The historic evolution of intracranial pressure and cerebrospinal fluid pulse pressure concepts: Two centuries of challenges

Observational study of intracranial compliance analysis in neurologically healthy pediatric patients using a non-invasive device

Information about the morphology of the intracranial pressure waveform, as well as the variations in intracranial pressure (ICP) and compliance in pediatric patients are essential to diagnose and predict the progression of various neurological conditions. However, there is no information on the morphology of the IP waveform in neurologically healthy pediatric patients. In the present study, intracranial compliance was therefore analyzed in neurologically healthy patients with the aid of a noninvasive device. The study was an observational, cross-sectional study. Fifty-five neurologically healthy participants were included. Data on intracranial compliance with the patient in two positions, lying down (0°) and seated (45°), were collected with a noninvasive extracranial sensor, which allowed the intracranial pressure waveforms to be recorded. The values of the ratio P2/P1 were then analyzed. A questionnaire (with a scale from zero to ten, where ten corresponds to the highest level of satisfaction) was applied for patients to evaluate their satisfaction with the sensor. Patients were 10 years old (average), and most of them were (58%). Mean P2/P1 ratio was 0.94 (sd = 0.14) in the supine position and 0.91 (sd = 0.15) in the seated position. Participants were satisfied with the length of time for which the equipment was used (9.8, sd = 0.71). The device did not cause any discomfort. The noninvasive method used was well accepted by the patients. Intracranial compliance values were determined by analysis of the P2/P1 ratio in neurologically healthy pediatric population.Trial registration: Brazilian Registry of Clinical Trials Identifier: RBR-5j74ddg.

A Comprehensive Perspective on Intracranial Pressure Monitoring and Individualized Management in Neurocritical Care: Results of a Survey with Global Experts

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.

The influence of spinal venous blood pressure on cerebrospinal fluid pressure

In Alligator mississippiensis the spinal dura is surrounded by a venous sinus; pressure waves can propagate in the spinal venous blood, and these spinal venous pressures can be transmitted to the spinal cerebrospinal fluid (CSF). This study was designed to explore pressure transfer between the spinal venous blood and the spinal CSF. At rest the cardiac-related CSF pulsations are attenuated and delayed, while the ventilatory-related pulsations are amplified as they move from the spinal venous blood to the spinal CSF. Orthostatic gradients resulted in significant alterations of both cardiac- and ventilatory-related CSF pulsations. Manual lateral oscillations of the alligator's tail created pressure waves in the spinal CSF that propagated, with slight attenuation but no delay, to the cranial CSF. Oscillatory pressure pulsations in the spinal CSF and venous blood had little influence on the underlying ventilatory pulsations, though the same oscillatory pulsations reduced the ventilatory- and increased the cardiac-related pulsations in the cranial CSF. In Alligator the spinal venous anatomy creates a more complex pressure relationship between the venous and CSF systems than has been described in humans.

Intracranial compliance and volumetry in patients with traumatic brain injury

BACKGROUND

Cerebral edema (CE) and intracranial hypertension (IHT) are complications of numerous neurological pathologies. However, the study of CE and noninvasive methods to predict IHT remains rudimentary. This study aims to identify in traumatic brain injury (TBI) patients the relationship between the volume of the lateral ventricles and the parameters of the noninvasive intracranial pressure waveform (nICPW).

METHODS

This is an analytical, descriptive, and cross-sectional study with nonsurgical TBI patients. The monitoring of nICPW was performed with a mechanical strain gauge, and the volumetry of the lateral ventricles was calculated using the free 3D Slicer software, both during the acute phase of the injury. The linear model of fixed and random mixed effects with Gamma was used to calculate the influence of nICPW parameters (P2/P1 and time-to-peak [TTP]) values on volumetry.

RESULTS

Considering only the fixed effects of the sample, there was P = 0.727 (95% CI [-0.653; 0.364]) for the relationship between P2/P1 and volumetry and 0.727 (95% CI [-1.657; 1.305]) for TTP and volumetry. Considering the fixed and random effects, there was P = 8.5e-10 (95% CI [-0.759; 0.355]) for the relationship between P2/P1 and volumetry and 8.5e-10 (95% CI [-2.001; 0.274]) for TTP and volumetry.

CONCLUSION

The present study with TBI patients found association between nICPW parameters and the volume of the lateral ventricles in the 1st days after injury.

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

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

Noninvasive intracranial pressure waveforms for estimation of intracranial hypertension and outcome prediction in acute brain-injured patients

Analysis of intracranial pressure waveforms (ICPW) provides information on intracranial compliance. We aimed to assess the correlation between noninvasive ICPW (NICPW) and invasively measured intracranial pressure (ICP) and to assess the NICPW prognostic value in this population. In this cohort, acute brain-injured (ABI) patients were included within 5 days from admission in six Intensive Care Units. Mean ICP (mICP) values and the P2/P1 ratio derived from NICPW were analyzed and correlated with outcome, which was defined as: (a) early death (ED); survivors on spontaneous breathing (SB) or survivors on mechanical ventilation (MV) at 7 days from inclusion. Intracranial hypertension (IHT) was defined by ICP > 20 mmHg. A total of 72 patients were included (mean age 39, 68% TBI). mICP and P2/P1 values were significantly correlated (r = 0.49, p < 0.001). P2/P1 ratio was significantly higher in patients with IHT and had an area under the receiving operator curve (AUROC) to predict IHT of 0.88 (95% CI 0.78–0.98). mICP and P2/P1 ratio was also significantly higher for ED group (n = 10) than the other groups. The AUROC of P2/P1 to predict ED was 0.71 [95% CI 0.53–0.87], and the threshold P2/P1 > 1.2 showed a sensitivity of 60% [95% CI 31–83%] and a specificity of 69% [95% CI 57–79%]. Similar results were observed when decompressive craniectomy patients were excluded. In this study, P2/P1 derived from noninvasive ICPW assessment was well correlated with IHT. This information seems to be as associated with ABI patients outcomes as ICP.

Trial registration: NCT03144219, Registered 01 May 2017 Retrospectively registered, https://www.clinicaltrials.gov/ct2/show/NCT03144219.

Microglia and Post-Subarachnoid Hemorrhage Vasospasm: Review of Emerging Mechanisms and Treatment Modalities

Vasospasm is a potentially severe complication of subarachnoid hemorrhage. It can be attributed to neuroinflammation and the robust recruitment of microglia. Emerging evidence has linked this sustained inflammation to the development of delayed cerebral ischemia following subarachnoid hemorrhage. In this focused review, we provide an overview of the historical understanding of vasospasm. We then delve into the role of neuroinflammation and the activation of microglia. These activated microglia releases a host of inflammatory cytokines contributing to an influx of peripheral macrophages. This thereby opens a new and innovative treatment strategy to prevent vasospasm. Pre-clinical work has been promising, and the transition to clinical trials is warranted. Finally, some of the key mechanistic targets are outlined with emphasis on translation. This review will serve as a catalyst for researchers and clinicians alike in the quest to improve treatment options for vasospasm.

Lessons from NATURE: methods for traumatic brain injury prevention

Multiple species obtain repetitive head collisions throughout the course of their lifetimes with minimal neurologic deficit. Nature has allowed the unique development of multiple protective mechanisms to help prevent neurotrauma. In this review, we examine the concept of rapid brain movement within the skull 'Slosh' and what nature teaches on how to prevent this from occurring. We look at individual animals and the protective mechanisms at play. Marching from macroscopic down to the molecular level, we pinpoint key elements of neuroprotection that are likely contributing. We also introduce new concepts for neuroprotection and address avenues of further discovery.