Central sympathetic nerve activation in subarachnoid hemorrhage

Remote Organ Damage Induced by Stroke: Molecular Mechanisms and Comprehensive Interventions

Significance: Damage after stroke is not only limited to the brain but also often occurs in remote organs, including the heart, lung, liver, kidney, digestive tract, and spleen, which are frequently affected by complex pathophysiological changes. The organs in the human body are closely connected, and signals transmitted through various molecular substances could regulate the pathophysiological changes of remote organs. Recent Advances: The latest studies have shown that inflammatory response plays an important role in remote organ damage after stroke, and can aggravate remote organ damage by activating oxidative stress, sympathetic axis, and hypothalamic axis, and disturbing immunological homeostasis. Remote organ damage can also cause damage to the brain, aggravating inflammatory response and oxidative damage. Critical Issues: Therefore, an in-depth exploration of inflammatory and oxidative mechanisms and adopting corresponding comprehensive intervention strategies have become necessary to reduce damage to remote organs and promote brain protection. Future Directions: The comprehensive intervention strategy involves multifaceted treatment methods such as inflammation regulation, antioxidants, and neural stem cell differentiation. It provides a promising treatment alternative for the comprehensive recovery of stroke patients and an inspiration for future research and treatment. The various organs of the human body are interconnected at the molecular level. Only through comprehensive intervention at the molecular and organ levels can we save remote organ damage and protect the brain after stroke to the greatest extent. Antioxid. Redox Signal. 00, 000-000.

Patients With

This study compared the roles of extraparenchymal autonomic nervous system (ANS) control of cerebral blood flow (CBF) versus intraparenchymal cerebrovascular autoregulation in 487 patients with aneurysmal subarachnoid hemorrhage (SAH) and 413 patients with traumatic brain injury (TBI). Vasomotion intensity of extraparenchymal and intraparenchymal vessels were quantified as the amplitude of oscillations of arterial blood pressure (ABP) and intracranial pressure (ICP) in the very low frequency range of 0.02-0.07 Hz, or periods of 55-15 sec, computed with a bandpass filter. A version of the pressure reactivity index (PRx-55-15) was computed as the correlation of the filtered waveforms, ABP-55-15 and ICP-55-15. Since ABP-55-15 is measured in the radial artery, any influence of cerebral factors must be mediated by the ANS. ICP-55-15 is measured in the brain and is influenced by intraparenchymal chemical and metabolic factors in addition to the ANS. Patient outcome was assessed using the Extended Glasgow Outcome Score (GOSe). Ten-day mean cerebral perfusion pressure (CPP) was negatively correlated with GOSe in the TBI cohort (R = -0.13, p = 0.01) but positively correlated with GOSe in the SAH cohort, (R = 0.32, p < 0.00001), indicating a much greater dependence on ANS support in the form of elevated CPP in SAH. The optimal CPP range for TBI was 60-70 mmHg, but for SAH it was 110-120 mmHg. The percentage of monitoring time with PRx-55-15 < 0.8, indicating very pressure-active cerebral vessels that resist ANS influence via systemic ABP, is positively correlated with GOSe in the TBI cohort (R = 0.14, p = 0.003), but negatively correlated with GOSe in the SAH cohort (R = -0.10, p = 0.004). The TBI cohort optimal PRx-55-15 for patient outcome was -1.0, while the SAH optimum was 0.3. For the TBI cohort, the correlation of ABP-55-15 amplitude with 10-day mean ICP-55-15 amplitude was 0.29. For the SAH cohort the correlation was 0.51, which is stronger (p = 0.0001). The TBI cohort had a median GOSe of 5 (interquartile range [IQR] 3-7), while SAH had a median of 3 (IQR 3-5), which is worse (p < 0.00001). The higher optimal CPP in patients with SAH, more passive optimal pressure reactivity, and greater dependence of cerebral on systemic vasomotion indicate that they require more active support by the ANS and systemic circulation for CBF than patients with TBI. CBF in patients with TBI is more reliant on cerebrovascular autoregulation based on metabolic demand. This appears to be deficient following SAH, making the heightened ANS support necessary. Although this support is beneficial, it does not fully compensate for the loss of cerebrovascular autoregulation, as reflected in the problems in the SAH cohort with delayed cerebral ischemia and poor outcome.

