Dynamic perfusion-CT assessment of early changes in blood brain barrier permeability of acute ischaemic stroke patients

Cerebral collaterals are associated with pre-treatment brain-blood barrier permeability in acute ischemic stroke patients

INTRODUCTION

To investigate the relationship between collaterals and blood-brain barrier (BBB) permeability on pre-treatment MRI in a cohort of acute ischemic stroke (AIS) patients treated with thrombectomy.

METHODS

We conducted a retrospective analysis of the HIBISCUS-STROKE cohort, a single-center observational study that enrolled patients treated with thrombectomy from 2016 to 2022. Dynamic-susceptibility MRIs were post-processed to generate K2 maps with arrival-time correction, which were co-registered with apparent diffusion coefficient (ADC) maps. The 90th percentile of K2 was extracted from the infarct core-defined by an ADC ≤ 620 × 10-6 mm2/s with manual adjustments-and expressed as a percentage change compared to the contralateral white matter. Collaterals were assessed using pre-thrombectomy digital subtraction arteriography with an ASITN/SIR score < 3 defining poor collaterals.

RESULTS

Out of 249 enrolled, 101 (40.6%) were included (median age: 72.0 years, 52.5% of males, median NIHSS score at admission: 15.0). Patients with poor collaterals (n = 44) had worse NIHSS scores (median: 16.0 vs 13.0, p = 0.04), larger infarct core volumes (median: 43.7 mL vs 9.5 mL, p < 0.0001), and higher increases in K2 (median: 346.3% vs 152.7%, p = 0.003). They were less likely to achieve successful recanalization (21/44 vs 51/57, p < 0.0001) and experienced more frequent hemorrhagic transformation (16/44 vs 9/57, p = 0.03). On multiple variable analysis, poor collaterals were associated with larger infarct cores (odds ratio (OR) = 1.12, 95% confidence interval (CI): [1.07, 1.17], p < 0.0001) and higher increases in K2 (OR = 6.63, 95% CI: [2.19, 20.08], p = 0.001).

CONCLUSION

Poor collaterals are associated with larger infarct cores and increased BBB permeability at admission MRI.

CLINICAL RELEVANCE STATEMENT

Poor collaterals are associated with a larger infarct core and increased BBB permeability at admission MRI of AIS patients treated with thrombectomy. These findings may have translational interests for extending thrombolytic treatment eligibility and developing neuroprotective strategies.

KEY POINTS

In AIS, collaterals and BBB disruption have been both linked to hemorrhagic transformation. Poor collaterals were associated with larger ischemic cores and increased BBB permeability on pre-treatment MRI. These findings could contribute to hemorrhagic transformation risk stratification, thereby refining clinical decision-making for reperfusion therapies.

Low blood flow ratio is associated with hemorrhagic transformation secondary to mechanical thrombectomy in patients with acute ischemic stroke

BACKGROUND AND PURPOSE

A significant decrease of cerebral blood flow (CBF) is a risk factor for hemorrhagic transformation (HT) in acute ischemic stroke (AIS). This study aimed to ascertain whether the ratio of different CBF thresholds derived from computed tomography perfusion (CTP) is an independent risk factor for HT after mechanical thrombectomy (MT).

METHODS

A retrospective single center cohort study was conducted on patients with AIS undergoing MT at the First Affiliated Hospital of Wenzhou Medical University from August 2018 to December 2023. The perfusion parameters before thrombectomy were obtained according to CTP automatic processing software. The low blood flow ratio (LFR) was defined as the ratio of brain volume with relative CBF <20 % over volume with relative CBF <30 %. HT was evaluated on the follow-up CT images. Binary logistic regression was used to analyze the correlation between parameters that differ between the two groups with regards to HT occurrence. The predictive efficacy was assessed utilizing the receiver operating characteristic curve.

RESULTS

In total, 243 patients met the inclusion criteria. During the follow-up, 46.5 % of the patients (113/243) developed HT. Compared with the Non-HT group, the HT group had a higher LFR (0.47 (0.34-0.65) vs. 0.32 (0.07-0.56); P < 0.001). According to the binary logistic regression analysis, the LFR (aOR: 6.737; 95 % CI: 1.994-22.758; P = 0.002), Hypertension history (aOR: 2.231; 95 % CI: 1.201-4.142; P = 0.011), plasma FIB levels before MT (aOR: 0.641; 95 % CI: 0.456-0.902; P = 0.011), and the mismatch ratio (aOR: 0.990; 95 % CI: 0.980-0.999; P = 0.030) were independently associated with HT secondary to MT. The area under the curve of the regression model for predicting HT was 0.741.

CONCLUSION

LFR, a ratio quantified via CTP, demonstrates potential as an independent risk factor of HT secondary to MT.

Synchronous Superficial Middle Cerebral Vein Outflow Correlates Favorable Tissue Fate After Mechanical Thrombectomy for Acute Ischemic Stroke

RATIONALE AND OBJECTIVES

The purpose of this study was to determine the association between hemispheric synchrony in venous outflow at baseline and tissue fate after mechanical thrombectomy (MT) for acute ischemic stroke (AIS).

