Stroke Care during the COVID-19 Pandemic: International Expert Panel Review.

BACKGROUND: Coronavirus disease 2019 (COVID-19) has placed a tremendous strain on healthcare services. This study, prepared by a large international panel of stroke experts, assesses the rapidly growing research and personal experience with COVID-19 stroke and offers recommendations for stroke management in this challenging new setting: modifications needed for prehospital emergency rescue and hyperacute care; inpatient intensive or stroke units; posthospitalization rehabilitation; follow-up including at-risk family and community; and multispecialty departmental developments in the allied professions. SUMMARY: The severe acute respiratory syndrome coronavirus 2 uses spike proteins binding to tissue angiotensin-converting enzyme (ACE)-2 receptors, most often through the respiratory system by virus inhalation and thence to other susceptible organ systems, leading to COVID-19. Clinicians facing the many etiologies for stroke have been sobered by the unusual incidence of combined etiologies and presentations, prominent among them are vasculitis, cardiomyopathy, hypercoagulable state, and endothelial dysfunction. International standards of acute stroke management remain in force, but COVID-19 adds the burdens of personal protections for the patient, rescue, and hospital staff and for some even into the postdischarge phase. For pending COVID-19 determination and also for those shown to be COVID-19 affected, strict infection control is needed at all times to reduce spread of infection and to protect healthcare staff, using the wealth of well-described methods. For COVID-19 patients with stroke, thrombolysis and thrombectomy should be continued, and the usual early management of hypertension applies, save that recent work suggests continuing ACE inhibitors and ARBs. Prothrombotic states, some acute and severe, encourage prophylactic LMWH unless bleeding risk is high. COVID-19-related cardiomyopathy adds risk of cardioembolic stroke, where heparin or warfarin may be preferable, with experience accumulating with DOACs. As ever, arteritis can prove a difficult diagnosis, especially if not obvious on the acute angiogram done for clot extraction. This field is under rapid development and may generate management recommendations which are as yet unsettled, even undiscovered. Beyond the acute management phase, COVID-19-related stroke also forces rehabilitation services to use protective precautions. As with all stroke patients, health workers should be aware of symptoms of depression, anxiety, insomnia, and/or distress developing in their patients and caregivers. Postdischarge outpatient care currently includes continued secondary prevention measures. Although hoping a COVID-19 stroke patient can be considered cured of the virus, those concerned for contact safety can take comfort in the increasing use of telemedicine, which is itself a growing source of patient-physician contacts. Many online resources are available to patients and physicians. Like prior challenges, stroke care teams will also overcome this one. Key Messages: Evidence-based stroke management should continue to be provided throughout the patient care journey, while strict infection control measures are enforced.

Efficacy of Alteplase in a Mouse Model of Acute Ischemic Stroke: A Retrospective Pooled Analysis.

BACKGROUND AND PURPOSE: The debate over the fact that experimental drugs proposed for the treatment of stroke fail in the translation to the clinical situation has attracted considerable attention in the literature. In this context, we present a retrospective pooled analysis of a large data set from preclinical studies, to examine the effects of early versus late administration of intravenous recombinant tissue-type plasminogen activator. METHODS: We collected data from 26 individual studies from 9 international centers (13 researchers; 716 animals) that compared recombinant tissue-type plasminogen activator with controls, in a unique mouse model of thromboembolic stroke induced by an in situ injection of thrombin into the middle cerebral artery. Studies were classified into early (<3 hours) versus late (≥3 hours) drug administration. Final infarct volumes, assessed by histology or magnetic resonance imaging, were compared in each study, and the absolute differences were pooled in a random-effect meta-analysis. The influence of time of administration was tested. RESULTS: When compared with saline controls, early recombinant tissue-type plasminogen activator administration was associated with a significant benefit (absolute difference, -6.63 mm(3); 95% confidence interval, -9.08 to -4.17; I(2)=76%), whereas late recombinant tissue-type plasminogen activator treatment showed a deleterious effect (+5.06 mm(3); 95% confidence interval, +2.78 to +7.34; I(2)=42%; Pint<0.00001). Results remained unchanged after subgroup analyses. CONCLUSIONS: Our results provide the basis needed for the design of future preclinical studies on recanalization therapies using this model of thromboembolic stroke in mice. The power analysis reveals that a multicenter trial would require 123 animals per group instead of 40 for a single-center trial.

