What every Intensivist should know about ... Ammonia in liver failure

PURPOSE

Acute liver failure (ALF) or acute-on-chronic liver failure (ACLF) patients have high short-term mortality and morbidity. In the context of liver failure, increased serum ammonia is associated with worse neurological outcomes, including high-grade hepatic encephalopathy (HE), cerebral edema, and intracranial hypertension. Besides its neurotoxicity, hyperammonemia may contribute to immune dysfunction and the risk of infection, a frequent trigger for multi-organ failure in these patients.

MATERIAL AND METHODS

We performed a literature-based narrative review. Publications available in PubMed® up to June 2023 were considered.

RESULTS

In the ICU management of liver failure patients, serum ammonia may play an important role. Accordingly, in this review, we focus on recent insights about ammonia metabolism, serum ammonia measurement strategies, hyperammonemia prognostic value, and ammonia-targeted therapeutic strategies.

CONCLUSIONS

Serum ammonia may have prognostic value in liver failure. Effective ammonia targeted therapeutic strategies are available, such as laxatives, rifaximin, L-ornithine-l-aspartate, and continuous renal replacement therapy.

Lymphatic network drainage resolves cerebral edema and facilitates recovery from experimental cerebral malaria

While brain swelling, associated with fluid accumulation, is a known feature of pediatric cerebral malaria (CM), how fluid and macromolecules are drained from the brain during recovery from CM is unknown. Using the experimental CM (ECM) model, we show that fluid accumulation in the brain during CM is driven by vasogenic edema and not by perivascular cerebrospinal fluid (CSF) influx. We identify that fluid and molecules are removed from the brain extremely quickly in mice with ECM to the deep cervical lymph nodes (dcLNs), predominantly through basal routes and across the cribriform plate and the nasal lymphatics. In agreement, we demonstrate that ligation of the afferent lymphatic vessels draining to the dcLNs significantly impairs fluid drainage from the brain and lowers anti-malarial drug recovery from the ECM syndrome. Collectively, our results provide insight into the pathways that coordinate recovery from CM.

Headache in Brain Tumors

The prevalence of brain tumors in patients with headache is very low; however, 48% to 71% of patients with brain tumors experience headache. The clinical presentation of headache in brain tumors varies according to age; intracranial pressure; tumor location, type, and progression; headache history; and treatment. Brain tumor-associated headaches can be caused by local and distant traction on pain-sensitive cranial structures, mass effect caused by the enlarging tumor and cerebral edema, infarction, hemorrhage, hydrocephalus, and tumor secretion. This article reviews the current findings related to epidemiologic details, clinical manifestations, mechanisms, diagnostic approaches, and management of headache in association with brain tumors.

The phosphokinase activity of IRE1ɑ prevents the oxidative stress injury through miR-25/Nox4 pathway after ICH

BACKGROUND

Endoplasmic reticulum (ER) stress and oxidative stress are the major pathologies encountered after intracerebral hemorrhage (ICH). Inositol-requiring enzyme-1 alpha (IRE1α) is the most evolutionarily conserved ER stress sensor, which plays a role in monitoring and responding to the accumulation of unfolded/misfolded proteins in the ER lumen. Recent studies have shown that ER stress is profoundly related to oxidative stress in physiological or pathological conditions. The purpose of this study was to investigate the role of IRE1α in oxidative stress and the potential mechanism.

METHODS

A mouse model of ICH was established by autologous blood injection. The IRE1α phosphokinase inhibitor KIRA6 was administrated intranasally at 1 h after ICH, antagomiR-25 and agomiR-25 were injected intraventricularly at 24 h before ICH. Western blot analysis, RT-qPCR, immunofluorescence staining, hematoma volume, neurobehavioral tests, dihydroethidium (DHE) staining, H2O2 content, brain water content, body weight, Hematoxylin and Eosin (HE) staining, Nissl staining, Morris Water Maze (MWM) and Elevated Plus Maze (EPM) were performed.

RESULTS

Endogenous phosphorylated IRE1α (p-IRE1α), miR-25-3p, and Nox4 were increased in the ICH model. Administration of KIRA6 downregulated miR-25-3p expression, upregulated Nox4 expression, promoted the level of oxidative stress, increased hematoma volume, exacerbated brain edema and neurological deficits, reduced body weight, aggravated spatial learning and memory deficits, and increased anxiety levels. Then antagomiR-25 further upregulated the expression of Nox4, promoted the level of oxidative stress, increased hematoma volume, exacerbated brain edema and neurological deficits, whereas agomiR-25 reversed the effects promoted by KIRA6.

CONCLUSION

The IRE1α phosphokinase activity is involved in the oxidative stress response through miR-25/Nox4 pathway in the mouse ICH brain.

