Intracranial Pressure Monitoring in Experimental Traumatic Brain Injury: Implications for Clinical Management

Pcv-aCO2/Ca-cvO2 Combined with Optic Nerve Sheath Diameter in Predicting Elevated Intracranial Pressure of Patients with Traumatic Brain Injury in Prehospital Setting

Purpose

To investigate a correlation between the central venous minus arterial CO2 pressure to arterial minus central venous O2 content ratio (Pcv-aCO2/Ca-cvO2) combined with optic nerve sheath diameter (ONSD) in predicting prehospital elevated intracranial pressure (ICP) in traumatic brain injury (TBI) patients.

Patients and Methods

This was a prospective observational study of all adult TBI patients from the surgical intensive care unit who underwent invasive ICP monitoring between January 2023 and December 2023. Using a Delica MVU-6300 machine with 14-5 MHz linear probe to measure ONSD. We drew blood samples for arterial and central venous blood gases to measure and calculate the following indicators such as Pcv-aCO2, Ca-cvO2, and Pcv-aCO2/Ca-cvO2 ratio. ONSD and Pcv-aCO2/Ca-cvO2 were recorded during the first 3 days after admission. Simultaneous ICP values were gained from the invasive monitoring. Associations between ONSD, Pcv-aCO2/Ca-cvO2 and simultaneous ICP were explored by Spearman correlation analysis. We constructed an ROC curve to identify the ONSD and Pcv-aCO2/Ca-cvO2 cutoff for the evaluation of elevated ICP.

Results

We included 54 patients aged mean 57.13 (standard deviation 4.02) years and 24 (44%) were male. A significant correlation was observed between ONSD and ICP (r = 0.74, P < 0.01). The AUC was 0.861 (95% CI: 0.727-0.951), with a best cutoff value of 5.62 mm. Using a cutoff of 5.62mm, ONSD had a sensitivity of 92.8%, specificity of 80.4%. The Pcv-aCO2/Ca-cvO2 ratio also significantly correlated with ICP (r = 0.70, P < 0.01). The AUC was 0.791 (95% CI: 0.673-0.889). The optimal Pcv-aCO2/Ca-cvO2 value for predicting elevated ICP was 1.98 mmHg/mL. Using a cutoff of 1.98 mmHg/mL, Pcv-aCO2/Ca-cvO2 had a sensitivity of 87.3%, specificity of 77.2%. The AUC for ONSD combined with Pcv-aCO2/Ca-cvO2 was 0.952 (95% CI: 0.869-0.971), which had a sensitivity of 95.1%, specificity of 93.9%.

Conclusion

Pcv-aCO2/Ca-cvO2 combined with ONSD performed best in predicting elevated intracranial pressure of patients with TBI in a prehospital setting. Our findings provide a crucial tool to improve earlier management of these patients in prehospital care, where the availability and utilization of invasive monitoring is limited. It could lead to significant changes in how TBI patients are monitored and treated before reaching a hospital.

Hinge craniotomy versus standard decompressive hemicraniectomy: an experimental preclinical comparative study

INTRODUCTION

Decompressive craniectomy (DC) is the most common surgical procedure to manage increased intracranial pressure (ICP). Hinge craniotomy (HC), which consists of fixing the bone operculum with a pivot, is an alternative method conceived to avoid some DC-related complications; nonetheless, it is debated whether it can provide enough volume expansion. In this study, we aimed to analyze the volume and ICP obtained with HC using an experimental cadaver-based preclinical model and compare the results to baseline and DC.

METHODS

Baseline conditions, HC, and DC were compared on both sides of five anatomical specimens. Volume and ICP values were measured with a custom-made system. Local polynomial regression was used to investigate volume differences.

RESULTS

The area of the bone opercula resulting from measurements was 115.55 cm2; the mean supratentorial volume was 955 mL. HC led to intermediate results compared to baseline and DC. At an ICP of 50 mmHg, HC offers 130 mL extra space but 172 mL less than a DC. Based on local polynomial regression, the mean volume difference between HC and the standard craniotomy was 10%; 14% between DC and HC; both are higher than the volume of brain herniation reported in the literature in the clinical setting. The volume leading to an ICP of 50 mmHg at baseline was less than the volume needed to reach an ICP of 20 mmHg after HC (10.05% and 14.95% from baseline, respectively).

CONCLUSIONS

These data confirm the efficacy of HC in providing sufficient volume expansion. HC is a valid intermediate alternative in case of potentially evolutionary lesions and non-massive edema, especially in developing countries.

Spindle wave in intracranial pressure signal analysis for patients with traumatic brain injury: A single-center prospective observational cohort study

