Collateral flow as causative of good outcomes in endovascular stroke therapy

Circle of Willis integrity in acute middle cerebral artery occlusion: does the posterior communicating artery matter?

BACKGROUND

Collateral circulation is an important determinant of outcome in people with acute ischemic stroke due to large vessel occlusion (LVO).

OBJECTIVE

To explore the impact of the circle of Willis (CW) anatomical characteristics ipsilateral to the occlusion site, particularly the posterior communicating artery (PComA) and the A1-portion of the anterior cerebral artery (A1-ACA), on stroke outcomes in a cohort of patients with LVO and middle cerebral artery (MCA) occlusion, undergoing endovascular thrombectomy (EVT).

METHODS

This is a retrospective cohort study performed in a comprehensive tertiary stroke center. The study population consisted of consecutive patients with LVO with proximal MCA occlusion (M1) between June 2016 and April 2021, undergoing EVT. Demographic, clinical, and imaging information was extracted from patient files. Patency and diameters of ipsilateral A1-ACA and PComA were manually measured on admission CT angiography images in the core laboratory.

RESULTS

One hundred and five patients with LVO comprised the study cohort, mean age 72.3 years, 43.8% were male, mean National Institutes of Health Stroke Scale score at admission 15.2. The cohort was grouped according to CW vessel characteristics. On univariate analysis, a well-developed PComA was associated with lower rates of hemorrhagic transformation (1.8% vs 14.3%, P=0.01) and a trend towards lower mortality rates (8.9% vs 20.4%, P=0.08).On multivariable regression analysis a well-developed PComA emerged as an independent predictor for survival (aOR=0.09, 95% CI 0.01 to 0.4 for survival at discharge, P=0.009, aOR=0.22, 95% CI 0.05 to 0.8 for survival at 90 days, P=0.02).

CONCLUSIONS

In a cohort of patients with LVO due to M1 occlusion undergoing EVT, a well-developed PComA was associated with significantly lower hemorrhagic transformation rates, a trend towards better functional outcomes, and independently predicted survival. Larger studies are needed to understand the differential effect of CW collateral conduits on stroke outcome and evaluate the practicality of incorporating such factors in the clinical decision-making process prior to EVT.

The clinical and imaging data fusion model for single-period cerebral CTA collateral circulation assessment

Background

The Chinese population ranks among the highest globally in terms of stroke prevalence. In the clinical diagnostic process, radiologists utilize computed tomography angiography (CTA) images for diagnosis, enabling a precise assessment of collateral circulation in the brains of stroke patients. Recent studies frequently combine imaging and machine learning methods to develop computer-aided diagnostic algorithms. However, in studies concerning collateral circulation assessment, the extracted imaging features are primarily composed of manually designed statistical features, which exhibit significant limitations in their representational capacity. Accurately assessing collateral circulation using image features in brain CTA images still presents challenges.

Methods

To tackle this issue, considering the scarcity of publicly accessible medical datasets, we combined clinical data with imaging data to establish a dataset named RadiomicsClinicCTA. Moreover, we devised two collateral circulation assessment models to exploit the synergistic potential of patients' clinical information and imaging data for a more accurate assessment of collateral circulation: data-level fusion and feature-level fusion. To remove redundant features from the dataset, we employed Levene's test and T-test methods for feature pre-screening. Subsequently, we performed feature dimensionality reduction using the LASSO and random forest algorithms and trained classification models with various machine learning algorithms on the data-level fusion dataset after feature engineering.

Results

Experimental results on the RadiomicsClinicCTA dataset demonstrate that the optimized data-level fusion model achieves an accuracy and AUC value exceeding 86% . Subsequently, we trained and assessed the performance of the feature-level fusion classification model. The results indicate the feature-level fusion classification model outperforms the optimized data-level fusion model. Comparative experiments show that the fused dataset better differentiates between good and bad side branch features relative to the pure radiomics dataset.

Conclusions

Our study underscores the efficacy of integrating clinical and imaging data through fusion models, significantly enhancing the accuracy of collateral circulation assessment in stroke patients.

