Patterns and predictors of blood-brain barrier permeability derangements in acute ischemic stroke

Intravenous Thrombolysis in Posterior versus Anterior Circulation Stroke: Clinical Outcome Differs Only in Patients with Large Vessel Occlusion

The safety and efficacy of intravenous thrombolysis (IVT) are well established in anterior circulation stroke (ACS) but are much less clear for posterior circulation stroke (PCS). The aim of this study was to evaluate the occurrence of parenchymal hematoma (PH) and 3-month clinical outcomes after IVT in PCS and ACS. In an observational, cohort multicenter study, we analyzed data from ischemic stroke patients treated with IVT prospectively collected in the SITS (Safe Implementation of Treatments in Stroke) registry in the Czech Republic between 2004 and 2018. Out of 10,211 patients, 1166 (11.4%) had PCS, and 9045 (88.6%) ACS. PH was less frequent in PCS versus ACS patients: 3.6 vs. 5.9%, odds ratio (OR) = 0.594 in the whole set, 4.4 vs. 7.8%, OR = 0.543 in those with large vessel occlusion (LVO), and 2.2 vs. 4.7%, OR = 0.463 in those without LVO. At 3 months, PCS patients compared with ACS patients achieved more frequently excellent clinical outcomes (modified Rankin scale [mRS] 0-1: 55.5 vs. 47.6%, OR = 1.371 in the whole set and 49.2 vs. 37.6%, OR = 1.307 in those with LVO), good clinical outcomes (mRS 0-2: 69.9 vs. 62.8%, OR = 1.377 in the whole set and 64.5 vs. 50.5%, OR = 1.279 in those with LVO), and had lower mortality (12.4 vs. 16.6%, OR = 0.716 in the whole set and 18.4 vs. 25.5%, OR = 0.723 in those with LVO) (p < 0.05 in all cases). In PCS versus ACS patients, an extensive analysis showed a lower risk of PH both in patients with and without LVO, more frequent excellent and good clinical outcomes, and lower mortality 3 months after IVT in patients with LVO.

Determinants and Clinical Relevance of Iodine Contrast Extravasation after Endovascular Thrombectomy: A Dual-Energy CT Study

BACKGROUND AND PURPOSE

Iodine contrast extravasation (ICE) is common in patients with acute ischemic stroke (AIS) after endovascular-thrombectomy (EVT). The aim of our study was to evaluate the incidence of ICE assessed by dual-energy CT (DECT), its determinants, and associations with clinical outcome.

MATERIALS AND METHODS

We retrospectively examined imaging parameters and clinical factors from consecutive patients with AIS treated with EVT who had a DECT 24 hours thereafter, identified at a single academic center. Associations between ICE, clinical, imaging, and procedural parameters, as well as clinical outcome were explored by using univariable and multivariable models.

RESULTS

A total of 197 consecutive patients were included (period 2019-2020), of which 53 (27%) demonstrated ICE that was pure ICE in 30/53 (57%) and mixed with intracranial hemorrhage (ICH) in 23/53 (43%). Low initial-ASPECTS, high per-procedural-contrast volume injected, and high admission-glycemia were independently associated with ICE (respectively, OR = 0.43, 95% CI, 0.16-1.13, P = .047; OR = 1.02, 95% CI, 1.00-1.04, P = .003; OR = 8.92, 95% CI, 0.63-125.77, P = .043). ICE was independently associated with ICH (P = .047), but not with poorer clinical outcome (6-month mRS >2, P = .223). Univariate analysis demonstrated that low ADC, higher ischemic volume, ICA occlusion, mass effect, longer procedure duration, combined thrombectomy technique, higher number of device passes, and lower recanalization rate were associated with ICE (respectively, P = .002; <.001; .002; <.001; .002; 0.011; <0.001; 0.015).

CONCLUSIONS

ICE evaluated with DECT is a relatively frequent finding after EVT, present in almost one-third of patients. Lower admission ASPECTS, higher glycemia, and high contrast volume injected per procedure were associated with ICE. We also found an association between ICE and ICH, confirming blood-brain barrier alteration as a major determinant of ICH.

Antithrombotic therapy and bleeding risk in the era of aggressive lipid-lowering: current evidence, clinical implications, and future perspectives

ABSTRACT

The clinical efficacy of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) in reducing major cardiovascular adverse events related to atherosclerotic cardiovascular disease (ASCVD) has been well established in recent large randomized outcome trials. Although the cardiovascular and all-cause mortality benefit of PCSK9i remains inconclusive, current cholesterol management guidelines have been modified toward more aggressive goals for lowering low-density lipoprotein cholesterol (LDL-C). Consequently, the emerging concept of "the lower the better" has become the paradigm of ASCVD prevention. However, there is evidence from observational studies of a U-shaped association between baseline LDL-C levels and all-cause mortality in population-based cohorts. Among East Asian populations, low LDL-C was associated with an increased risk for hemorrhagic stroke in patients not on antithrombotic therapy. Accumulating evidence showed that low LDL-C was associated with an enhanced bleeding risk in patients on dual antiplatelet therapy following percutaneous coronary intervention. Additionally, low LDL-C was associated with a higher risk for incident atrial fibrillation and thereby, a possible increase in the risk for intracranial hemorrhage after initiation of anticoagulation therapy. The mechanism of low-LDL-C-related bleeding risk has not been fully elucidated. This review summarizes recent evidence of low-LDL-C-related bleeding risk in patients on antithrombotic therapy and discusses potential measures for reducing this risk, underscoring the importance of carefully weighing the pros and cons of aggressive LDL-C lowering in patients on antithrombotic therapy.

Pathophysiology of Blood-Brain Barrier Permeability Throughout the Different Stages of Ischemic Stroke and Its Implication on Hemorrhagic Transformation and Recovery

The blood-brain barrier (BBB) is a dynamic interface responsible for maintaining the central nervous system homeostasis. Its unique characteristics allow protecting the brain from unwanted compounds, but its impairment is involved in a vast number of pathological conditions. Disruption of the BBB and increase in its permeability are key in the development of several neurological diseases and have been extensively studied in stroke. Ischemic stroke is the most prevalent type of stroke and is characterized by a myriad of pathological events triggered by an arterial occlusion that can eventually lead to fatal outcomes such as hemorrhagic transformation (HT). BBB permeability seems to follow a multiphasic pattern throughout the different stroke stages that have been associated with distinct biological substrates. In the hyperacute stage, sudden hypoxia damages the BBB, leading to cytotoxic edema and increased permeability; in the acute stage, the neuroinflammatory response aggravates the BBB injury, leading to higher permeability and a consequent risk of HT that can be motivated by reperfusion therapy; in the subacute stage (1-3 weeks), repair mechanisms take place, especially neoangiogenesis. Immature vessels show leaky BBB, but this permeability has been associated with improved clinical recovery. In the chronic stage (>6 weeks), an increase of BBB restoration factors leads the barrier to start decreasing its permeability. Nonetheless, permeability will persist to some degree several weeks after injury. Understanding the mechanisms behind BBB dysregulation and HT pathophysiology could potentially help guide acute stroke care decisions and the development of new therapeutic targets; however, effective translation into clinical practice is still lacking. In this review, we will address the different pathological and physiological repair mechanisms involved in BBB permeability through the different stages of ischemic stroke and their role in the development of HT and stroke recovery.