The story of dexamethasone and how it became one of the most widely used drugs in neurosurgery

Dexamethasone, a long-acting potent glucocorticoid, is one of the most widely used medications in neurosurgery. In this paper, the authors recount the history of dexamethasone's rise in neurosurgery and discuss its use in brain tumors in the context of emerging neuro-oncological immunotherapies. In 1958, Glen E. Arth synthesized a 16-alpha-methylated analog of cortisone (dexamethasone) for treatment of rheumatoid arthritis. Joseph Galicich, a neurosurgery resident at the time, applied the rheumatological drug to neurosurgery. He gave doses to patients who had undergone craniotomy for tumor removal and saw their paresis improve, midline shift resolve, and mortality rates decrease. He advocated for clinical trials and the drug became a mainstay in neurosurgery. As neuro-oncological treatments evolve to include immunotherapy, the immunosuppressive effects of dexamethasone are becoming an unwanted effect. The question then becomes: how does one treat the patient's symptoms if the only drug that has been used throughout history may become a detriment to their oncological treatment? Since its discovery, dexamethasone has maintained an impressive staying power in the field, acting as a standard drug for cerebral edema for more than 60 years. However, with the advent of immunotherapy, research is warranted to evaluate ways of treating symptomatic edema in the context of modern neuro-oncological therapies.

Children with severe neurological symptoms associated with SARS-CoV-2 infection during Omicron pandemic in China

BACKGROUND

To analyze the clinical characteristics and outcomes of children with severe neurological symptoms associated with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection during the Omicron pandemic in China.

METHODS

This study used a questionnaire to obtain data from pediatric intensive care unit (PICU) centers in seven tertiary hospitals in Northeast China from December 1, 2022, to January 31, 2023.

RESULTS

A total of 255 patients were confirmed to have SARS-CoV-2 infection, and 45 patients (17.65 %) were included in this study. Of these, seven (15.6%) patients died, and the median time from admission to death was 35 h (IQR, 14-120 h). Twenty (52.6%) survivors experienced neurological sequelae. Patients with platelet counts lower than 100 × 109/L had a higher incidence of complications such as multiple organ dysfunction, mechanical ventilation rate, and mortality. Cranial magnetic resonance imaging (MRI) always reveals cerebral tissue edema, with some severe lesions forming a softening site.

CONCLUSION

Children infected with SARS-CoV-2 often exhibit severe neurological symptoms, and in some cases, they may rapidly develop malignant cerebral edema or herniation, leading to a fatal outcome. An early decrease in platelet count may associated with an unfavorable prognosis.

IMPACT

Since early December 2022, China has gradually adjusted its prevention and control policy of SARS-CoV-2; Omicron outbreaks have occurred in some areas for a relatively short period. Due to the differences in ethnicity, endemic strains and vaccination status, there was a little difference from what has been reported about children with SARS-CoV-2 infection with severe neurological symptoms in abroad. This is the first multicenter clinical study in children with nervous system involvement after acute SARS-CoV-2 infection in China, and helpful for pediatricians to have a more comprehensive understanding of the clinical symptoms and prognosis of such disease.

A case of meningoencephalitis caused by multisystem inflammatory syndrome in adult SARS-CoV-2 infection

A 37-year-old woman was hospitalized with fever and consciousness disturbance. She showed systemic inflammation with stress cardiomyopathy. Brain computed tomography showed diffuse brain edema. Cerebrospinal fluid (CSF) findings revealed markedly elevated cerebrospinal fluid pressure with pleocytosis, elevated protein, and elevated interleukin 6. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nicking enzyme amplification reaction test using a nasopharyngeal swab was positive, and the patient was diagnosed with SARS-CoV-2 infection. From the negative result of the CSF SARS-CoV-2 polymerase chain reaction test and no findings of bacterial or viral infection, we diagnosed meningoencephalitis by multisystem inflammation syndrome in adults (MIS-A). Intravenous methylprednisolone pulse therapy improved her symptoms and brain edema. There have been no cases of MIS-A with meningoencephalitis, and no initial treatment strategy has been established, especially in emergency cases of suspected MIS-A. The present case suggested Early intravenous methylprednisolone pulse with anti-coronaviral therapies after the exclusion of bacterial infection would be useful in suspected MIS-A with emergent meningoencephalitis cases.

Primary anaplastic large cell lymphoma arising from central nervous system

A 22-year-old man presented at the emergency department with progressive headache, vomiting and horizontal diplopia over 2-month period. He also developed blurred vision in his left eye. He complained of loss of appetite for the past 2 months, resulting in a 5-kg weight loss. Examination upon arrival revealed papilledema and bilateral abducens nerve palsy. Motor and sensory functions were intact. Magnetic resonance imaging (MRI) of the brain revealed multiple extra-axial nodular enhancing lesions with size of 5-10 mm mainly along with both sides of falx cerebri and vasogenic brain oedema (Fig. 1). Stereotactic brain biopsy was performed to obtain tissue diagnosis. Histologic examination revealed brain infiltration by few atypical cells hidden amongst abundant and mixed population of inflammatory cells including lymphocytes and histiocytes. The atypical cells are large cells with horseshoe nuclei (red arrow; Fig. 2A ×100 and Fig. 2B ×400). Immunohistochemistry showed strong, uniform CD30 expression (Fig. 2C ×400) and cytoplasmic ALK staining (Fig. 2D ×400), as well as for CD3 (Fig. 2E ×400) and CD68 (Fig. 2F ×400). B-cell markers (CD20) were negative (Fig. 2G ×400).

MRI of cerebral oedema in ischaemic stroke and its current use in routine clinical practice

Currently, with the knowledge of the role of collateral circulation in the development of cerebral ischaemia, traditional therapeutic windows are being prolonged, with time not being the only criterion. Instead, a more personalised approach is applied to select additional patients who might benefit from active treatment. This review briefly describes the current knowledge of the pathophysiology of the development of early ischaemic changes, the capabilities of MRI to depict such changes, and the basics of the routinely used imaging techniques broadly available for the assessment of individual phases of cerebral ischaemia, and summarises the possible clinical use of routine MR imaging, including patient selection for active treatment and assessment of the outcome on the basis of imaging.