Numerical Modeling of Flow in the Cerebral Vasculature: Understanding Changes in Collateral Flow Directions in the Circle of Willis for a Cohort of Vasospasm Patients Through Image-Based Computational Fluid Dynamics

The Circle of Willis (CoW) is a ring-like network of blood vessels that perfuses the brain. Flow in the collateral pathways that connect major arterial inputs in the CoW change dynamically in response to vessel narrowing or occlusion. Vasospasm is an involuntary constriction of blood vessels following subarachnoid hemorrhage (SAH), which can lead to stroke. This study investigated interactions between localization of vasospasm in the CoW, vasospasm severity, anatomical variations, and changes in collateral flow directions. Patient-specific computational fluid dynamics (CFD) simulations were created for 25 vasospasm patients. Computed tomographic angiography scans were segmented capturing the anatomical variation and stenosis due to vasospasm. Transcranial Doppler ultrasound measurements of velocity were used to define boundary conditions. Digital subtraction angiography was analyzed to determine the directions and magnitudes of collateral flows as well as vasospasm severity in each vessel. Percent changes in resistance and viscous dissipation were analyzed to quantify vasospasm severity and localization of vasospasm in a specific region of the CoW. Angiographic severity correlated well with percent changes in resistance and viscous dissipation across all cerebral vessels. Changes in flow direction were observed in collateral pathways of some patients with localized vasospasm, while no significant changes in flow direction were observed in others. CFD simulations can be leveraged to quantify the localization and severity of vasospasm in SAH patients. These factors as well as anatomical variation may lead to changes in collateral flow directions. Future work could relate localization and vasospasm severity to clinical outcomes like the development of infarct.

Uncertainty-aware deep learning for trustworthy prediction of long-term outcome after endovascular thrombectomy

Acute ischemic stroke (AIS) is a leading global cause of mortality and morbidity. Improving long-term outcome predictions after thrombectomy can enhance treatment quality by supporting clinical decision-making. With the advent of interpretable deep learning methods in recent years, it is now possible to develop trustworthy, high-performing prediction models. This study introduces an uncertainty-aware, graph deep learning model that predicts endovascular thrombectomy outcomes using clinical features and imaging biomarkers. The model targets long-term functional outcomes, defined by the three-month modified Rankin Score (mRS), and mortality rates. A sample of 220 AIS patients in the anterior circulation who underwent endovascular thrombectomy (EVT) was included, with 81 (37%) demonstrating good outcomes (mRS ≤ 2). The performance of the different algorithms evaluated was comparable, with the maximum validation under the curve (AUC) reaching 0.87 using graph convolutional networks (GCN) for mRS prediction and 0.86 using fully connected networks (FCN) for mortality prediction. Moderate performance was obtained at admission (AUC of 0.76 using GCN), which improved to 0.84 post-thrombectomy and to 0.89 a day after stroke. Reliable uncertainty prediction of the model could be demonstrated.

Impact of Internal Carotid Stenosis Treatment on Cerebral Blood Flow Volume: A Comparative Study between Preoperative and Postoperative Values

BACKGROUND Among patients with ICA stenosis, there are some cases with elevated, undisrupted, and diminished cerebral blood flow (CBF). The aim of this study was to assess the influence of ICA stenosis treatment on postoperative CBF changes in relation to preoperative CBF values. MATERIAL AND METHODS We qualified 58 patients ≥65 years old (28 males, 30 females, mean age 71.02±6.34 years) for surgical intervention due to symptomatic ≥70% ICA stenosis. In all patients, a flow volume in all extracranial arteries (internal carotid [ICA], external carotid [ECA], and vertebral arteries [VA]) was measured preoperatively and 2-3 days following the surgery. The CBF values were compared with the ones established for a healthy population of the same age. RESULTS Preoperatively, there were 3 subgroups of patients, comparing to healthy population: with elevated CBF - "significant compensation," with undisrupted CBF - "mild compensation," and with diminished CBF - "no compensation." Postoperatively, a significant CBF increase was observed in patients with preoperative "no" and "mild compensation" - 277.18±154.26 ml/min (P=0.0000001) and 221.56±98.8 ml/min (P=0.0000001). In a "significant compensation" group, there was no flow increase observed (CBF change of 2.57±58.5 ml/min, P=0.954) - a redistribution of flow was observed. CONCLUSIONS In patients with lower preoperative CBF values, surgical treatment caused a significant increase in global cerebral inflow, which was more prominent in patients with the lowest preoperative CBF. In patients with high preoperative CBF, surgical treatment resulted in a flow redistribution, but did not cause a CBF increase. Volumetric flow assessment in DUS can predict hemodynamic benefit from surgery in terms of CBF increase.