Investigating potentially salvageable penumbra tissue in an in vivo model of transient ischemic stroke using sodium, diffusion, and perfusion magnetic resonance imaging.

BACKGROUND: Diffusion magnetic resonance imaging (MRI) is the current-state-of-the-art technique to clinically investigate acute (0-24 h) ischemic stroke tissue. However, reduced apparent diffusion coefficient (ADC)-considered a marker of tissue damage-was observed to reverse spontaneously during the subacute stroke phase (24-72 h) which means that low ADC cannot be used to reflect the damaged tissue after 24 h in experimental and clinical studies. One reason for the change in ADC is that ADC values drop with cytotoxic edema (acute phase) and rise when vasogenic edema begins (subacute phase). Recently, combined 1H- and 23Na-MRI was proposed as a more accurate approach to improve delineation between reversible (penumbra) and irreversible ischemic injury (core). The aim of this study was to investigate the effects of reperfusion on the ADC and the sodium MRI signal after experimental ischemic stroke in rats in well-defined areas of different viability levels of the cerebral lesion, i.e. core and penumbra as defined via perfusion and histology. Transient middle cerebral artery occlusion was induced in male rats by using the intraluminal filament technique. MRI sodium, perfusion and diffusion measurement was recorded before reperfusion, shortly after reperfusion and 24 h after reperfusion. The animals were reperfused after 90 min of ischemia. RESULTS: Sodium signal in core did not change before reperfusion, increased after reperfusion while sodium signal in penumbra was significantly reduced before reperfusion, but showed no changes after reperfusion compared to control. The ADC was significantly decreased in core tissue at all three time points compared to contralateral side. This decrease recovered above commonly applied viability thresholds in the core after 24 h. CONCLUSIONS: Reduced sodium-MRI signal in conjunction with reduced ADC can serve as a viability marker for penumbra detection and complement hydrogen diffusion- and perfusion-MRI in order to facilitate time-independent assessment of tissue fate and cellular bioenergetics failure in stroke patients.

Thrombolysis in experimental cerebral amyloid angiopathy and the risk of secondary intracerebral hemorrhage.

BACKGROUND AND PURPOSE: Intracerebral hemorrhage (ICH) is the most adverse event of thrombolysis in ischemic stroke. Cerebral amyloid angiopathy increases the risk for spontaneous lobar ICH. Although thrombolysis may be performed in cerebral amyloid angiopathy-affected patients, there is still little knowledge available on the risk for secondary ICH. METHODS: We investigated the effect of recombinant tissue-type plasminogen activator on experimental ischemic stroke in APP23 transgenic mice (n=18) and wild-type littermates (n=15). Focal ischemic stroke was induced in 26-month-old mice by temporal middle cerebral artery occlusion (filament model), followed by treatment with 10 mg/kg recombinant tissue-type plasminogen activator. Twenty-four hours later, a functional score was assessed and the mice were euthanized for histological analysis. ICH was classified as grades 1 to 3 depending on severity. RESULTS: The groups did not differ regarding mortality (P=0.67) and functional deficit (P=0.18). Compared with wild-type mice, the APP23 genotype was associated with a higher appearance for ICH in the infarct area (P=0.05). ICH severity grades 2 and 3 correlated significantly with infarct size (P=0.004 and 0.008, respectively). CONCLUSIONS: The APP23 genotype was not associated with increased mortality or worse functional outcome. Our results suggest an increased risk for ICH in the cerebral amyloid angiopathy-affected brain; however, no ICH was observed outside the ischemic area.

Temporal profile of matrix metalloproteinases and their inhibitors in a human endothelial cell culture model of cerebral ischemia.