The Usefulness of Quantitative Analysis of Blood-Brain Barrier Disruption Measured Using Contrast-Enhanced Magnetic Resonance Imaging to Predict Neurological Prognosis in Out-of-Hospital Cardiac Arrest Survivors: A Preliminary Study

We aimed to evaluate neurological outcomes associated with blood-brain barrier (BBB) disruption using contrast-enhanced magnetic resonance imaging (CE-MRI) in out-of-hospital cardiac arrest (OHCA) survivors. This retrospective observational study involved OHCA survivors who had undergone CE-MRI for prognostication. Qualitative and quantitative analyses were performed using the presence of BBB disruption (pBD) and the BBB disruption score (sBD) in CE-MRI scans, respectively. For the sBD, 1 point was assigned for each area of BBB disruption, and 6 points were assigned when an absence of intracranial blood flow due to severe brain oedema was confirmed. The primary outcome was poor neurological outcome at 3 months (defined as cerebral performance categories 3-5). We analysed 46 CE-MRI brain scans (27 patients). Of these, 15 (55.6%) patients had poor neurological outcomes. Poor neurological outcome group patients showed a significantly higher proportion of pBD than those in the good neurological outcome group (22 (88%) vs. 6 (28.6%) patients, respectively, p < 0.001) and a higher sBD (5.0 (4.0-5.0) vs. 0.0 (0.0-1.0) patients, p < 0.001). Poor neurological outcome predictions showed that the sBD had a significantly better prognostic performance (area under the curve (AUC) 0.95, 95% confidence interval (CI) 0.84-0.99) than the pBD (AUC 0.80, 95% CI 0.65-0.90). The sBD cut-off value was >1 point (sensitivity, 96.0%; specificity, 81.0%). The sBD is a highly predictive and sensitive marker of 3-month poor neurological outcome in OHCA survivors. Multicentre prospective studies are required to determine the generalisability of these results.

Comparison of the risk factors of hemorrhagic transformation between large artery atherosclerosis stroke and cardioembolism after intravenous thrombolysis

OBJECTIVE

Hemorrhagic transformation (HT) is a common complication of ischemic stroke after intravenous thrombolytic therapy (IVT), especially in cardioembolism (CE) and large artery atherosclerosis stroke (LAA) patients. Whether there are different risk factors for HT in LAA and CE patients remains unclear. The aim of this study was to explore the differences in risk factors for HT in patients with LAA and CE after IVT.

PATIENTS AND METHODS

A retrospective analysis was conducted on LAA and CE patients who were treated with intravenous tissue plasminogen activator at our hospital from 2015 to 2019. Demographic and clinical information was collected, and HT was evaluated within 72 h after stroke onset. Lipids levels, albumin, uric acid (UA), platelet volume indices, as well as potential predictors of HT were analyzed between patients with and without HT (non-HT group).

RESULTS

A total of 247 patients (168 LAA and 79 CE) were included in the study, out of which 62 (25.1 %) had HT. HT was more prevalent in the CE subgroup (30.3 %) than in the LAA subgroup (22.6 %). Compared with non-HT, patients with HT showed a higher rate of the previous stroke, baseline NIHSS scores, and mean platelet volume (MPV), lower levels of platelet count (PC), triglycerides, total cholesterol, low-density lipoprotein cholesterol (LDL-C), albumin, and UA (P < 0.05). Multivariate logistic regression analysis showed that lower LDL (OR = 0.547, 95 % CI 0.321-0.932, P = 0.027), and higher blood glucose (OR = 1.137, 95 % CI 1.015-1.247, P = 0.026) were independent risk factors for HT in LAA patients, while lower albumin (OR = 0.989, 95 % CI 0.977-1.000, P = 0.048), and lower PC(OR = 0.868, 95 % CI 0.754-0.989, P = 0.047) were independent risk factors for HT in CE patients.

CONCLUSION

Patients with different etiologies may have different risk factors of HT following IVT. Lower LDL-C and higher blood glucose are independent risk factors of LAA, while lower albumin and PC are independent risk factors of CE.

Neurorestoration Approach by Biomaterials in Ischemic Stroke

Ischemic stroke (IS) is the leading cause of disability in the western world, assuming a high socio-economic cost. One of the most used strategies in the last decade has been biomaterials, which have been initially used with a structural support function. They have been perfected, different compounds have been combined, and they have been used together with cell therapy or controlled release chemical compounds. This double function has driven them as potential candidates for the chronic treatment of IS. In fact, the most developed are in different phases of clinical trial. In this review, we will show the ischemic scenario and address the most important criteria to achieve a successful neuroreparation from the point of view of biomaterials. The spontaneous processes that are activated and how to enhance them is one of the keys that contribute to the success of the therapeutic approach. In addition, the different routes of administration and how they affect the design of biomaterials are analyzed. Future perspectives show where this broad scientific field is heading, which advances every day with the help of technology and advanced therapies.

Pattern recognition analysis of dynamic susceptibility contrast (DSC)‐MRI curves automatically segments tissue areas with intact blood–brain barrier in a rat stroke model: A feasibility and comparison study

Background

The manual segmentation of intact blood–brain barrier (BBB) regions in the stroke brain is cumbersome, due to the coexistence of infarction, large blood vessels, ventricles, and intact BBB regions, specifically in areas with weak signal enhancement following contrast agent injection.

Hypothesis

That from dynamic susceptibility contrast (DSC)‐MRI alone, without user intervention, regions of weak BBB damage can be segmented based on the leakage‐related parameter K 2 and the extent of intact BBB regions, needed to estimate K 2 values, determined.

Study Type

Feasibility.

Animal Model

Ten female Sprague–Dawley rats (SD, 200–250g) underwent 1‐hour middle carotid artery occlusion (MCAO) and 1‐day reperfusion. Two SD rats underwent 1‐hour MCAO with 3‐day and 5‐day reperfusion.

Field Strength/Sequence

7T; ADC and T1 maps using diffusion‐weighted echo planar imaging (EPI) and relaxation enhancement (RARE) with variable repetition time (TR), respectively. dynamic contrast‐enhanced (DCE)‐MRI using FLASH. DSC‐MRI using gradient‐echo EPI.

Assessment

Constrained nonnegative matrix factorization (cNMF) was applied to the dynamic ‐curves of DSC‐MRI (<4 min) in a BBB‐disrupted rat model. Areas of voxels with intact BBB, classified by automated cNMF analyses, were then used in estimating K 1 and K 2 values, and compared with corresponding values from manually‐derived areas.

Statistical Tests

Mean ± standard deviation of ΔT1‐differences between ischemic and healthy areas were displayed with unpaired Student's t‐tests. Scatterplots were displayed with slopes and intercepts and Pearson's r values were evaluated between K 2 maps obtained with automatic (cNMF)‐ and manually‐derived regions of interest (ROIs) of the intact BBB region.