Analysis of the posterior cerebral perfusion status and clinical prognostic value in chronic unilateral middle cerebral artery occlusion using SWAN combined with 3D-ASL

To investigate the predictive value of T2 star-weighted angiography (SWAN) combined with 3-dimensional (3D) arterial spin labeling (3D-ASL) to assess cerebral perfusion status and clinical prognosis in chronic unilateral middle cerebral artery (MCA) M1 occlusion. This study included 55 patients diagnosed with chronic unilateral MCA M1 occlusion using 3D time-of-flight magnetic resonance angiography between January 2018 and July 2022. Based on the prominent vessel sign (PVS) shown in the SWAN sequence, the patients were divided into PVS-positive (n = 26) and PVS-negative (n = 29) groups. Cerebral blood flow (CBF) was selected in the affected regions of the frontal, parietal, and temporal lobes (regions of interest = 200 ± 20 mm2) using pseudo-color maps in the 3D-ASL sequence. Each patient was followed up for ischemic cerebrovascular disease within 12 months of diagnosis. The collected data were statistically analyzed to evaluate the predictive value of SWAN and 3D-ASL for the clinical prognosis of patients with chronic unilateral MCA M1 occlusion. Patients were divided into 2 groups based on the occurrence of an ischemic cerebrovascular event within 12 months (ischemic cerebrovascular event [acute ischemic stroke + transient ischemic attack] and non-ischemic cerebrovascular event groups, including 30 and 25 cases, respectively). The incidence of ischemic cerebrovascular events within 12 months was significantly higher in the PVS-positive group than in the PVS-negative group (92.31% vs 20.69%). Furthermore, the CBF values of the affected frontal, parietal, and temporal lobes were significantly lower in the ischemic cerebrovascular event group than in the non-ischemic cerebrovascular event group (P < .05). According to the receiver operating characteristic curve, the CBF values of the affected frontal, parietal, and temporal lobes in patients with chronic unilateral MCA M1 occlusion strongly correlated with ischemic cerebrovascular disease within 12 months. PVS-negative display and good collateral circulation were closely related to clinical prognosis in patients with chronic unilateral MCA M1 occlusion.

Automatic Evaluating of Multi-Phase Cranial CTA Collateral Circulation Based on Feature Fusion Attention Network Model

Stroke is one of the main causes of disability and death, and it can be divided into hemorrhagic stroke and ischemic stroke. Ischemic stroke is more common, and about 8 out of 10 stroke patients suffer from ischemic stroke. In clinical practice, doctors diagnose stroke by using computed tomography angiography (CTA) image to accurately evaluate the collateral circulation in stroke patients. This imaging information is of great significance in assisting doctors to determine the patient's treatment plan and prognosis. Currently, great progress has been made in the field of computer-aided diagnosis technology in medicine by using artificial intelligence. However, in related research based on deep learning algorithms, researchers usually only use single-phase data for training, lacking the temporal dimension information of multi-phase image data. This makes it difficult for the model to learn more comprehensive and effective collateral circulation feature representation, thereby limiting its performance. Therefore, combining data for training is expected to improve the accuracy and reliability of collateral circulation evaluation. In this study, we propose an effective hybrid mechanism to assist the feature encoding network in evaluating the degree of collateral circulation in the brain. By using a hybrid attention mechanism, additional guidance and regularization are provided to enhance the collateral circulation feature representation across multiple stages. Time dimension information is added to the input, and multiple feature-level fusion modules are designed in the multi-branch network. The first fusion module in the single-stage feature extraction network completes the fusion of deep and shallow vessel features in the single-branch network, followed by the multi-stage network feature fusion module, which achieves feature fusion for four stages. Tested on a dataset of multi-phase cranial CTA images, the accuracy rate exceeding 90.43%. The experimental results demonstrate that the addition of these modules can fully explore collateral vessel features, improve feature expression capabilities, and optimize the performance of deep learning network model.