All Three Supersystems-Nervous, Vascular, and Immune-Contribute to the Cortical Infarcts After Subarachnoid Hemorrhage

The recently published DISCHARGE-1 trial supports the observations of earlier autopsy and neuroimaging studies that almost 70% of all focal brain damage after aneurysmal subarachnoid hemorrhage are anemic infarcts of the cortex, often also affecting the white matter immediately below. The infarcts are not limited by the usual vascular territories. About two-fifths of the ischemic damage occurs within ~ 48 h; the remaining three-fifths are delayed (within ~ 3 weeks). Using neuromonitoring technology in combination with longitudinal neuroimaging, the entire sequence of both early and delayed cortical infarct development after subarachnoid hemorrhage has recently been recorded in patients. Characteristically, cortical infarcts are caused by acute severe vasospastic events, so-called spreading ischemia, triggered by spontaneously occurring spreading depolarization. In locations where a spreading depolarization passes through, cerebral blood flow can drastically drop within a few seconds and remain suppressed for minutes or even hours, often followed by high-amplitude, sustained hyperemia. In spreading depolarization, neurons lead the event, and the other cells of the neurovascular unit (endothelium, vascular smooth muscle, pericytes, astrocytes, microglia, oligodendrocytes) follow. However, dysregulation in cells of all three supersystems-nervous, vascular, and immune-is very likely involved in the dysfunction of the neurovascular unit underlying spreading ischemia. It is assumed that subarachnoid blood, which lies directly on the cortex and enters the parenchyma via glymphatic channels, triggers these dysregulations. This review discusses the neuroglial, neurovascular, and neuroimmunological dysregulations in the context of spreading depolarization and spreading ischemia as critical elements in the pathogenesis of cortical infarcts after subarachnoid hemorrhage.

How the brain impacts the heart: lessons from ischaemic stroke and other neurological disorders

Cardiovascular alterations are common in patients who had ischaemic stroke, haemorrhagic stroke and other acute brain disorders such as seizures. These cardiac complications are important drivers of morbidity and mortality and comprise blood-based detection of cardiomyocyte damage, ECG changes, heart failure and arrhythmia. Recently, the concept of a distinct 'stroke-heart syndrome' has been formulated as a pathophysiological framework for poststroke cardiac complications. The concept considers cardiac sequelae after stroke to be the result of a stroke-induced disturbance of the brain-heart axis. In this review, we describe the spectrum of cardiac changes secondary to ischaemic stroke and other acute brain disorders. Furthermore, we focus on Takotsubo syndrome secondary to acute brain disorders as a model disease of disturbed brain-heart interaction. Finally, we aim to provide an overview of the anatomical and functional links between the brain and the heart, with emphasis on the autonomic network and the role of inflammation. Given the clinical relevance of the deleterious impact of acute brain injury on the heart, we call for clinical awareness and for starting joint efforts combining expertise of neurology and cardiology to identify specific therapeutic interventions.

Association between skin sympathetic nerve activity and electrocardiogram alterations after subarachnoid hemorrhage

While autonomic dysregulation and repolarization abnormalities are observed in subarachnoid hemorrhage (SAH), their relationship remains unclear. We aimed to measure skin sympathetic nerve activity (SKNA), a novel method to estimate stellate ganglion nerve activity, and investigate its association with electrocardiogram (ECG) alterations after SAH. We recorded a total of 179 SKNA data from SAH patients at three distinct phases and compared them with 20 data from controls. Compared with control data, in the acute phase data (days 1-3 of SAH), T peak-to-end (Tp-e) interval was significantly prolonged (81 [interquartile range {IQR}: 71-93] vs. 58 [IQR: 54-64] ms, p < 0.001), non-burst amplitude of SKNA was significantly increased (2.4 [IQR: 1.3-4.1] vs. 0.7 [IQR: 0.5-1.7] μV, p < 0.001), and the ratio of low frequency to high frequency (HF) was significantly decreased (0.8 [IQR: 0.5-1.1] vs. 1.1 [IQR: 0.7-1.3], p = 0.028). Linear mixed model revealed a relationship between Tp-e interval and SKNA. Although these abnormalities gradually normalized, delayed cerebral ischemia episodes were associated with increased HF oscillation. Transient sympathetic dysregulation contributes to repolarization impairment after SAH. SKNA may have the potential to monitor adverse outcomes.