MATERIALS AND METHODS

A two-center retrospective analysis involving AIS patients who underwent MT was performed. The four cortical veins of interest include the superficial middle cerebral vein (SMCV), sphenoparietal sinus (SS), vein of Labbé (VOL), and vein of Trolard (VOT). Baseline computed tomography perfusion data were used to compare the following outflow parameters between the hemispheres: first filling time (△FFT), time to peak (△TTP) and total filling time (△TFT). Synchronous venous outflow was defined as △FFT = 0. Multivariable regression analyses were performed to evaluate the association of venous outflow synchrony with penumbral salvage, infarct growth, and intracranial hemorrhage (ICH) after MT.

RESULTS

A total of 151 patients (71.4 ± 13.2 years, 65.6% women) were evaluated. Patients with synchronous SMCV outflow demonstrated significantly greater penumbral salvage (41.3 mL vs. 33.1 mL, P = 0.005) and lower infarct growth (9.0 mL vs. 14.4 mL, P = 0.015) compared to those with delayed SMCV outflow. Higher △FFTSMCV (β = -1.44, P = 0.013) and △TTPSMCV (β = -0.996, P = 0.003) significantly associated with lower penumbral salvage, while higher △FFTSMCV significantly associated with larger infarct growth (β = 1.09, P = 0.005) and increased risk of ICH (odds ratio [OR] = 1.519, P = 0.047).

CONCLUSION

Synchronous SMCV outflow is an independent predictor of favorable tissue outcome and low ICH risk, and thereby carries the potential as an auxiliary radiological marker aiding the treatment planning of AIS patients.

Novel advanced imaging techniques for cerebral oedema

Cerebral oedema following acute ischemic infarction has been correlated with poor functional outcomes and is the driving mechanism of malignant infarction. Measurements of midline shift and qualitative assessment for herniation are currently the main CT indicators for cerebral oedema but have limited sensitivity for small cortical infarcts and are typically a delayed sign. In contrast, diffusion-weighted (DWI) or T2-weighted magnetic resonance imaging (MRI) are highly sensitive but are significantly less accessible. Due to the need for early quantification of cerebral oedema, several novel imaging biomarkers have been proposed. Based on neuroanatomical shift secondary to space-occupying oedema, measures such as relative hemispheric volume and cerebrospinal fluid displacement are correlated with poor outcomes. In contrast, other imaging biometrics, such as net water uptake, T2 relaxometry and blood brain barrier permeability, reflect intrinsic tissue changes from the influx of fluid into the ischemic region. This review aims to discuss quantification of cerebral oedema using current and developing advanced imaging techniques, and their role in predicting clinical outcomes.

Cerebrolysin as an Early Add-on to Reperfusion Therapy: Risk of Hemorrhagic Transformation after Ischemic Stroke (CEREHETIS), a prospective, randomized, multicenter pilot study

BACKGROUND

Cerebrolysin could mitigate reperfusion injury and hemorrhagic transformation (HT) in animal models of acute ischemic stroke.

METHODS

This was a prospective, randomized, open-label, parallel-group with active control, multicenter pilot study. Cerebrolysin (30 mL/day over 14 days) was administered concurrently with alteplase (0.9 mg/kg) in 126 patients, whereas 215 control patients received alteplase alone. The primary outcomes were the rate of any and symptomatic HT assessed from day 0 to 14. The secondary endpoints were drug safety and functional outcome measured with the National Institutes of Health Stroke Scale (NIHSS) on day 1 and 14, and the modified Rankin scale (mRS) on day 90. Advanced brain imaging analysis was applied on day 1 and 14 as a marker for in vivo pharmacology of Cerebrolysin.

RESULTS

Cerebrolysin treatment resulted in a substantial decrease of the symptomatic HT rate with an odds ratio (OR) of 0.248 (95% CI: 0.072-0.851; p = 0.019). No serious adverse events attributed to Cerebrolysin occurred. On day 14, the Cerebrolysin arm showed a significant decrease in the NIHSS score (p = 0.045). However, no difference in the mRS score was observed on day 90. A substantial improvement in the advanced brain imaging parameters of the infarcted area was evident in the Cerebrolysin group on day 14.

CONCLUSIONS

Early add-on of Cerebrolysin to reperfusion therapy was safe and significantly decreased the rate of symptomatic HT as well as early neurological deficit. No effect on day 90 functional outcome was detected. Improvements in the imaging metrics support the neuroprotective and blood-brain barrier stabilizing activity of Cerebrolysin.

TRIAL REGISTRATION

Name of Registry: ISRCTN.

TRIAL REGISTRATION NUMBER

ISRCTN87656744 . Trial Registration Date: 16/02/2021.

Pre-treatment spectral CT combined with CT perfusion can predict hemorrhagic transformation after thrombolysis in patients with acute ischemic stroke

OBJECTIVE

To investigate the value of pre-treatment spectral CT angiography (CTA) in predicting hemorrhagic transformation (HT) after intravenous thrombolysis (IVT) treatment in acute ischemic stroke (AIS) patients.