Association Between Cerebral Angiography and Asymmetrical Cortical and Deep/Medullary Vein Signs on T2 Star Magnetic Resonance Imaging in Patients with Hyperacute Horizontal Segment of the Middle Cerebral Artery Occlusion

BACKGROUND

When treating acute ischemic stroke patients, evaluation of collateral flow to the ischemic area is essential. Blood-oxygen-level-dependent imaging, including T2 star (T2∗), can identify elevated deoxyhemoglobin levels, reflecting an increase in the oxygen extraction fraction. Prominent veins on T2∗ represent increased deoxyhemoglobin and cerebral blood volume. This study compared asymmetrical vein signs (AVSs) on T2∗ and digital subtraction angiography findings during mechanical thrombectomy (MT) in patients with hyperacute middle cerebral artery occlusion.

METHODS

Clinical and imaging data of 41 patients with occlusion of the horizontal segment of the middle cerebral artery who underwent MT were collected. Patients were divided into 2 groups based on angiographic occlusion sites as: proximal and distal to the lenticulostriate artery (LSA). AVSs on T2∗ were divided into asymmetrical cortical vein sign (cortical AVS) and asymmetrical deep/medullary vein sign (deep/medullary AVS), and were compared with the findings of intraoperative digital subtraction angiography.

RESULTS

Twenty-seven patients had AVSs. Cortical AVS was the only parameter with a significant association with poor angiographic collateral supply. In terms of occlusion site, deep/medullary AVS was the only parameter with a significant association with occlusion proximal to the LSA.

CONCLUSIONS

In patients with occlusion of the horizontal segment of the middle cerebral artery, presence of the cortical AVS on T2∗ suggests a poor angiographic collateral supply, while presence of the deep/medullary AVS suggests impaired blood flow to the basal ganglia through LSAs. Both these signs contribute to poor outcomes in patients undergoing MT.

FLAIR vascular hyperintensity-DWI mismatch and DWI-FLAIR mismatch ASPECTS for prediction of good outcome after recanalization in anterior circulation stroke; multicenter observational study

INTRODUCTION

Acute ischemic stroke is a medical emergency caused by decreased blood flow to the brain, leading cause of long-term disability. Recanalization, one of the most concerning difficulties linked with intracranial arterial occlusion, has been used to reduce mortality in ischemic stroke treatment. The mismatch concepts MR PWI-DWI or DWI-FLAIR can help identify patients for thrombolysis.

PURPOSE

This paper introduces a novel method of predicting revascularization using the value of fluid-attenuated inversion recovery vascular hyperintensity FVH-DWI mismatch and DWI-FLAIR mismatch, which releases anterior circulation large vessel occlusion (LVO) after endovascular thrombectomy (EVT). Moreover, we present a new scoring system following anatomical region distributed for MCA territory called a DWI-FLAIR MISMATCH ASPECTS.

RESULT

Statistical analysis was performed to predict revascularization and functional outcome with 110 patients with anterior circulation LVO treated with EVT. We found that FVH-DWI mismatch was present in 71 patients (89.9 %) with complete revascularization and present in 8 patients (10.1 %) with no/partial revascularization, which had no significant difference (p = 0.12), and there was no significant difference between good functional outcome and poor functional outcome. Moreover, in 76 patients with DWI-FLAIR mismatch ASPECTS of > 6 point-group, present FVH-DWI mismatch in 57 patients (83.8 %) with complete revascularization had a significant difference as compared to 11 patients (16.2 %) with absent FVH-DWI mismatch (p < 0.05). The clinical outcome in complete revascularization is better than no/partial revascularization, and complete revascularization is independently associated with good functional outcomes (p < 0.05).