BACKGROUND: Matrix metalloproteinases (MMPs) are key players in proteolytic blood-brain barrier (BBB) disruption during ischemic stroke, leading to vascular edema, hemorrhagic transformation and infiltration by leukocytes. Their effect is dampened by the endogenous tissue inhibitors of metalloproteinases (TIMPs). The respective cellular source of specific MMPs and TIMPs during BBB breakdown is still under investigation. METHODS: We analyzed the MMP and TIMP release of human brain microvascular endothelial cells (BMECs) under oxygen glucose deprivation (OGD). Cultured human BMECs (the hCMEC/D3 cell line) were subjected to OGD (6, 12, 18 and 24 h). Gene expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 were serially measured by quantitative real time-PCR and compared to ELISA-detected cell culture medium levels. RESULTS: OGD induced a significant and long-lasting increase in MMP-2 gene expression, reaching a plateau after 12 h. Medium protein levels of MMP-2 were correspondingly elevated at 12 h of OGD. The MMP-9 synthesis rate was detectable at very low levels and remained unaffected by OGD. TIMP-1 gene expression and secretion declined under OGD, whereas both expression and secretion of TIMP-2 remained stable. Contrary to the respective gene expression rate, medium levels of MMP-2, TIMP-1 and TIMP-2 started a simultaneous decline after 12 h of OGD. This is most likely due to an impaired synthesis and enhanced consumption rate under OGD. CONCLUSIONS: The objective of our study was to determine the contribution of human BMECs to the MMP metabolism under in vitro OGD conditions simulating ischemic stroke. Our results suggest that human BMECs switch to a proinflammatory state by means of an enhanced production of MMP-2, attenuated release of TIMP-1, and unaffected production of TIMP-2. Thus, human BMECs might participate in the MMP-mediated BBB breakdown during ischemic stroke. However, our data does not support human BMECs to be a source of MMP-9.

Chemical shift sodium imaging in a mouse model of thromboembolic stroke at 9.4 T.

PURPOSE: To estimate changes in the (23)Na density and in the (23)Na relaxation time T(2) * in the anatomically small murine brain after stroke. MATERIALS AND METHODS: Three-dimensional acquisition weighted chemical shift imaging at a resolution of 0.6 × 0.6 × 1.2 mm(3) was used for sodium imaging and relaxation parameter mapping. In vivo measurements of the mouse brain (n = 4) were performed 24 hours after stroke, induced by microinjection of purified murine thrombin into the right middle cerebral artery. The measurement time was 14 minutes in one mouse and 65 minutes in the other three. An exponential fit estimation of the free induction decay was calculated for each voxel enabling the reconstruction of locally resolved relaxation parameter maps. RESULTS: The infarcted areas showed an increase in sodium density between 160% and 250%, while the T(2) * relaxation time increased by 5%-72% compared to unaffected contralateral brain tissue. CONCLUSION: (23)Na chemical shift imaging at a resolution of 0.6 × 0.6 × 1.2 mm(3) enabled sodium imaging of the anatomical small mouse brain and the acquired data allowed calculating relaxation parameter maps and hence a more exact evaluation of sodium signal changes after stroke.

Elucidating the mechanisms behind sonoporation with adeno-associated virus-loaded microbubbles.

Microbubbles are Food and Drug Administration (FDA) approved contrast agents for ultrasound imaging. It has been reported that applying ultrasound on drug-loaded microbubbles facilitates drug uptake by cells, due to so-named sonoporation. However, the biophysics behind sonoporation are not fully understood. It is believed that sonoporation results in a "direct" delivery of drugs in the cytoplasm of cells, though it has been suggested as well that sonoporation facilitates endocytosis which would improve the internalization of drugs by cells. To get a better understanding of sonoporation, this study reports on the ultrasound assisted delivery of adeno-associated virus (AAV) loaded on the surface of microbubbles. AAVs rely on endocytosis for efficient transduction of cells and are, consequently, an elegant tool to evaluate whether endocytosis is involved in ultrasound-induced sonoporation. Applying ultrasound on AAV-loaded microbubbles clearly improved the internalization of AAVs by cells, though transduction of the cells did not occur, indicating that by sonoporation substances become directly delivered in the cytosol of cells.

Ultrasound contrast agents in ischemic stroke.