Scalp incision technique for decompressive hemicraniectomy: comparative systematic review and meta-analysis of the reverse question mark versus alternative retroauricular and Kempe incision techniques

Decompressive hemicraniectomy (DHC) is a critical procedure used to alleviate elevated intracranial pressure (ICP) in emergent situations. It is typically performed to create space for the swelling brain and to prevent dangerous and potentially fatal increases in ICP. DHC is indicated for pathologies ranging from MCA stroke to traumatic subarachnoid hemorrhage-essentially any cause of refractory brain swelling and elevated ICPs. Scalp incisions for opening and closing the soft tissues during DHC are crucial to achieve optimal outcomes by promoting proper wound healing and minimizing surgical site infections (SSIs). Though the reverse question mark (RQM) scalp incision has gained significant traction within neurosurgical practice, alternatives-including the retroauricular (RA) and Kempe incisions-have been proposed. As choice of technique can impact postoperative outcomes and complications, we sought to compare outcomes associated with different scalp incision techniques used during DHC. We queried three databases according to PRISMA guidelines in order to identify studies comparing outcomes between the RQM versus "alternative" scalp incision techniques for DHC. Our primary outcome of interest in the present study was postoperative wound infection rates according to scalp incision type. Secondary outcomes included estimated blood loss (EBL) and operative duration. We identified seven studies eligible for inclusion in the formal meta-analysis. The traditional RQM technique shortened operative times by 36.56 min, on average. Additionally, mean EBL was significantly lower when the RQM scalp incision was used. Postoperatively, there was no significant association between DHC incision type and mean intensive care unit (ICU) length of stay (LOS), nor was there a significant difference in predisposition to developing wound complications or infections between the RQM and retroauricular/Kempe incision cohorts. Superficial temporal artery (STA) preservation and reoperation rates were collected but could not be analyzed due to insufficient number of studies reporting these outcomes. Our meta-analysis suggests that there is no significant difference between scalp incision techniques as they relate to surgical site infection and wound complications. At present, it appears that outcomes following DHC can be improved by ensuring that the bone flap is large enough to enable sufficient cerebral expansion and decompression of the temporal lobe, the latter of which is of particular importance. Although previous studies have suggested that there are several advantages to performing alternative scalp incision techniques during DHC, the present study (which is to our knowledge the first to meta-analyze the literature on outcomes in DHC by scalp incision type) does not support these findings. As such, further investigations in the form of prospective trials with high statistical power are merited.

Intermittent hypoxia training effectively protects against cognitive decline caused by acute hypoxia exposure

Intermittent hypoxia training (IHT) is a promising approach that has been used to induce acclimatization to hypoxia and subsequently lower the risk of developing acute mountain sickness (AMS). However, the effects of IHT on cognitive and cerebrovascular function after acute hypoxia exposure have not been characterized. In the present study, we first confirmed that the simplified IHT paradigm was effective at relieving AMS at 4300 m. Second, we found that IHT improved participants' cognitive and neural alterations when they were exposed to hypoxia. Specifically, impaired working memory performance, decreased conflict control function, impaired cognitive control, and aggravated mental fatigue induced by acute hypoxia exposure were significantly alleviated in the IHT group. Furthermore, a reversal of brain swelling induced by acute hypoxia exposure was visualized in the IHT group using magnetic resonance imaging. An increase in cerebral blood flow (CBF) was observed in multiple brain regions of the IHT group after hypoxia exposure as compared with the control group. Based on these findings, the simplified IHT paradigm might facilitate hypoxia acclimatization, alleviate AMS symptoms, and increase CBF in multiple brain regions, thus ameliorating brain swelling and cognitive dysfunction.

Intensive mannitol slow infusion post-stenting may attenuate stenting-related early adverse effects in patients with cerebral venous sinus stenosis

AIMS

To analyze intensive slow mannitol poststenting on attenuating stenting-related early adverse effects in cerebral venous sinus stenosis (CVSS).

METHODS

This real-world study enrolled subacute or chronic CVSS patients from January 2017 through March 2022 and divided them into DSA only and stenting post-DSA groups. The later group was subdivided into control (without extra mannitol use) and intensive slow mannitol subgroup (immediate extra mannitol 250-500 mL, 2 mL/min infusion post-stenting) after signed informed consent. All data were compared.

RESULTS

A total of 95 eligible patients entered into final analysis, in which 37 cases underwent DSA only and 58 cases underwent stenting post-DSA. Finally, 28 patients were entered into intensive slow mannitol subgroup and 30 in control. Stenting group vs. DSA group, HIT-6 scores and WBC counts were higher in the former (both p < 0.001). Intensive slow mannitol subgroup vs. control on the third day post-stenting, a statistically significant reductions were noticed in the former on WBC counts (6.19 ± 1.86 × 109 /L vs. 9.59 ± 2.05 × 109 /L); HIT-6 scores (degree of headache) (40.00 (38.00-40.00) vs. 49.00 (41.75-55.25)) and brain edema surrounding the stent on CT maps (17.86% vs.96.67%), all p < 0.001.