CONCLUSION

FVH-DWI mismatch paired with DWI-FLAIR mismatch ASPECTS > 6 points may be possible to predict revascularization in patients with anterior circulation LVO.

Under (back) pressure: Better collateral flow may facilitate clot removal in ischemic stroke: A systematic review and meta-analysis

BACKGROUND

Collateral status may facilitate clot removal and affect rates of successful reperfusion following endovascular therapy (EVT) for acute ischemic stroke (AIS).

METHODS

Following the PRISMA guidelines, a systematic literature review of the English language literature was conducted using PubMed, Scopus, Web of Science, and Embase. Papers which focused on collateral status and patients treated with EVT for AIS were included in our analysis. Outcomes of interest included collateral score grading, rates of successful reperfusion defined as thrombolysis in cerebral infarction (TICI) score 2b-3 and onset to revascularization time. We calculated pooled odds ratio (OR) or mean difference (MD) and their corresponding 95% confidence intervals (CI) based on collateral status.

RESULTS

16 studies, with 6073 patients, were included in our analysis. Among the included studies, there were six different collateral grading scales, which were dichotomized into "good to moderate" and "poor" collaterals. Odds of successful reperfusion were significantly higher among patients with good to moderate collateral circulation compared to those with poor collaterals (OR =  1.61; 95% CI = 1.24 to 2.09; P-value < 0.001); however, there was heterogeneity among included studies (I2= 5 4%; P-value = 0.008). Onset to revascularization time was comparable between patients with good to moderate collateral circulation compared to those with poor collaterals (MD = 3.91 min; 95% CI = -8.71 to 16.53; P-value = 0.544); however, there was heterogeneity among included studies (I2= 60%; P-value = 0.014).

CONCLUSIONS

The presence of good collaterals may increase the odds of achieving successful reperfusion following EVT for AIS. Improved collateral flow was associated with improved angiographic outcomes, although future work is needed to determine if a causal relationship exists.

The impact of leptomeningeal collaterals in acute ischemic stroke: a systematic review and meta-analysis

OBJECTIVES

Leptomeningeal collaterals provide an alternate pathway to maintain cerebral blood flow in stroke to prevent ischemia, but their role in predicting the outcome is still unclear. So, our study aims at assessing the significance of collateral blood flow (CBF) in acute stroke.

METHODS

Electronic databases were searched under different MeSH terms from January 2000 to February 2019. Studies were included if there was available data on good and poor CBF in acute ischemic stroke (AIS). The clinical outcomes included were modified Rankin scale (mRS), recanalization, mortality, and symptomatic intracranial hemorrhage (sICH) at 90 days. Data was analyzed using a random-effect model.

RESULTS

A total of 47 studies with 8194 patients were included. Pooled meta-analysis revealed that there exist twofold higher likelihood of favorable clinical outcome (mRS ≤ 2) at 90 days with good CBF compared with poor CBF (RR: 2.27; 95% CI: 1.94-2.65; p < 0.00001) irrespective of the thrombolytic therapy [RR with IVT: 2.90; 95% CI: 2.14-3.94; p < 0.00001, and RR with IAT/EVT: 1.99; 95% CI: 1.55-2.55; p < 0.00001]. Moreover, there exists onefold higher probability of successful recanalization with good CBF (RR: 1.31; 95% CI: 1.15-1.49; p < 0.00001). However, there was 54% and 64% lower risk of sICH and mortality respectively in patients with good CBF in AIS (p < 0.00001).

CONCLUSIONS

The relative risk of favorable clinical outcome is more in patients with good pretreatment CBF. This could be explained due to better chances of recanalization combined with a lesser risk of intracerebral hemorrhage with good CBF status.

Prognostic accuracy and impact of cerebral collateral status on clinical and safety outcomes in acute ischemic stroke patients receiving reperfusion therapy: a systematic meta-analysis

BACKGROUND

Cerebral collateral status has a potential role in mediating postreperfusion clinical and safety outcomes in acute ischemic stroke (AIS).

PURPOSE

To investigate the prognostic accuracy and impact of collateral status on clinical and safety outcomes in patients with AIS receiving reperfusion therapy.