Prevalence, risk factors and prognostic value of atrial fibrillation detected after stroke after haemorrhagic versus ischaemic stroke

BACKGROUND AND OBJECTIVES

Prior evidence suggests that atrial fibrillation detected after stroke (AFDAS) is distinct from known atrial fibrillation (KAF), with particular clinical characteristics and impacts on outcomes in ischaemic stroke. However, the results remained inconsistent in ischaemic stroke, and the role of AFDAS in haemorrhagic stroke remains unclear. Therefore, we aimed to estimate the prevalence, risk factors and prognostic value of AFDAS in haemorrhagic stroke in comparison with ischaemic stroke.

METHODS

This was a multicentre cohort study. Patients who had an ischaemic and haemorrhagic stroke hospitalised in the Chinese Stroke Center Alliance hospitals were enrolled and classified as AFDAS, KAF or sinus rhythm (SR) based on heart rhythm. Univariate and multivariate logistic regression analyses were used to assess the prevalence, characteristics, risk factors and outcomes of AFDAS, KAF and SR in different stroke subtypes.

RESULTS

A total of 913 163 patients, including 818 799 with ischaemic stroke, 83 450 with intracerebral haemorrhage (ICH) and 10 914 with subarachnoid haemorrhage (SAH), were enrolled. AFDAS was the most common in ischaemic stroke. There were differences in the risk factor profile between stroke subtypes; older age is a common independent risk factor shared by ischaemic stroke (OR 1.06, 95% CI 1.06 to 1.06), ICH (OR 1.08, 95% CI 1.07 to 1.09) and SAH (OR 1.07, 95% CI 1.05 to 1.10). Similar to KAF, AFDAS was associated with an increased risk of in-hospital mortality compared with SR in both ischaemic stroke (OR 2.23, 95% CI 1.94 to 2.56) and ICH (OR 2.84, 95% CI 1.84 to 4.38).

DISCUSSION

There are differences in the prevalence, characteristics and risk factors for AFDAS and KAF in different stroke subtypes. AFDAS was associated with an increased risk of mortality compared with SR in both ischaemic stroke and ICH. Rhythm monitoring and risk factor modification after both ischaemic and haemorrhagic stroke are essential in clinical practice. More emphasis and appropriate treatment should be given to AFDAS.

Association between platelet-to-red cell distribution width ratio and all-cause mortality in critically ill patients with non-traumatic cerebral hemorrhage: a retrospective cohort study

Background

The purpose of this study was to investigate the relationship between platelet-to-red cell distribution width ratio (PRR) and all-cause mortality in critically ill patients with non-traumatic cerebral hemorrhage (NCH).

Methods

The Medical Information Mart for Intensive Care (MIMIC-IV) database was used to identify patients with NCH who needed to be admitted to intensive care unit (ICU). The outcomes of the study included both ICU and in-hospital mortality. Restricted cubic splines and Cox proportional hazards regression analysis were used to clarify the relationship between PRR and clinical outcomes in critically ill patients with NCH.

Results

A total of 3,094 patients (54.0% male) were included in the study, with in-hospital mortality and ICU mortality rates of 16.5 and 11.8%, respectively. A substantial correlation was found by multivariate Cox proportional hazards analysis between increased PRR and a lower risk of in-hospital and ICU mortality. Following adjustment for confounding factors, patients with elevated PRR exhibited a significantly decreased risk of in-hospital death (HR, 0.98; 95% CI, 0.96-0.99; p = 0.006) and ICU death (HR, 0.98; 95% CI, 0.96-0.99; p = 0.027). As PRR increased, restrictive cubic splines showed a progressive decrease in the probability of all-cause mortality. Stratified analyses indicated a consistent association between PRR and both in-hospital and ICU mortality.

Conclusion

Among critically ill patients with NCH, lower PRR was substantially correlated with the increased probability of all-cause mortality in both the ICU and hospital. According to this research, PRR might be a valuable indicator for identifying NCH patients at risk of all-cause mortality.