Results

Mildly BBB‐damaged areas (indistinguishable from DCE‐MRI (10 min) parameters) were automatically segmented. Areas of voxels with intact BBB, classified by automated cNMF, matched closely the corresponding, manually‐derived areas when respective areas were used in estimating K 2 maps (Pearson's r = 0.97, 12 slices).

Data Conclusion

Automatic segmentation of short DSC‐MRI data alone successfully identified areas with intact and compromised BBB in the stroke brain and compared favorably with manual segmentation.

Level of Evidence: 3

Technical Efficacy: Stage 1

J. Magn. Reson. Imaging 2020;51:1369–1381.

Radiological predictors of hemorrhagic transformation after acute ischemic stroke: An evidence-based analysis

Hemorrhagic transformation (HT) is one of the most common adverse events related to acute ischemic stroke (AIS) that affects the treatment plan and clinical outcome. Identification of a sensitive radiological marker may influence the controversial thrombolytic decision in the setting of AIS and may at a minimum indicate more intensive monitoring or further prophylactic interventions. In this article we summarize possible radiological biomarkers and the role of different radiological modalities including computed tomography (CT), magnetic resonance imaging, angiography, and ultrasound in predicting HT. Different radiological indices of early ischemic changes, large ischemic lesion volume, severe blood flow restriction, blood-brain barrier disruption, poor collaterals and high blood flow velocities have been reported to be associated with higher risk of HT. The current levels of evidence of the available studies highlight the role of the different CT perfusion parameters in predicting HT. Further large standardized studies are recommended to compare the sensitivity and specificity of the different radiological markers combined and delineate the most reliable predictor.

Sex-specific differences in white matter microvascular integrity after ischaemic stroke

Background and purpose

Functional outcomes after ischaemic stroke are worse in women, despite adjusting for differences in comorbidities and treatment approaches. White matter microvascular integrity represents one risk factor for poor long-term functional outcomes after ischaemic stroke. The aim of the study is to characterise sex-specific differences in microvascular integrity in individuals with acute ischaemic stroke.

Methods

A retrospective analysis of subjects with acute ischaemic stroke and brain MRI with diffusion-weighted (DWI) and dynamic-susceptibility contrast-enhanced (DSC) perfusion-weighted imaging obtained within 9 hours of last known well was performed. In the hemisphere contralateral to the acute infarct, normal-appearing white matter (NAWM) microvascular integrity was measured using the K₂ coefficient and apparent diffusion coefficient (ADC) values. Regression analyses for predictors of K₂ coefficient, DWI volume and good outcome (90-day modified Rankin scale (mRS) score <2) were performed.

Results

105 men and 79 women met inclusion criteria for analysis. Despite no difference in age, women had increased NAWM K₂ coefficient (1027.4 vs 692.7×10^–6/s; p=0.006). In women, atrial fibrillation (β=583.6; p=0.04) and increasing NAWM ADC (β=4.4; p=0.02) were associated with increased NAWM K₂ coefficient. In multivariable regression analysis, the K₂ coefficient was an independent predictor of DWI volume in women (β=0.007; p=0.01) but not men.

Conclusions

In women with acute ischaemic stroke, increased NAWM K₂ coefficient is associated with increased infarct volume and chronic white matter structural integrity. Prospective studies investigating sex-specific differences in white matter microvascular integrity are needed.

Contrast Staining may be Associated with Intracerebral Hemorrhage but Not Functional Outcome in Acute Ischemic Stroke Patients Treated with Endovascular Thrombectomy

To evaluate the incidence of post-interventional contrast staining (PICS) in acute ischemic stroke (AIS) Chinese patients who were treated with endovascular thrombectomy (ET) and investigate potential association of PICS with functional outcome and intracerebral hemorrhage (ICH). This observational study was based on a single-center prospective registry study. AIS patients who underwent ET from January 2013 to February 2017 were recruited into this study. All patients had dual-energy CT (DECT) scan of the head at 12 to 24 hours post-ET. The primary outcome was the incidence of PICS. Secondary outcomes were total ICH, symptomatic ICH (sICH), 3-month functional outcome, and long-term functional outcome. One hundred and eighty patients were enrolled in this study. PICS was detected in 50 patients (28%) based on the post-interventional CT scan. We first used basic statistical analyses, showing that the incidence of both total ICH (60% vs. 25%, p<0.001) and sICH (18% vs. 8%, p=0.044) were higher in patients with PICS than those without, and fewer patients achieved no disability (mRS≤1) in the PICS group compared to the control group at both 3-month and long-term follow-up (p<0.01 each). However, multivariate regression analysis further revealed that PICS only increased total (adjusted odds ratio, 7.38; 95% confidence interval 1.66 to 32.9; p=0.009) but not sICH risk. Furthermore, the logistic regression analyses did not show statistical difference in good clinical outcomes or mortality between the two groups. PICS is a common phenomenon in Chinese AIS patients. It is associated with total ICH after ET, but it seems to have no effect on functional outcome and sICH. Further large-scale studies are warranted to validate these results.

Impact of basal ganglia damage after successful endovascular recanalization for acute ischemic stroke involving lenticulostriate arteries

OBJECTIVE

Regional ischemic vulnerability of the brain reportedly differs between the cortex and basal ganglia and has been poorly assessed in the setting of endovascular mechanical thrombectomy. This study was conducted to determine the fate of an ischemic basal ganglia and its contribution to the clinical outcome after successful endovascular recanalization for acute ischemic stroke with large vessel occlusion involving the lenticulostriate arteries.

METHODS

Clinical and radiological findings were retrospectively analyzed in consecutive patients with acute ischemic stroke characterized by large vessel occlusion involving the lenticulostriate arteries. Mechanical thrombectomy was performed in all patients using a stent retriever. The fate of ischemic basal ganglia based on location (lentiform nucleus, caudate nucleus, and internal capsule) and insular cortex was assessed according to the Alberta Stroke Programme Early CT Score (ASPECTS).

RESULTS

Of 170 patients with large intracranial vessel occlusion who achieved successful endovascular recanalization, defined as a thrombolysis in cerebral infarction grade of ≥ 2B, involvement of the lenticulostriate arteries was seen in 55 patients (internal carotid artery, n = 35; proximal middle cerebral artery, n = 20). Preoperative infarction was detected in the lentiform nucleus (66.7%), internal capsule (11.1%), and caudate nucleus (33.3%), all of which showed secondary advancement despite successful recanalization (85.4%, 27.3%, and 54.5%, respectively; p < 0.05). Lenticulostriate arteries with a lateral proximal and/or medial proximal origin significantly affected the development of mature infarction in the lentiform nucleus. Postoperative hemorrhagic transformation was detected in 25 of 55 patients, mostly in the lentiform nucleus. Involvement of insular ribbon infarction was significantly high in patients with hemorrhagic transformation in the basal ganglia. Age, initial National Institutes of Health Stroke Scale (NIHSS) score, initial ASPECTS, postoperative ASPECTS, postoperative infarction in the insular ribbon, and lesions in the middle cerebral artery area (M1-M6) were significantly different between patients with good and poor modified Rankin Scale scores. Interestingly, no differences were detected in postoperative infarction or hemorrhagic transformation in the basal ganglia. Multivariate analysis showed that only age (p = 0.02, OR 0.88) and the initial NIHSS score (p = 0.01, OR 0.86) independently affected favorable clinical outcomes.

