Changes in nationwide in-hospital stroke care during the first four waves of COVID-19 in Germany.

Introduction: In the early stages of the global COVID-19 pandemic hospital admissions for acute ischemic stroke (AIS) decreased substantially. As health systems have become more experienced in dealing with the pandemic, and as the proportion of the population vaccinated rises, it is of interest to determine whether the prevalence of AIS hospitalization and outcomes from hospitalization have returned to normal. Patients and methods: In this observational, retrospective cohort study, we compared the prevalence and outcomes of AIS during the first four waves of the pandemic to corresponding pre-pandemic periods in 2019 using administrative data collected from a nationwide network of 76 hospitals that manages 7% of all in-hospital cases in Germany. Results: We included 25,821 AIS cases in the study period (2020/2021) and used 26,295 AIS cases as controls (2019). Compared to pre-pandemic numbers, mean daily AIS admissions decreased only during wave 1 (from 39.6 to 34.1; p < 0.01) and wave 2 (from 39.9 to 38.3; p = 0.03) and returned to normal levels during waves 3 and 4. AIS case fatality increased in wave 1 only (from 6.0% to 7.6%; p = 0.03). We observed a consistent decrease in the prevalences of arterial hypertension, diabetes, and obesity among AIS cases throughout the pandemic and no changes in rates of systemic thrombolysis, mechanical thrombectomy, or decompressive craniectomy. The rate of transfer to stroke units increased only during waves 2 (by 4.6%; p < 0.01) and 3 (by 3.0%; p < 0.01). The proportion of patients with coinciding SARS-CoV-2 and AIS was low, peaking at 3.4% in wave 2 and subsequently decreasing to 0.4% in wave 4. Conclusion: In Germany, the COVID-19 pandemic seems to have had a larger effect on nationwide in-hospital AIS care during the early pandemic stages, in which AIS case numbers decreased and case fatality rose. This may reflect a nationwide "learning curve" within health care systems in providing AIS care in times of a pandemic.

Reversal learning reveals cognitive deficits and altered prediction error encoding in the ventral striatum in Huntington's disease.

Huntington's disease (HD) is an autosomal dominant neurodegenerative condition characterized by a triad of movement disorder, neuropsychiatric symptoms and cognitive deficits. The striatum is particularly vulnerable to the effects of mutant huntingtin, and cell loss can already be found in presymptomatic stages. Since the striatum is well known for its role in reinforcement learning, we hypothesized to find altered behavioral and neural responses in HD patients in a probabilistic reinforcement learning task performed during functional magnetic resonance imaging. We studied 24 HD patients without central nervous system (CNS)-active medication and 25 healthy controls. Twenty HD patients and 24 healthy controls were able to complete the task. Computational modeling was used to calculate prediction error values and estimate individual parameters. We observed that gray matter density and prediction error signals during the learning task were related to disease stage. HD patients in advanced disease stages appear to use a less complex strategy in the reversal learning task. In contrast, HD patients in early disease stages show intact encoding of learning signals in the degenerating left ventral striatum. This effect appears to be lost with disease progression.

Preventive antibacterial therapy in acute ischemic stroke: a randomized controlled trial.

BACKGROUND: Pneumonia is a major risk factor of death after acute stroke. In a mouse model, preventive antibacterial therapy with moxifloxacin not only prevents the development of post-stroke infections, it also reduces mortality, and improves neurological outcome significantly. In this study we investigate whether this approach is effective in stroke patients. METHODS: Preventive ANtibacterial THERapy in acute Ischemic Stroke (PANTHERIS) is a randomized, double-blind, placebo-controlled trial in 80 patients with severe, non-lacunar, ischemic stroke (NIHSS>11) in the middle cerebral artery (MCA) territory. Patients received either intravenous moxifloxacin (400 mg daily) or placebo for 5 days starting within 36 hours after stroke onset. Primary endpoint was infection within 11 days. Secondary endpoints included neurological outcome, survival, development of stroke-induced immunodepression, and induction of bacterial resistance. FINDINGS: On intention-to treat analysis (79 patients), the infection rate at day 11 in the moxifloxacin treated group was 15.4% compared to 32.5% in the placebo treated group (p = 0.114). On per protocol analysis (n = 66), moxifloxacin significantly reduced infection rate from 41.9% to 17.1% (p = 0.032). Stroke associated infections were associated with a lower survival rate. In this study, neurological outcome and survival were not significantly influenced by treatment with moxifloxacin. Frequency of fluoroquinolone resistance in both treatment groups did not differ. On logistic regression analysis, treatment arm as well as the interaction between treatment arm and monocytic HLA-DR expression (a marker for immunodepression) at day 1 after stroke onset was independently and highly predictive for post-stroke infections. INTERPRETATION: PANTHERIS suggests that preventive administration of moxifloxacin is superior in reducing infections after severe non-lacunar ischemic stroke compared to placebo. In addition, the results emphasize the pivotal role of immunodepression in developing post-stroke infections. TRIAL REGISTRATION: Controlled-Trials.com ISRCTN74386719.