Transcriptomics and metabolomics reveal hypothalamic metabolic characteristics and key genes after subarachnoid hemorrhage in rats

Subarachnoid hemorrhage (SAH) is a serious hemorrhagic event with high mortality and morbidity. Multiple injurious events produced by SAH can lead to a series of pathophysiologic processes in the hypothalamus that can severely impact patients' life. These pathophysiologic processes usually result in physiologic derangements and dysfunction of the brain and multiple organs. This dysfunction involved multiple dimensions of the genome and metabolome. In our study, we induced the SAH model in rats to obtain hypothalamic tissue and serum. The samples were subsequently analyzed by transcriptomics and metabolomics. Next, the functional enrichment analysis of the differentially expressed genes and metabolites were performed by GO and KEGG pathway analysis. Through transcriptomic analysis of hypothalamus samples, 263 up-regulated differential genes, and 207 down-regulated differential genes were identified in SAH groups compared to Sham groups. In the KEGG pathway analysis, a large number of differential genes were found to be enriched in IL-17 signaling pathway, PI3K-Akt signaling pathway, and bile secretion. Liquid chromatography-mass spectrometry metabolomics technology was conducted on the serum of SAH rats and identified 11 up-regulated and 26 down-regulated metabolites in positive ion model, and 1 up-regulated and 10 down-regulated metabolites in negative ion model. KEGG pathways analysis showed that differentially expressed metabolites were mainly enriched in pathways of bile secretion and primary bile acid biosynthesis. We systematically depicted the neuro- and metabolism-related biomolecular changes occurring in the hypothalamus after SAH by performing transcriptomics and metabolomics studies. These biomolecular changes may provide new insights into hypothalamus-induced metabolic changes and gene expression after SAH.

Auricular Vagus Nerve Stimulation Mitigates Inflammation and Vasospasm in Subarachnoid Hemorrhage: A Randomized Trial

Background

Inflammation contributes to morbidity following subarachnoid hemorrhage (SAH). Transauricular vagus nerve stimulation (taVNS) offers a noninvasive approach to target the inflammatory response following SAH.

Methods

In this prospective, triple-blinded, randomized, controlled trial, twenty-seven patients were randomized to taVNS or sham stimulation. Blood and cerebrospinal fluid (CSF) were collected to quantify inflammatory markers. Cerebral vasospasm severity and functional outcomes (modified Rankin Scale, mRS) were analyzed.

Results

No adverse events occurred. Radiographic vasospasm was significantly reduced (p = 0.018), with serial vessel caliber measurements demonstrating a more rapid return to normal than sham (p < 0.001). In the taVNS group, TNF-α was significantly reduced in both plasma (days 7 and 10) and CSF (day 13); IL-6 was also significantly reduced in plasma (day 4) and CSF (day 13) (p < 0.05). Patients receiving taVNS had higher rates of favorable outcomes at discharge (38.4% vs 21.4%) and first follow-up (76.9% vs 57.1%), with significant improvement from admission to first follow-up (p = 0.014), unlike the sham group (p = 0.18). The taVNS group had a significantly lower rate of discharge to skilled nursing facility or hospice (p = 0.04).

Conclusion

taVNS is a non-invasive method of neuro- and systemic immunomodulation. This trial supports that taVNS following SAH can mitigate the inflammatory response, reduce radiographic vasospasm, and potentially improve functional and neurological outcomes. Clinical Trial Registration: https://clinicaltrials.gov/ct2/show/NCT04557618.