MATERIALS AND METHODS

AIS patients who underwent IVT with recombinant tissue plasminogen activator and pre-treatment head and neck spectral CTA and head CT perfusion (CTP) from January 2018 to June 2020 were reviewed retrospectively. Finally, 20 patients were included in the HT group and 22 age-matched patients were included in the non-HT group. Spectral and CTP parameters of the region of interest on pre-treatment CTA axial raw images and CTP images, including the infarct core (IC) and ischemic penumbral (IP) regions, were recorded. The differences in clinical variables, CTP, collateral scores and spectral parameters between the two groups were analyzed. Three multivariate logistic regression models were then developed, where model 1 included clinical and spectral parameters, model 2 included clinical and CTP parameters and a combined model included clinical, CTP, and spectral parameters. Receiver operating characteristic analysis was used to evaluate the performance of the multivariate model.

RESULTS

Patients with HT had higher Safe Implementation of Treatments in Stroke (SITS) score (p = 0.023), the volume of perfusion lesions (p = 0.005), the volume of IP (p = 0.003), the mean transit time (MIT) in the IC area (p = 0.012), as well as the TTP in IP area (p = 0.015) compared with patients without HT. The HT group showed significantly lower CBF in the IC area (p = 0.019), iodine concentration (p = 0.017) and the effective atomic number (p = 0.024) in the IP area than non-HT group. And the slope of the spectral curve of the HT group in the IP region was larger than that of the non-HT group (p = 0.023). Gender, age, SITS score, the volume of entire perfusion lesion, CBF and MIT in the IC area, TTP in the IP area, as well as iodine concentration in the IP area were included in the final multivariate model for predicting HT. And CBF in the IC area (OR = 0.779, 95 % CI:0.609-0.996, p = 0.046) as well as the iodine concentration of IP area (OR = 0.343, 95 % CI: 0.131-0.901, p = 0.030) were proved to be independent predictors for HT. The combined model including clinical, spectral, and CTP parameters, showed improved accuracy compared to the other two models, while the Delong test did not suggest a statistically significant difference (both p values > 0.05).

CONCLUSIONS

The iodine concentration of IP area derived from pre-treatment spectral CTA was an independent predictor of HT after IVT treatment for AIS patients. Moreover, multivariate models combined with clinical, spectral, and CTP parameters may be able to predict HT.

Nomogram to predict haemorrhagic transformation after stroke thrombolysis: a combined brain imaging and clinical study

AIM

To construct a novel nomogram by integrating computed tomography perfusion (CTP) and clinical parameters for individualised prediction of haemorrhagic transformation (HT) in intravenous thrombolysis (IVT)-treated acute ischaemic stroke (AIS) patients.

METHODS

Anterior circulation AIS patients who underwent IVT at a single centre from January 2018 to June 2020 were reviewed retrospectively. The CTP parameters of two regions of interest (ROI), the entire perfusion lesion areas, and the infract core areas, were assessed. HT was documented by follow-up CT 24 ± 2 h after IVT. Multivariable logistic regression was conducted by including clinical variables and CTP parameters to identify the independent predictors of HT. A nomogram was developed based on the independent predictors. The discriminative value and calibration of the nomogram were tested by concordance indexes (C-indexes) and calibration plots. Internal validation was performed using fivefold cross-validation.

RESULTS

The nomogram was generated using the complete data from 341 patients. Seven variables were included in the final nomogram, including: the relative cerebral blood volume (rCBV), permeability surface (PS), and relative PS (rPS) in infract core areas, the relative time to maximum (rTmax) and rPS in entire perfusion lesion areas, the National Institutes of Health Stroke Scale (NIHSS), and atrial fibrillation (AF). The C-indexes were 0.815 and 0.817 for the nomogram and internal validation. The calibration plots showed excellent agreement.

CONCLUSION

This is the first study establishing a nomogram based on CTP and clinical parameters to predict HT after stroke thrombolysis.

Stem Cell Repair of the Microvascular Damage in Stroke

Stroke is a life-threatening disease that leads to mortality, with survivors subjected to long-term disability. Microvascular damage is implicated as a key pathological feature, as well as a therapeutic target for stroke. In this review, we present evidence detailing subacute diaschisis in a focal ischemic stroke rat model with a focus on blood–brain barrier (BBB) integrity and related pathogenic processes in contralateral brain areas. Additionally, we discuss BBB competence in chronic diaschisis in a similar rat stroke model, highlighting the pathological changes in contralateral brain areas that indicate progressive morphological brain disturbances overtime after stroke onset. With diaschisis closely approximating stroke onset and progression, it stands as a treatment of interest for stroke. Indeed, the use of stem cell transplantation for the repair of microvascular damage has been investigated, demonstrating that bone marrow stem cells intravenously transplanted into rats 48 h post-stroke survive and integrate into the microvasculature. Ultrastructural analysis of transplanted stroke brains reveals that microvessels display a near-normal morphology of endothelial cells and their mitochondria. Cell-based therapeutics represent a new mechanism in BBB and microvascular repair for stroke.

Permeability-surface area product of the penumbra as a predictor of outcome after endovascular treatment of anterior circulation acute ischemic stroke

Background

Permeability-surface product is a predictor of blood–brain barrier disruption, a condition that may be related to higher likelihoods of hemorrhagic transformations in acute stroke.

Purpose

To investigate whether permeability-surface product can be used as a parameter for predicting outcome after mechanical thrombectomy in patients with anterior circulation acute ischemic stroke.

