured in real time. Endoscopic endonasal skull base approaches are performed, to create different skull base openings and CSF leaks. Participants were tasked with reconstruction of the defects using a standardized multilayered approach, with the goal of obtaining a watertight closure under normal intracranial pressure ranges. Compiled data included time of reconstruction, years of experience of participants, and success/failure to achieve a watertight reconstruction. A Likert questionnaire was also used., Results: The cadaveric model reproduced CSF circulation in 4 types of dural defects: sellar, suprasellar, transcribriform, and transclival. Intracranial pressures were similar to physiological conditions and were reproducible. Each model was tested multiple times, over several months. Success rates concurred with training levels (r = .8282 and P = .0017). A strong inverse correlation was also found between years of experience and time of reconstruction (r = .4977 and P < .0001). Participants agreed that the model was realistic (median Likert score of 4), and they strongly agreed that it allowed for the improvement of their surgical skills (median Likert score of 5)., Conclusion: This novel human-fixed cadaveric model for CSF circulation is efficient and adequately reproduces surgical conditions for skull base approaches. The model is unique, easy to reproduce, and reusable. It can be used as a tool for teaching and for research purposes., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Purpose: Intracranial pressure (ICP) monitoring is in most studies considered essential in avoiding secondary brain injury in patients with intracranial pathologies. Invasive monitoring of ICP is accurate but is unavailable in many clinical and prehospital settings. Non-invasive modalities have historically been difficult to implement clinically. The retinal arteriovenous ratio (A/V ratio) has shown promise through its relationship with ICP. This study aimed to further elucidate the relationship between ICP, A/V ratio and the intraocular pressure (IOP) measured with non-invasive fundoscopy in a porcine model., Methods: We achieved controlled values of ICP ranging from normal (5-15 mmHg) to elevated (> 20 mmHg) within the same animal subject. Six pigs were included. ICP and IOP was measured using an intraparenchymal pressure monitor and a tonometer, respectively. Fundoscopy was performed at baseline and at predefined ICP values., Results: Mixed-effects linear regression revealed a significant inverse correlation between A/V ratio and ICP ≥ 20 mmHg (slope coefficient - 0.0026734 [95%-CI: -0.0039347 - (-0.0014121)], p < 0.001). For ICP < 20 mmHg there was no change in A/V ratio (p = 0.987). Similar results were seen for ICP > IOP with a mean IOP of 10 mmHg. A Wald test showed no significant difference between ICP > IOP and ICP ≥ 20 mmHg. ROC curve analysis revealed an AUC of 0.64 for ICP ≥ 20 mmHg and 0.71 for ICP > IOP., Conclusion: The results support the hypothesis that an increase in ICP was associated with a decrease in A/V ratio. Although a slightly better fit, the model of ICP > IOP was deemed less clinically relevant than ICP ≥ 20 mmHg because of the subjects' IOP. Further research integrating multifactorial models and machine learning is needed to enhance the diagnostic accuracy of A/V ratio via fundoscopy, enabling it to serve as a cost-effective screening tool., Competing Interests: Declarations. Ethics approval: The study was registered and approved by the Animal Experiments Inspectorate (Journal no. 2023-15-0201-01457). Picture materials are original and the authors have the right to their usage. Competing interests: The study was funded by Statumanu ICP ApS that is working on an algorithm for measuring the A/V ratio on fundus images. Niclas Lynge Eriksen has received funding from Statumanu ICP ApS for this study. Prior to this study being conceptualized, Mathias Just Nortvig received funding for his PhD from Statumanu ICP ApS. He also provided medical consulting to Statumanu ICP ApS. Prior to this study being conceptualized, Mikkel Schou Andersen received partial funding for his PhD from Statumanu ICP ApS. Frantz Rom Poulsen has no interests to declare., (© 2025. The Author(s).)

Background: Acute and critical neurological diseases are often accompanied with elevated intracranial pressure (ICP), leading to insufficient cerebral perfusion, which may cause severe secondary lesion. Existing ICP monitoring techniques often fail to effectively meet the demand for real-time noninvasive ICP monitoring and warning. This study aimed to explore the use of electrical impedance tomography (EIT) to provide real-time early warning of elevated ICP by observing cerebral perfusion., Methods: An intracranial hypertension model was prepared by injecting autologous un-anticoagulated blood into the brain parenchyma of twelve Landrace swine. Invasive ICP monitoring was used as a control method, and a high-precision EIT system was used to acquire and analyze the changing patterns of cerebral perfusion EIT image parameters with respect to ICP. Four EIT parameters related to cerebral perfusion were extracted from the images, and their potential application in detecting ICP elevation was analyzed., Results: When ICP increased, all EIT perfusion parameters decreased significantly (P < 0.05). When the subjects were in a state of intracranial hypertension (ICP > 22 mmHg), the correlation between EIT perfusion parameters and ICP was more significant (P < 0.01), with correlation coefficients ranging from -0.72 to -0.83. We tested the objects when they were in baseline ICP and in ICP of 15-40 mmHg. Under both circumstances, ROC curve analysis showed that the comprehensive model of perfusion parameters based on the random forest algorithm had a sensitivity and specificity of more than 90% and an area under the curve (AUC) of more than 0.9 for detecting ICP increments of both 5 and 10 mmHg., Conclusion: This study demonstrates the feasibility of using perfusion EIT to detect ICP increases in real time, which may provide a new method for real-time non-invasive monitoring of patients with increased ICP., Competing Interests: Declarations. Ethics approval and consent to participate: All experimental procedures and investigations performed during this study were ethically approved by the Animal Research Ethics Committee of the Air Force Medical University and conducted based on its guidelines on animal experiments (Ethical permission number: IACUC-20241299). Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Goal: Current methodologies for assessing cerebral compliance using pressure sensor technologies are prone to errors and issues with inter- and intra-observer consistency. RAP, a metric for measuring intracranial compensatory reserve (and therefore compliance), holds promise. It is derived using the moving correlation between intracranial pressure (ICP) and the pulse amplitude of ICP (AMP). RAP remains largely unexplored in cases of moderate to severe acute traumatic neural injury (also known as traumatic brain injury (TBI)). The goal of this work is to explore the general description of (a) RAP signal patterns and behaviors derived from ICP pressure transducers, (b) temporal statistical relationships, and (c) the characterization of the artifact profile., Methods: Different summary and statistical measurements were used to describe RAP's pattern and behaviors, along with performing sub-group analyses. The autoregressive integrated moving average (ARIMA) model was employed to outline the time-series structure of RAP across different temporal resolutions using the autoregressive ( p -order) and moving average orders ( q -order). After leveraging the time-series structure of RAP, similar methods were applied to ICP and AMP for comparison with RAP. Finally, key features were identified to distinguish artifacts in RAP. This might involve leveraging ICP/AMP signals and statistical structures., Results: The mean and time spent within the RAP threshold ranges ([0.4, 1], (0, 0.4), and [-1, 0]) indicate that RAP exhibited high positive values, suggesting an impaired compensatory reserve in TBI patients. The median optimal ARIMA model for each resolution and each signal was determined. Autocorrelative function (ACF) and partial ACF (PACF) plots of residuals verified the adequacy of these median optimal ARIMA models. The median of residuals indicates that ARIMA performed better with the higher-resolution data. To identify artifacts, (a) ICP q -order, AMP p -order, and RAP p -order and q -order, (b) residuals of ICP, AMP, and RAP, and (c) cross-correlation between residuals of RAP and AMP proved to be useful at the minute-by-minute resolution, whereas, for the 10-min-by-10-min data resolution, only the q -order of the optimal ARIMA model of ICP and AMP served as a distinguishing factor., Conclusions: RAP signals derived from ICP pressure sensor technology displayed reproducible behaviors across this population of TBI patients. ARIMA modeling at the higher resolution provided comparatively strong accuracy, and key features were identified leveraging these models that could identify RAP artifacts. Further research is needed to enhance artifact management and broaden applicability across varied datasets.