Perivascular macrophages in cerebrovascular diseases

Cerebrovascular diseases are a major cause of stroke and dementia, both requiring long-term care. These diseases involve multiple pathophysiologies, with mitochondrial dysfunction being a crucial contributor to the initiation of inflammation, apoptosis, and oxidative stress, resulting in injuries to neurovascular units that include neuronal cell death, endothelial cell death, glial activation, and blood-brain barrier disruption. To maintain brain homeostasis against these pathogenic conditions, brain immune cells, including border-associated macrophages and microglia, play significant roles as brain innate immunity cells in the pathophysiology of cerebrovascular injury. Although microglia have long been recognized as significant contributors to neuroinflammation, attention has recently shifted to border-associated macrophages, such as perivascular macrophages (PVMs), which have been studied based on their crucial roles in the brain. These cells are strategically positioned around the walls of brain vessels, where they mainly perform critical functions, such as perivascular drainage, cerebrovascular flexibility, phagocytic activity, antigen presentation, activation of inflammatory responses, and preservation of blood-brain barrier integrity. Although PVMs act as scavenger and surveillant cells under normal conditions, these cells exert harmful effects under pathological conditions. PVMs detect mitochondrial dysfunction in injured cells and implement pathological changes to regulate brain homeostasis. Therefore, PVMs are promising as they play a significant role in mitochondrial dysfunction and, in turn, disrupt the homeostatic condition. Herein, we summarize the significant roles of PVMs in cerebrovascular diseases, especially ischemic and hemorrhagic stroke and dementia, mainly in correlation with inflammation. A better understanding of the biology and pathobiology of PVMs may lead to new insights on and therapeutic strategies for cerebrovascular diseases.

Ferroptosis in early brain injury after subarachnoid hemorrhage: review of literature

Spontaneous subarachnoid hemorrhage (SAH), mainly caused by ruptured intracranial aneurysms, is a serious acute cerebrovascular disease. Early brain injury (EBI) is all brain injury occurring within 72 h after SAH, mainly including increased intracranial pressure, decreased cerebral blood flow, disruption of the blood-brain barrier, brain edema, oxidative stress, and neuroinflammation. It activates cell death pathways, leading to neuronal and glial cell death, and is significantly associated with poor prognosis. Ferroptosis is characterized by iron-dependent accumulation of lipid peroxides and is involved in the process of neuron and glial cell death in early brain injury. This paper reviews the research progress of ferroptosis in early brain injury after subarachnoid hemorrhage and provides new ideas for future research.

Autonomic dysfunction and treatment strategies in intracerebral hemorrhage

AIMS

Autonomic dysfunction with central autonomic network (CAN) damage occurs frequently after intracerebral hemorrhage (ICH) and contributes to a series of adverse outcomes. This review aims to provide insight and convenience for future clinical practice and research on autonomic dysfunction in ICH patients.

DISCUSSION

We summarize the autonomic dysfunction in ICH from the aspects of potential mechanisms, clinical significance, assessment, and treatment strategies. The CAN structures mainly include insular cortex, anterior cingulate cortex, amygdala, hypothalamus, nucleus of the solitary tract, ventrolateral medulla, dorsal motor nucleus of the vagus, nucleus ambiguus, parabrachial nucleus, and periaqueductal gray. Autonomic dysfunction after ICH is closely associated with neurological functional outcomes, cardiac complications, blood pressure fluctuation, immunosuppression and infection, thermoregulatory dysfunction, hyperglycemia, digestive dysfunction, and urogenital disturbances. Heart rate variability, baroreflex sensitivity, skin sympathetic nerve activity, sympathetic skin response, and plasma catecholamine concentration can be used to assess the autonomic functional activities after ICH. Risk stratification of patients according to autonomic functional activities, and development of intervention approaches based on the restoration of sympathetic-parasympathetic balance, would potentially improve clinical outcomes in ICH patients.

CONCLUSION

The review systematically summarizes the evidence of autonomic dysfunction and its association with clinical outcomes in ICH patients, proposing that targeting autonomic dysfunction could be potentially investigated to improve the clinical outcomes.

Percutaneous cervical sympathetic block to treat cerebral vasospasm and delayed cerebral ischemia: a review of the evidence

Delayed cerebral ischemia (DCI) affects 30% of patients following aneurysmal subarachnoid hemorrhage (aSAH) and is a major driver of morbidity, mortality, and intensive care unit length of stay for these patients. DCI is strongly associated with cerebral arterial vasospasm, reduced cerebral blood flow and cerebral infarction. The current standard treatment with intravenous or intra-arterial calcium channel antagonist and balloon angioplasty or stent has limited efficacy. A simple treatment such as a cervical sympathetic block (CSB) may be an effective therapy but is not routinely performed to treat vasospasm/DCI. CSB consists of injecting local anesthetic at the level of the cervical sympathetic trunk, which temporarily blocks the innervation of the cerebral arteries to cause arterial vasodilatation. CSB is a local, minimally invasive, low cost and safe technique that can be performed at the bedside and may offer significant advantages as complementary treatment in combination with more conventional neurointerventional surgery interventions. We reviewed the literature that describes CSB for vasospasm/DCI prevention or treatment in humans after aSAH. The studies outlined in this review show promising results for a CSB as a treatment for vasospasm/DCI. Further research is required to standardize the technique, to explore how to integrate a CSB with conventional neurointerventional surgery treatments of vasospasm and DCI, and to study its long-term effect on neurological outcomes.