CONCLUSIONS

The basal ganglia are vulnerable and readily develop secondary infarction and hemorrhagic transformation despite successful recanalization. However, this does not have a significant impact on the clinical outcome of acute ischemic stroke with large vessel occlusion involving the lenticulostriate arteries.

Influences of blood lipids on the occurrence and prognosis of hemorrhagic transformation after acute cerebral infarction: a case-control study of 732 patients

BACKGROUND

To study the influence of blood lipid levels on hemorrhagic transformation (HT) and prognosis after acute cerebral infarction (ACI).

METHODS

Patients with ACI within 72 h of symptoms onset between January 1st, 2015, and December 31st, 2016, were retrospectively analyzed. Patients were divided into group A (without HT) and group B (HT). The outcomes were assessed after 3 months of disease onset using the modified Rankin Scale (mRS). An mRS score of 0-2 points indicated excellent prognosis, and an mRS score of 3-6 points indicated poor prognosis.

RESULTS

A total of 732 patients conformed to the inclusion criteria, including 628 in group A and 104 in group B. The incidence of HT was 14.2%, and the median onset time was 2 d (interquartile range, 1-7 d). The percentages of patients with large infarct size and cortex involvement in group B were 80.8 and 79.8%, respectively, which were both significantly higher than those in group A (28.7 and 33.4%, respectively). The incidence rate of atrial fibrillation (AF) in group B was significantly higher than that in group A (39.4% vs. 13.9%, P < 0.001). The adjusted multivariate analysis results showed that large infarct size, cortex involvement and AF were independent risk factors of HT, while total cholesterol (TC) was a protective factor of HT (OR = 0.359, 95% CI 0.136-0.944, P = 0.038). With every 1 mmol/L reduction in normal TC levels, the risk of HT increased by 64.1%. The mortality and morbidity at 3 months in group B (21.2 and 76.7%, respectively) were both significantly higher than those in group A (8.0 and 42.8%, respectively). The adjusted multivariate analysis results showed that large infarct size (OR = 12.178, 95% CI 5.390-27.516, P < 0.001) was an independent risk factor of long-term unfavorable outcomes, whereas low-density lipoprotein cholesterol (LDL-C) was a protective factor (OR = 0.538, 95% CI 0.300-0.964, P = 0.037). With every 1 mmol/L reduction in normal LDL-C levels, the risk of an unfavorable outcome increased by 46.2%. Major therapies, including intravenous recombinant human tissue plasminogen activator (rTPA), intensive lipid-lowering statins and anti-platelets, were not significantly related to either HT or long-term, post-ACI poor prognosis.

CONCLUSION

For patients with large infarct sizes, especially those with cortex involvement, AF, or lower levels of TC, the risk of HT might increase after ACI. The risk of a long-term unfavorable outcome in these patients might increase with a reduction in LDL-C.

Increased blood-brain barrier permeability in contralateral hemisphere predicts worse outcome in acute ischemic stroke after reperfusion therapy

AIMS

We sought to investigate the risk factors of blood-brain barrier (BBB) disruption, and its potential impact on 90-day clinical outcome in acute ischemic stroke (AIS) patients after reperfusion therapy.

METHODS

Consecutive acute anterior circulation AIS patients imaged with computed tomographic perfusion (CTP) before reperfusion therapy were included. Tmax >6 s was used for the volumetric measurement of the hypoperfusion area. BBB permeability (BBBP) was calculated as the average relative permeability-surface area product (rPS) within the hypoperfusion region (rPS_hypo-i) and its contralateral mirror region (rPS_hypo-c) on CTP-derived PS color maps. Modified Rankin Scale (mRS) score was obtained at 90-day post-stroke.

RESULTS

A total of 187 patients were included, among whom the median age was 73 (61-80) years and 76 (40.6%) were women. Median baseline NIHSS score was 12 (7- 16). Ninety-eight (52.4%) patients had mRS score >2. Increased rPS_hypo-i and rPS_hypo-c were both independently associated with males and large infarct volume. The increased rPS_hypo-i was also independently associated with a history of atrial fibrillation and high NIHSS score. Multivariable analysis showed higher rPS_hypo-c was independently associated with higher mRS (OR: 1.064, 95% CI 1.011 to 1.121; P=0.018).

CONCLUSION

BBBP in both the hypoperfusion region and its contralateral mirror region are associated with stroke severity, but only increased BBBP in the contralateral mirror hypoperfusion region relates to worse outcome after reperfusion therapy.

Prediction of Hemorrhagic Transformation Severity in Acute Stroke From Source Perfusion MRI

OBJECTIVE

Hemorrhagic transformation (HT) is the most severe complication of reperfusion therapy in acute ischemic stroke (AIS) patients. Management of AIS patients could benefit from accurate prediction of upcoming HT. While prediction of HT occurrence has recently provided encouraging results, the prediction of the severity and territory of the HT could bring valuable insights that are beyond current methods.

METHODS

This study tackles these issues and aims to predict the spatial occurrence of HT in AIS from perfusion-weighted magnetic resonance imaging (PWI) combined with diffusion weighted imaging. In all, 165 patients were included in this study and analyzed retrospectively from a cohort of AIS patients treated with reperfusion therapy in a single stroke center.

RESULTS

Machine learning models are compared within our framework; support vector machines, linear regression, decision trees, neural networks, and kernel spectral regression were applied to the dataset. Kernel spectral regression performed best with an accuracy of $\text{83.7} \pm \text{2.6}\%$.

CONCLUSION

The key contribution of our framework formalize HT prediction as a machine learning problem. Specifically, the model learns to extract imaging markers of HT directly from source PWI images rather than from pre-established metrics.

SIGNIFICANCE

Predictions visualized in terms of spatial likelihood of HT in various territories of the brain were evaluated against follow-up gradient recalled echo and provide novel insights for neurointerventionalists prior to endovascular therapy.

The role of neuroimaging in elucidating the pathophysiology of cerebral ischemia

Neuroimaging provides detailed information regarding the hemodynamic, metabolic and cellular parameters of cerebral ischemia (CI). Although providing just a snapshot in time, it assists in delineating the boundaries and extent of this continually evolving process, from the irreversibly damaged infarct core to the penumbral tissue, where salvage via reperfusion has been the focus of acute stroke therapies. Beyond the extent of the ischemic lesion, neuroimaging elucidates the topography and underlying mechanism of CI. Finally, based on the pathophysiological information, neuroimaging assists in the selection of optimal therapeutic strategies, from hyperacute to chronic phases of CI. Here we review different neuroimaging techniques by which the pathophysiology of cerebral ischemia can be delineated. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Multiparametric Magnetic Resonance Imaging for Prediction of Parenchymal Hemorrhage in Acute Ischemic Stroke After Reperfusion Therapy

Background and Purpose—

Patients with acute ischemic stroke are at increased risk of developing parenchymal hemorrhage (PH), particularly in the setting of reperfusion therapies. We have developed a predictive model to examine the risk of PH using combined magnetic resonance perfusion and diffusion parameters, including cerebral blood volume (CBV), apparent diffusion coefficient, and microvascular permeability (K2).