Inducible nitric oxide synthase does not mediate brain damage after transient focal cerebral ischemia in mice.

Nitric oxide produced by the inducible nitric oxide synthase (iNOS) is believed to participate in the pathogenic events after cerebral ischemia. In this study, we examined the expression of iNOS in the brain after transient focal cerebral ischemia in mice. We detected differential expression of exons 2 and 3 of iNOS mRNA (16-fold upregulation at 24 to 72 h after middle cerebral artery occlusion, MCAO) compared with exons 6 to 8, 12 to 14, 21 to 22, and 26 to 27 (2- to 5-fold upregulation after 72 and 96 h), which would be compatible with alternative splicing. Expression levels of iNOS mRNA were too low for detection by the Northern blot analysis. Using specific antibodies, we did not detect any iNOS immunoreactivity in the mouse brain 1 to 5 days after MCAO, although we detected iNOS immunoreactivity in the lungs of mice with stroke-associated pneumonia, and in mouse and rat dura mater after lipopolysaccharide administration. In chimeric iNOS-deficient mice transplanted with wild-type bone marrow (BM) cells expressing the green fluorescent protein (GFP) or in wild-type mice transplanted with GFP(+) iNOS-deficient BM cells, no expression of iNOS was detected in GFP(+) leukocytes invading the ischemic brain or in resident brain cells. Moreover, both experimental groups did not show any differences in infarct size. Analysis of three different strains of iNOS-deficient mice and wild-type controls confirmed that infarct size was independent of iNOS deletion, but strongly confounded by the genetic background of mouse strains. In conclusion, our data suggest that iNOS is not a universal mediator of brain damage after cerebral ischemia.

Protection from brain damage and bacterial infection in murine stroke by the novel caspase-inhibitor Q-VD-OPH.

Infarction size and infections are important determinants of stroke outcome in humans. Bacterial infections are promoted by stroke-induced immunodeficiency which in experimental stroke is mainly characterized by extensive lymphocyte apoptosis and dysfunction. Pharmacological inhibition of caspases may improve stroke outcome not only by reducing apoptotic brain damage but also by attenuating stroke-induced immunodeficiency. We investigated the effects of systemic administration of the novel, non-toxic caspase-inhibitor quinolyl-valyl-O-methylaspartyl-[-2,6-difluorophenoxy]-methyl ketone (Q-VD-OPH) on stroke-induced neuronal and lymphocyte apoptosis, susceptibility to infections, and mortality in a murine model of stroke induced by middle cerebral artery occlusion (MCAO). Q-VD-OPH reduced ischemic brain damage and stroke-induced programmed cell death in thymus and spleen, decreased susceptibility to post-stroke bacteremia, and improved survival. Therefore, Q-VD-OPH may be a promising therapeutic agent in stroke.

Stroke-induced immunodepression: experimental evidence and clinical relevance.

Stroke affects the normally well-balanced interplay of the 2 supersystems: the nervous and the immune system. Recent research elucidated some of the involved signals and mechanisms and, importantly, was able to demonstrate that brain-immune interactions are highly relevant for functional outcome after stroke. Immunodepression after stroke increases the susceptibility to infection, the most relevant complication in stroke patients. However, immunodepression after stroke may also have beneficial effects, for example, by suppressing autoaggressive responses during lesion-induced exposure of central nervous system-specific antigens to the immune system. Thus, before immunomodulatory therapy can be applied to stroke patients, we need to understand better the interaction of brain and immune system after focal cerebral ischemia. Until then, anticipating an important consequence of stroke-induced immunodepression, bacterial infection, preventive antibiotic strategies have been proposed. In mouse experiments, preventive antibiotic treatment dramatically improves mortality and outcome. Results of clinical studies on this issue are contradictory at present, and larger trials are needed to settle the question whether (and which) stroke patients should be preventively treated. Nevertheless, clinical evidence is emerging demonstrating that stroke-induced immunodepression in humans not only exists, but has very similar features to those characterized in rodent experiments.