Cervical sympathectomy to treat cerebral vasospasm: a scoping review

BACKGROUND/IMPORTANCE

Delayed cerebral ischemia (DCI) is the second-leading cause of death and disability in patients with aneurysmal subarachnoid hemorrhage (aSAH), and is associated with cerebral arterial vasospasm (CAV). Current treatments for CAV are expensive, invasive, and have limited efficacy. Cervical sympathetic block (CSB) is an underappreciated, but potentially highly effective therapy for CAV.

OBJECTIVE

To provide a comprehensive review of the preclinical and human literature pertinent to CSB in the context of CAV.

EVIDENCE REVIEW

This study followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews guidelines. We conducted a literature search using Embase, PubMed, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, Scopus and Web of Science until February 2022, to identify abstracts, conference proceedings, and full-text papers pertinent to cervical sympathectomy and CAV in animal/adult patients.

FINDINGS

We included six human and six experimental studies. Human studies were mostly prospective observational, except one retrospective and one randomized clinical trial, and used various imaging modalities to measure changes in arterial diameter after the block. Studies that used digital subtraction angiography showed an improvement in cerebral perfusion without change in vessel diameter. Transcranial Doppler studies found an approximately 15% statistically significant decrease in velocities consistent with arterial vasodilatation. Overall, the results suggest an increase in cerebral arterial diameter and neurological improvement in patients receiving a CSB. Animal studies demonstrate that sympathetic system ablation vasodilates cerebral vasculature and decreases the incidence of symptomatic vasospasm.

CONCLUSIONS

This scoping review suggests that CSB may be a viable option for treatment and prevention of CAV/DCI in patients with aSAH, although the included studies were heterogeneous, mostly observational, and with a small sample size. Further research is needed to standardize the technique and prove its effectiveness to treat patients suffering of CAV/DCI after aSAH.

Pretreatment with Clodronate Improved Neurological Function by Preventing Reduction of Posthemorrhagic Cerebral Blood Flow in Experimental Subarachnoid Hemorrhage

BACKGROUND

Brain perivascular macrophages (PVMs) are potential treatment targets for subarachnoid hemorrhage (SAH), and previous studies revealed that their depletion by clodronate (CLD) improved outcomes after experimental SAH. However, the underlying mechanisms are not well understood. Therefore, we investigated whether reducing PVMs by CLD pretreatment improves SAH prognosis by inhibiting posthemorrhagic impairment of cerebral blood flow (CBF).

METHODS

In total, 80 male Sprague-Dawley rats received an intracerebroventricular injection of the vehicle (liposomes) or CLD. Subsequently, the rats were categorized into the prechiasmatic saline injection (sham) and blood injection (SAH) groups after 72 h. We assessed its effects on weak and severe SAH, which were induced by 200- and 300-µL arterial blood injections, respectively. In addition, neurological function at 72 h and CBF changes from before the intervention to 5 min after were assessed in rats after sham/SAH induction as the primary and secondary end points, respectively.

RESULTS

CLD significantly reduced PVMs before SAH induction. Although pretreatment with CLD in the weak SAH group provided no additive effects on the primary end point, rats in the severe SAH group showed significant improvement in the rotarod test. In the severe SAH group, CLD inhibited acute reduction of CBF and tended to decrease hypoxia-inducible factor 1α expression. Furthermore, CLD reduced the number of PVMs in rats subjected to sham and SAH surgery, although no effects were observed in oxidative stress and inflammation.

CONCLUSIONS

Our study proposes that pretreatment with CLD-targeting PVMs can improve the prognosis of severe SAH through a candidate mechanism of inhibition of posthemorrhagic CBF reduction.