The general indication for the use of ultrasound contrast agents in neurosonologic applications is an insufficient signal-to-noise ratio when investigating the cerebral macro- and microcirculation. Clinical problems that are often encountered in native sonography are 'no flow, slow flow and low flow' phenomena. In these cases, ultrasound contrast agents are used to differentiate between vessel occlusion and insufficient insonation conditions, as well as for the detection of very slow blood flow velocities and low flow volumes. Echo-contrast agents significantly increase the success rate of transcranial color duplex examinations of patients with acute cerebrovascular disease. Ultrasound contrast imaging also allows assessment of the cerebral microcirculation. There are a number of techniques available for performing perfusion studies. These generally utilize high mechanical index imaging, since until recently lower acoustic outputs were unable to detect microbubbles in the brain. New-generation microbubbles in combination with very sensitive contrast-specific ultrasound techniques now enable real-time visualization of stroke. Moreover, destruction sequences with assessment of microbubble replenishment using real-time, low mechanical index imaging are now available. This article reviews of state-of-the-art contrast-specific imaging techniques for ultrasound evaluation of acute stroke patients.

Microbubbles for thrombolysis of acute ischemic stroke.

Improved treatment of acute ischemic stroke with ultrasound and microbubbles in combination with thrombolytic drugs shows great promise, but the optimal techniques, indications, and contraindications have not yet been well defined. Moreover, details such as microbubble dosage, delivery, required thrombolytic drug dosage, and optimal ultrasound characteristics all remain uncertain. Recent results suggest that ultrasound and microbubbles may be effective in clot lysis of ischemic stroke without additional thrombolytic drugs. Moreover, targeting thrombus with specific immunobubbles may improve the efficacy of sonothrombolysis. Safety remains a major concern in the further development of ultrasound-enhanced thrombolysis and extensive animal work is required to define the most promising methods to translate into human application.

Effects of prophylactic antibiotic therapy with mezlocillin plus sulbactam on the incidence and height of fever after severe acute ischemic stroke: the Mannheim infection in stroke study (MISS).

BACKGROUND AND PURPOSE: Fever after stroke is a strong predictor for a negative outcome with infections as the most common cause. The aim of this pilot study was to evaluate the effects of prophylactic antibiotic therapy on the incidence and height of fever after acute ischemic stroke. METHODS: This is a randomized, controlled study of antibiotic prophylaxis in patients with ischemic stroke enrolled within 24 hours from clinical onset who presented bedridden (modified Rankin score >3) with no significant infection. Interventions included prophylactic mezlocillin plus sulbactam (3 x 2 g/1 g for 4 days) or conventional management. Over 10 days, body temperature was continuously monitored, and the presence of infection was daily assessed. Primary end points were incidence and height of fever; secondary end points included rate of infection and clinical outcome. RESULTS: Sixty patients were included (mean, 75 years; median National Institutes of Health Stroke Scale score, 16). Over the first 3 days, patients in the intervention group showed lower mean body temperatures as well as lower daily peak temperatures (P<0.05). Throughout the observation period, 15 of 30 patients in the intervention group but 27 of 30 patients in the conventionally treated group developed an infection (P<0.05). Mean interval until the diagnosis of infection was 5.1 days in the intervention group and 3.3 days in the control group (P<0.05). Clinical outcome was more favorable in patients with prophylactic therapy (P=0.01). CONCLUSIONS: In patients with acute severe stroke, prophylactic administration of mezlocillin plus sulbactam over 4 days decreases body temperature, lowers the rate of infection, and may be associated with a better clinical outcome.

Assessment of intracranial collateral flow by using dynamic arterial spin labeling MRA and transcranial color-coded duplex ultrasound.

BACKGROUND AND PURPOSE: To evaluate the potential of a new dynamic MRA sequence (DynAngio) based on arterial spin labeling for the assessment of intracranial collateral flow. METHODS: Twelve patients with unilateral internal carotid artery obstruction were investigated. Different patterns of collateral flow were compared between DynAngio, transcranial color-coded duplex ultrasound, and time-of-flight MRA. RESULTS: There was a good agreement between the methods, with sensitivities between 80% and 90%. Small collateral vessels were detected more frequently with DynAngio compared to time-of-flight MRA. CONCLUSIONS: DynAngio provides anatomic and similar to transcranial color-coded duplex ultrasound functional information on collateral flow for the assessment of intracranial hemodynamics.