Objective: Increased intracranial pressure (ICP) can worsen the clinical condition of traumatic brain injury (TBI) patients. One non-invasive and easily bedside-performed technique to estimate ICP is ultrasonographic measurement of optic nerve sheath diameter (ONSD). This study aimed to analyze ONSD and correlate it with ICP values obtained by intraparenchymal monitoring to establish the ONSD threshold value for elevated ICP and reference range of ONSD in severe TBI patients., Methods: Forty severe TBI patients (Glasgow Coma Scale Score ≤ 8) were included. Ultrasonographic measurement of ONSD was performed and compared with intraparenchymal ICP monitoring to assess their association and determine the ONSD threshold value. Exclusion criteria included individuals under eighteen years old, penetrating TBI, or direct ocular trauma., Results: Fifty-three ONSD measurements were conducted in all patients. The mean ONSD value in the group with intracranial pressure < 20 mmHg was 5.4 mm ± 1.0, while in the group with intracranial pressure ≥ 20 mmHg, it was 6.4 mm ± 0.7 (p = 0.0026). A positive and statistically significant correlation, albeit weak (r = 0.33), was observed between ultrasonographic measurement of ONSD and intraparenchymal ICP monitoring. The statistical analysis of the ROC curve identified the best cut-off as 6.18 mm, with 77.8% sensitivity and 81.8% specificity., Conclusion: Our results reveal a positive, albeit weak, correlation between ultrasonographic measurement of ONSD and intraparenchymal ICP monitoring, with an ONSD threshold value of 6.18 mm. Achieving only 77.8% sensitivity and considering the substantial variability between ONSD measurements (standard deviation at 1.0) might limit the reliability of ICP assessment based solely on ONSD measurements., Competing Interests: Declarations. Competing Interests: The authors declare no competing interests. Ethics approval: This study was performed in line with the principles of the Declaration of Helsinki. Approval was granted by the Ethics Committee of the João XXIII Hospital (Date November 2017/No 78743317.8.0000.5119). Consent to participate: Written informed consent was obtained from family members or legal representatives of the participants., (© 2025. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Cerebral autoregulation is a robust regulatory mechanism that stabilizes cerebral blood flow in response to reduced blood pressure, thereby preventing cerebral ischaemia. Scientists have long believed that cerebral autoregulation also stabilizes cerebral blood flow against increases in intracranial pressure, which is another component that determines cerebral perfusion pressure. However, this idea was inconsistent with the complex pathogenesis of normal pressure hydrocephalus, which includes components of chronic cerebral ischaemia due to mild increases in intracranial pressure., Methods: Twenty-one patients who underwent ventriculoperitoneal shunt surgery for normal pressure hydrocephalus were included in this study. To determine the pressure setting of the Codman-Hakim programmable valve, intracranial pressure was measured after shunt surgery by puncturing the Ommaya reservoir, which formed a closed circuit with the needle and the syringe. Then, intracranial pressure was continuously measured with intermittent infusion of cerebrospinal fluid from the same closed circuit. We also continuously measured oximetry data, such as regional cerebral oxygen saturation derived from near-infrared spectroscopy monitoring. These data were digitized, recorded, and used for calculating intracranial compliance and the relationship between cerebrospinal fluid volume loading and intracranial pressure., Results: This study demonstrates that in patients with normal pressure hydrocephalus, cerebral venous vascular bed compression induces mild cerebral ischaemia when intracranial pressure is slightly higher than physiological venous pressure. Cerebral venous compression impairs cerebral blood flow by quadratically increasing circulatory resistance according to Poiseuille's law. Furthermore, chronic cerebral ischaemia occurred even at low or normal intracranial pressures when deep and subcortical white matter hyperintensities (DSWMHs) were severe., Conclusion: The fact that cerebral blood flow impairment begins at very low intracranial pressures indicates that cerebral autoregulation to compensate for reduced venous blood flow is not functioning adequately in NPH. These processes provide a link between impaired cerebrospinal fluid circulation, cerebral autoregulation, and neurological dysfunction, which has been missing in patients with NPH involving small vessel arteriosclerosis. These findings may provide insight into similar conditions, such as normal-tension glaucoma and chronic kidney disease, in which a mild increase in local compartment pressure leads to chronic ischemia in organs protected by autoregulatory mechanisms., Competing Interests: Declarations. Consent for publication: I confirm the corresponding author has read the journal policies and submit this manuscript in accordance with those policies. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Background: The oxygen reactivity index (ORx) reflects the correlation between focal brain tissue oxygen (pbtO 2 ) and the cerebral perfusion pressure (CPP). Previous, small cohort studies were conflicting on whether ORx conveys cerebral autoregulatory information and if it is related to outcome in traumatic brain injury (TBI). Thus, we aimed to investigate these issues in a larger TBI cohort., Methods: 425 TBI patients with intracranial pressure (ICP)- and pbtO 2 -monitoring for at least 12 h, who had been treated at Addenbrooke's Hospital, Cambridge, UK, were included. Association between ORx and ICP, pressure reactivity index (PRx), CPP, ΔCPPopt (actual CPP-CPPopt [PRx based optimal CPP]), and pbtO 2 were evaluated with generalized additive models (GAMs). Association between ORx and outcome (Glasgow Outcome Scale [GOS]) was investigated with logistic regressions and heatmaps for those 239 patients with GOS data., Results: GAMs showed that ORx increased with higher ICP, PRx above + 0.30, CPP below 60-70 mmHg, and negative ΔCPPopt. In contrast to PRx, ORx did not increase at higher CPP. In outcome heatmaps, there was a transition towards unfavourable outcome when ORx exceeded + 0.50, particularly for longer durations, and in combination with high ICP, high PRx, low CPP, negative ΔCPPopt, and low pbtO 2 . In multivariable logistic regressions, higher ORx was associated with increased mortality., Conclusions: ORx seemed to be sensitive to the lower, but not the upper, limit of autoregulation, in contrast to PRx which was sensitive to both. The combination of high values for both ORx and PRx was particularly associated with worse outcome and, thus, ORx may provide a complementary value to the global index PRx. ORx could also be useful to determine the safe and dangerous perfusion target intervals., Competing Interests: Declarations. Competing interests: Peter Smielewski receives part of the licensing fees for ICM + software, licensed by Cambridge Enterprise Ltd, University of Cambridge, Cambridge. Ethics approval and consent to participate: The Brain Physics Lab research database was approved by the Research Ethics Committee (REC 23/YH/0085). Informed consent was waived in this retrospective, observational study., (© 2025. The Author(s).)

Background/objectives: Our aim was to compare factors associated with poor versus good visual outcomes in idiopathic intracranial hypertension (IIH) patients with severe papilledema at initial presentation., Subjects/methods: Retrospective review of consecutive IIH patients (1/1/2013-6/10/2023) with severe papilledema (Frisén grade 4-5 and/or atrophy in at least one eye); Patients were divided into "poor visual outcome" (poor visual acuity and constricted visual field in at least one eye) and "good visual outcome" (good visual acuity and only mild visual field changes in both eyes) at >6 months for medically-treated patients and >3 months follow-up for surgically-treated patients., Results: We included 134 IIH patients with severe papilledema (70 had poor and 64 had good visual outcomes). No significant differences existed for age, gender, race, hypertension, haemoglobin, or cerebrospinal fluid opening pressure. The poor-outcome group had significantly greater BMI (mean 39.2 vs 35.1 kg/m 2 , p = 0.004), and worse initial HVF-MD (-20.04 vs -5.81 dB, p < 0.0001). Poor-outcome patients saw more prior health-care providers (4.7 vs 2.4, p < 0.0001), with delayed neuro-ophthalmology encounters (58.5 vs 15.2 weeks, p = 0.001). 41.4% of poor-outcome patients were initially seen in outside emergency departments (ED) (vs 14.1% of good-outcome patients, p = 0.0005), while only 27.1% were seen by eye-care providers (vs 53.1% of good-outcome patients, p = 0.0027). No poor-outcome patients initially consulted our institution's ED vs 7.8% of good-outcome patients., Conclusions: Although patients with poor visual outcome did not seek medical care later than good outcome patients, they had delayed diagnosis/treatment because of prior outside ED visits and lack of prior eye-care provider evaluations, suggesting that early diagnosis and specialized management of papilledema is essential for patients with symptoms of intracranial hypertension., Competing Interests: Competing interests: None of the authors have any competing interest. VB is consultant for GenSight Biologics, Neurophoenix and Topcon. NJN is consultant for GenSight Biologics, Santhera/Chiesi, Stoke, and Neurophoenix; receives research support from GenSight Biologics and Santhera/Chiesi. VB, NJN are supported by the National Institutes of Health’s National Eye Institute core grant P30-EY06360 (Department of Ophthalmology, Emory University School of Medicine) and by a departmental grant from Research to Prevent Blindness (New York, NY). WB received a scholarship from Geneva University Hospitals, Geneva, Switzerland., (© 2024. The Author(s), under exclusive licence to The Royal College of Ophthalmologists.)