MATERIAL AND METHODS

Studies with AIS patients treated with reperfusion therapy, collateral status assessed using Tan, ASITN/SIR, or similar collateral grading methods and data stratified according to collateral status were included. Relevant data on clinical outcomes, such as functional outcome at 90 days, mortality at 90 days, angiographic reperfusion, symptomatic intracerebral hemorrhage (sICH) and hemorrhagic transformation (HT), were collated and analyzed.

RESULTS

A meta-analysis of 18 studies involving 4132 patients with AIS was conducted. Good collateral status was significantly associated with angiographic reperfusion (odds ratio [OR]=1.97, 95% confidence interval [CI]=1.38-2.80; P < 0.0001), sICH (OR=0.67, 95% CI=0.46-0.99; P = 0.042), and 90-day functional outcome (OR=3.05, 95% CI=1.78-5.24; P < 0.0001). However, its association with HT (OR=0.76, 95% CI=0.38-1.51; P = 0.425) and three-month mortality (OR=0.53, 95% CI=0.17-1.69; P = 0.280) did not reach statistical significance. The prognostic accuracy of collaterals for predicting angiographic reperfusion, HT, functional outcome (at 90 days), and mortality (at 90 days) were 63%, 49%, 66%, and 48%, respectively.

CONCLUSION

Cerebral collaterals are significantly associated with clinical and safety outcomes, albeit with a prognostic accuracy range of 48%-66%; thus, evaluation of their patency is a useful prognostic tool in patients with AIS receiving reperfusion therapy.

Correlation Between Pre-treatment Collateral Status and Short-Term Functional Outcome in Patients With Mild to Moderate Stroke After Reperfusion Therapy in a Local Primary Stroke Center in the Southwestern Part of Saudi Arabia

Background Stroke is a substantial cause of disability and mortality worldwide and is characterized by the sudden onset of acute neurological deficit. During acute ischemia, cerebral collateral circulations are crucial in preserving blood supply to the ischemic region. Recombinant tissue plasminogen activator (r-tPA) and endovascular mechanical thrombectomy (MT) are the primary standards of care for acute recanalization therapy. Methodology From August 2019 through December 2021, we enrolled patients treated in our local primary stroke center with anterior circulation acute ischemic stroke (AIS) treated with intravenous thrombolysis (IVT) with or without MT. Only patients diagnosed with mild to moderate anterior ischemic stroke, as measured by the National Institutes of Health Stroke Scale (NIHSS), were included in the study. The candidate patients underwent non-contrast CT scanning (NCCT) and CT angiography (CTA) at admission. The modified Rankin scale (mRS) was used to assess the functional outcome of the stroke. The modified Tan scale, graded on a scale of 0-3, was used to determine the collateral status. Results This study comprised a total of 38 patients who had anterior circulation ischemic strokes. The mean age was 34. 8±13. All patients received IVT; eight patients (21.1%) underwent MT following r-tPA. In 26.3% of cases, hemorrhagic transformation (HT), both symptomatic and asymptomatic, was evident. Thirty-three participants (86.8%) had a moderate stroke, whereas five participants (13.2%) had a minor stroke. With a P-value of 0.003, a poor collateral status on the modified Tan score is substantially associated with a short, poor functional outcome. Conclusion In our study, patients with mild to moderate AIS with good collateral scores at admission had better short-term outcomes. Patients with poor collaterals tend to present with a disturbed level of consciousness more than patients with good collaterals.

Neutrophil dynamics and inflammaging in acute ischemic stroke: A transcriptomic review

Stroke is among the leading causes of death and disability worldwide. Restoring blood flow through recanalization is currently the only acute treatment for cerebral ischemia. Unfortunately, many patients that achieve a complete recanalization fail to regain functional independence. Recent studies indicate that activation of peripheral immune cells, particularly neutrophils, may contribute to microcirculatory failure and futile recanalization. Stroke primarily affects the elderly population, and mortality after endovascular therapies is associated with advanced age. Previous analyses of differential gene expression across injury status and age identify ischemic stroke as a complex age-related disease. It also suggests robust interactions between stroke injury, aging, and inflammation on a cellular and molecular level. Understanding such interactions is crucial in developing effective protective treatments. The global stroke burden will continue to increase with a rapidly aging human population. Unfortunately, the mechanisms of age-dependent vulnerability are poorly defined. In this review, we will discuss how neutrophil-specific gene expression patterns may contribute to poor treatment responses in stroke patients. We will also discuss age-related transcriptional changes that may contribute to poor clinical outcomes and greater susceptibility to cerebrovascular diseases.