Material and Methods

We retrospectively identified patients with acute middle cerebral artery stroke who underwent successful mechanical thrombectomy between November 2009 and July 2015. Multiple parameters (including age) and CT perfusion-related parameters (including permeability-surface product) were compared between patients with favorable (modified Rankin Scale [mRS] = 0–2) and unfavorable (mRS > 2) outcome.

Results

Thirty patients were included, 50% having favorable and 50% having unfavorable outcome. Younger age was significantly associated with favorable outcome ( P < 0.03). Other baseline characteristics, such as size of CT perfusion core infarction, perfusion abnormality, and presentation of subcortical infarction were not significantly different between groups. No significant difference was observed between groups for permeability-surface product in the ipsilateral penumbra or for the ratio between permeability-surface product penumbra value and contralateral normal brain (permeability-surface product ratio).

Conclusions

No significant difference was observed between patients with and without favorable outcome after mechanical thrombectomy for either permeability-surface product value or permeability-surface product ratio. Although permeability-surface product is a good predictor of blood–brain barrier disruption, this study revealed no evidence that either permeability-surface product value or permeability-surface product ratio is associated with future change in the penumbra.

Increased microvascular permeability and low level of low-density lipoprotein cholesterol predict symptomatic intracerebral hemorrhage in acute ischemic stroke

Symptomatic intracerebral hemorrhage is a serious potential complication of recombinant tissue-type plasminogen activator thrombolysis in acute ischemic stroke. We investigated the optimal imaging and clinical parameters to predict symptomatic intracerebral hemorrhage in acute ischemic stroke patients after recombinant tissue-type plasminogen activator therapy. We retrospectively reviewed 151 acute ischemic stroke patients with thrombolytic therapy, who were dichotomized into symptomatic intracerebral hemorrhage group and non-symptomatic intracerebral hemorrhage group. They underwent multimodal computed tomography, including the measurement of permeability surface. We compared the clinical and radiological characteristics between symptomatic intracerebral hemorrhage group and non-symptomatic intracerebral hemorrhage group, using univariate analysis. Receiver operating characteristic analysis and multivariate logistic regression analyses were then used to determine symptomatic intracerebral hemorrhage predictors. Of 151 patients, 14 patients (9.27%) developed symptomatic intracerebral hemorrhage on follow-up imaging. Relative permeability surface (infarct permeability surface/contralateral normal permeability surface) (p < 0.05) and baseline low-density lipoprotein cholesterol level (p < 0.05) were both predictors of symptomatic intracerebral hemorrhage. Receiver operating characteristic analysis of relative permeability surface revealed an optimal relative permeability surface threshold of 2.239, with an area under the curve of 0.87 (95% confidence interval, 0.732-1.0). The relative permeability surface was 2.239, the sensitivity for symptomatic intracerebral hemorrhage was 85.7%, the specificity was 94.9%, the positive predictive value was 70.6%, and the negative predictive value was 95.5%. For low-density lipoprotein cholesterol, the optimal threshold was 2.45, with an area under the curve of 0.726 (95% confidence interval, 0.586-0.867), the sensitivity for symptomatic intracerebral hemorrhage was 73.0%, the specificity was 64.3%, the positive predictive value was 67.16%, and the negative predictive value was 79.09%. Our study demonstrated that increased infarct permeability surface and low level of low-density lipoprotein cholesterol can be two predictors of symptomatic intracerebral hemorrhage. Detection of relative permeability surface and low-density lipoprotein cholesterol may help clinicians to identify acute ischemic stroke patients with the higher risk of symptomatic intracerebral hemorrhage; intravenous thrombolytic therapy should be carefully performed for patients with high relative permeability surface and low low-density lipoprotein cholesterol. We may take relative permeability surface and low-density lipoprotein cholesterol into account to refine therapeutic decision-making in acute ischemic stroke.

Would antioxidant-loaded nanoparticles present an effective treatment for ischemic stroke?

Ischemic stroke is a leading cause of death and disability worldwide and is in urgent need of new treatment options. The only approved treatment for stroke restores blood flow to the brain, but much of the tissue damage occurs during the subsequent reperfusion. Antioxidant therapies that directly address ischemia-reperfusion injury have shown promise in preclinical results. In this review, we discuss that reformulating antioxidant therapies as nanomedicine can potentially overcome the barriers that have kept these therapies from succeeding in the clinic. We begin by reviewing the pathophysiology of ischemic stroke with a focus on the effects of reperfusion injury. Next, we review nanotherapeutic systems designed to treat the disease with a focus on those addressing reperfusion injury. Mechanisms of passive and active transport required to traverse a blood–brain barrier are discussed. Finally, we conclude by outlining design parameters for potentially successful nanomedicines as front-line therapeutics for ischemic stroke.

Aging- and vascular-related pathologies

Our aging population is set to grow considerably in the coming decades. In fact, the number of individuals older than 65 years will double by 2050. This projected increase in people living with extended life expectancy represents an inevitable upsurge in the presentation of age-related pathologies. However, our current understanding of the impact of aging on a number of biological processes is unfortunately inadequate. Cardiovascular, cerebrovascular, and neurodegenerative diseases are particularly prevalent in the elderly population. Intriguingly, these pathologies are all associated with vascular dysfunction, suggesting that the process of aging can induce structural and functional impairments in vascular networks. Together with elevated cell senescence, pre-existing comorbidities, and the emerging concept of age-associated inflammatory imbalance, impaired vascular functions can significantly increase one's risk in acquiring age-related diseases. In this short review, we highlight some current clinical and experimental evidence of how biological aging contributes to three vascular-associated pathologies: atherosclerosis, stroke, and Alzheimer's disease.