CONCLUSIONS

Stenting-related severe headache, inflammatory biomarkers elevation, and brain edema aggravation can be attenuated by intensive slow mannitol infusion.

Nrf-2 modulates excitability of hippocampal neurons by regulating ferroptosis and neuroinflammation after subarachnoid hemorrhage in rats

Excitability of hippocampal neurons in subarachnoid hemorrhage (SAH) rats has not been well studied. The rat SAH model was applied in this study to explore the role of nuclear factor E2-related factor (Nrf-2) in the early brain injury of SAH. The neural excitability of CA1 pyramidal cells (PCs) in SAH rats was evaluated by using electrophysiology experiments. Ferroptosis and neuroinflammation were measured by ELISA, transmission electron microscopy and western blotting. Our results indicated that SAH induced neurological deficits, brain edema, ferroptosis, neuroinflammation and neural excitability in rats. Ferrostatin-1 treatment significantly decreased the expression and distribution of IL-1β, IL-6, IL-10, TGF-β and TNF-α. Inhibiting ferroptosis by ferrostatin-1 can attenuate neural excitability, neurological deficits, brain edema and neuroinflammation in SAH rats. Inhibiting the expression of Nrf-2 significantly increased the neural excitability and the levels of IL-1β, IL-6, IL-10, TGF-β and TNF-α in Fer-1-treated SAH rats. Taken together, inhibiting the Nrf-2 induces early brain injury, brain edema and the inflammatory response with increasing of neural excitability in Fer-1-treated SAH rats. These results have indicated that inhibiting ferroptosis, neuroinflammation and neural excitability attenuates early brain injury after SAH by regulating the Nrf-2.

Emergency decompressive surgery in patients with transtentorial brain herniation and pupillary abnormalities: the importance of improved pupillary response after osmotherapy and surgery

OBJECTIVE

The predictors of survival and functional recovery following emergency decompressive surgery in patients with transtentorial brain herniation, particularly those with pupillary abnormalities, have not been established. In this study, the authors aimed to assess the outcome of patients with intracranial mass lesions, transtentorial brain herniation, and nonreactive mydriasis, following emergency surgical decompression.

METHODS

A retrospective chart review was performed of all patients with transtentorial herniation and pupillary abnormalities who underwent craniotomy or craniectomy at two trauma and stroke centers between 2016 and 2022. The functional outcome was determined using the modified Rankin Scale (mRS).

RESULTS

Forty-three patients, 34 men and 9 women with a mean age of 47 years (range 16-92 years), were included. The underlying etiology was traumatic brain injury in 33 patients, hemorrhagic stroke in 8 patients, and tumor in 2 patients. The median preoperative Glasgow Coma Scale score was 3 (range 3-8), and the median midline shift was 9 mm (range 1-29 mm). Thirty-two patients (74.4%) had bilaterally fixed and dilated pupils. The median time to surgery (from pupillary changes) was 133 minutes (mean 169 minutes, range 30-900 minutes). Eighteen patients (41.9%) died postoperatively. After a median follow-up of 12 months (range 3-12 months), 11 patients (26.8%) had a favorable functional outcome, while 10 remained severely disabled (mRS score 5). On univariate analysis, younger age (p < 0.001), less midline shift (p = 0.049), and improved pupillary response after osmotic therapy (p < 0.01) or decompressive surgery (p < 0.001) were associated with favorable outcomes at 3 months.

CONCLUSIONS

With aggressive medical and surgical management, patients with transtentorial brain herniation, including those with bilaterally fixed and dilated pupils, may have considerable rates of survival and functional recovery. Young age, less midline shift, and improved pupillary response following osmotic therapy or decompressive surgery are favorable prognosticators.

Sensing Swelling: Towards Remote Monitoring of Craniectomy Patients

Decompressive craniectomy (DC) is a surgical procedure where a portion of the skull is removed to relieve potentially fatal brain swelling. As the swelling can take months to subside, the patient is discharged from an acute care facility to recover prior to cranioplasty (reconstruction surgery). Cranioplasty is associated with complications due to infection, seizure, haematoma and death. The interval between these surgeries is potentially a modifiable risk factor to reduce the rate of complication. We aim to allow clinicians to remotely monitor patients to facilitate an optimal pre-operative review. We have developed a platform technology encompassing a 'smart' device fitted into a skullcap to measure physiological parameters, such as changes in brain swelling, and a clinician portal that allows remote viewing of the patients' physiological data. The use of patient generated data during the transition between craniectomy and cranioplasty has the potential to significantly improve neurorehabilitation outcomes for patients.