Objective: To evaluate optic nerve head (ONH) morphology in children with craniosynostosis versus healthy controls., Design: Single-center, prospective cohort study., Methods: Handheld optical coherence tomography (OCT) was performed in 110 eyes of 58 children (aged 0-13 years) with craniosynostosis. Inclusion criteria were as follows: normal intracranial pressure on invasive overnight monitoring, or clinically stable intracranial pressure. The latter was defined as stable VA within 1 logMAR line and no papilledema on fundoscopy for at least 4 months following OCT, and normal/stable visual evoked potentials. Control data for 218 eyes of 218 children were obtained from a published normative dataset. The main outcome measures were disc width, cup width, rim width, and retinal nerve layer thickness (nasal and temporal). Outcome measures were compared using three-way linear mixed model regression analysis (fibroblast growth factor receptor [FGFR] 1/2-associated craniosynostosis, non-FGFR 1/2-associated craniosynostosis, and controls)., Results: Out of 63 eligible children with craniosynostosis, handheld OCT imaging was successful in 110 eyes of 58 children (92%). Of these, 22 (38%) were female. Median subject age at OCT examination was 53 months (range: 2-157; IQR: 39-73). Twelve children (21%) had FGFR1/2-associated syndromes (Crouzon, n = 6; Apert, n = 4; Pfeiffer, n = 2). Control data were available for 218 eyes of 218 healthy children. 122 controls (56%) were female. Median control age at OCT examination was 20 months (range: 0-163; IQR: 6-59). When comparing ONH morphology in craniosynostosis (n = 58) versus controls (n = 218), disc width was 6% greater (P = .001), temporal cup width was 13% smaller (P = .027), rim width was 16% greater (P < .001) and temporal retinal nerve fiber layer was 11% smaller (P = .027). When comparing FGFR1/2-associated syndromes (Crouzon, Apert, and Pfeiffer syndromes, n = 12) to the rest of the craniosynostosis group (n = 46), disc width was 10% smaller (P = .014) and temporal cup width was 38% smaller (P = .044)., Conclusions: This cohort demonstrated morphological differences of the ONH in craniosynostosis, most markedly in Crouzon, Apert, and Pfeiffer syndromes. These findings could help improve ophthalmological monitoring and surgical decision-making in children with craniosynostosis. Further work on longitudinal ONH changes in syndromic and nonsyndromic craniosynostosis would be valuable., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background and Objectives: The influence of the intracranial pressure field must be discussed with the development of a single-element transducer for low-intensity transcranial focused ultrasound because the skull plays a significant role in blocking and dispersing ultrasound wave propagation. Ultrasound propagation is mainly affected by the structure and acoustic properties of the skull; thus, we aimed to investigate the impact of simplifying the acoustic properties of the skull on the simulation of the transcranial pressure field to present guidance for efficient skull modeling in full-wave simulations., Materials and Methods: We constructed a three-dimensional computational model for ultrasound transmission with the same structure but varying acoustic properties of the skull. The structural information and heterogeneous acoustic properties of the skull were acquired from computed tomography images, and we segmented the skull into three layers (3 L), including spongy and compact bones. We then assigned homogeneous acoustic properties to a single layer (1 L) or 3 L of the skull. In addition, we investigated the influence of different types of transducers and different ultrasound frequencies (1.1 MHz, 0.5 MHz, and 0.25 MHz) on the intracranial pressure field to provide a comparison of the heterogenous and homogeneous models., Results: We indicated the importance of numerical simulations in estimating the intracranial pressure field of the skull owing to beam distortions. When we simplified the skull model, both the 1 L and 3 L models showed contours of the acoustic focus comparable to those of the heterogeneous model. When we evaluated the peak pressure and volume of the acoustic focus, the 1 L model produced a better estimation of peak pressure with a difference <10%, and the 3 L model is suitable to obtain smaller errors in the volume of the acoustic focus., Conclusions: In conclusion, we examined the possibility of simplification of skull models using 1 L and 3 L homogeneous properties in the numerical simulation for focused ultrasound. The results show that the layered homogeneous model can provide characteristics comparable to those of the acoustic focus in heterogeneous models., Competing Interests: Conflict of Interest The authors reported no conflict of interest., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Invasive systems are commonly used for monitoring intracranial pressure (ICP) in traumatic brain injury (TBI) and are considered the gold standard. The availability of invasive ICP monitoring is heterogeneous, and in low- and middle-income settings, these systems are not routinely employed due to high cost or limited accessibility. The aim of this consensus was to develop recommendations to guide monitoring and ICP-driven therapies in TBI using non-invasive ICP (nICP) systems., Methods: A panel of 41 experts, that regularly use nICP systems for guiding TBI care, was established. Three scoping and four systematic reviews with meta-analysis were performed summarizing the current global-literature evidence. A modified Delphi method was applied for the development of recommendations. An in-person meeting with group discussions and voting was conducted. Strong recommendations were defined for an agreement of at least 85%. Weak recommendations were defined for an agreement of 75-85%., Results: A total of 34 recommendations were provided (32 Strong, 2 Weak) divided into three domains: general consideration for nICP use, management of ICP using nICP methods and thresholds of nICP tools for escalating/de-escalating treatment. We developed four clinical algorithms for escalating treatment and heatmaps for de-escalating treatment., Conclusions: Using a mixed-method approach involving literature review and an in-person consensus by experts, a set of recommendations designed to assist clinicians managing TBI patients using nICP systems plus clinical assessment, in the presence or absence of brain imaging, were built. Further clinical studies are required to validate the potential use of these recommendations in the daily clinical practice., Competing Interests: Declarations. Conflicts of interest: SB-DC serves as a scientific advisor for brain4care.CR received fees as speaker from Edwards, and Integra. GC received consulting fees from Integra and Neuroptics., (© 2025. Springer-Verlag GmbH Germany, part of Springer Nature.)

Aim: To assess the changes of intracranial pressure waveforms (ICPW) acquired noninvasively in a set of acute hydrocephalus patients prior to and posterior to interventions., Material and Methods: Patients with clinical and radiological diagnosis of hydrocephalus were evaluated for alterations in ICPW by means of a system that detects cranial micro expansions just before and immediately after interventions. The system quantified the difference between ICPW peaks (P1 and P2), providing the P2/P1 ratio., Results: Fourteen patients aged from 26 to 73 years old met the inclusion criteria. Hydrocephalus etiologies were normal pressure hydrocephalus, post-traumatic and all patients had an abnormal intracranial compliance waveform, with P2 > P1 before the procedure (5 external ventricular drains (EVD) and 9 ventriculoperitoneal shunts (VPS). Immediately after, 75% of the patients changed to a standard pattern with P1 > P2., Conclusion: In this exploratory study using a novel noninvasive technique, rapid cerebrospinal fluid drainage by means of EVD and VPS was effectively assessed and had a positive impact on intracranial compliance.

A wide range of acute brain injuries, including both traumatic and non-traumatic causes, can result in elevated intracranial pressure (ICP), which in turn can cause further secondary injury to the brain, initiating a vicious cascade of propagating injury. Elevated ICP is therefore a neurological injury that requires intensive monitoring and time-sensitive interventions. Patients at high risk for developing elevated ICP undergo placement of invasive ICP monitors including external ventricular drains, intraparenchymal ICP monitors, and lumbar drains. These monitors all generate an ICP waveform, but each has its own unique caveats in monitoring and accuracy. Current ICP monitoring and management clinical guidelines focus on the mean ICP derived from the ICP waveform, with standard thresholds of treating ICP greater than 20 ​mmHg or 22 ​mmHg applied broadly to a wide range of patients. However, this one-size fits all approach has been criticized and there is a need to develop personalized, evidence-based and possibly multi-factorial precision-medicine based approaches to the problem. This paper provides historical and physiological context to the problem of elevated ICP, provides an overview of the challenges of the current paradigm of ICP management strategies, and discusses advances in ICP waveform analysis, emerging non-invasive ICP monitoring techniques, and applications of machine learning to create predictive algorithms., Competing Interests: Declaration of competing interest RM was supported through an NIH Ruth L. Kirschstein Research Service Award T32-GM075774-16 and additional funding awarded through the Department of Anesthesiology and Critical Care Medicine at Johns Hopkins. Vishank Shah disclosures: VS received honoraria (<$1000 USD) from Astra Zeneca and serves on the Editorial Board for Neurohospitalist. Sudha Yellapantula works as a Researcher for Medical Informatics Corp (MIC, Houston TX) and reports no competing interests. MIC is a company that provides the Sickbay platform to various hospitals, for clinical and research use of the data. Medical Informatics provided no funding and/or support for this review paper. Jose I Suarez disclosures: ex-officio member of the Board of Directors of the Neurocritical Care Society; member of the Scientific Advisory Board for Cyban; Member of the Data Safety Monitoring Board for clinical trials sponsored by Acasti and Perfuze; member of the Advisory Board for AstraZeneca for Andexxa Medical Strategy. Susanne Muehlschlegel disclosures: ex-officio member of the Board of Directors of the Neurocritical Care Society; Consultant for Acasti Pharma as a member of the clinical endpoint adjudication committee. Has received speaking and writing honoraria from the American Academy of Neurology. Serves on the Editorial Board for Neurocritical Care and Stroke (unpaid)., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Sleep-disordered breathing, with both central and obstructive sleep apneas, has been reported in association with Chiari malformation type 1. Chiari malformation type 1 is a congenital or acquired herniation of the cerebellar tonsils through the foramen magnum. In this case, a 5-year-old girl with a history of Chiari malformation type 1 and syringomyelia experienced worsening intracranial pressure secondary to sleep-disordered breathing. This case highlights the importance of early recognition of sleep-related respiratory disorders in patients with Chiari malformation and its association with increased intracranial pressure., Citation: Machin Y, Morales DS, Garagozlo K, Graw-Panzer K. A case of sleep-disordered breathing presenting with increased intracranial pressure in a child with type 1 Chiari malformation. J Clin Sleep Med . 2025;21(1):215-217., (© 2025 American Academy of Sleep Medicine.)

Primary intracranial pressure disorders include idiopathic intracranial hypertension and spontaneous intracranial hypotension. Remarkable advances have been made in the diagnosis and treatment of these 2entities in recent years. Therefore, the Spanish Society of Neurology's Headache Study Group (GECSEN) deemed it necessary to prepare this consensus statement, including diagnostic and therapeutic algorithms to facilitate and improve the management of these disorders in clinical practice. This document was created by a committee of experts belonging to GECSEN, and is based on a systematic review of the literature, incorporating the experience of the participants, and establishes practical recommendations with levels of evidence and grades of recommendation., (Copyright © 2024 Sociedad Española de Neurología. Published by Elsevier España, S.L.U. All rights reserved.)