Impact of Subarachnoid Hemorrhage on the Cardiac Autonomic Function During Rehabilitation in Children After Severe Traumatic Brain Injury

This study aimed to investigate the impact of traumatic subarachnoid hemorrhage (tSAH) on cardiac autonomic control system (CACS) function in children after severe traumatic brain injury (TBI) during the subacute rehabilitation period. Thirty-three participants, 8-18 years of age, 42 (14-149) days after severe TBI at the beginning of the subacute rehabilitation, were included in the study. Six participants were diagnosed with tSAH during acute medical care (tSAH group). Heart rate variability (HRV) was assessed by the standard deviation of the N-N interval (SDNN) and the square root of the mean square differences of successive R-R interval (RMSSD) using a Polar RS800CX device while sitting at rest for 5 min. A second assessment was performed 8 weeks later. No significant difference between the tSAH and non-tSAH groups were found in the demographic and functional characteristics or injury severity. However, in comparison to the non-tSAH group, the tSAH group had lower SDNN (23.9 [10.5-47.3] vs. 43.9 [21.8-118.8], respectively; p = 0.005) and RMSSD values (11.8 [5.9-24.5] vs. 29.6 [8.9-71.7], respectively; p = 0.004). Neither group demonstrated changes in HRV values at rest in the second assessment, whereas the significant difference in SDNN (p = 0.035) and RMSSD (p = 0.008) remained. Children diagnosed with SAH after severe TBI presented poorer CACS function during the subacute rehabilitation. Given that reduced HRV values may be a marker for potential heart disease, the medical team should be aware of the influence of existing tSAH. Future studies with larger sample sizes and longer follow-up periods are warranted to further investigate this topic. ClinicalTrials.gov number: NCT03215082.

Systemic Inflammation after Aneurysmal Subarachnoid Hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is one of the most severe neurological disorders, with a high mortality rate and severe disabling functional sequelae. Systemic inflammation following hemorrhagic stroke may play an important role in mediating intracranial and extracranial tissue damage. Previous studies showed that various systemic inflammatory biomarkers might be useful in predicting clinical outcomes. Anti-inflammatory treatment might be a promising therapeutic approach for improving the prognosis of patients with aSAH. This review summarizes the complicated interactions between the nervous system and the immune system.

Systemic innate myeloid responses to acute ischaemic and haemorrhagic stroke

Acute ischaemic and haemorrhagic stroke account for significant disability and morbidity burdens worldwide. The myeloid arm of the peripheral innate immune system is critical in the immunological response to acute ischaemic and haemorrhagic stroke. Neutrophils, monocytes, and dendritic cells (DC) contribute to the evolution of pathogenic local and systemic inflammation, whilst maintaining a critical role in ongoing immunity protecting against secondary infections. This review aims to summarise the key alterations to myeloid immunity in acute ischaemic stroke, intracerebral haemorrhage (ICH), and subarachnoid haemorrhage (SAH). By integrating clinical and preclinical research, we discover how myeloid immunity is affected across multiple organ systems including the brain, blood, bone marrow, spleen, and lung, and evaluate how these perturbations associate with real-world outcomes including infection. These findings are placed in the context of the rapidly developing field of human immunology, which offers a wealth of opportunity for further research.

Pathophysiology of Early Brain Injury and Its Association with Delayed Cerebral Ischemia in Aneurysmal Subarachnoid Hemorrhage: A Review of Current Literature

Background: Delayed cerebral ischemia (DCI) is a common and serious complication of aneurysmal subarachnoid hemorrhage (aSAH). Though many clinical trials have looked at therapies for DCI and vasospasm in aSAH, along with reducing rebleeding risks, none have led to improving outcomes in this patient population. We present an up-to-date review of the pathophysiology of DCI and its association with early brain injury (EBI). Recent Findings: Recent studies have demonstrated that EBI, as opposed to delayed brain injury, is the main contributor to downstream pathophysiological mechanisms that play a role in the development of DCI. New predictive models, including advanced monitoring and neuroimaging techniques, can help detect EBI and improve the clinical management of aSAH patients. Summary: EBI, the severity of subarachnoid hemorrhage, and physiological/imaging markers can serve as indicators for potential early therapeutics in aSAH. The microcellular milieu and hemodynamic pathomechanisms should remain a focus of researchers and clinicians. With the advancement in understanding the pathophysiology of DCI, we are hopeful that we will make strides toward better outcomes for this unique patient population.