Methods—

Voxel-based values of CBV, K2, and apparent diffusion coefficient from the ischemic core were obtained using pretreatment magnetic resonance imaging data from patients enrolled in the MR RESCUE clinical trial (Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy). The associations between PH and extreme values of imaging parameters were assessed in univariate and multivariate analyses. Receiver-operating characteristic curve analysis was performed to determine the optimal parameter(s) and threshold for predicting PH.

Results—

In 83 patients included in this analysis, 20 developed PH. Univariate analysis showed significantly lower 10th percentile CBV and 10th percentile apparent diffusion coefficient values and significantly higher 90th percentile K2 values within the infarction core of patients with PH. Using classification tree analysis, the 10th percentile CBV at threshold of 0.47 and 90th percentile K2 at threshold of 0.28 resulted in overall predictive accuracy of 88.7%, sensitivity of 90.0%, and specificity of 87.3%, which was superior to any individual or combination of other classifiers.

Conclusions—

Our results suggest that combined 10th percentile CBV and 90th percentile K2 is an independent predictor of PH in patients with acute ischemic stroke with diagnostic accuracy superior to individual classifiers alone. This approach may allow risk stratification for patients undergoing reperfusion therapies.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov. Unique identifier: NCT00389467.

Prediction of Blood–Brain Barrier Disruption and Intracerebral Hemorrhagic Infarction Using Arterial Spin-Labeling Magnetic Resonance Imaging

Background and Purpose—

Arterial spin-labeling magnetic resonance imaging is sensitive for detecting hyperemic lesions (HLs) in patients with acute ischemic stroke. We evaluated whether HLs could predict blood–brain barrier (BBB) disruption and hemorrhagic transformation (HT) in acute ischemic stroke patients.

Methods—

In a retrospective study, arterial spin-labeling was performed within 6 hours of symptom onset before revascularization treatment in 25 patients with anterior circulation large vessel occlusion on baseline magnetic resonance angiography. All patients underwent angiographic procedures intended for endovascular therapy and a noncontrast computed tomography scan immediately after treatment. BBB disruption was defined as a hyperdense lesion present on the posttreatment computed tomography scan. A subacute magnetic resonance imaging or computed tomography scan was performed during the subacute phase to assess HTs. The relationship between HLs and BBB disruption and HT was examined using the Alberta Stroke Program Early Computed Tomography Score locations in the symptomatic hemispheres.

Results—

A HL was defined as a region where CBF relative ≥1.4 (CBF relative =CBF HL /CBF contralateral ). HLs, BBB disruption, and HT were found in 9, 15, and 15 patients, respectively. Compared with the patients without HLs, the patients with HLs had a higher incidence of both BBB disruption (100% versus 37.5%; P =0.003) and HT (100% versus 37.5%; P =0.003). Based on the Alberta Stroke Program Early Computed Tomography Score locations, 21 regions of interests displayed HLs. Compared with the regions of interests without HLs, the regions of interests with HLs had a higher incidence of both BBB disruption (42.8% versus 3.9%; P <0.001) and HT (85.7% versus 7.8%; P <0.001).

Conclusions—

HLs detected on pretreatment arterial spin-labeling maps may enable the prediction and localization of subsequent BBB disruption and HT.

Brain hemorrhage after endovascular reperfusion therapy of ischemic stroke: a threshold-finding whole-brain perfusion CT study

Endovascular reperfusion therapy is increasingly used for acute ischemic stroke treatment. The occurrence of parenchymal hemorrhage is clinically relevant and increases with reperfusion therapies. Herein we aimed to examine the optimal perfusion CT-derived parameters and the impact of the duration of brain ischemia for the prediction of parenchymal hemorrhage after endovascular therapy. A cohort of 146 consecutive patients with anterior circulation occlusions and treated with endovascular reperfusion therapy was analyzed. Recanalization was assessed at the end of reperfusion treatment, and the rate of parenchymal hemorrhage at follow-up neuroimaging. In regression analyses, cerebral blood volume and cerebral blood flow performed better than Delay Time maps for the prediction of parenchymal hemorrhage. The most informative thresholds (receiver operating curves) for relative cerebral blood volume and relative cerebral blood flow were values lower than 2.5% of normal brain. In binary regression analyses, the volume of regions with reduced relative cerebral blood volume and/or relative cerebral blood flow was significantly associated with an increased risk of parenchymal hemorrhage, as well as delayed vessel recanalization. These results highlight the relevance of the severity and duration of ischemia as drivers of blood-brain barrier disruption in acute ischemic stroke and support the role of perfusion CT for the prediction of parenchymal hemorrhage.

Neurocritical Care of Emergent Large-Vessel Occlusion: The Era of a New Standard of Care

Acute ischemic stroke continues to be one of the leading causes of morbidity and mortality worldwide. Recent advances in mechanical thrombectomy techniques combined with prereperfusion computed tomographic angiography for patient selection have revolutionized stroke care in the past year. Peri- and postinterventional neurocritical care of the patient who has had an emergent large-vessel occlusion is likely an equally important contributor to the outcome but has been relatively neglected. Critical periprocedural management issues include streamlining care to speed intervention, blood pressure optimization, reversal of anticoagulation, management of agitation, and selection of anesthetic technique (ie, general vs monitored anesthesia care). Postprocedural critical care issues that might modulate neurological outcome include blood pressure and glucose optimization, avoidance of fever or hyperoxia, fluid and nutritional management, and early integration of rehabilitation into the intensive care unit setting. In this review, we sought to lay down an evidence-based strategy for patients with acute ischemic stroke undergoing emergent endovascular reperfusion.

Intravenous thrombolysis is more safe and effective for posterior circulation stroke: Data from the Thrombolysis Implementation and Monitor of Acute Ischemic Stroke in China (TIMS-China)

We aimed to compare the safety and efficacy of intravenous thrombolysis (IVT) with alteplase for anterior circulation stroke (ACS) and posterior circulation stroke (PCS). From a large multicenter prospective registry-the Thrombolysis Implementation and Monitor of Acute Ischemic Stroke in China database-all patients who received IVT within 4.5 hours after stroke onset was reviewed. According to the clinical presentations and imaging findings, the eligible patients were divided into ACS and PCS groups. The safety and efficacy outcome measures included post-IVT symptomatic intracranial hemorrhage (sICH), parenchymal hematoma, and all intracranial hemorrhage (aICH) within 7 days, mortality within 90 days, excellent recovery (modified Rankin Scale 0-1), and functional independence (modified Rankin Scale 0-2) at 90 days. For comparing the outcomes between both groups, the odds ratios (ORs) with 95% confidence intervals (CIs) and the adjusted ORs with 95% CIs were analyzed by univariate and multivariate logistic regression models. Of 953 patients enrolled, 829 patients had ACS and 124 had PCS. The patients with PCS had less often atrial fibrillation (11.3% vs 19.8%; P = 0.02), higher blood glucose level (8.31 vs 7.63 mmol/L; P = 0.02), and more white blood cell counts (8.79 vs 7.75 × 10/L; P = 0.001) than those with ACS. After adjustment for the potential confounders, multivariate logistic analysis showed that PCS patients had not only lower rates of sICH (3.2% vs 7.7%; OR 0.28, 95% CI 0.09-0.90), parenchymal hematoma (1.6% vs 9.2%; OR 0.13, 95% CI 0.03-0.57), and aICH (8.1% vs 20.4%; OR 0.26, 95% CI 0.12-0.54), but also higher proportions of excellent recovery (55.7% vs 41.6%; OR 2.27, 95% CI 1.42-3.61) and functional independence (63.9% vs 53.0%; OR 2.33, 95% CI 1.40-3.89) compared with ACS patients. However, there was no significant difference in the occurrence of mortality (OR 0.86, 95% CI 0.39-1.91) between both groups in the multivariate model, although more PCS patients seemed to die within 90 days than did ACS patients (15.6% vs 10.1%; OR 1.64, 95% CI 0.96-2.82) in the univariate analysis. Our study suggests that IVT with alteplase is more safe and effective for PCS.