Improved reperfusion and neuroprotection by creatine in a mouse model of stroke.

Stroke leads to energy failure and subsequent neuronal cell loss. Creatine and phosphocreatine constitute a cellular energy buffering and transport system, and dietary creatine supplementation was shown to protect neurons in several models of neurodegeneration. Although creatine has recently been found to reduce infarct size after cerebral ischemia in mice, the mechanisms of neuroprotection remained unclear. We provide evidence for augmented cerebral blood flow (CBF) after stroke in creatine-treated mice using a magnetic resonance imaging (MRI)-based technique of CBF measurement (flow-sensitive alternating inversion recovery-MRI). Moreover, improved vasodilatory responses were detected in isolated middle cerebral arteries obtained from creatine-treated animals. After 3 weeks of dietary creatine supplementation, minor changes in brain creatine, phosphocreatine, adenosine triphosphate, adenosine diphosphate and adenosine monophosphate levels were detected, which did not reach statistical significance. However, we found a 40% reduction in infarct volume after transient focal cerebral ischemia. Our data suggest that creatine-mediated neuroprotection can occur independent of changes in the bioenergetic status of brain tissue, but may involve improved cerebrovascular function.

Stroke propagates bacterial aspiration to pneumonia in a model of cerebral ischemia.

BACKGROUND AND PURPOSE: Bacterial pneumonia is the most common cause of death in patients sustaining acute stroke and is believed to result from an increased aspiration. Recently, stroke-induced immunodeficiency was described in a mouse model of cerebral ischemia, which is primarily caused by overactivation of sympathetic nervous system. We tested if stroke-induced immunodeficiency increases the risk of pneumonia after aspiration in a newly developed model of poststroke pneumonia. METHODS: Experimental stroke in mice was induced by occlusion of the middle cerebral artery (MCAO) for 60 minutes. Aspiration pneumonia was induced by intranasal application of 20 microL of a defined suspension of Streptococcus pneumoniae in phosphate-buffered saline 4 or 14 days after MCAO. Treatment comprised moxifloxacin (100 mg/kg body weight, six times every 2 hours after operation) or propranolol (30 mg/kg body weight, immediately before as well as 4 and 8 hours after MCAO). Readout was lung histology and bacterial counts in lung and blood. RESULTS: Nasal inoculation of only 200 colony-forming units of S. pneumoniae caused severe pneumonia and bacteremia after experimental stroke, whereas 200,000 colony-forming units are needed to induce comparable disease in sham animals. Aspiration pneumonia in stroke animals outlasted acute stroke state but was preventable by beta-adrenoreceptor blockade. CONCLUSIONS: Experimental stroke propagates bacterial aspiration from harmless intranasal colonization to harmful pneumonia. Prevention of infections by beta-adrenoreceptor blockade suggests that immunodepression by sympathetic hyperactivity is essential for progression of bacterial aspiration to pneumonia.

Central nervous system injury-induced immune deficiency syndrome.

Infections are a leading cause of morbidity and mortality in patients with acute CNS injury. It has recently become clear that CNS injury significantly increases susceptibility to infection by brain-specific mechanisms: CNS injury induces a disturbance of the normally well balanced interplay between the immune system and the CNS. As a result, CNS injury leads to secondary immunodeficiency - CNS injury-induced immunodepression (CIDS) - and infection. CIDS might serve as a model for the study of the mechanisms and mediators of brain control over immunity. More importantly, understanding CIDS will allow us to work on developing effective therapeutic strategies, with which the outcome after CNS damage by a host of diseases could be improved by eliminating a major determinant of poor recovery.

Preventive antibacterial treatment improves the general medical and neurological outcome in a mouse model of stroke.