Value of CT Perfusion for Collateral Status Assessment in Patients with Acute Ischemic Stroke

Good collateral status in acute ischemic stroke patients is an important indicator for good outcomes. Perfusion imaging potentially allows for the simultaneous assessment of local perfusion and collateral status. We combined multiple CTP parameters to evaluate a CTP-based collateral score. We included 85 patients with a baseline CTP and single-phase CTA images from the MR CLEAN Registry. We evaluated patients' CTP parameters, including relative CBVs and tissue volumes with several time-to-maximum ranges, to be candidates for a CTP-based collateral score. The score candidate with the strongest association with CTA-based collateral score and a 90-day mRS was included for further analyses. We assessed the association of the CTP-based collateral score with the functional outcome (mRS 0-2) by analyzing three regression models: baseline prognostic factors (model 1), model 1 including the CTA-based collateral score (model 2), and model 1 including the CTP-based collateral score (model 3). The model performance was evaluated using C-statistic. Among the CTP-based collateral score candidates, relative CBVs with a time-to-maximum of 6-10 s showed a significant association with CTA-based collateral scores (p = 0.02) and mRS (p = 0.05) and was therefore selected for further analysis. Model 3 most accurately predicted favorable outcomes (C-statistic = 0.86, 95% CI: 0.77-0.94) although differences between regression models were not statistically significant. We introduced a CTP-based collateral score, which is significantly associated with functional outcome and may serve as an alternative collateral measure in settings where MR imaging is not feasible.

Volumetric Flow Assessment in Extracranial Arteries in Patients with 70-99% Internal Carotid Artery Stenosis

Background: Cerebral blood flow (CBF) can be related to the risk of occurrence of neurological symptoms. Well-developed collateral circulation is a good prognostic factor in patients with cerebrovascular disease. Understanding the mechanisms of collateral circulation may be important in the diagnosis, treatment, and monitoring in this group of patients. The aim of this study covered the assessment of CBF in patients with 70−99% Internal carotid artery (ICA) stenosis, focusing on the circulation pathways and flow volume in extracranial arteries. Materials and methods: 53 patients with 70−99% ICA stenosis (mean age 73.4 ± 7 years old; 17 female, mean age 73.9 ± 7.5 years old; 36 male, mean age 73.2 ± 6.8 years old) were included in the study. In all patients a Doppler ultrasound (DUS) examination, measuring blood flow volume in the internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA), was performed. The cerebral blood flow (CBF) was compared to the previously reported CBF values in the healthy population > 65 years old. Results: Among the study groups three subgroups with flow differences were identified: patients with elevated CBF (significant volumetric flow compensation—26/53, 49%), patients with CBF similar to (mild compensation—17/53, 32%), and patients with CBF lower than (no compensation—10/53, 19%) the healthy, equally aged population. The percentage of patients with significant volumetric flow compensation was the highest in age groups 65−69 years old (62.5%) and >80 years old (60%). In the oldest age group (>80 years old) no patients without flow compensation (0%) were observed. The level of compensation depends on the number of the arteries with compensatory increased flow. In patients with significant volumetric flow compensation, the compensatory increased flow was observed, on average, in 3.31 arteries, in the mild compensation group—in 2.18 arteries, and in the no compensation group only in 1 artery. ICA plays the most important role in the volumetric flow compensation—the increase in the flow volume, in comparison to the reference values, was between 116.7 mL/min and 251.9 mL/min (in the ECA 57.6 mL/min−110.4 mL/min; in the VA 73.9 mL/min−104.9 mL/min). The relative flow increase was highest in the VA: 215−246%, then in the ECA: 163−206%, and finally in the ICA: 148.6−192%. The increased flow was most commonly observed in the VA—57 arteries, in second place in the ECA—42 arteries, and ICA—31 arteries. In patients with unilateral ICA stenosis, the volumetric flow increase was stated more frequently in the ipsilateral ECAs then in the contralateral ones (23 vs. 14). In the VA the opposite tendency was observed (29 contralateral vs. 23 ipsilateral). The ability of volumetric flow compensation decreased significantly with increasing age. Conclusions: Understanding the mechanisms of collateral circulation and their assessment in Doppler ultrasonography may provide a novel and easily accessible tool of identifying and monitoring patients with cerebrovascular disease.