Severe Blood-Brain Barrier Disruption in Cardioembolic Stroke

Background

Previous studies demonstrated that cardioembolism (CE) was prone to develop hemorrhagic transformation (HT), whereas hyper-permeability of blood–brain barrier (BBB) might be one reason for the development of HT. We, thus, aimed to investigate whether the BBB permeability (BBBP) was higher in CE stroke than other stroke subtypes in acute ischemic stroke (AIS) patients.

Methods

This study was a retrospective review of prospectively collected clinical and imaging database of AIS patients who underwent CT perfusion. Hypoperfusion was defined as Tmax >6 s. The average relative permeability-surface area product (rPS), reflecting the BBBP, was calculated within the hypoperfusion region (rPS_hypo). CE was diagnosed according to the international Trial of Org 10172 in Acute Stroke Treatment criteria. Receiver operating characteristics (ROC) curve analysis was used to determine predictive value of rPS_hypo for CE. Logistic regression was used to identify independent predictors for CE.

Results

A total of 187 patients were included in the final analysis [median age, 73 (61–80) years; 75 (40.1%) females; median baseline National Institutes of Health Stroke Scale score, 12 (7–16)]. Median rPS_hypo was 65.5 (35.8–110.1)%. Ninety-seven (51.9%) patients were diagnosed as CE. ROC analysis revealed that the optimal rPS_hypo threshold for CE was 86.71%. The value of rPS_hypo and the rate of rPS_hypo>86.71% were significantly higher in patients with CE than other stroke subtypes (p < 0.05), after adjusting for the potential confounds.

Conclusion

The extent of BBB disruption is more severe in CE stroke than other stroke subtypes during the hyperacute stage.

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.

Carotid Artery Stenting and Blood-Brain Barrier Permeability in Subjects with Chronic Carotid Artery Stenosis

Failure of the blood-brain barrier (BBB) is a critical event in the development and progression of diseases such as acute ischemic stroke, chronic ischemia or small vessels disease that affect the central nervous system. It is not known whether BBB breakdown in subjects with chronic carotid artery stenosis can be restrained with postoperative recovery of cerebral perfusion. The aim of the study was to assess the short-term effect of internal carotid artery stenting on basic perfusion parameters and permeability surface area-product (PS) in such a population. Forty subjects (23 males) with stenosis of >70% within a single internal carotid artery and neurological symptoms who underwent a carotid artery stenting procedure were investigated. Differences in the following computed tomography perfusion (CTP) parameters were compared before and after surgery: global cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT), time to peak (TTP) and PS. PS acquired by CTP is used to measure the permeability of the BBB to contrast material. In all baseline cases, the CBF and CBV values were low, while MTT and TTP were high on both the ipsi- and contralateral sides compared to reference values. PS was approximately twice the normal value. CBF was higher (+6.14%), while MTT was lower (−9.34%) on the contralateral than on the ipsilateral side. All perfusion parameters improved after stenting on both the ipsilateral (CBF +22.66%; CBV +18.98%; MTT −16.09%, TTP −7.62%) and contralateral (CBF +22.27%, CBV +19.72%, MTT −14.65%, TTP −7.46%) sides. PS decreased by almost half: ipsilateral −48.11%, contralateral −45.19%. The decline in BBB permeability was symmetrical on the ipsi- and contralateral sides to the stenosis. Augmented BBB permeability can be controlled by surgical intervention in humans.

Intravenously Transplanted Human Bone Marrow Endothelial Progenitor Cells Engraft Within Brain Capillaries, Preserve Mitochondrial Morphology, and Display Pinocytotic Activity Toward Blood-Brain Barrier Repair in Ischemic Stroke Rats

Stroke is a life-threatening disease with limited therapeutic options. Cell therapy has emerged as an experimental stroke treatment. Blood-brain barrier (BBB) impairment is a key pathological manifestation of ischemic stroke, and barrier repair is an innovative target for neurorestoration in stroke. Here, we evaluated via electron microscopy the ability of transplanted human bone marrow endothelial progenitor cells (hBMEPCs) to repair the BBB in adult Sprague-Dawley rats subjected to transient middle cerebral artery occlusion (tMCAO). β-galactosidase prelabeled hBMEPCs were intravenously transplanted 48 hours post-tMCAO. Ultrastructural analysis of microvessels in nontransplant stroke rats revealed typical BBB pathology. At 5 days post-transplantation with hBMEPCs, stroke rats displayed widespread vascular repair in bilateral striatum and motor cortex, characterized by robust cell engraftment within capillaries. hBMEPC transplanted stroke rats exhibited near normal morphology of endothelial cells (ECs), pericytes, and astrocytes, without detectable perivascular edema. Near normal morphology of mitochondria was also detected in ECs and perivascular astrocytes from transplanted stroke rats. Equally notable, we observed numerous pinocytic vesicles within engrafted cells. Robust engraftment and intricate functionality of transplanted hBMEPCs likely abrogated stroke-altered vasculature. Preserving mitochondria and augmenting pinocytosis in cell-based therapeutics represent a new neurorestorative mechanism in BBB repair for stroke. Stem Cells 2017;35:1246-1258.