BACKGROUND AND PURPOSE: Epidemiological studies have demonstrated a high incidence of infections after severe stroke and their prominent role in morbidity and mortality in stroke patients. In a mouse model, it has been shown recently that stroke is coupled with severe and long-lasting immunosuppression, which is responsible for the development of spontaneous systemic infections. Here, we investigated in the same model the effects of preventive antibiotic treatment on survival and functional outcome of experimental stroke. METHODS: Mice were subjected to experimental stroke by occlusion of the middle cerebral artery (MCAO) for 60 minutes. A group of mice received moxifloxacin (6x100 mg/kg body weight every 2 hours over 12 hours) either immediately or 12 hours after MCAO. Control animals received the vector only. Behavior, neurological deficit, fever, survival, and body weight were monitored over 14 days. In a subgroup, infarct volume was measured 4 days after MCAO. Microbiological assessment was based on cultures of lung tissue, blood, and feces of animals 3 days after stroke. For a dose-response study, moxifloxacin was given immediately after MCAO in different doses and at different time points. RESULTS: Microbiological analyses of blood and lung tissue demonstrated high bacterial burden, mainly Escherichia coli, 3 days after stroke. Accordingly, we observed clinical and histological signs of septicemia and pneumonia. Moxifloxacin prevented the development of infections and fever, significantly reduced mortality, and improved neurological outcome. CONCLUSIONS: Preventive antibiotic treatment may be an important new therapeutical approach to improve outcome in patients with severe stroke.

Stroke-induced immunodeficiency promotes spontaneous bacterial infections and is mediated by sympathetic activation reversal by poststroke T helper cell type 1-like immunostimulation.

Infections are a leading cause of death in stroke patients. In a mouse model of focal cerebral ischemia, we tested the hypothesis that a stroke-induced immunodeficiency increases the susceptibility to bacterial infections. 3 d after ischemia, all animals developed spontaneous septicemia and pneumonia. Stroke induced an extensive apoptotic loss of lymphocytes and a shift from T helper cell (Th)1 to Th2 cytokine production. Adoptive transfer of T and natural killer cells from wild-type mice, but not from interferon (IFN)-gamma-deficient mice, or administration of IFN-gamma at day 1 after stroke greatly decreased the bacterial burden. Importantly, the defective IFN-gamma response and the occurrence of bacterial infections were prevented by blocking the sympathetic nervous system but not the hypothalamo-pituitary-adrenal axis. Furthermore, administration of the beta-adrenoreceptor blocker propranolol drastically reduced mortality after stroke. These data suggest that a catecholamine-mediated defect in early lymphocyte activation is the key factor in the impaired antibacterial immune response after stroke.

Bone marrow-derived cells expressing green fluorescent protein under the control of the glial fibrillary acidic protein promoter do not differentiate into astrocytes in vitro and in vivo.

Differentiation of bone marrow (BM) cells into astroglia expressing the glial fibrillary acidic protein (GFAP) has been reported in vitro and after intracerebral or systemic BM transplantation. In contrast, recent data suggest that astrocytic differentiation does not occur from BM-derived cells in vivo. Using transgenic mice that express the enhanced green fluorescent protein (GFP) under the control of the human glial fibrillary acidic protein (GFAP) promoter, we investigated the potential of adult murine BM-derived cells to differentiate into macroglia. In the brains of GFAP-GFP transgenic mice, astrocytes were brightly fluorescent from the expression of GFP. When BM from these animals was transplanted into lethally irradiated wild-type animals, the transgene was detected in the reconstituted hematopoietic system, but no GFP expression was found in the nervous system. In contrast, GFAP-GFP neuroectodermal anlage grafted into adult wild-type striatum gave rise to GFP-expressing astrocytes. Because cerebral ischemia has been suggested to promote the differentiation of BM-derived cells into astrocytes, BM chimeric mice were subjected to focal cerebral ischemia. No GFP-positive cells were found in the ischemic or contralateral hemispheres of these brains. Even after direct injection of GFAP-GFP transgenic BM cells into wild-type striatum, no GFP-expressing astroglia were detected. To test the hypothesis that the in vitro environment might be more permissible for astroglial differentiation, we cultured BM from mice that constitutively express GFP, BM cells expressing GFP from a retroviral vector, and BM from GFAP-GFP transgenic mice on astrocytes and on organotypic hippocampal slices. In all experimental paradigms, BM-derived cells were found to differentiate into ramified microglia but not into GFAP-expressing astrocytes.

Hypoxia-induced stroke tolerance in the mouse is mediated by erythropoietin.