Background: Entropy quantifies the level of disorder within a system. Low entropy reflects increased rigidity of homeostatic feedback systems possibly reflecting failure of protective physiological mechanisms like cerebral autoregulation. In traumatic brain injury (TBI), low entropy of heart rate and intracranial pressure (ICP) predict unfavorable outcome. Based on the hypothesis that entropy is a dynamically changing process, we explored the origin and value of entropy time trends., Methods: 232 continuous recordings of arterial blood pressure and ICP of TBI patients with available clinical information and 6-month outcome (Glasgow Outcome Scale) were accessed form the Brain Physics database. Biosignal entropy was estimated as multiscale entropy (MSE) that aggregates entropy at several time scales (20 coarse graining steps starting from 0.1 Hz). MSE was calculated repeatedly for consecutive, overlapping 6 h segments. Percentage monitoring time (ptime) or dosage (duration*level/hour) below different cutoffs were evaluated against outcome using univariable and multivariable analyses, and propensity score matching. Associations to clinical and monitoring metrics were explored using correlation coefficients. Lastly, individual secondary brain insults (deviations in ICP, cerebral perfusion pressure - CPP, or pressure reactivity) were assessed in relation to changes in MSE., Results: Increased MSE abp and MSE cpp ptime (OR 1.28 (1.07-1.58) and OR 1.50 (1.16-2.03) for MSE abp and cpp respectively) and dose (OR 1.12 (1.02-1.27) and OR 1.21 (1.06-1.46) for MSE abp and cpp respectively) were associated with poor outcome even after propensity score matching within multivariable models correcting for ICP, CPP, and the pressure reactivity index. MSE trajectories differed significantly dependent on outcome. The entropy metrics displayed weak correlations to clinical parameters. Individual episodes of deranged physiology were associated with decreases in the MSE metrics from both cerebral and systemic biosignals., Conclusions: Biosignal entropy of changes dynamically after TBI. The assessment of these variations augments individualized, dynamic, outcome prognostication and identification of secondary cerebral insults. Additionally, these explorations allow for further exploitation of the extensive physiological data lakes acquired for each TBI patient within an intensive care environment., Competing Interests: Declarations. Conflicts of interest: Peter Smielewski receives part of the licensing fees for ICM + software, licensed by Cambridge Enterprise Ltd, University of Cambridge, Cambridge. The other authors declare no financial or non-financial conflicts of interest. Ethics approval: The data was accessed through the Brain Physics database that is approved by the local ethics committee (REC 23/YH/0085). Consent to participate: Informed consent was waived by the local ethics committee., (© 2024. The Author(s).)

Monitoring cerebral oxygenation and metabolism, using a combination of invasive and non-invasive sensors, is vital due to frequent disruptions in hemodynamic regulation across various diseases. These sensors generate continuous high-frequency data streams, including intracranial pressure (ICP) and cerebral perfusion pressure (CPP), providing real-time insights into cerebral function. Analyzing these signals is crucial for understanding complex brain processes, identifying subtle patterns, and detecting anomalies. Computational models play an essential role in linking sensor-derived signals to the underlying physiological state of the brain. Multivariate machine learning models have proven particularly effective in this domain, capturing intricate relationships among multiple variables simultaneously and enabling the accurate modeling of cerebral physiologic signals. These models facilitate the development of advanced diagnostic and prognostic tools, promote patient-specific interventions, and improve therapeutic outcomes. Additionally, machine learning models offer great flexibility, allowing different models to be combined synergistically to address complex challenges in sensor-based data analysis. Ensemble learning techniques, which aggregate predictions from diverse models, further enhance predictive accuracy and robustness. This review explores the use of multivariate machine learning models in cerebral physiology as a whole, with an emphasis on sensor-derived signals related to hemodynamics, cerebral oxygenation, metabolism, and other modalities such as electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) where applicable. It will detail the operational principles, mathematical foundations, and clinical implications of these models, providing a deeper understanding of their significance in monitoring cerebral function.

Purpose of Review: The objective of this review is to provide a comprehensive management protocol for the treatment of intracranial pressure (ICP) crises based on the latest evidence., Recent Findings: The review discusses updated information on various aspects of critical care management in patients experiencing ICP crises, including mechanical ventilation, fluid therapy, hemoglobin targets, and hypertonic saline infusion, the advantages of ICP monitoring, the critical ICP threshold, and bedside neuromonitoring. All aspects of critical care treatment, including hemodynamic and respiratory support and adjustment of ICP reduction therapy, may impact patient outcomes. ICP monitoring allows ICP values, trends, waveforms, and CPP calculation, which are helpful to guide patient care. Advanced neuromonitoring devices are available at the bedside to diagnose impaired intracranial compliance and intracranial hypertension, assess brain function, and optimize cerebral perfusion. Future research should focus on developing appropriate intervention protocols for both invasive and noninvasive neuromonitoring in managing ICP crisis patients., Competing Interests: Declarations. Conflict of Interest: TV reported an honorarium for a lecture from Edwards Lifesciences and support for attending a meeting from Nikkiso outside the submitted work. Human and Animal Rights and Informed Consent: This article does not contain any studies with human or animal subjects performed by any of the authors., (© 2024. The Author(s).)

Background: Growing evidence suggests that for rodents, a substantial fraction of cerebrospinal fluid (CSF) drains by crossing the cribriform plate into the nasopharyngeal lymphatics, eventually reaching the cervical lymphatic vessels (CLVs). Disruption of this drainage pathway is associated with various neurological disorders., Methods: We employ a lumped parameter method to numerically model CSF drainage across the cribriform plate to CLVs. Our model uses intracranial pressure as an inlet pressure and central venous blood pressure as an outlet pressure. The model incorporates initial lymphatic vessels (modeling those in the nasal region) that absorb the CSF and collecting lymphatic vessels (modeling CLVs) to transport the CSF against an adverse pressure gradient. To determine unknown parameters such as wall stiffness and valve properties, we utilize a Monte Carlo approach and validate our simulation against recent in vivo experimental measurements., Results: Our parameter analysis reveals the physical characteristics of CLVs. Our results suggest that the stiffness of the vessel wall and the closing state of the valve are crucial for maintaining the vessel size and volume flow rate observed in vivo. We find that a decreased contraction amplitude and frequency leads to a reduction in volume flow rate, and we test the effects of varying the different pressures acting on the CLVs. Finally, we provide evidence that branching of initial lymphatic vessels may deviate from Murray's law to reduce sensitivity to elevated intracranial pressure., Conclusions: This is the first numerical study of CSF drainage through CLVs. Our comprehensive parameter analysis offers guidance for future numerical modeling of CLVs. This study also provides a foundation for understanding physiology of CSF drainage, helping guide future experimental studies aimed at identifying causal mechanisms of reduction in CLV transport and potential therapeutic approaches to enhance flow., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

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., (Creative Commons Attribution license.)

Background: Traumatic brain injury (TBI) can significantly disrupt autonomic nervous system (ANS) regulation, increasing the risk for secondary complications, hemodynamic instability, and adverse outcome. This retrospective study evaluated windowed time-lagged cross-correlation (WTLCC) matrices for describing cerebral hemodynamics-ANS interactions to predict outcome, enabling identifying high-risk patients who may benefit from enhanced monitoring to prevent complications., Methods: The first experiment aimed to predict short-term outcome using WTLCC-based convolution neural network models on the Wroclaw University Hospital (WUH) database (P training  = 31 with 1,079 matrices, P val  = 16 with 573 matrices). The second experiment predicted long-term outcome, training on the CENTER-TBI database (P training  = 100 with 17,062 matrices) and validating on WUH (P val  = 47 with 6,220 matrices). Cerebral hemodynamics was characterized using intracranial pressure (ICP), cerebral perfusion pressure (CPP), pressure reactivity index (PRx), while ANS metrics included low-to-high-frequency heart rate variability (LF/HF) and baroreflex sensitivity (BRS) over 72 h. Short-term outcome at WUH was assessed using the Glasgow Outcome Scale (GOS) at discharge. Long-term outcome was evaluated at 3 months at WUH and 6 months at CENTER-TBI using GOS and GOS-Extended, respectively. The XGBoost model was used to compare performance of WTLCC-based model and averaged neuromonitoring parameters, adjusted for age, Glasgow Coma Scale, major extracranial injury, and pupil reactivity in outcome prediction., Results: For short-term outcome prediction, the best-performing WTLCC-based model used ICP-LF/HF matrices. It had an area under the curve (AUC) of 0.80, vs. 0.71 for averages of ANS and cerebral hemodynamics metrics, adjusted for clinical metadata. For long-term outcome prediction, the best-score WTLCC-based model used ICP-LF/HF matrices. It had an AUC of 0.63, vs. 0.66 for adjusted neuromonitoring parameters., Conclusions: Among all neuromonitoring parameters, ICP and LF/HF signals were the most effective in generating the WTLCC matrices. WTLCC-based model outperformed adjusted neuromonitoring parameters in short-term but had moderate utility in long-term outcome prediction., Competing Interests: Declarations. Ethics approval and consent to participate: The CENTER-TBI study (European Commission Grant 602150) was conducted in accordance with all relevant laws of the European Union that are directly applicable or of direct effects and all relevant laws of the country where the recruiting sites were located, including but not limited to, the relevant privacy and data protection laws and regulations (the “Privacy Law”), the relevant laws and regulations on the use of human materials, and all relevant guidance relating to clinical studies from time to time in force, including but not limited to, the ICH Harmonized Tripartite Guideline for Good Clinical Practice (CPMP/ICH/135/95) (“ICH GCP”) and the World Medical Association Declaration of Helsinki entitled “Ethical Principles for Medical Research Involving Human Subjects.” Informed consent by the patients and/or the legal representative/next of kin was obtained, according to the local legislations, for all patients recruited in the Core Dataset of CENTER-TBI and documented in the e-CRF. Ethical approval was obtained for each recruiting site from the appropriate local ethics committee, and the full list of approvals is available on the website: https://www.center-tbi.eu/project/ethical-approval . The retrospective analysis of data recorded at Wroclaw University Hospital (WUH) was approved by the bioethical committee of WUH (approval KB-133/2023). All volunteers were required to provide written consent before entering the study. The data were fully anonymised, and no data protection issues were involved. Consent for publication: The manuscript has not been submitted elsewhere or published elsewhere in whole or in part. Some of the results have been accepted as poster presentations for the 2024 meeting of the International NeuroTrauma Society (INTS) conference, which took place in September 2024 in Cambridge, UK. Figure 1 was created in BioRender.com. Competing interests: Prof. Robba received fees for lectures from Massimo and GE. Prof. Czosnyka has a financial interest in a part of the intensive care monitoring (ICM +) licensing fee., (© 2024. The Author(s).)