Blood-Spinal Cord Barrier Alterations in Subacute and Chronic Stages of a Rat Model of Focal Cerebral Ischemia

We previously demonstrated blood-brain barrier impairment in remote contralateral brain areas in rats at 7 and 30 days after transient middle cerebral artery occlusion (tMCAO), indicating ischemic diaschisis. Here, we focused on effects of subacute and chronic focal cerebral ischemia on the blood-spinal cord barrier (BSCB). We observed BSCB damage on both sides of the cervical spinal cord in rats at 7 and 30 days post-tMCAO. Major BSCB ultrastructural changes in spinal cord gray and white matter included vacuolated endothelial cells containing autophagosomes, pericyte degeneration with enlarged mitochondria, astrocyte end-feet degeneration and perivascular edema; damaged motor neurons, swollen axons with unraveled myelin in ascending and descending tracts and astrogliosis were also observed. Evans Blue dye extravasation was maximal at 7 days. There was immunofluorescence evidence of reduction of microvascular expression of tight junction occludin, upregulation of Beclin-1 and LC3B immunoreactivities at 7 days and a reduction of the latter at 30 days post-ischemia. These novel pathological alterations on the cervical spinal cord microvasculature in rats after tMCAO suggest pervasive and long-lasting BSCB damage after focal cerebral ischemia, and that spinal cord ischemic diaschisis should be considered in the pathophysiology and therapeutic approaches in patients with ischemic cerebral infarction.

CT Permeability Imaging Predicts Clinical Outcomes in Acute Ischemic Stroke Patients Treated with Intra-arterial Thrombolytic Therapy

In this study, we determined whether a prediction of final infarct volume (FIV) and clinical outcomes in patients with an acute stroke is improved by using a contrast transfer coefficient (K ^trans) as a biomarker for blood-brain barrier (BBB) dysfunction. Here, consecutive patients admitted with signs and symptoms suggesting acute hemispheric stroke were included in this study. Ninety-eight participants with intra-arterial therapy were assessed (46 female). Definition of predicted FIV was performed using conventional perfusion CT (PCT-PIV) parameters alone and in combination with K ^trans (K ^trans-PIV). Multiple logistic regression analyses and linear regression modeling were conducted to determine independent predictors of the 90-day modified Rankin score (mRS) and FIV, respectively. We found that patients with favorable outcomes were younger and had lower National Institutes of Health Stroke Scale (NIHSS) score, smaller PCT-PIV, K ^trans-PIV, and smaller FIV (P < 0.001). K ^trans-PIV showed good correlation with FIV (P < 00.001, R ² = 0.6997). In the regression analyses, K ^trans-PIV was the best predictor of clinical outcomes (P = 0.009, odds ratio (OR) = 1.960) and also the best predictor for FIV (F = 75.590, P < 0.0001). In conclusion, combining PCT and K ^trans maps derived from first-pass PCT can identify at-risk cerebral ischemic tissue more precisely than perfusion parameters alone. This provides improved accuracy in predicting FIV and clinical outcomes.

Diagnosis of acute ischemia using dual energy CT after mechanical thrombectomy

BACKGROUND AND PURPOSE

To assess the performance of dual energy unenhanced CT in the detection of acute ischemia after mechanical thrombectomy.

METHODS

Retrospective study, approved by the local institutional review board, including all patients that underwent intra-arterial thrombectomy in our institution over a period of 2 years. The presence of acute ischemia and hemorrhage was evaluated by three readers. Sensitivity and specificity of the non-contrast CT weighted sum image (NCCT) and the virtual non-contrast reconstructed image (VNC) were estimated and compared using generalized estimating equations to account for the non-independence of regions in each patient.

RESULTS

58 patients (27 women and 31 men; mean age 70.4 years) were included in the study, yielding 580 regions of interest. Sensitivity and specificity in detecting acute ischemia were higher for all readers when using VNC, with a significant increase in sensitivity for two readers (p<0.001 and 0.01) and a significant increase in specificity in one reader (p<0.001). Specificity in detecting hemorrhage was excellent for all readers.

CONCLUSIONS

Dual energy unenhanced CT VNC images were superior in the identification of acute ischemia in comparison with NCCT.

Compromised blood-brain barrier competence in remote brain areas in ischemic stroke rats at the chronic stage

Stroke is a life-threatening disease leading to long-term disability in stroke survivors. Cerebral functional insufficiency in chronic stroke might be due to pathological changes in brain areas remote from the initial ischemic lesion, i.e., diaschisis. Previously, we showed that the damaged blood-brain barrier (BBB) was involved in subacute diaschisis. The present study investigated BBB competence in chronic diaschisis by using a transient middle cerebral artery occlusion (tMCAO) rat model. Our results demonstrated significant BBB damage mostly in the ipsilateral striatum and motor cortex in rats at 30 days after tMCAO. The BBB alterations were also determined in the contralateral hemisphere via ultrastructural and immunohistochemical analyses. Major BBB pathological changes in contralateral remote striatum and motor cortex areas included 1) vacuolated endothelial cells containing large autophagosomes, 2) degenerated pericytes displaying mitochondria with cristae disruption, 3) degenerated astrocytes and perivascular edema, 4) Evans blue extravasation, and 5) appearance of parenchymal astrogliosis. Discrete analyses of striatal and motor cortex areas revealed significantly higher autophagosome accumulation in capillaries of ventral striatum and astrogliosis in dorsal striatum in both cerebral hemispheres. These widespread microvascular alterations in ipsilateral and contralateral brain hemispheres suggest persistent and/or continued BBB damage in chronic ischemia. The pathological changes in remote brain areas likely indicate chronic ischemic diaschisis, which should be considered in the development of treatment strategies for stroke.