BACKGROUND AND PURPOSE: Cellular response to hypoxia is mainly controlled by hypoxia-inducible factor 1 (HIF-1). The HIF-1 target gene erythropoietin (EPO) has been described as neuroprotective. Thus, we hypothesize EPO to be an essential mediator of protection in hypoxic preconditioning. METHODS: We randomized Sv129 mice into groups for different pretreatments, different hypoxia-ischemia intervals, or different durations of ischemia. For hypoxic preconditioning, the animals were exposed to a hypoxic gas mixture (8% O2 and 92% N2) for 30, 60, 180, 300, or 360 minutes. At 0, 24, 48, 72, or 144 hours later, we performed middle cerebral artery occlusion and allowed reperfusion after 30, 45, 60, or 120 minutes, or occlusion was left to be permanent. We studied EPO gene expression in brain tissue with a real-time reverse transcriptase-polymerase chain reaction and measured HIF-1 DNA-binding activity with an electrophoretic mobility shift assay. To block endogenously produced EPO, we instilled soluble EPO receptor into the cerebral ventricle. RESULTS: Hypoxic preconditioning for 180 or 300 minutes induced relative tolerance to transient focal cerebral ischemia, as evidenced by a reduction of infarct volumes to 75% or 54% of the control, respectively. Hypoxic pretreatment was effective only when applied 48 or 72 hours before middle cerebral artery occlusion. Sixty minutes after hypoxia, we found a marked activation of HIF-1 DNA-binding activity and a 7-fold induction of EPO transcription. Infusion of soluble EPO receptor significantly reduced the protective effect of hypoxic pretreatment by 40%. CONCLUSIONS: Endogenously produced EPO is an essential mediator of ischemic preconditioning.

Isoflurane induced prolonged protection against cerebral ischemia in mice: a redox sensitive mechanism?

We here demonstrate that general anesthesia with isoflurane can have profound effects on the brain of mice long after the anesthetic has been discontinued. Three hours of exposure to 1% isoflurane induced rapid and longlasting protection against 60 min transient focal cerebral ischemia induced by filament occlusion of the middle cerebral artery (MCAO). Mean infarct volumes were significantly smaller in animals pretreated with isoflurane 0, 12, and 24 h before MCAO (-38%, -31%, -24%, respectively). Mild hypoxia (17% O(2)) during or 5 mg/kg desferrioxiamine administered at the onset of isoflurane pretreatment completely abrogated the development of delayed tolerance (12 h) against focal cerebral ischemia, suggesting that the signaling of delayed protection induced by isoflurane is sensitive to the intracellular oxygenation state.

Serial analysis of gene expression identifies metallothionein-II as major neuroprotective gene in mouse focal cerebral ischemia.

We applied serial analysis of gene expression (SAGE) to study differentially expressed genes in mouse brain 14 hr after the induction of focal cerebral ischemia. Analysis of >60,000 transcripts revealed 83 upregulated and 94 downregulated transcripts (more than or equal to eightfold). Reproducibility was demonstrated by performing SAGE in duplicate on the same starting material. Metallothionein-II (MT-II) was the most significantly upregulated transcript in the ischemic hemisphere. MT-I and MT-II are assumed to be induced by metals, glucocorticoids, and inflammatory signals in a coordinated manner, yet their function remains elusive. Upregulation of both MT-I and MT-II was confirmed by Northern blotting. MT-I and MT-II mRNA expression increased as early as 2 hr after 2 hr of transient ischemia, with a maximum after 16 hr. Western blotting and immunohistochemistry revealed MT-I/-II upregulation in the ischemic hemisphere, whereas double labeling demonstrated the colocalization of MT with markers for astrocytes as well as for monocytes/macrophages. MT-I- and MT-II-deficient mice developed approximately threefold larger infarcts than wild-type mice and a significantly worse neurological outcome. For the first time we make available a comprehensive data set on brain ischemic gene expression and underscore the important protective role of metallothioneins in ischemic damage of the brain. Our results demonstrate the usefulness of SAGE to screen functionally relevant genes and the power of knock-out models in linking function to expression data generated by high throughput techniques.

Desferrioxamine induces delayed tolerance against cerebral ischemia in vivo and in vitro.

The widely prescribed drug desferrioxamine is a known activator of the hypoxia-inducible transcription factor 1 (HIF-1) and the subsequent transcription of erythropoietin. In the brain, HIF-1 is a master switch of the transcriptional response to hypoxia, whereas erythropoietin is a potent neuroprotectant. The authors show that desferrioxamine dose-dependently and time-dependently induces tolerance against focal cerebral ischemia in rats and mice, and against oxygen-glucose deprivation in purified cortical neurons. Desferrioxamine induced HIF-1 DNA binding and transcription of erythropoietin in vivo, the temporal kinetics of which were congruent with tolerance induction. Desferrioxamine is a promising drug for the induction of tolerance in humans when ischemia can be anticipated.