Long-term hypothermia has been reported to prevent intracranial pressure (ICP) rebound in clinical patients, but the duration for hypothermia and the corresponding ICP data are not available. This study investigated the optimal duration of long-term hypothermia in traumatic brain injury (TBI) rats, and observed the effect on ICP and neurological function. In this study, we established a rat severe TBI model with electronic Controlled Cortical Injury device, and implemented hypothermia (33 °C) for different durations. The motor function of the rats in each group was evaluated by beam walking test and inclined-grid climbing test, brain water content was calculated by the wet-dry weight method, Evan's blue staining was used to measure the blood-brain barrier (BBB) permeability, the change of hippocampal neurons was observed by Nissl staining, the expressions of BrdU, NeuN, and CD86 positive cells were detected by immunofluorescence staining, and the expressions of Bcl-2, Bax, iNOS, IL-10, and Arg-1 were detected by Western blot. We found that therapeutic hypothermia improved neurological recovery after TBI with declining ICP, reducing brain edema, decreasing BBB permeability, promoting neurogenesis, inhibiting apoptosis, and regulating inflammation. Moreover, 48 h hypothermia amplified the neuroprotective effect after injury on the basis of 4 or 24 h hypothermic treatment. Both 4 and 24 h hypothermia led to ICP rebound during or after rewarming, whereas 48 h hypothermia completely abolished ICP rebound. Our study suggests that long-term hypothermia amplifies neuroprotection after TBI by antagonizing ICP rebound., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Pediatric idiopathic intracranial hypertension (IIH) is a rare and challenging condition. As implied by the nomenclature, the etiologies remain unknown, and multiple etiologies are being investigated. In this study, we explored the potential role of increased systemic or cerebral venous pressure in the pathogenesis., Method: An observational cohort study following the STROBE guidelines, including prepubertal children with clinical symptoms and imaging findings consistent with IIH referred to the neurosurgical department, was conducted. The patients underwent a comprehensive diagnostic protocol, including MRI, continuous intracranial pressure (ICP) monitoring, and endovascular venography with venous pressure measurements., Results: The study included 11 consecutive patients (six boys and five girls) with an average age of 2.3 years, and an average BMI of 18.4. Among these, one patient was found to have venous stenosis with a gradient; the other 10 patients presented with normal intracranial anatomy. All patients exhibited elevated venous pressures, with an average superior sagittal sinus pressure of 18.9 mmHg, average internal jugular vein pressure of 17.0 mmHg, and average central venous pressure of 15.9 mmHg. Daytime ICP averaged 12.9 mmHg, whereas nighttime ICP averaged 17.2 mmHg with either A- or B-waves in 10 of the 11 patients. Despite pathological ICP, only three patients had papilledema., Conclusions: All patients had an increased systemic venous pressure, indicating a possible pathological factor for prepubertal IIH. Additionally, our findings show that young children often only partly meet the Friedman criteria due to a lack of papilledema, emphasizing the need for pediatric-specific diagnostic criteria. Further large-scale studies are needed to confirm these findings and to explore the underlying reasons for this increase in venous pressure and potential new treatment avenues., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Purpose: To assess changes of cerebral haemodynamic and intracranial pressure (ICP) in animals, with or without elevated ICP, during controlled haemorrhagic shock and resuscitation with Total REBOA (tREBOA)., Method: In 22 anaesthetized and normoventilated pigs, after placement of catheters for monitoring invasive proximal blood pressure (pMAP), ICP, and vital parameters, and 60 min stabilisation phase, a controlled haemorrhagic shock (HS), was conducted. In 11 pigs (EICPG), an elevated ICP of 25-30 mmHg at the end HS was achieved by simulating an epidural mass. In 11 pigs (NICPG), the ICP was normal. tREBOA was then applied for 120 min. The changes of pMAP and ICP were followed, and cerebral perfusion pressure (CPP) calculated. The integrity of the autoregulation was estimated using a calculated Modified-Long Pressure Reactivity Index (mL-PRx)., Results: After stabilisation, hemodynamics and physiological parameters were similar and normal in both groups. At the end of the HS, ICP was 16 mmHg in NICPG vs. 32 in EICPG (p = 0.0010). CPP was 30 mmHg in NICPG vs. 6 mmHg in EICPG (p = 0.0254). After aorta occlusion CPP increased immediately in both groups reaching after 15 min up to104 mmHg in NICPG vs. 126 mmHg in EICPG. Cerebrovascular reactivity seems to be altered during bleeding and occlusion phases in both groups with positive mL-PRx. The alteration was more pronounced in EICPG, but reversible in both groups., Conclusion: tREBOA is lifesaving by restoration the cerebral circulation defined as CPP in animals with HS with normal or elevated ICP. Despite the observation of short episodes of cerebral autoregulation impairment during the occlusion, mainly in EICPG, tREBOA seems to be an effective tool for improving cerebral perfusion in HS that extends the crucial early window sometimes known as the "golden hour" for resuscitation even after a traumatic brain injury., Competing Interests: Declarations. Ethical approval: The study was approved by the Animal Experimental Ethics Committee at Umeå University, Sweden (A 32–19) and conducted in accordance with Directive 2010/63/EU on protection of animals used for scientific purposes, and the Guide for the Care and Use of Laboratory Animals, National Research Council, Washington, DC, USA, 1996. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Background: Severe traumatic brain injury (TBI) is a condition burdened by high morbidity and mortality. Prevention of secondary insults is 1 of the main goals of management and intracranial pressure (ICP) monitoring is a cornerstone in management of TBI. The relationship between ICP and optic nerve sheath is known from the literature. Optic nerve sheath ultrasonography could represent a method added to our armamentarium for monitoring ICP., Methods: We investigated how ultrasound-measured optic nerve sheath diameter (ONSD) varies as a function of ICP in a cohort of patients with severe blunt head injury in whom an intraparenchymal sensor was placed. We evaluated the accuracy of ONSD in distinguishing dichotomized ICP cut-offs and analyzed the learning curve and its potential as screening tool to select TBI patients most in need of invasive ICP monitoring in a setting with constraints on resources., Results: ONSD and ICP have a linear relationship. Nevertheless, there are limits of evaluating the one-to-one correspondence between those 2 variables. We selected a cut-off of sonographic ONSD above which there is a concernable elevation of ICP (ICP >15 mmHg) worthy of invasive second-line monitoring. Thus, it is possible to use ONSD as a first-line noninvasive tool to intercept patients at risk of developing frank intracranial hypertension., Conclusions: We propose the use of ONSD ultrasound as a screening investigation for post-traumatic intracranial hypertension in the context of an emergency department, especially in contexts where there is limited availability of ICP monitors., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The blast shock waves generated by the explosion are severe threat to soldiers on the battlefield, while the helmets currently equipped for the soldiers cannot offer sufficient blast protection. Some helmet pads have been developed to improve the protection performance of the combat helmets against shock waves. However, it remains unclear how to design the helmet pads to protect the head more effectively against blast shock waves. This study aims to design a new mechanics-guided helmet pad and evaluate its protection performance by numerical simulations. The design of the new helmet pad is guided by the oblique reflection theory (ORT), and the advanced combat helmet (ACH) pad is applied for comparison. The protection performance of the pads against blast waves from two directions (frontal and lateral) was investigated. The differences in the distributions of overpressure inside the helmet using two types of pads were analyzed, and the intracranial pressure (ICP) of head was compared. The ORT-guided pads can reduce the overpressure inside the helmet, minimizing the possibility of blast-induced traumatic brain injury. Furthermore, the underwash phenomenon can also be controlled when the new pads are applied. The results in this study provide an important theoretical basis and some guidelines on the design of helmet pads for the protection of human brain from blast shock waves., (© 2024 John Wiley & Sons Ltd.)