Toward New AQP4 Inhibitors: ORI-TRN-002

Cerebral edema is a life-threatening condition that can cause permanent brain damage or death if left untreated. Existing therapies aim at mitigating the associated elevated intracranial pressure, yet they primarily alleviate pressure rather than prevent edema formation. Prophylactic anti-edema therapy necessitates novel drugs targeting edema formation. Aquaporin 4 (AQP4), an abundantly expressed water pore in mammalian glia and ependymal cells, has been proposed to be involved in cerebral edema formation. A series of novel compounds have been tested for their potential inhibitory effects on AQP4. However, selectivity, toxicity, functional inhibition, sustained therapeutic concentration, and delivery into the central nervous system are major challenges. Employing extensive density-functional theory (DFT) calculations, we identified a previously unreported thermodynamically stable tautomer of the recently identified AQP4-specific inhibitor TGN-020 (2-(nicotinamide)-1,3,4-thiadiazol). This novel form, featuring a distinct hydrogen-bonding pattern, served as a template for a COSMOsim-3D-based virtual screen of proprietary compounds from Origenis™. The screening identified ORI-TRN-002, an electronic homologue of TGN-020, demonstrating high solubility and low protein binding. Evaluating ORI-TRN-002 on AQP4-expressing Xenopus laevis oocytes using a high-resolution volume recording system revealed an IC50 of 2.9 ± 0.6 µM, establishing it as a novel AQP4 inhibitor. ORI-TRN-002 exhibits superior solubility and overcomes free fraction limitations compared to other reported AQP4 inhibitors, suggesting its potential as a promising anti-edema therapy for treating cerebral edema in the future.

Factors associated with an increased risk of developing pneumonia during acute ischemic stroke hospitalization

Stroke-associated pneumonia (SAP) is a common complication of acute ischemic stroke (AIS). This single-center retrospective observational study aimed to identify factors associated with SAP and predictors of poor outcomes in hospitalized patients with AIS. The study included patients admitted to Chumphon Khet Udomsakdi Hospital in Thailand within 7 days of the onset of AIS between July 2019 and July 2020. The patients were divided according to whether they were diagnosed with SAP during hospitalization into a pneumonia group and a non-pneumonia (control) group. Factors associated with SAP were identified. After 3 months, the patients with AIS were divided into those with a poor outcome (modified Rankin scale [mRS] score ≥4) and those with a non-poor outcome (mRS score <4). Factors associated with a poor outcome were sought. During the study period, 342 patients (mean age 65 years, 61% men) were admitted with AIS, of whom 54 (15.8%) developed SAP. Multivariate analysis identified a failed water-swallowing test (WST; adjusted odds ratio [aOR] 87.48, 95% confidence interval [CI] 21.00-364.51, p<0.001), endotracheal intubation with invasive mechanical ventilation (aOR 12.38, 95% CI 2.44-101.35, p = 0.001), and a retained Foley catheter (aOR 5.67, 95% CI 2.03-15.83, p = 0.001) to be associated with SAP. Of the 342 patients, 112 (32.7%) had a poor outcome at 3 months, predictors of which included having hypertension as a comorbidity (aOR 2.87, 95% CI 1.18-6.98, p = 0.020), a pre-stroke mRS score ≥2 (aOR 4.53, 95% CI 1.50-12.72, p = 0.007), an initial Barthel Index score <40 (aOR 3.35, 95% CI 1.57-7.16, p = 0.002), a failed WST (aOR 5.04, 95% CI 2.00-12.74, p = 0.001), and brain edema (aOR 20.67, 95% CI 2.10-203.26, p = 0.009). This study emphasized the association of SAP with a failed WST, endotracheal intubation with invasive mechanical ventilation, and a retained Foley catheter but also identified hypertension, a pre-stroke mRS score ≥2, an initial BI score <40, a failed WST, and brain edema as predictors of a poor outcome for patients 3 months after AIS.

[Diseases of the nervous system as the underlying cause of death]

OBJECTIVE

To identify the leading causes of death in the adult population from the class of diseases of the nervous system (DNS, class G) according to medical death certificates (MDC) and to discuss the problems of their assessment.

MATERIAL AND METHODS

The source of information was the electronic database of the Main Department of the Civil Registry Office of the Moscow Region. All cases of class G deaths were selected (total 10.739), an analysis was carried out according to underlying cause of death (UCD) codes and the immediate cause of death.

RESULTS

In 2022, mortality from diseases included in the DNS amounted to 130.7 per 100 000 of the population over 18 years old (100.3 among men, 191.0 among women). The average age of men is 74.3±14.1, women - 83.5±9.9 years (p<0.0001) due to the younger age of death of men from «G31.2 Degeneration of the nervous system caused by alcohol» and a higher contribution of this cause to male mortality; 82.5% of deaths were for codes G90-G99 («Other disorders of the nervous system»); 15.5% were neurodegenerative diseases (G10-G32). Sixty-six percent of all UCD in both women and men accounted for «unspecified encephalopathy» (G93.4), in 2nd place (10.5%) was «cerebral cyst» (G93.0). In 45 cases, code G93.6 (cerebral edema) was mistakenly used as UCD. Differences in the structure of causes of death at home, in hospital and elsewhere are statistically significant (p<0.00001). In 58.3%, cerebral edema and herniation were indicated as the immediate cause of death (G93.6 and G93.5).

CONCLUSIONS

Nosologically unfounded, insufficiently well-defined UCD were established in most cases of death from DNS, In 0.5% of the total number of deaths from DNS, an erroneous presentation as UCD of transient disorders of cerebral circulation or cerebral edema was noted. The results indicate the need for an analysis of the causes of death based on a comparison of medical records and MDC.