Ultrasound, microbubbles and the blood-brain barrier.

The blood-brain barrier (BBB) is a specialized system of capillary endothelial cells that protects the brain from harmful substances in the blood stream, while supplying the brain with the required nutrients for proper function. The BBB controls transport through both tight junctions and metabolic barriers and is often a rate-limiting factor in determining permeation of therapeutic drugs into the brain. It is a significant obstacle for delivery of both small molecules and macromolecular agents. Although many drugs could be potentially used to treat brain disease, there has been no method that allows non-invasive-targeted delivery through the BBB. Recently, promising studies indicate that ultrasound can be used to locally deliver a drug or gene to a specific region of interest in the brain. If microbubbles are combined with ultrasound exposure, the effects of ultrasound can be focused upon the vasculature to reduce the acoustic intensity needed to produce BBB opening. Several avenues of transcapillary passage after ultrasound sonication have been identified including transcytosis, passage through endothelial cell cytoplasmic openings, opening of tight junctions and free passage through injured endothelium. This article reviews the topic of transient disruption of the BBB with ultrasound and microbubbles and addresses related safety issues. It also discusses possible roles of the BBB in brain disease and potential interactions with ultrasound and microbubbles in such disease states.

Lipoaspirate-derived adult mesenchymal stem cells improve functional outcome during intracerebral hemorrhage by proliferation of endogenous progenitor cells stem cells in intracerebral hemorrhages.

Stem cell therapy seems promising in reducing deficits after focal cerebral ischemia. As stroke may result from intracerebral hemorrhage (ICH) in up to 20% we investigated whether human processed lipoaspirate mesenchymal stem cells (PLA-MSC) influence the functional outcome, migration behavior and the activation of endogenous progenitor cells. Experimental ICH was induced by stereotactic administration of collagenase in rats randomly assigned to the control or treatment group. The latter received 3 x 10(6) PLA-MSC by intravenous (i.v.) injection 24h after ICH induction. The outcome was continuously monitored using the RotaRod test over a period of 4 weeks. Morphometric analysis of ICH was performed consecutively by magnetic resonance imaging (MRI) studies and immunohistochemical analysis. The RotaRod test revealed a significant 1.5-fold improvement (p<0.005) in functional outcome for the PLA-MSC treated group after 4 weeks compared to controls. Histological and MRI assessment of lesion size showed no difference between the two groups. Although i.v. injected human cells could not be detected in the post mortem brain, evaluation of the number of endogenous progenitor cells revealed a twofold increase in the treated animals compared to controls. Treatment with PLA-MSC improved the functional outcome significantly in an experimental ICH model. This effect was achieved by stimulation of endogenous progenitor cells rather than integration and differentiation of the infused PLA-MSC.

Improved detection of intracerebral hemorrhage with transcranial ultrasound perfusion imaging.

BACKGROUND: Ultrasound perfusion imaging (UPI) is a new approach for the assessment of brain perfusion. In contrast to the increasing experience with this method in patients with ischemic stroke, data on the value of UPI for the diagnosis of intracerebral hemorrhage (ICH) are lacking. METHODS: We investigated 12 consecutive patients with sufficient temporal bone windows and a CT diagnosis of acute supratentorial ICH (basal ganglia n = 9 and lobar n = 3). Native transcranial B-mode ultrasound and UPI studies with echo contrast agents were performed on day 1 and on days 5-7 including volume measurements using the maximum extension on transverse and coronal ultrasound planes. RESULTS: ICH was identified as hyperechogenic mass on B-mode ultrasound in 11/12 patients, but the correlation with CT volume measurements was poor (day 1: r = 0.4, 95% confidence interval, CI: -0.23-0.79; p = 0.1; follow-up: r = 0.58, 95% CI: 0.04-0.86; p = 0.21). Volume measurement was more precise using UPI with a significant correlation on day 1 (r = 0.8, 95% CI: 0.47-0.94; p < 0.001) and during the follow-up (r = 0.94, 95% CI: 0.81-0.98; p < 0.001). Using UPI the typical finding was a focal reduction of contrast agent arrival in the ICH core which led to better delineation of the lesion borders from adjacent tissue. Depiction of lobar ICH was difficult with ultrasound, and lesion sizes tended to be underestimated. CONCLUSIONS: This study supports earlier work demonstrating the usefulness of native transcranial ultrasound for the diagnosis of ICH. UPI further improves diagnostic reliability and allows very precise ICH volume measurements. If confirmed in larger studies, this approach may be useful for bedside monitoring of ICH progression and regression.