Background: Numerous trials have addressed intracranial pressure (ICP) management in neurocritical care. However, identifying its harmful thresholds and controlling ICP remain challenging in terms of improving outcomes. Evidence suggests that an individualized approach is necessary for establishing tolerance limits for ICP, incorporating factors such as ICP waveform (ICPW) or pulse morphology along with additional data provided by other invasive (e.g., brain oximetry) and noninvasive monitoring (NIM) methods (e.g., transcranial Doppler, optic nerve sheath diameter ultrasound, and pupillometry). This study aims to assess current ICP monitoring practices among experienced clinicians and explore whether guidelines should incorporate ancillary parameters from NIM and ICPW in future updates., Methods: We conducted a survey among experienced professionals involved in researching and managing patients with severe injury across low-middle-income countries (LMICs) and high-income countries (HICs). We sought their insights on ICP monitoring, particularly focusing on the impact of NIM and ICPW in various clinical scenarios., Results: From October to December 2023, 109 professionals from the Americas and Europe participated in the survey, evenly distributed between LMIC and HIC. When ICP ranged from 22 to 25 mm Hg, 62.3% of respondents were open to considering additional information, such as ICPW and other monitoring techniques, before adjusting therapy intensity levels. Moreover, 77% of respondents were inclined to reassess patients with ICP in the 18-22 mm Hg range, potentially escalating therapy intensity levels with the support of ICPW and NIM. Differences emerged between LMIC and HIC participants, with more LMIC respondents preferring arterial blood pressure transducer leveling at the heart and endorsing the use of NIM techniques and ICPW as ancillary information., Conclusions: Experienced clinicians tend to personalize ICP management, emphasizing the importance of considering various monitoring techniques. ICPW and noninvasive techniques, particularly in LMIC settings, warrant further exploration and could potentially enhance individualized patient care. The study suggests updating guidelines to include these additional components for a more personalized approach to ICP management., Competing Interests: Conflict of interest: SB is scientific advisor for Brain4care. The other authors have no COI related to the present work. Ethical Approval/Informed Consent: Not applicable., (© 2024. The Author(s).)

Background: Among the symptoms seen in idiopathic intracranial hypertension (IIH), hemifacial spasm (HFS) is rare. Orthostatic-induced HFS preceding lumbar puncture (LP) is previously unreported. We treated two patients with unusual IIH presentations. This case series reviews the few reports of HFS in IIH and proposes a mechanism for spasm occurrence., Methods: Case 1: A woman in her mid-40s with previously controlled IIH developed daily headache, pulsatile tinnitus, right-sided trigeminal paresthesia, and right-sided HFS. The latter 2 symptoms occurred exclusively when moving from a sitting to a standing position. Imaging was unremarkable; opening pressure (OP) on LP was 46 cmH 2 O with normal cerebrospinal fluid (CSF) components. Case 2: A woman in her late 40s presented with severe daily headache, pulsatile tinnitus, and left-sided HFS following weight gain. Imaging was unremarkable; OP on LP was 32 cmH 2 O with normal CSF components., Results: HFS episodes persisted following LP in both patients. Increasing and initiating acetazolamide, respectively, resolved all symptoms., Conclusions: Earlier suggested mechanisms of HFS are based on elevated intracranial pressure (ICP) shifting the facial nerve into proximity of a vascular structure. HFS appearing upon standing and continuing after LP, and thus a lower ICP, contradicts this. We propose a mechanism based on the degree of ICP change. This theory is grounded in the lack of intracranial compliance in IIH, wherein substantial pressure changes occur following small volume changes., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 by North American Neuro-Ophthalmology Society.)

Severe traumatic brain injury (TBI) is a leading cause of death and disability. Monitoring intracranial pressure (ICP) is recommended, but the data on the outcomes are conflicting. Adding continuous brain tissue oxygen partial pressure (PbtO2) monitoring may have some benefit but the OXY-TC suggested it did not improve 6-month neurological outcomes. This single-center pilot randomized controlled study aimed to evaluate whether adding PbtO2 monitoring was feasible and could improve the prognosis of severe TBI. The participants were randomized into either an ICP alone or an ICP + PbtO2 group for 7 days, with treatment protocols based on existing guidelines. Clinical parameters were collected hourly. The primary outcome was the feasibility of using PbtO2 monitoring. The secondary outcomes were 6-month survival, analyzed by the log-rank test, the 3- and 6-month Glasgow Outcome Scale (GOS) scores, compared between groups by chi-squared test. Seventy patients were included (36 ICP, 34 ICP + PbtO2). The ICP + PbtO2 group had lower mean daily ICP (13.4 vs. 18.2 mmHg, P = 0.0024) and higher mean daily cerebral perfusion pressure (82.1 vs. 74.5 mmHg, P = 0.0055). The ICP + PbtO2 group had higher 6-month survival (79.4 % vs. 55.6 %, P = 0.0337) and more favorable outcomes at 3 months (67.6 % vs. 38.9 %, P = 0.0160) and 6 months (70.6 % vs. 41.7 %, P = 0.0149). Adding PbtO2 monitoring to ICP monitoring is feasible in patients with severe TBI and could maybe improve the intermediate-term outcomes. The results will serve to design larger trials., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background and Objectives: Pressure reactivity index (PRx) has been proposed as a metric associated with cerebrovascular autoregulatory (CA) function and has been thoroughly investigated in clinical research. In this study, PRx is validated in a porcine cranial window model, developed to visualize pial arteriolar autoregulation and its limits., Methods: We measured arterial blood pressure, intracranial pressure, pial arteriolar diameter, and red blood cell (RBC) velocity in a closed cranial window piglet model during gradual balloon catheter-induced arterial hypotension (n = 10) or hypertension (n = 10). CA limits were derived through piecewise linear regression of calculated RBC flux vs cerebral perfusion pressure (CPP), leading for each arteriole to 1 lower limit of autoregulation (LLA) and 2 upper limits of autoregulation (ULA1 and ULA2). Autoregulation limits were compared with PRx thresholds, and receiver operating curve analysis was performed with and without CPP binning. A linear mixed effects model of PRx was performed., Results: Receiver operating curve analysis indicated an area under the curve (AUC) for LLA prediction by a PRx of 0.65 (95% CI: 0.64-0.67) and 0.77 (95% CI: 0.69-0.86) without and with CPP binning, respectively. The AUC for ULA1 prediction by PRx was 0.69 (95% CI: 0.68-0.69) without and 0.75 (95% CI: 0.68-0.82) with binning. The AUC for ULA2 prediction was 0.55 (95% CI: 0.55-0.58) without and 0.63 (95% CI 0.53-0.72) with binning. The sensitivity and specificity of binned PRx were 65%/90% for LLA, 69%/71% for ULA1, and 59%/74% for ULA2, showing wide interindividual variability. In the linear mixed effects model, pial arteriolar diameter changes were significantly associated with PRx changes ( P = .002), whereas RBC velocity ( P = .28) and RBC flux ( P = .24) were not., Conclusion: We conclude that PRx is predominantly determined by pial arteriolar diameter changes and moderately predicts CA limits. Performance to detect the CA limits varied highly on an individual level. Active therapeutic strategies based on PRx and the associated correlation metrics should incorporate these limitations., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Purpose of Review: Critically ill children are at risk of neurologic dysfunction and acquiring primary and secondary brain injury. Close monitoring of cerebral function is crucial to prevent, detect, and treat these complications., Recent Findings: A variety of neuromonitoring modalities are currently used in pediatric and neonatal ICUs. These include noninvasive modalities, such as electroencephalography, transcranial Doppler, and near-infrared spectroscopy, as well as invasive methods including intracranial pressure monitoring, brain tissue oxygen measurement, and cerebral microdialysis. Each modality offers unique insights into neurologic function, cerebral circulation, or metabolism to support individualized neurologic care based on a patient's own physiology. Utilization of these modalities in ICUs results in reduced neurologic injury and mortality and improved neurodevelopmental outcomes., Summary: Monitoring of neurologic function can significantly improve care of critically ill children. Additional research is needed to establish normative values in pediatric patients and to standardize the use of these modalities., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Intracranial pressure (ICP) is a well-established measure in managing not only traumatic brain injury but also nontraumatic intracranial bleeding or edema. When ICP increases despite nursing or medical management, ICP may be reduced via surgical measures. Deciding whether to perform a craniotomy vs. craniectomy (whether the bone flap is replaced or not, respectively) is commonly made intraoperatively following preoperative planning. While ICP monitoring (ICPm) is standard pre- and postoperatively, its intraoperative utility remains understudied., Methods: We conducted a study utilizing prospectively gathered and retrospectively analyzed data from 25 traumatic brain injury surgical decompression cases at a single center. All cases had intraoperative ICPm throughout surgery., Results: Our findings indicate that ICPm significantly influenced real-time intraoperative decision-making, diverging from preoperative., Conclusions: These results bring forward the potential pivotal role of intraoperative ICPm in guiding surgical strategies for elevated ICP, suggesting a novel data-driven approach to intraoperative management of decompression surgery., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Background: Head elevation is recommended as a tier zero measure to decrease high intracranial pressure (ICP) in neurocritical patients. However, its quantitative effects on cerebral perfusion pressure (CPP), jugular bulb oxygen saturation (SjvO 2 ), brain tissue partial pressure of oxygen (PbtO 2 ), and arteriovenous difference of oxygen (AVDO 2 ) are uncertain. Our objective was to evaluate the effects of head elevation on ICP, CPP, SjvO 2 , PbtO 2 , and AVDO 2 among patients with acute brain injury., Methods: We conducted a systematic review and meta-analysis on PubMed, Scopus, and Cochrane Library of studies comparing the effects of different degrees of head elevation on ICP, CPP, SjvO 2 , PbtO 2 , and AVDO 2 ., Results: A total of 25 articles were included in the systematic review. Of these, 16 provided quantitative data regarding outcomes of interest and underwent meta-analyses. The mean ICP of patients with acute brain injury was lower in group with 30° of head elevation than in the supine position group (mean difference [MD] - 5.58 mm Hg; 95% confidence interval [CI] - 6.74 to - 4.41 mm Hg; p < 0.00001). The only comparison in which a greater degree of head elevation did not significantly reduce the ICP was 45° vs. 30°. The mean CPP remained similar between 30° of head elevation and supine position (MD - 2.48 mm Hg; 95% CI - 5.69 to 0.73 mm Hg; p = 0.13). Similar findings were observed in all other comparisons. The mean SjvO 2 was similar between the 30° of head elevation and supine position groups (MD 0.32%; 95% CI - 1.67% to 2.32%; p = 0.75), as was the mean PbtO 2 (MD - 1.50 mm Hg; 95% CI - 4.62 to 1.62 mm Hg; p = 0.36), and the mean AVDO 2 (MD 0.06 µmol/L; 95% CI - 0.20 to 0.32 µmol/L; p = 0.65).The mean ICP of patients with traumatic brain injury was also lower with 30° of head elevation when compared to the supine position. There was no difference in the mean values of mean arterial pressure, CPP, SjvO 2 , and PbtO 2 between these groups., Conclusions: Increasing degrees of head elevation were associated, in general, with a lower ICP, whereas CPP and brain oxygenation parameters remained unchanged. The severe traumatic brain injury subanalysis found similar results., Competing Interests: Declarations. Conflicts of interest: The authors declare that they have no conflicts of interest. Ethical approval/informed consent: This article complies with ethical standards, and institutional review board approval was not required., (© 2024. Springer Science+Business Media, LLC, part of Springer Nature and Neurocritical Care Society.)