Limitation of cerebral blood flow by increased venous outflow resistance in elevated ICP

Extensive investigation and modeling efforts have been dedicated to cerebral pressure autoregulation, which is primarily regulated by the ability of the cerebral arterioles to change their resistance and modulate cerebral blood flow (CBF). However, the mechanisms by which elevated intracranial pressure (ICP) leads to increased resistance to venous outflow have received less attention. We modified our previously described model of intracranial fluid interactions with a newly developed model of a partially collapsed blood vessel, which we termed the "flow control zone" (FCZ). We sought to determine the degree to which ICP elevation causing venous compression at the FCZ becomes the main parameter limiting CBF. The FCZ component was designed using nonlinear functions representing resistance as a function of cross-sectional area and the pressure-volume relations of the vessel wall. We used our previously described swine model of cerebral edema with graduated elevation of ICP to calculate venous outflow resistance and a newly defined parameter, the cerebral resistance index (CRI), which is the ratio between venous outflow resistance and cerebrovascular resistance. Model simulations of cerebral edema and increased ICP led to increased venous outflow resistance. There was a close similarity between model predictions of venous outflow resistance and experimental results in the swine model (cross-correlation coefficient of 0.97, a mean squared error of 0.087, and a mean absolute error of 0.15). CRI was strongly correlated to ICP in the swine model (r2 = 0.77, P = 0.00012, 95% confidence interval [0.15, 0.45]). A CRI value of 0.5 was associated with ICP values above clinically significant thresholds (24 mmHg) in the swine model and a diminished capacity of changes in arteriolar resistance to influence flow in the mathematical model. Our results demonstrate the importance of venous compression at the FCZ in determining CBF when ICP is elevated. The cerebral resistance index may provide an indication of when compression of venous outflow becomes the dominant factor in limiting CBF following brain injury.NEW & NOTEWORTHY The goal of this study was to investigate the effects of venous compression caused by elevated intracranial pressure (ICP) due to cerebral edema, validated through animal experiments. The flow control zone model highlights the impact of cerebral venous compression on cerebral blood flow (CBF) during elevated ICP. The cerebral venous outflow resistance-to-cerebrovascular resistance ratio may indicate when venous outflow compression becomes the dominant factor limiting CBF. CBF regulation descriptions should consider how arterial or venous factors may predominantly influence flow in different clinical scenarios.

Pediatric posterior reversible encephalopathy syndrome: Can MR imaging features predict outcomes in non-oncologic patients?

PURPOSE

Identify MR features predictive of poor outcomes in non-oncologic pediatric PRES.

METHOD

A six-year search of all non-oncologic pediatric patients with clinical and MR features of PRES was performed. Modified Rankin scores were used to classify clinical outcomes into good versus poor, then clinical and MR features were compared among groups. Univariate and multivariate analysis was performed to identify MR predictors of poor outcomes for various imaging features, and p-values < 0.05 were considered statistically significant.

RESULTS

One hundred and forty-one patients (mean age 10.1 ± 3.0 years, male to female ratio 1:1.1) were included. Clinically, nephrotic syndrome (p = 0.03), focal deficits (p = 0.04), longer hospitalization (p < 0.001), and mechanical ventilation (p < 0.001) were significantly associated with poor outcomes. Univariate analysis revealed that deep grey matter nuclei (OR = 5.29, 95 % CI: 1.6-18.0) and cerebellar edema patterns (OR = 3.49, 95 % CI: 1.3-9.5), cytotoxic edema (OR = 63.6, 95 % CI:16.5-244.2), hemorrhage (OR = 16.58, 95 % CI: 4.3-64.2), and severe PRES patterns (OR = 11.0, 95 % CI: 3.5-34.7) on MR were all significantly associated with poor outcomes (p-values = 0.008 and 0.014, <0.001, <0.001, and < 0.001, respectively). This remained true for cytotoxic edema (OR = 84.26, 95 % CI: 17.3-410.9, p-value < 0.001) and hemorrhage (OR = 44.56, 95 % CI: 6.9-289.7, p-value < 0.001) on multivariate analysis.

CONCLUSION

Diffusion restriction and hemorrhage on initial MR scans were the two independent predictors of poor outcomes in non-oncologic pediatric patients.

Mannitol inhibits the proliferation of neural stem cell by a p38 mitogen-activated protein kinase-dependent signaling pathway

PURPOSE

Mannitol is one of the first-line drugs for reducing cerebral edema through increasing the extracellular osmotic pressure. However, long-term administration of mannitol in the treatment of cerebral edema triggers damage to neurons and astrocytes. Given that neural stem cell (NSC) is a subpopulation of main regenerative cells in the central nervous system after injury, the effect of mannitol on NSC is still elusive. The present study aims to elucidate the role of mannitol in NSC proliferation.

METHODS

C57 mice were derived from the animal house of Zunyi Medical University. A total of 15 pregnant mice were employed for the purpose of isolating NSCs in this investigation. Initially, mouse primary NSCs were isolated from the embryonic cortex of mice and subsequently identified through immunofluorescence staining. In order to investigate the impact of mannitol on NSC proliferation, both cell counting kit-8 assays and neurospheres formation assays were conducted. The in vitro effects of mannitol were examined at various doses and time points. In order to elucidate the role of Aquaporin 4 (AQP4) in the suppressive effect of mannitol on NSC proliferation, various assays including reverse transcription polymerase chain reaction, western blotting, and immunocytochemistry were conducted on control and mannitol-treated groups. Additionally, the phosphorylated p38 (p-p38) was examined to explore the potential mechanism underlying the inhibitory effect of mannitol on NSC proliferation. Finally, to further confirm the involvement of the p38 mitogen-activated protein kinase-dependent (MAPK) signaling pathway in the observed inhibition of NSC proliferation by mannitol, SB203580 was employed. All data were analyzed using SPSS 20.0 software (SPSS, Inc., Chicago, IL). The statistical analysis among multiple comparisons was performed using one-way analysis of variance (ANOVA), followed by Turkey's post hoc test in case of the data following a normal distribution using a Shapiro-Wilk normality test. Comparisons between 2 groups were determined using Student's t-test, if the data exhibited a normal distribution using a Shapiro-Wilk normality test. Meanwhile, data were shown as median and interquartile range and analyzed using the Mann-Whitney U test, if the data failed the normality test. A p < 0.05 was considered as significant difference.