Improving outcome after stroke: overcoming the translational roadblock.

Stroke poses a massive burden of disease, yet we have few effective therapies. The paucity of therapeutic options stands contrary to intensive research efforts. The failure of these past investments demands a thorough re-examination of the pathophysiology of ischaemic brain injury. Several critical areas hold the key to overcoming the translational roadblock: (1) vascular occlusion: current recanalization strategies have limited effectiveness and may have serious side effects; (2) complexity of stroke pathobiology: therapy must acknowledge the 'Janus-faced' nature of many stroke targets and must identify endogenous neuroprotective and repair mechanisms; (3) inflammation and brain-immune-system interaction: inflammation contributes to lesion expansion, but is also instrumental in lesion containment and repair; stroke outcome is modulated by the interaction of the injured brain with the immune system; (4) regeneration: the potential of the brain for reorganization, plasticity and repair after injury is much greater than previously thought; (5) confounding factors, long-term outcome and predictive modelling. These 5 areas are linked on all levels and therefore need to be tackled by an integrative approach and innovative therapeutic strategies.

Contrast-enhanced ultrasound perfusion imaging in acute stroke patients.

The field of neurovascular ultrasound is expanding rapidly with exciting new applications. While ultrasound contrast agents were initially used to overcome insufficient transcranial bone windows for identification of the basal cerebral arteries, new-generation microbubbles in combination with very sensitive contrast-specific ultrasound techniques now enable real-time visualization of stroke. This article will provide a review of recent and emerging developments in ultrasound technology and contrast-specific imaging techniques for evaluation of acute stroke patients.

Molecular imaging of human thrombus with novel abciximab immunobubbles and ultrasound.

BACKGROUND AND PURPOSE: Molecular imaging of therapeutic interventions with targeted agents that simultaneously carry drugs or genes for local delivery is appealing. We investigated the ability of a novel microbubble carrier (immunobubble) for abciximab, a glycoprotein IIb/IIIa receptor inhibitor, for ultrasonographic molecular imaging of human clots. METHODS: Human thrombi were incubated with immunobubbles conjugated with abciximab. Control clots were incubated in either saline or with immunobubbles conjugated with nonspecific antibody. We evaluated immunobubble suspensions with variable concentrations of encapsulated gas and measured mean acoustic intensity of the incubated clots. In vivo molecular imaging of human thrombi with abciximab immunobubbles was evaluated in a rat model of carotid artery occlusion. RESULTS: Mean acoustic intensity was significantly higher for abciximab immunobubbles as compared with control immunobubbles under all conditions tested with maximum difference in intensity at a gas volume of 0.2 microL (P=0.0013 for mechanical index 0.05, P=0.0001 for mechanical index 0.7). Binding of abciximab immunobubbles to clots in vitro led to enhanced echogenicity dependent on bubble concentration. In vivo ultrasonic detectability of carotid thrombi was significantly higher for clots targeted with abciximab immunobubbles (P<0.05). Quantification of in vivo contrast enhancement displayed a highly significant increment for abciximab immunobubble-targeted clots compared with nonspecific immunobubble-targeted clots (P<0.0001) and to native clots (P<0.0001). CONCLUSIONS: This study demonstrates the feasibility of using a therapeutic agent for selective targeting in vascular imaging. Abciximab immunobubbles improve visualization of human clots both in vitro and in an in vivo model of acute arterial thrombotic occlusion.