Acute Cardioembolic and Thrombotic Middle Cerebral Artery Occlusions Have Different Morphological Susceptibility Signs on T2 (∗) -Weighted Magnetic Resonance Images

Presence of susceptibility sign on middle cerebral artery (MCA) in T2 (∗) -weighted magnetic resonance (MR) images has been reported to detect acute MCA thromboembolic occlusion. However, the pathophysiologic course of thrombotic MCA occlusion differs from embolic occlusion, which might induce different imaging characters. Our study found that the occurrence rate of the MCA susceptibility sign in cardioembolism (CE) patients was significantly higher than in large artery atherosclerosis (LAA) patients, and the diameter of the MCA susceptibility sign for CE was greater than for LAA. Moreover, the patients with hemorrhagic transformation had MCA susceptibility signs with a significant larger mean diameter than patients without hemorrhagic transformation. Therefore, we hypothesized that the morphology of susceptibility signs could be used to differentiate acute cardioembolic and thrombotic MCA occlusions, which helped to select appropriate treatment strategies for different patients.

Detection of Hyperperfusion on Arterial Spin Labeling using Deep Learning

Hyperperfusion detected on arterial spin labeling (ASL) images acquired after acute stroke onset has been shown to correlate with development of subsequent intracerebral hemorrhage. We present in this study a quantitative hyperperfusion detection model that can provide an objective decision support for the interpretation of ASL cerebral blood flow (CBF) maps and rapidly delineate hyperperfusion regions. The detection problem is solved using Deep Learning such that the model relates ASL image patches to the corresponding label (normal or hyperperfused). Our method takes into account the regional intensity values of contralateral hemisphere during the labeling of a pixel. Each input vector is associated to a label corresponding to the presence of hyperperfusion that was manually established by a clinical researcher in Neurology. When compared to the manually established hyperperfusion, the predicted maps reached an accuracy of 97.45 ± 2.49% after crossvalidation. Pattern recognition based on deep learning can provide an accurate and objective measure of hyperperfusion on ASL CBF images and could therefore improve the detection of hemorrhagic transformation in acute stroke patients.

Permeability Parameters Measured with Dynamic Contrast-Enhanced MRI: Correlation with the Extravasation of Evans Blue in a Rat Model of Transient Cerebral Ischemia

OBJECTIVE

The purpose of this study was to correlate permeability parameters measured with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a clinical 3-tesla scanner with extravasation of Evans blue in a rat model with transient cerebral ischemia.

MATERIALS AND METHODS

Sprague-Dawley rats (n = 13) with transient middle cerebral artery occlusion were imaged using a 3-tesla MRI with an 8-channel wrist coil. DCE-MRI was performed 12 hours, 18 hours, and 36 hours after reperfusion. Permeability parameters (K(trans), ve, and vp) from DCE-MRI were calculated. Evans blue was injected after DCE-MRI and extravasation of Evans blue was correlated as a reference with the integrity of the blood-brain barrier. Correlation analysis was performed between permeability parameters and the extravasation of Evans blue.

RESULTS

All permeability parameters (K(trans), ve, and vp) showed a linear correlation with extravasation of Evans blue. Among them, K(trans) showed highest values of both the correlation coefficient and the coefficient of determination (0.687 and 0.473 respectively, p < 0.001).

CONCLUSION

Permeability parameters obtained by DCE-MRI at 3-T are well-correlated with Evans blue extravasation, and K(trans) shows the strongest correlation among the tested parameters.

[Neurovisualisation predictors of malignant cerebral infarction and hemorrhagic transformation]

Neuroimaging plays a central role in the assessment of patients with acute ischemic stroke. Within a few minutes, modern multimodal imaging protocols can provide one with comprehensive information about prognosis, management, and outcome of the disease, and may detect changes in the intracranial structures reflecting severity of the ischemic injury depicted by four Ps: parenchyma (of the brain), pipes (i.e., the cerebral blood vessels), penumbra, and permeability (of the blood brain barrier). In this article, we have reviewed neuroradiological predictors of malignant middle cerebral artery infarction and hemorrhagic transformation in light of the aforementioned four Ps.

Thrombin regulation of synaptic transmission and plasticity: implications for health and disease

Thrombin, a serine protease involved in the blood coagulation cascade has been shown to affect neural function following blood-brain barrier breakdown. However, several lines of evidence exist that thrombin is also expressed in the brain under physiological conditions, suggesting an involvement of thrombin in the regulation of normal brain functions. Here, we review ours’ as well as others’ recent work on the role of thrombin in synaptic transmission and plasticity through direct or indirect activation of Protease-Activated Receptor-1 (PAR1). These studies propose a novel role of thrombin in synaptic plasticity, both in physiology as well as in neurological diseases associated with increased brain thrombin/PAR1 levels.

Relation between stroke severity, patient characteristics and CT-perfusion derived blood-brain barrier permeability measurements in acute ischemic stroke

Purpose

Increased blood-brain barrier permeability (BBBP) can result from ischemia. In this study the relation between stroke severity, patient characteristics and admission BBBP values measured with CT-perfusion (CTP) was investigated in acute ischemic stroke patients.

Methods

From prospective data of the Dutch Acute Stroke Study 149 patients with a middle cerebral artery stroke and extended CTP were selected. BBBP values were measured in the penumbra and infarct core as defined by CTP thresholds, and in the contra-lateral hemisphere. The relation between stroke (severity) variables and patient characteristics, including early CT signs, dense vessel sign (DVS), time to scan and National Institute of Health Stroke Score (NIHSS), and BBBP parameters in penumbra and infarct core was quantified with regression analysis.

Results

Early CT signs were related to higher BBBP values in the infarct core (B = 0.710), higher ipsi- to contra-lateral BBBP ratios (B = 0.326) and higher extraction ratios in the infarct core (B = 16.938). Females were found to have lower BBBP values in penumbra and infarct core (B = − 0.446 and − 0.776 respectively) and lower extraction ratios in the infarct core (B = − 10.463). If a DVS was present the ipsi- to contra-lateral BBBP ratios were lower (B = − 0.304). There was no relation between NIHSS or time to scan and BBBP values.