RESULTS

Primary NSC were isolated from the mice, and the characteristics were identified using immunostaining analysis. Thereafter, the results indicated that mannitol held the capability of inhibiting NSC proliferation in a dose-dependent and time-dependent manner using cell counting kit-8, neurospheres formation, and immunostaining of Nestin and Ki67 assays. During the process of mannitol suppressing NSC proliferation, the expression of AQP4 mRNA and protein was downregulated, while the gene expression of p-p38 was elevated by reverse transcription polymerase chain reaction, immunostaining, and western blotting assays. Subsequently, the administration of SB203580, one of the p38 MAPK signaling pathway inhibitors, partially abrogated this inhibitory effect resulting from mannitol, supporting the fact that the p38 MAPK signaling pathway participated in curbing NSC proliferation induced by mannitol.

CONCLUSIONS

Mannitol inhibits NSC proliferation through downregulating AQP4, while upregulating the expression of p-p38 MAPK.

Ultrasound-Targeted Microbubble Destruction Increases BBB Permeability and Promotes Stem Cell-Induced Regeneration of Stroke by Downregulating MMP8

The objective of this study was to evaluate the feasibility, safety, and effectiveness of intravenous stem cell delivery utilizing ultrasound-targeted microbubble destruction (UTMD) in a rat model of middle cerebral artery occlusion (MCAO), while investigating the underlying mechanisms. Acute cerebral infarction (ACI) was induced surgically in adult rats to create the MCAO rat model. Intravenous injection of SonoVue microbubbles and bone marrow-derived mesenchymal stem cells (BMSC) was performed concurrently, with or without ultrasound targeting the stroke. The animals were divided into four groups: sham-operated group, ACI-MCAO rats treated with phosphate-buffered saline (ACI+PBS), rats receiving intravenous delivery of BMSC expressing green fluorescent protein (GFP-BMSC; ACI+BMSC), and rats receiving intravenous GFP-BMSC with simultaneous UTMD exposure (ACI+BMSC+UTMD). The efficacy of the treatments was assessed by evaluating the animals' neurological function using the Longa score and examining histopathological changes such as cerebral infarct volume, cerebral edema, and cell apoptosis. A rat cytokine array was utilized to identify the potential cytokines that may be responsible for the therapeutic effect of UTMD-mediated BMSC treatment. Optimal UTMD parameters resulted in an increase in blood-brain barrier (BBB) permeability after 30 min, which returned to baseline 72 h later without causing any residual injury. UTMD application significantly increased the homing of intravenously delivered BMSC, resulting in a 2.2-fold increase in GFP-BMSC cell count on day 3 and a 2.6-fold increase on day 7 compared with intravenous delivery alone. This effect persisted for up to 6 weeks after injection. Intravenous BMSC delivery significantly reduced the volume of cerebral infarct and decreased cerebral edema, leading to a lower Longa score. Furthermore, this effect was further enhanced by UTMD. Acute cerebral infarction induced by MCAO led to elevated matrix metalloproteinase 8 (MMP8) levels in the cerebrospinal fluid, which were significantly reduced following UTMD-mediated BMSC treatment. Ultrasound-targeted microbubble destruction facilitates the migration and homing of BMSC into the brain, possibly by transiently increasing blood-brain barrier (BBB) permeability, thereby improving therapeutic outcomes in an ACI rat model. The observed effect may be partly attributed to modulation of MMP8 levels.Advances in knowledge: UTMD-mediated intravenously delivered BMSC transplantation led to a significant increase in cell homing and reduction of MMP8 levels, resulting in increased therapeutic effect in an acute ischemic cerebral infarction model.

Co-activation of NMDAR and mGluRs controls protein nanoparticle-induced osmotic pressure in neurotoxic edema

BACKGROUND

Glutamate stimuli and hyperactivation of its receptor are predominant determinants of ischemia-induced cytotoxic cerebral edema, which is closely associated with protein nanoparticle (PN)-induced increases in osmotic pressure. Herein, we investigated the electrochemical and mechanical mechanisms underlying the neuron swelling induced by PNs via the co-activation of N-methyl-D-aspartate receptor subunit (NMDAR) and excitatory metabotropic glutamate receptors (mGluRs).