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.

Combination approaches to attenuate hemorrhagic transformation after tPA thrombolytic therapy in patients with poststroke hyperglycemia/diabetes

To date, tissue type plasminogen activator (tPA)-based thrombolytic stroke therapy is the only FDA-approved treatment for achieving vascular reperfusion and clinical benefit, but this agent is given to only about 5% of stroke patients in the USA. This may be related, in part, to the elevated risk of symptomatic intracranial hemorrhage, and consequently limited therapeutic time window. Clinical investigations demonstrate that poststroke hyperglycemia is one of the most important risk factors that cause intracerebral hemorrhage and worsen neurological outcomes. There is a knowledge gap in understanding the underlying molecular mechanisms, and lack of effective therapeutics targeting the severe complication. This short review summarizes clinical observations and experimental investigations in preclinical stroke models of the field. The data strongly suggest that interactions of multiple pathogenic factors including hyperglycemia-mediated vascular oxidative stress and inflammation, ischemic insult, and tPA neurovascular toxicity in concert contribute to the BBB damage-intracerebral hemorrhagic transformation process. Development of combination approaches targeting the multiple pathological cascades may help to attenuate the hemorrhagic complication.

Increased blood-brain barrier permeability on perfusion computed tomography predicts hemorrhagic transformation in acute ischemic stroke

BACKGROUND/PURPOSE

Perfusion computed tomography (CT) is capable of measuring the permeability surface product (PS). PS reflects the permeability of the blood-brain barrier, involved in the pathophysiology of hemorrhagic transformation (HT) of ischemic stroke. The aim of our study was to determine if an increased PS can predict HT.

METHODS

A total of 86 patients with ischemic stroke were included. They underwent multimodality CT, including the measurement of PS. We compared the clinical and radiological characteristics of patients who developed HT to those who did not, using univariate analysis. Multivariate regression analyses were then used to determine HT predictors.

RESULTS

HT was observed in 27 patients (31%). Infarct PS was significantly associated with HT (p = 0.047), as were atrial fibrillation (p = 0.03), admission National Institute of Health Stroke Scale score (p = 0.02), infarct volume (p = 0.0004), presence of large-vessel occlusion (p = 0.0005) and a poorer collateral status (p = 0.003). Using logistic regression modeling, an infarct PS >0.84 ml/100 g/min was an independent predictor of HT (OR 28, 95% CI 1.75-452.98; p = 0.02). Other independent predictors of HT were infarct volume and a history of atrial fibrillation.

CONCLUSIONS

Our findings suggest that infarct PS can be a predictor of HT and may help clinicians to improve patient care around thrombolysis decisions in the acute phase of ischemic stroke.

Blood-brain barrier alterations provide evidence of subacute diaschisis in an ischemic stroke rat model

BACKGROUND

Comprehensive stroke studies reveal diaschisis, a loss of function due to pathological deficits in brain areas remote from initial ischemic lesion. However, blood-brain barrier (BBB) competence in subacute diaschisis is uncertain. The present study investigated subacute diaschisis in a focal ischemic stroke rat model. Specific focuses were BBB integrity and related pathogenic processes in contralateral brain areas.

METHODOLOGY/PRINCIPAL FINDINGS

In ipsilateral hemisphere 7 days after transient middle cerebral artery occlusion (tMCAO), significant BBB alterations characterized by large Evans Blue (EB) parenchymal extravasation, autophagosome accumulation, increased reactive astrocytes and activated microglia, demyelinization, and neuronal damage were detected in the striatum, motor and somatosensory cortices. Vascular damage identified by ultrastuctural and immunohistochemical analyses also occurred in the contralateral hemisphere. In contralateral striatum and motor cortex, major ultrastructural BBB changes included: swollen and vacuolated endothelial cells containing numerous autophagosomes, pericyte degeneration, and perivascular edema. Additionally, prominent EB extravasation, increased endothelial autophagosome formation, rampant astrogliosis, activated microglia, widespread neuronal pyknosis and decreased myelin were observed in contralateral striatum, and motor and somatosensory cortices.

CONCLUSIONS/SIGNIFICANCE

These results demonstrate focal ischemic stroke-induced pathological disturbances in ipsilateral, as well as in contralateral brain areas, which were shown to be closely associated with BBB breakdown in remote brain microvessels and endothelial autophagosome accumulation. This microvascular damage in subacute phase likely revealed ischemic diaschisis and should be considered in development of treatment strategies for stroke.