Objective: Intracranial pressure (ICP) monitoring is an integral part of the multimodality monitoring system in the neural intensive care unit. The present study aimed to describe the morphology of the spindle wave (a shuttle shape with wide middle and narrow ends) during ICP signal monitoring in TBI patients and to investigate its clinical significance. Methods: Sixty patients who received ICP sensor placement and admitted to the neurosurgical intensive care unit between January 2021 and September 2021 were prospectively enrolled. The patient's Glasgow Coma Scale (GCS) score on admission and at discharge and length of stay in hospital were recorded. ICP monitoring data were monitored continuously. The primary endpoint was 6-month Glasgow Outcome Scale-Extended (GOSE) score. Patients with ICP spindle waves were assigned to the spindle wave group and those without were assigned to the control group. The correlation between the spindle wave and 6-month GOSE was analyzed. Meanwhile, the mean ICP and two ICP waveform-derived indices, ICP pulse amplitude (AMP) and correlation coefficient between AMP and ICP (RAP) were comparatively analyzed. Results: There were no statistically significant differences between groups in terms of age (p = 0.89), gender composition (p = 0.62), and GCS score on admission (p = 0.73). Patients with spindle waves tended to have a higher GCS score at discharge (12.75 vs. 10.90, p = 0.01), a higher increment in GCS score during hospitalization (ΔGCS, the difference between discharge GCS score and admission GCS score) (4.95 vs. 2.80, p = 0.01), and a better 6-month GOSE score (4.90 vs. 3.68, p = 0.04) compared with the control group. And the total duration of the spindle wave was positively correlated with 6-month GOSE (r = 0.62, p = 0.004). Furthermore, the parameters evaluated during spindle waves, including mean ICP, AMP, and RAP, demonstrated significant decreases compared with the parameters before the occurrence of the spindle wave (all p < 0.025). Conclusion: The ICP spindle wave was associated with a better prognosis in TBI patients. Physiological parameters such as ICP, AMP, and RAP were significantly improved when spindle waves occurred, which may explain the enhancement of clinical outcomes. Further studies are needed to investigate the pathophysiological mechanisms behind this wave.

Effects of increased intracranial pressure on cerebrospinal fluid influx, cerebral vascular hemodynamic indexes, and cerebrospinal fluid lymphatic efflux

The glymphatic-lymphatic fluid transport system (GLFTS) consists of glymphatic pathway and cerebrospinal fluid (CSF) lymphatic outflow routes, allowing biological liquids from the brain parenchyma to access the CSF along with perivascular space and to be cleaned out of the skull through lymphatic vessels. It is known that increased local pressure due to physical compression of tissue improves lymphatic transport in peripheral organs, but little is known about the exact relationship between increased intracranial pressure (IICP) and GLFTS. In this study, we verify our hypothesis that IICP significantly impacts GLFTS, and this effect depends on severity of the IICP. Using a previously developed inflating balloon model to induce IICP and inject fluorescent tracers into the cisterna magna, we found significant impairment of the glymphatic circulation after IICP. We further found that cerebrovascular occlusion occurred, and cerebrovascular pulsation decreased after IICP. IICP also interrupted the drainage of deep cervical lymph nodes and dorsal meningeal lymphatic function, enhancing spinal lymphatic outflow to the sacral lymph nodes. Notably, these effects were associated with the severity of IICP. Thus, our findings proved that the intensity of IICP significantly impacts GLFTS. This may have translational applications for preventing and treating related neurological disorders.

Post-injury ventricular enlargement associates with iron in choroid plexus but not with seizure susceptibility nor lesion atrophy-6-month MRI follow-up after experimental traumatic brain injury

Ventricular enlargement is one long-term consequence of a traumatic brain injury, and a risk factor for memory disorders and epilepsy. One underlying mechanisms of the chronic ventricular enlargement is disturbed cerebrospinal-fluid secretion or absorption by choroid plexus. We set out to characterize the different aspects of ventricular enlargement in lateral fluid percussion injury (FPI) rat model by magnetic resonance imaging (MRI) and discovered choroid plexus injury in rats that later developed hydrocephalus. We followed the brain pathology progression for 6 months and studied how the ventricular growth was associated with the choroid plexus injury, cortical lesion expansion, hemorrhagic load or blood perfusion deficits. We correlated MRI findings with the seizure susceptibility in pentylenetetrazol challenge and memory function in Morris water-maze. Choroid plexus injury was validated by ferric iron (Prussian blue) and cytoarchitecture (Nissl) stainings. We discovered choroid plexus injury that accumulates iron in 90% of FPI rats by MRI. The amount of the choroid plexus iron remained unaltered 1-, 3- and 6-month post-injury. During this time, the ventricles kept on growing bilaterally. Ventricular growth did not depend on the cortical lesion severity or the cortical hemorrhagic load suggesting a separate pathology. Instead, the results indicate choroidal injury as one driver of the post-traumatic hydrocephalus, since the higher the choroid plexus iron load the larger were the ventricles at 6 months. The ventricle size or the choroid plexus iron load did not associate with seizure susceptibility. Cortical hypoperfusion and memory deficits were worse in rats with greater ventricular growth.

Intravenous Immunomodulatory Nanoparticle Treatment for Traumatic Brain Injury

OBJECTIVE

There are currently no definitive disease-modifying therapies for traumatic brain injury (TBI). In this study, we present a strong therapeutic candidate for TBI, immunomodulatory nanoparticles (IMPs), which ablate a specific subset of hematogenous monocytes (hMos). We hypothesized that prevention of infiltration of these cells into brain acutely after TBI would attenuate secondary damage and preserve anatomic and neurologic function.

METHODS

IMPs, composed of US Food and Drug Administration-approved 500nm carboxylated-poly(lactic-co-glycolic) acid, were infused intravenously into wild-type C57BL/6 mice following 2 different models of experimental TBI, controlled cortical impact (CCI), and closed head injury (CHI).

RESULTS

IMP administration resulted in remarkable preservation of both tissue and neurological function in both CCI and CHI TBI models in mice. After acute treatment, there was a reduction in the number of immune cells infiltrating into the brain, mitigation of the inflammatory status of the infiltrating cells, improved electrophysiologic visual function, improved long-term motor behavior, reduced edema formation as assessed by magnetic resonance imaging, and reduced lesion volumes on anatomic examination.

INTERPRETATION

Our findings suggest that IMPs are a clinically translatable acute intervention for TBI with a well-defined mechanism of action and beneficial anatomic and physiologic preservation and recovery. Ann Neurol 2020;87:442-455.