Conclusion

Early CT signs are related to higher BBBP values in the infarct core, suggesting that only severe ischemic damage alters BBBP within the first hours after symptom onset.

Early Blood Brain Barrier Changes in Acute Ischemic Stroke: A Sequential MRI Study

BACKGROUND AND PURPOSE

We sought to identify MRI factors associated with BBB changes at the acute stage of ischemic stroke.

METHODS

We analyzed BBB changes on admission and within 3 hours after the first scan. BBB changes was defined as the presence of leptomeningeal and parenchymal contrast enhancement on T1-weighted imaging. Tmax , CBV, and DWI lesion volume were assessed on baseline MRI. Clinical and MRI factors associated with BBB changes were assessed by univariate and multivariate logistic regressions analyses.

RESULTS

Forty-four patients were included. BBB changes on baseline MRI was observed in 2 of 44 patients (3%). BBB disruption on H3-MRI was present in 19 of 44 patients (43%). Hemodynamic status and baseline ischemic core size were not different between patients with or without BBB changes. BBB alteration on H3 MRI was strongly associated with FLAIR MRI sequence positivity, 16/19 patients (83%) P = .001.

CONCLUSION

BBB changes are exceptional during the first 3 hours after stroke onset. Delayed BBB alteration was associated with FLAIR positivity mainly reflecting vasogenic edema.

Hemicraniectomy for malignant middle cerebral artery infarction: current status and future directions

Malignant middle cerebral artery infarction is a life-threatening sub-type of ischemic stroke that may only be survived at the expense of permanent disability. Decompressive hemicraniectomy is an effective surgical therapy to reduce mortality and improve functional outcome without promoting most severe disability. Evidence derives from three European randomized controlled trials in patients up to 60 years. The recently finished DEcompressive Surgery for the Treatment of malignant INfarction of the middle cerebral arterY - II trial gives now high-level evidence for the effectiveness of decompressive hemicraniectomy in patients older than 60 years. Nevertheless, pressing issues persist that need to be answered in future clinical trials, e.g. the acceptable degree of disability in survivors of malignant middle cerebral artery infarction, the importance of aphasia, and the best timing for decompressive hemicraniectomy. This review provides an overview of the current diagnosis and treatment of malignant middle cerebral artery infarction with a focus on decompressive hemicraniectomy and outlines future perspectives.

Relationship between Chinese medicine pattern types, clinical severity, and prognosis in patients with acute cerebral infarct

We investigated the relationship between Chinese medicine pattern (CMP) types, their severity, and prognosis in patients (n = 187) with acute cerebral infarct (ACI). Six CMPs (wind, phlegm, fire-heat, blood stasis, qi deficiency, and yin deficiency and yang hyperactivity) were evaluated according to inspection, listening and smelling, inquiry, and palpitation. The severity and prognosis of each pattern type was determined according to the Glasgow Coma Scale (GCS), Modified Rankin Scale (MRS), National Institutes of Health Stroke Scale (NIHSS), Barthel Index (BI), and Functional Independence Measure (FIM), recorded at stroke onset and 12 weeks after stroke onset. The phlegm pattern (PP) patients displayed lower GCS, BI, and FIM scales scores, and higher MRS and NIHSS scales scores, than the nonphlegm pattern (N-PP) patients at, and 12 weeks after stroke onset, suggesting the clinical severity is greater and the prognosis is worse in PP patients with ACI than in non-PP patients with ACI.

Oxfordshire Community Stroke Project classification improves prediction of post-thrombolysis symptomatic intracerebral hemorrhage

Background

The Oxfordshire Community Stroke Project (OCSP) classification is a simple stroke classification system with value in predicting clinical outcomes. We investigated whether and how the addition of OCSP classification to the Safe Implementation of Thrombolysis in Stroke (SITS) symptomatic intracerebral hemorrhage (SICH) risk score improved the predictive performance.

Methods

We constructed an extended risk score by adding an OCSP component, which assigns 3 points for total anterior circulation infarcts, 0 point for partial anterior circulation infarcts or lacunar infarcts. Patients with posterior circulation infarcts were assigned an extended risk score of zero. We analyzed prospectively collected data from 4 hospitals to compare the predictive performance between the original and the extended scores, using area under the receiver operating characteristic curve (AUC) and net reclassification improvement (NRI).

Results

In a total of 548 patients, the rates of SICH were 7.3% per the National Institute of Neurological Diseases and Stroke (NINDS) definition, 5.3% per the European-Australasian Cooperative Acute Stroke Study (ECASS) II, and 3.5% per the SITS-Monitoring Study (SITS-MOST). Both scores effectively predicted SICH across all three definitions. The extended score had a higher AUC for SICH per NINDS (0.704 versus 0.624, P = 0.015) and per ECASS II (0.703 versus 0.612, P = 0.016) compared with the SITS SICH risk score. NRI for the extended risk score was 22.3% (P = 0.011) for SICH per NINDS, 21.2% (P = 0.018) per ECASS II, and 24.5% (P = 0.024) per SITS-MOST.

Conclusions

Incorporation of the OCSP classification into the SITS SICH risk score improves risk prediction for post-thrombolysis SICH.

MRI of blood-brain barrier permeability in cerebral ischemia

Quantitative measurement of blood-brain barrier (BBB) permeability using MRI and its application to cerebral ischemia are reviewed. Measurement of BBB permeability using MRI has been employed to evaluate ischemic damage during acute and subacute phases of stroke and to predict hemorrhagic transformation. There is also an emerging interest on the development and use of MRI to monitor vascular structural changes and angiogenesis during stroke recovery. In this review, we describe MRI BBB permeability and susceptibility-weighted MRI measurements and its applications to evaluate ischemic damage during the acute and subacute phases of stroke and vascular remodeling during stroke recovery.

Imaging of cerebral ischemia: from acute stroke to chronic disorders

Cerebral ischemia manifests widely in patient symptoms. Along with the clinical examination, imaging serves as a powerful tool throughout the course of ischemia-from acute onset to evolution. A thorough understanding of imaging modalities, their strengths and their limitations, is essential for capitalizing on the benefit of this complementary source of information for understanding the mechanism of disease, making therapeutic decisions, and monitoring patient response over time.

Predicting symptomatic intracerebral hemorrhage after intravenous thrombolysis: stroke territory as a potential pitfall

BACKGROUND

Stroke vascular territories may influence response to thrombolysis, although supporting data are limited. The aim of the study was to test the hypothesis that the current available prediction scores might inaccurately estimate the risk of symptomatic intracerebral hemorrhage (SICH) after intravenous thrombolysis in patients with posterior circulation stroke.

METHODS

We applied the Safe Implementation of Thrombolysis in Stroke (SITS) SICH risk score to data from four hospital-based stroke registries. Patients were grouped according to anterior or posterior circulation stroke. The main outcome measure was SICH per various definitions. Performance of the risk score was assessed with the c statistic.

RESULTS

Data of 518 thrombolyzed patients (434 anterior, 84 posterior) were studied. The overall rate of SICH varied from 3.5% to 6.9% depending on the SICH definition. Patients with posterior circulation stroke were less likely to have post-thrombolysis SICH per NINDS (P=0.042), per ECASS II (P=0.013), or any ICH (P=0.001), and their rate of SICH was markedly lower than predicted (1.2% versus 7.1% by the NINDS definition; 0% versus 4.8%, ECASS II; 0% versus 1.6%, SITS-MOST). The SITS SICH risk score shows moderate model discrimination across the SICH definitions, with c statistic ranging from 0.64 to 0.70.