Measurement of blood-brain barrier permeability in acute ischemic stroke using standard first-pass perfusion CT data

Background and purpose

Increased blood–brain barrier permeability is believed to be associated with complications following acute ischemic stroke and with infarct expansion. Measurement of blood–brain barrier permeability requires a delayed image acquisition methodology, which prolongs examination time, increasing the likelihood of movement artefacts and radiation dose. Existing quantitative methods overestimate blood–brain barrier permeability when early phase CT perfusion data are used. The purpose of this study is to develop a method that yields the correct blood–brain barrier permeability value using first-pass perfusion CT data.

Methods

We acquired 43 CT perfusion datasets, comprising experimental (n = 30) and validation subject groups (n = 13). The Gjedde–Patlak method was used to estimate blood–brain barrier permeability using first-pass (30–60 s after contrast administration) and delayed phase (30–200 s) data. In the experimental group, linear regression was used to obtain a function predicting first-pass blood–brain barrier permeability estimates from delayed phase estimates in each stroke compartment. The reliability of prediction with this function was then tested using data from the validation group.

Results

The predicted delayed phase blood–brain barrier permeability was strongly correlated with the measured delayed phase value (r = 0.67 and 0.6 for experimental and validation group respectively; p < 0.01). Predicted and measured delayed phase blood–brain barrier permeability in each stroke compartment were not significantly different in both experimental and validation groups.

Conclusion

We have developed a method of estimating blood–brain barrier permeability using first-pass perfusion CT data. This predictive method allows reliable blood–brain barrier permeability estimation within standard acquisition time, minimizing the likelihood of motion artefacts thereby improving image quality and reducing radiation dose.

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Delayed phase BBBP can be predicted from first-pass perfusion CT data.

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Predicted BBBP was not significantly different from delayed phase measurements.

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Prediction model allows reliable BBBP estimation within the standard acquisition time.

Quantification of blood-to-brain transfer rate in multiple sclerosis

Blood-brain barrier (BBB) disruption visualized in lesions by MRI is a major biomarker of disease activity in multiple sclerosis (MS). However, in MS, destruction occurs to a variable extent in lesions as well as in gray matter (GM) and in the normal appearing white matter (NAWM). A method to quantify the BBB disruption in lesions as well as in non-lesion areas would be useful for assessment of MS progression and treatments. The objective of this study was to quantify the BBB transfer rate (Ki) in WM lesions, in the NAWM, and in the full-brain of MS patients. Thirteen MS patients with active lesions and 10 healthy controls with age and gender matching were recruited for full-brain and WM Ki studies. Dynamic contrast-enhanced MRI (DCEMRI) scans were conducted using T1 mapping with partial inversion recovery (TAPIR), a fast T1 mapping technique, following administration of a quarter-dose of the contrast agent Gadolinium-DTPA (Gd-DTPA). The Patlak modeling technique was used to derive a voxel-based map of Ki. In all patients contrast-enhanced lesions, quantified by Ki maps, were observed. Compared with controls, patients with MS exhibited an increase in mean Ki of the full-brain (P-value<0.05) but no significant difference in mean Ki of NAWM. The identified increase in full-brain Ki of MS patients suggests a global vascular involvement associated with MS disease. The lack of observed significant decrease in Ki in NAWM suggests lower involvement of WM vasculature than full-brain vasculature in MS. Ki maps constructed from time series data acquired by DCEMRI provide additional information about BBB that could be used for evaluation of vascular involvement in MS and monitoring treatment effectiveness.

Admission CT perfusion is an independent predictor of hemorrhagic transformation in acute stroke with similar accuracy to DWI

BACKGROUND

The utility of admission CT perfusion (CTP) to that of diffusion-weighted imaging (DWI) as a predictor of hemorrhagic transformation (HT) in acute stroke was compared.

METHODS

We analyzed the admission CTP and DWI scans of 96 consecutive stroke patients. HT was present in 22 patients (23%). Infarct core was manually segmented on the admission DWI. We determined the: (1) hypoperfused tissue volume in the ischemic hemisphere using a range of thresholds applied to multiple different CTP parameter maps, and (2) mean relative CTP (rCTP) voxel values within both the DWI-segmented lesions and the thresholded CTP parameter maps. Receiver operating characteristic area under curve (AUC) analysis and multivariate regression were used to evaluate the test characteristics of each set of volumes and mean rCTP parameter values as predictors of HT.

RESULTS

The hypoperfused tissue volumes with either relative cerebral blood flow (rCBF) <0.48 (AUC = 0.73), or relative mean transit time (rMTT) >1.3 (AUC = 0.70), had similar accuracy to the DWI-segmented core volume (AUC = 0.68, p = 0.2 and p = 0.1, respectively) as predictors of HT. The mean rMTT voxel values within the rMTT >1.3 segmented lesion (AUC = 0.71) had similar accuracy to the mean rMTT voxel values (AUC = 0.65, p = 0.24) and mean rCBF voxel values (AUC = 0.64, p = 0.22) within the DWI-segmented lesion. The only independent predictors of HT were: (1) mean rMTT with rMTT >1.3, and (2) mechanical thrombectomy.

CONCLUSION

Admission CTP-based hypoperfused tissue volumes and thresholded mean voxel values are markers of HT in acute stroke, with similar accuracy to DWI. This could be of value when MRI cannot be obtained.