RESULTS

We observed that co-activation of ionic glutamate receptor NMDAR and Group I metabotropic mGluRs promoted alteration of PN-induced membrane potential and increased intracellular osmosis, which was closely associated with calcium and voltage-dependent ion channels. In addition, activation of NMDAR-induced calmodulin (CaM) and mGluR downstream diacylglycerol (DAG)/protein kinase C α (PKCα) were observed to play crucial roles in cytotoxic hyperosmosis. The crosstalk between CaM and PKCα could upregulate the sensitivity and sustained opening of sulfonylurea receptor 1 (SUR1)-transient receptor potential cation channel subfamily M member 4 (TRPM4) and transmembrane protein 16 A (TMEM16A) channels, respectively, maintaining the massive Na+/Cl- influx, and the resultant neuron hyperosmosis and swelling. Intracellular PNs and Na+/Cl- influx were found to be as potential targets for cerebral edema treatment, using the neurocyte osmosis system and a cerebral ischemic rat model.

CONCLUSIONS

This study highlights PNs as a key factor in "electrochemistry-tension" signal transduction controlling Na+/Cl- ion channels and increased osmotic pressure in ischemia-induced cytotoxic edema. Moreover, enhanced sensitivity in both Na+ and Cl- ion channels also has a crucial role in cerebral edema.

Poor Accuracy of Manually Derived Head Computed Tomography Parameters in Predicting Intracranial Hypertension After Nontraumatic Intracranial Hemorrhage

BACKGROUND

The utility of head computed tomography (CT) in predicting elevated intracranial pressure (ICP) is known to be limited in traumatic brain injury; however, few data exist in patients with spontaneous intracranial hemorrhage.

METHODS

We conducted a retrospective review of prospectively collected data in patients with nontraumatic intracranial hemorrhage (subarachnoid hemorrhage [SAH] or intraparenchymal hemorrhage [IPH]) who underwent external ventricular drain (EVD) placement. Head CT scans performed immediately prior to EVD placement were quantitatively reviewed for features suggestive of elevated ICP, including temporal horn diameter, bicaudate index, basal cistern effacement, midline shift, and global cerebral edema. The modified Fisher score (mFS), intraventricular hemorrhage score, and IPH volume were also measured, as applicable. We calculated the accuracy, positive predictive value (PPV), and negative predictive value (NPV) of these radiographic features for the coprimary outcomes of elevated ICP (> 20 mm Hg) at the time of EVD placement and at any time during the hospital stay. Multivariable backward stepwise logistic regression analysis was performed to identify significant radiographic factors associated with elevated ICP.

RESULTS

Of 608 patients with intracranial hemorrhages enrolled during the study time frame, 243 (40%) received an EVD and 165 (n = 107 SAH, n = 58 IPH) had a preplacement head CT scan available for rating. Elevated opening pressure and elevated ICP during hospitalization were recorded in 48 of 152 (29%) and 103 of 165 (62%), respectively. The presence of ≥ 1 radiographic feature had only 32% accuracy for identifying elevated opening pressure (PPV 30%, NPV 58%, area under the curve [AUC] 0.537, 95% asymptotic confidence interval [CI] 0.436-0.637, P = 0.466) and 59% accuracy for predicting elevated ICP during hospitalization (PPV 63%, NPV 40%, AUC 0.514, 95% asymptotic CI 0.391-0.638, P = 0.820). There was no significant association between the number of radiographic features and ICP elevation. Head CT scans without any features suggestive of elevated ICP occurred in 25 of 165 (15%) patients. However, 10 of 25 (40%) of these patients had elevated opening pressure, and 15 of 25 (60%) had elevated ICP during their hospital stay. In multivariable models, mFS (adjusted odds ratio [aOR] 1.36, 95% CI 1.10-1.68) and global cerebral edema (aOR 2.93, 95% CI 1.27-6.75) were significantly associated with elevated ICP; however, their accuracies were only 69% and 60%, respectively. All other individual radiographic features had accuracies between 38 and 58% for identifying intracranial hypertension.

CONCLUSIONS

More than 50% of patients with spontaneous intracranial hemorrhage without radiographic features suggestive of elevated ICP actually had ICP > 20 mm Hg during EVD placement or their hospital stay. Morphological head CT findings were only 32% and 59% accurate in identifying elevated opening pressure and ICP elevation during hospitalization, respectively.

Brain water content in sudden unexpected infant death

The extensive and rapid development of the human brain during the first years of life complicates the postmortem diagnosis of brain edema in infancy. The aim of this study was to describe brain water content, the brain weight/body weight ratio, and the brain weight/head circumference ratio throughout the first years of life. Furthermore, we examined the relationship between these parameters and rs2075575 in the AQP4 gene. Our hypothesis was that dysregulated water homeostasis might be a risk factor for sudden infant death syndrome (SIDS), which may be reflected by increased water content in the brain. The study included 90 subjects with sudden unexpected death < 4 years of age: 22 cases of sudden infant death syndrome, 11 cases of sudden unexplained death in childhood, 47 cases of death due to disease, and 10 cases of accident/violent death. Brain water content, brain weight/body weight ratio, and brain weight/head circumference ratio were investigated according to corrected age, diagnosis group, attempt to resuscitate, and presence of brain edema. We found that brain water content and brain weight/body weight ratio were significantly reduced with increasing age, while brain weight/head circumference were increased. Brain weight/head circumference was correlated with brain water content. Cases with brain edema had a significantly higher brain weight/head circumference than the non-edematous cases. No differences were found between the diagnosis groups for any of the investigated parameters. In summary, the findings contribute to the current body of knowledge regarding brain growth during the first months of life.