CONCLUSIONS

The risk of SICH after intravenous thrombolysis in patients with posterior circulation stroke was low enough to render the SITS SICH risk score or other similar prediction models unnecessary. Awareness of stroke territory might help clinicians judiciously use the risk assessment models.

CLOTBUST-hands free: initial safety testing of a novel operator-independent ultrasound device in stroke-free volunteers

BACKGROUND AND PURPOSE

We aimed to evaluate safety and tolerability of a novel operator-independent ultrasound device among stroke-free volunteers.

METHODS

A headframe containing 18 ultrasound transducers (each operating at 2 MHz, pulsed-wave) was used to expose both temporal windows and the suboccipital window. The transmission characteristics were set to emulate the acoustic characteristics of the exposure levels in the Combined Lysis of Thrombus in Brain Ischemia using Transcranial Ultrasound and Systemic tPA (CLOTBUST) trial and to never exceed Food and Drug Administration mandated diagnostic ultrasound exposure limits. Volunteers underwent 2 hours of insonation with transducer activation one at a time. Safety was captured using serial neurological examinations and pre- and postinsonation MRI for detection of the blood brain barrier permeability.

RESULTS

A total of 15 volunteers (40% men; 49 ± 16 years; 27% black; all pre-exposure National Institutes of Health Stroke Scale scores 0) were enrolled. Five volunteers received pulsed-wave ultrasound via the best pair temporal transducers, 5 via sequential activation of the suboccipital transducers, and 5 via sequential activation of all bilateral temporal and suboccipital transducers. All subjects were safely insonated with no adverse effects as indicated by the neurological examinations during, immediately after the exposure, and at 24 hours, and no abnormality of the blood brain barrier was found on any of the MRIs.

CONCLUSIONS

Our novel device was well tolerated by stroke-free volunteers and did not cause any neurological dysfunction nor did it affect blood brain barrier integrity. The safety and efficacy of the device are now being tested in stroke patients receiving intravenous tissue-type plasminogen activator in phase II-III clinical trials.

Multi-center prediction of hemorrhagic transformation in acute ischemic stroke using permeability imaging features

Permeability images derived from magnetic resonance (MR) perfusion images are sensitive to blood-brain barrier derangement of the brain tissue and have been shown to correlate with subsequent development of hemorrhagic transformation (HT) in acute ischemic stroke. This paper presents a multi-center retrospective study that evaluates the predictive power in terms of HT of six permeability MRI measures including contrast slope (CS), final contrast (FC), maximum peak bolus concentration (MPB), peak bolus area (PB), relative recirculation (rR), and percentage recovery (%R). Dynamic T2*-weighted perfusion MR images were collected from 263 acute ischemic stroke patients from four medical centers. An essential aspect of this study is to exploit a classifier-based framework to automatically identify predictive patterns in the overall intensity distribution of the permeability maps. The model is based on normalized intensity histograms that are used as input features to the predictive model. Linear and nonlinear predictive models are evaluated using a cross-validation to measure generalization power on new patients and a comparative analysis is provided for the different types of parameters. Results demonstrate that perfusion imaging in acute ischemic stroke can predict HT with an average accuracy of more than 85% using a predictive model based on a nonlinear regression model. Results also indicate that the permeability feature based on the percentage of recovery performs significantly better than the other features. This novel model may be used to refine treatment decisions in acute stroke.

Treating seizures and epilepsy with anticoagulants?

Thrombin is a serine protease playing an essential role in the blood coagulation cascade. Recent work, however, has identified a novel role for thrombin-mediated signaling pathways in the central nervous system. Binding of thrombin to protease-activated receptors (PARs) in the brain appears to have multiple actions affecting both health and disease. Specifically, thrombin has been shown to lead to the onset of seizures via PAR-1 activation. In this perspective article, we review the putative mechanisms by which thrombin causes seizures and epilepsy. We propose a potential role of PAR-1 antagonists and novel thrombin inhibitors as new, possible antiepileptic drugs.

Arrival time correction for dynamic susceptibility contrast MR permeability imaging in stroke patients

PURPOSE

To determine if applying an arrival time correction (ATC) to dynamic susceptibility contrast (DSC) based permeability imaging will improve its ability to identify contrast leakage in stroke patients for whom the shape of the measured curve may be very different due to hypoperfusion.

MATERIALS AND METHODS

A technique described in brain tumor patients was adapted to incorporate a correction for delayed contrast delivery due to perfusion deficits. This technique was applied to the MRIs of 9 stroke patients known to have blood-brain barrier (BBB) disruption on T1 post contrast imaging. Regions of BBB damage were compared with normal tissue from the contralateral hemisphere. Receiver operating characteristic (ROC) analysis was performed to compare the detection of BBB damage before and after ATC.

RESULTS

ATC improved the area under the curve (AUC) of the ROC from 0.53 to 0.70. The sensitivity improved from 0.51 to 0.67 and the specificity improved from 0.57 to 0.66. Visual inspection of the ROC curve revealed that the performance of the uncorrected analysis was worse than random guess at some thresholds.

CONCLUSIONS

The ability of DSC permeability imaging to identify contrast enhancing tissue in stroke patients improved considerably when an ATC was applied. Using DSC permeability imaging in stroke patients without an ATC may lead to false identification of BBB disruption.

Recirculation usually precedes malignant edema in middle cerebral artery infarcts

OBJECTIVES

In patients with large middle cerebral artery (MCA) infarcts, maximum brain swelling leading to cerebral herniation and death usually occurs 2-5 days after onset of stroke. The study aimed at exploring the pattern of compounds related to cerebral energy metabolism in infarcted brain tissue.

METHODS

Forty-four patients with malignant MCA infarcts were included after decision to perform decompressive hemicraniectomy (DHC). Cerebral energy metabolism was in all patients monitored bedside by 1-3 microdialysis catheters inserted into the infarcted hemisphere during DHC. In 29 of the patients, one microdialysis catheter was also placed in the non-infarcted hemisphere. MCA blood-flow velocity was monitored bilaterally by transcranial Doppler ultrasound.

RESULTS

The interstitial glucose levels were in both sides within normal limits throughout the monitoring period. Mean lactate/pyruvate (LP) ratio was very high in infarcted tissue immediately after DHC. The ratio slowly decreased but did not reach normal level during the study period. In the infarcted hemisphere, MCA blood-flow velocities increased from approximately 42 cm/s 1 day prior to DHC (nine of nine patients) to approximately 60 cm/s at day 4.

CONCLUSIONS

Normal interstitial glucose level in the infarcted hemisphere in combination with substantial MCA blood-flow velocities bilaterally even before DHC was performed indicates that malignant brain swelling usually commences when the embolus/thrombosis has been largely resolved and recirculation of the infarcted area has started. The protracted increase of the LP ratio in infarcted tissue might indicate mitochondrial dysfunction.