Introduction: The dialysis disequilibrium syndrome (DDS) is a complication in those undergoing dialysis for chronic kidney disease (CKD) or acute kidney injury (AKI), characterized by nonspecific symptoms that may progress to coma and death secondary to cerebral edema. This syndrome is associated with rapid change in electrolytes during dialysis with changes in intracranial pressure (ICP) and may have a higher incidence in the elderly neurosurgical patient population., Methods: Literature review and illustrative case example., Results: A 62-year-old female presented with acute mental status change during hemodialysis (HD), with a history of a nonsurgical acute subdural hematoma (SDH) 10 days prior. Imaging showed a conversion of the acute SDH to chronic SDH of 12.2 mm in size with a 14.1 midline shift, for which she underwent a hemicraniectomy with SDH evacuation, with a gradual return to baseline. The literature review identified 5 publications meeting the inclusion criteria. Major theories of DDS include a reverse urea effect, intracerebral acidosis, idiogenic osmoles, and local inflammation. This complication may occur more frequently in the elderly neurosurgical patient population, likely due to age-related comorbidities, preexisting neurological insult, and increased permeability of the blood-brain barrier (BBB), leading to cerebral edema., Conclusion: DDS is a rare and potentially fatal complication of HD that may have a higher incidence in the elderly neurosurgical patient population, yet remains to be fully understood. Further study is recommended to characterize the pathophysiological mechanism and incidence of DDS in neurosurgical patients., (© 2024. The Author(s), under exclusive licence to American Aging Association.)

Selective distribution of cerebral blood flow (CBF) to vital brain regions likely occurs during rapid severe hypotension caused by tachyarrhythmia but has not yet been demonstrated. In this study, we aimed to test the hypothesis that CBF is differentially preserved between brain regions depending on the degree of hypotension. In anesthetized rats, CBF was measured in the motor cortex (MC), medial prefrontal cortex, amygdala, thalamus, dorsal hypothalamus, hippocampus, ventral tegmental area, dorsolateral periaqueductal gray (dlPAG), and parabrachial nucleus (PB) by using laser-Doppler flowmetry. Ventricular pacing was performed for 30 s at 550-800 beats/min. The cerebrovascular CO 2 response time and reactivity were evaluated during 5% CO 2 exposure. During 1-4 s of ventricular pacing, mean arterial pressure (MAP) rapidly decreased, with minor changes in central venous and intracranial pressures. CBF was relatively well maintained in brain regions other than the MC ( P s ≤ 0.012) when moderate hypotension occurred (-34 mmHg ≤ ΔMAP ≤ -15 mmHg), whereas severe hypotension (-54 mmHg ≤ ΔMAP ≤ -35 mmHg) induced selective CBF distribution to regions other than the MC, thalamus, and dlPAG. The cerebrovascular CO 2 response time/reactivity was rapid or high in the thalamus, dlPAG, and PB, which almost completely differed from the brain regions in which CBF was relatively maintained during pacing-induced severe hypotension. These results suggest that regional heterogeneity of CBF arises depending on the degree of tachyarrhythmia-induced hypotension. Clarifying the mechanisms and functions of CBF maintenance would be beneficial to syncope and cerebral ischemia management in patients with arrhythmia. NEW & NOTEWORTHY When lethal tachyarrhythmia occurs, survival is prioritized by counterregulating the cardiovascular system, which is driven by vital brain regions. However, whether limited cerebral blood flow is selectively distributed to vital brain regions is unknown. We demonstrated the preferential maintenance of cerebral blood flow in vital brain regions, depending on the degree of hypotension caused by ventricular pacing, in anesthetized rats. Our data may have clinical implications for syncope and cerebral ischemia management in patients with arrhythmia.

Purpose: To investigate the potential correlation between prolonged exposure to microgravity on the International Space Station and increased intracranial fluid pressure, which is considered a risk factor for the astronauts' vision, and to explore the feasibility of using distortion product otoacoustic emissions as a non-invasive in-flight monitor for intracranial pressure changes., Methods: Distortion product otoacoustic emission phase measurements were taken from both ears of five astronauts pre-flight, in-flight, and post-flight. These measurements served as indirect indicators of intracranial pressure changes, given their high sensitivity to middle ear transmission alterations. The baseline pre-flight ground measurements were taken in the seated upright position., Results: In-flight measurements revealed a significant systematic increase in otoacoustic phase, indicating elevated intracranial pressure during spaceflight compared to seated upright pre-flight ground baseline. Noteworthy, in two astronauts, strong agreement was also observed between the time course of the phase changes measured in the two ears during and after the mission. Reproducibility and stability of the probe placement in the ear canal were recognized as a critical issue., Conclusions: The study suggests that distortion product otoacoustic emissions hold promise as a non-invasive tool for monitoring intracranial pressure changes in astronauts during space missions. Pre-flight measurements in different body postures and probe fitting strategies based on the individual ear morphology are needed to validate and refine this approach., Competing Interests: Declarations. Competing Interests: The authors declare no competing interests., (© 2024. The Author(s).)

Background and Objectives: Craniosynostosis can lead to progressive cranial and skull base deformities and can be associated with increased intracranial pressure (ICP), ophthalmological manifestations, behavioral changes, and developmental delay. Most published data on the incidence of elevated ICP include older children undergoing open surgical correction. Endoscopic-assisted release of fused sutures with postoperative helmet therapy is an established method for managing craniosynostosis presenting at an early age; however, the immediate effect of this approach on ICP in a young cohort has not been previously reported., Methods: Prospective data on 52 children undergoing endoscopic-assisted release of stenosed cranial sutures were included. Individuals were excluded if they underwent open correction or had previous cranial surgery. Individuals underwent a standardized endoscopic approach for each suture type. ICP was measured using an intraparenchymal sensor both before creation of the neosuture and after complete release of the stenosed suture. An ICP reading of >10 mm Hg was considered elevated., Results: The mean age was 5.3 months, range 1 to 32 months, and 94% was younger than 12 months. The mean opening pressure was 12.7 mm Hg, and the mean closing pressure was 2.9 mm Hg. Opening ICP ≥10 mm Hg was present in 58%, ≥15 mm Hg was present in 31%, and ≥20 mm Hg was present in 23%. No patient had an ICP above 10 mm Hg at closing. The mean percentage change in ICP among all craniosynostosis cases was a 64% decrease. Optic disk swelling was identified in 28 children preoperatively and improved in 22 children at follow-up., Conclusion: Elevated ICP may occur in infants with craniosynostosis at higher rates than previously reported. Endoscopic-assisted craniectomy has an immediate effect on lowering ICP and improving postoperative ophthalmological findings., (Copyright © Congress of Neurological Surgeons 2024. All rights reserved.)