Trimethylamine N-oxide (TMAO) in patients with subarachnoid hemorrhage: a prospective observational study

BACKGROUND

It is suspected that microbiome-derived trimethylamine N-oxide (TMAO) may enhance platelet responsiveness and accordingly be thrombophilic. The purpose of this prospective observational study is to evaluate TMAO in patients with subarachnoid hemorrhage (SAH) and compare it with a control group. A secondary aim was to investigate TMAO in the cerebrospinal fluid (CSF) from SAH patients. This should provide a better understanding of the role of TMAO in the pathogenesis of SAH and its thrombotic complications.

METHODS

The study included patients with diagnosed spontaneous SAH recruited after initial treatment on admission and patients with nerve, nerve root, or plexus disorders serving as controls. Blood samples were gathered from all patients at recruitment. Additionally, sampling of SAH patients in the intensive care unit continued daily for 14 days. The CSF was collected out of existing external ventricular drains whenever possible.

RESULTS

Thirty-four patients diagnosed with SAH, and 108 control patients participated in this study. Plasma TMAO levels at baseline were significantly lower in the SAH group (1.7 μmol/L) compared to the control group (2.9 μmol/L). TMAO was detectable in the CSF (0.4 μmol/L) and significantly lower than in plasma samples of the SAH group at baseline. Plasma and CSF TMAO levels correlated positively. The TMAO levels did not differ significantly during the observation period of 15 days.

CONCLUSIONS

Although we assumed that patients with higher TMAO levels were at higher risk for SAH a priori, plasma TMAO levels were lower in patients with SAH compared with control subjects with nerve, nerve root, or plexus disorders on admission to the hospital. A characteristic pattern of plasma TMAO levels in patients with SAH was not found.

Plasma Amino Acids May Improve Prediction Accuracy of Cerebral Vasospasm after Aneurysmal Subarachnoid Haemorrhage

Aneurysmal subarachnoid haemorrhages (aSAH) account for 5% of strokes and continues to place a great burden on patients and their families. Cerebral vasospasm (CVS) is one of the main causes of death after aSAH, and is usually diagnosed between day 3 and 14 after bleeding. Its pathogenesis remains poorly understood. To verify whether plasma concentration of amino acids have prognostic value in predicting CVS, we analysed data from 35 patients after aSAH (median age 55 years, IQR 39-62; 20 females, 57.1%), and 37 healthy volunteers (median age 50 years, IQR 38-56; 19 females, 51.4%). Fasting peripheral blood samples were collected on postoperative day one and seven. High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis was performed. The results showed that plasma from patients after aSAH featured a distinctive amino acids concentration which was presented in both principal component analysis and direct comparison. No significant differences were noted between postoperative day one and seven. A total of 18 patients from the study group (51.4%) developed CVS. Hydroxyproline (AUC = 0.7042, 95%CI 0.5259-0.8826, p = 0.0248) and phenylalanine (AUC = 0.6944, 95%CI 0.5119-0.877, p = 0.0368) presented significant CVS prediction potential. Combining the Hunt-Hess Scale and plasma levels of hydroxyproline and phenylalanine provided the model with the best predictive performance and the lowest leave-one-out cross-validation of performance error. Our results suggest that plasma amino acids may improve sensitivity and specificity of Hunt-Hess scale in predicting CVS.

Disturbed cerebral circulation and metabolism matters: A preface to the special issue "Stroke and Energy Metabolism": A preface to the special issue "Stroke and Energy Metabolism"

Stroke is a serious neurological disorder caused by blockage or rupture of cerebral blood vessels. Two main aims in acute stroke therapy include the restoration of cerebral blood flow in order to preserve energy supply to neurons and other brain cells, and minimizing neuronal loss. Maintenance of energy homeostasis in the brain drives neural network dynamics, which preserves normal brain function under physiological conditions. As such, cerebral energy homeostasis is a key target in stroke therapy. The various articles in this special issue highlight energy metabolism changes following stroke, including disturbed cerebral blood circulation, mitochondrial dysfunction, programmed neuronal cell death and cell-cell communication in brain metabolism. Collectively, this series of articles provides insight and presents new avenues for further research to improve the clinical management of stroke patients.