Background: Liver diseases often occur with hepatic encephalopathy (HE), whose pathophysiology may involve increased intracranial pressure (ICP). Tools for monitoring ICP and its pulse morphology can be useful for assessing HE. The use of a non-invasive and sensitive procedure would be extremely useful in managing these cases., Objective: To evaluate the feasibility and performance of a new, non-invasive method of monitoring ICP, as an alternative to invasive methods, and to correlate the clinical diagnosis of HE with the morphological findings of ICP., Methods: This is a cross-sectional analytical study, conducted in a tertiary hospital and pioneer in the application of Brain4Care® BWS equipment. The ICP pulse morphology is parallel to the arterial one, where there are three frequent peaks: percussion peak (P1), due to plasma extravasated by the choroid plexus; tidal wave (P2), due to the degree of intracranial compliance to the reflection of P1, and dicrotic notch (P3), due to the closure of the aortic valve. Normality indicates P1>P2>P3. These peaks determine intracranial compliance through their relationship with cerebral blood volume, where P2/P1 ratio >1 suggests a pathological morphology, with a sustained increase in ICP and decreased compliance. Another way to evaluate this would be by a change in the time-to-peak (TTP). These data were compared between patients with and without clinical signs indicative of HE. The study was approved by the Institution's Research Ethics Committee (number 5.493.775)., Results: A total of 40 liver disease patients were evaluated, of which, at the time of collection, 20 did not have a clinical picture of HE (59.5±9.3 years; 70.0% male) and 20 had a clinical picture of HE (59.6±11.9 years; 65.0% male). The groups are demographically, clinically and laboratory similar; and statistically significant differences were identified in the morphological patterns of ICP between the groups evaluated, as well as trends in the parameters. The difference in the P2/P1 ratio was not significant (Mann Whitney: two-tailed P=0.2978); however, TTP proved to be a parameter with a statistically significant difference between the groups (Mann Whitney: two-tailed P=0.0282; median difference = 0.04). Analysis using the C statistic, using the ROC curve, suggested P2/P1=1.31 (AUROC: 0.5975) and TTP=0.22 (AUROC: 0.7013) as optimal cutoff points, where the presence of HE in liver disease patients would be associated with obtaining parameters below these thresholds., Conclusion: The brain4care® BWS system proved to be feasible for use in liver disease patients with or without clinical signs of hepatic encephalopathy and was able to differentiate them. Pathophysiological explanations, however, still require better causality explanation and understanding of the intracerebral hydrodynamic picture in hepatic encephalopathy. Given the low sample power found, new studies need better clinical heterogeneity and longer-term follow-up for definitive conclusions.

Background: We assessed the correlation between optic nerve sheath diameter (ONSD) values measured by bedside ultrasound and intracranial pressure (ICP) changes among patients under neurocritical care and evaluated the diagnostic performance of ONSD for increased ICP., Methods: Sixty-seven neurologically critical patients who were hospitalised in the intensive care unit (ICU) of Jining No.1 People's Hospital between September 2023 and March 2024 and underwent lumbar puncture were included. The ONSD was measured and recorded using bedside ultrasound before the lumbar puncture. Patients were divided into normal and increased ICP groups on the basis of the initial lumbar puncture pressure on admission, and both groups were compared. Spearman's correlation analysis was used for evaluating the correlation between ONSD values and ICP. Receiver operating characteristic (ROC) curves were employed for evaluating the diagnostic performance of ONSD for increased ICP., Result: At admission, the Glasgow Coma Scale scores of patients in the increased ICP group were significantly lower than those of patients in the normal ICP group (P < 0.05). The ONSD level of patients in the increased ICP group was significantly higher than that of patients in the normal ICP group (P < 0.05). Spearman's correlation analysis revealed that ONSD positively correlated with ICP among patients with severe neurological diseases (r = 0.777, P < 0.001). The area under the ROC curve when using ONSD for diagnosing lumbar puncture opening pressure ≥ 200 mmH 2 O was 0.896 (95% confidence interval, 0.817-0.974). When using ONSD ≥ 4.74 mm as the threshold for diagnosing lumbar puncture opening pressure ≥ 200 mmH 2 O, the sensitivity and specificity were 0.909 and 0.765, respectively., Conclusion: In patients with critical neurological illness, ONSD measured using bedside ultrasound positively correlated with ICP. Increased ICP can be diagnosed for ONSD ≥ 4.74 mm. The ONSD value measured by bedside ultrasound can be used for evaluating ICP among patients with critical neurological illness., Competing Interests: Declarations Ethics approval and consent to participate This study was approved by the Medical Ethics Committee of Jining No.1 People’s Hospital (approval number: KYLL-202308-150), and informed consent was obtained from either the patient or their adult caregivers prior to enrolment. Consent for publication Not applicable. Competing interests The authors declare no competing interests., (© 2024. The Author(s).)

Purpose: Intracranial pressure (ICP) control is important to avoid secondary brain injury in patients with intracranial pathologies. Current methods for measuring ICP are invasive and carry risks of infection and hemorrhage. Previously we found correlation between ICP and the arteriole-venous ratio (A/V ratio) of retinal vessels in an outpatient setting. This study investigated the usability of fundoscopy for non-invasive ICP estimation with the addition of intraocular pressure (IOP) in patients in a neuro-intensive care unit (NICU)., Methods: This single-center prospective cohort study was conducted at the NICU of Odense University Hospital from September 2020 to May 2021. Adult patients with a Glasgow Coma Score of 8 or less, who underwent invasive pressure neuromonitoring were included. Fundoscopy videos were captured daily and analyzed using deep learning algorithms. The A/V ratio was calculated and correlated with ICP. The data was analyzed using mixed-effect linear regression models., Results: Forty patients were enrolled. Fifteen were included in the final analysis. ICP ranged from -1 to 31 mmHg (mean: 10.9, SD: 5.7), and IOP ranged from 4 to 13 mmHg (mean: 7.4, SD: 2.1). The A/V ratio showed a significant negative correlation with ICP > 15 mmHg (regression slope: -0.0659, 95%-CI: [-0.0665;-0.0653], p < 0.001). No significant change in A/V ratio was observed for ICP ≤ 15 mmHg. A similar significant correlation was found for ICP > IOP (regression slope: -0.0055, 95%-CI: [-0.0062;-0.0048], p < 0.001). Taking the IOP into account did not improve the model. The sensitivity analysis showed a sensitivity of 80.08% and a specificity of 22.51%, with an AUC of 0.6389., Conclusion: In line with our previous work, non-invasive fundoscopy is a potential tool for detecting elevated ICP. However, challenges such as image quality and diagnostic specificity remains. Further research with larger, multi-center studies are needed to validate the utility. Standardization may enhance the technique's clinical applicability., (© 2024. The Author(s).)

The accurate monitoring of vital physiological parameters, exemplified by heart rate, respiratory rate, and intracranial pressure (ICP), is of paramount importance, particularly for managing severe cranial injuries. Despite the rapid development of implantable ICP sensing systems over the past decades, they still suffer from, for example, wire connection, low sensitivity, poor resolution, and the inability to monitor multiple variables simultaneously. Here, we propose an ultrasensitive multimodal biotelemetric system that amalgamates an iontronic pressure transducer with exceptional point (EP) operation for the monitoring of ICP signals. The proposed system can exhibit extraordinary performance regarding the detection of minuscule ICP fluctuation, demonstrated by the sensitivity of 115.95 kHz/mmHg and the sensing resolution down to 0.003 mmHg. Our system excels not only in the accurate quantification of ICP levels but also in distinguishing respiration and cardiac activities from ICP signals, thereby achieving the multimodal monitoring of ICP, respiratory, and heart rates within a single system. Our work may provide a pragmatic avenue for the real-time wireless monitoring of ICP and thus hold great potential to be extended to the monitoring of other vital physiological indicators., (© 2024. The Author(s).)

Patients with acute brain injury (ACI) often require mechanical ventilation (MV) and are subject to pulmonary complications, thus justifying the use of Airway Clearance Techniques (ACTs), but their effects on intracranial pressure (ICP) are unknown. This study investigates the neurological and hemodynamics safety of an ACT called ventilator hyperinflation (VHI) in patients with ACI. This was a randomized clinical equivalence trial, which included patients aged ≥ 18 years with a clinical diagnosis of hemorrhagic stroke, with symptom onset within 48 h. The participants were randomly allocated to the Experimental Group (EG, n = 15), which underwent VHI followed by tracheal aspiration (TA), and the Control Group (CG, n = 15), which underwent TA only. Neurological safety was verified by analyzing the morphology of the ICP wave through the non-invasive B4C sensor, which detects bone deformation of the skull, resulting in a P2/P1 ratio and TTP, and hemodynamics through a multi-parameter monitor. Evaluations were recorded during five instances: T1 (baseline/pre-VHI), T2 (post-VHI and before TA), T3 (post-TA), T4 and T5 (monitoring 10 and 20 min after T3). The comparison between groups showed that there was no effect of the technique on the neurological variables with a mean P2/P1 ratio [F (4,112) = 1.871; p = 0.120; np2 = 0.063] and TTP [F (4,112) = 2.252; p = 0.068; np2 = 0.074], and for hemodynamics, heart rate [F (4,112) = 1.920; p = 0.112; np2 = 0.064] and mean arterial pressure [F(2.73, 76.57) = 0.799; p = 0.488; np2 = 0.028]. Our results showed that VHI did not pose a neurological or hemodynamics risk in neurocritical patients after ACI.