Evaluation of collateral status and outcome in patients with middle cerebral artery stenosis in late time window by CT perfusion imaging

Objectives

Collateral status (CS) is a crucial determinant of outcome in patients with ischemic stroke. We aimed to test whether the cerebral blood volume (CBV) and cerebral blood flow (CBF) based on computed tomography perfusion (CTP) measurements can quantitatively evaluate CS and explore the predictive ability of CTP parameters in determining clinical outcomes in patients with MCA severe stenosis or occlusion presenting beyond 24 h.

Materials and methods

In this retrospective study, data obtained from September 2018 to March 2022 in consecutive stroke patients caused by isolated middle cerebral artery severe stenosis or occlusion were reviewed within 24–72 h after onset. Correlation between the collateral score systems assessed with CT angiography (CTA) and CTP parameters was calculated using the Spearman correlation. The optimal threshold of the CBV ratio for predicting a good outcome was determined using receiver operating characteristic curve (ROC) analysis.

Results

A total of 69 patients met inclusion criteria. Both the CBV ratio and the CBF ratio had significant correlation with collateral score systems assessed with CTA [CBV ratio and Tan score: rs = 0.702, P &lt; 0.0001; CBV ratio and regional leptomeningeal collateral (rLMC) score: rs = 0.705, P &lt; 0.0001; CBV ratio and Miteff score: rs = 0.625, P &lt; 0.0001. CBF ratio and Tan score: rs= 0.671, P &lt; 0.0001; CBF ratio and rLMC score: rs = 0.715, P &lt; 0.0001; CBF ratio and Miteff score: rs = 0.535, P &lt; 0.0001]. ROC analysis revealed the CBV ratio performed better than the qualitative collateral assessments and the CBF ratio in the prediction of a favorable 90-day modified Rankin scale score. The CBV ratio was a useful parameter that predicted a good functional outcome [area under the curve (AUC), 0.922; 95% CI, 0.862 ± 0.982].

Conclusions

In late time window stroke patients, the CBV and CBF ratio on CTP may be valuable parameters for quantitatively revealing the collateral status after stroke. In addition, the CBV ratio was the predictor of clinical outcomes in patients with MCA severe stenosis or occlusion.

Predictors of three months mortality after endovascular mechanical thrombectomy for acute ischemic stroke

Objective

This study aims to determine predictive factors of mortality within 3 months after mechanical thrombectomy (MT) for patients with acute ischemic stroke (AIS).

Methods

This prospective cohort study was carried out at Assiut University stroke center in collaboration with Ain Shams University Egypt. Forty-four patients with anterior circulation AIS underwent MT between the first of January 2020 to the end of December 2020. They were evaluated for detection of death rates and identification of risks of 3-month mortality after MT.

Results

This study comprised 44 patients (52.3% male) with a mean age of 64.3 years. The mean time from onset to femoral arterial puncture was 304.1 min. The mean Alberta Stroke Program Early CT Score (ASPECTS) and National Institutes of Health Stroke Scale (NIHSS) score were 9.3 and 19.2, respectively. The 3-month mortality rate was 13.6%. Univariate analyses found that higher baseline NIHSS score (mean 22.2 vs. 18.7, p = 0.021), absence of good collateral (16.7% vs. 68.4%, p = 0.02), longer duration of procedure ≥ 60 min (66.7% vs. 23.7%, p = 0.032), lower rates of successful recanalization (83.3% vs. 28.9%, p = 0.01) and developing symptomatic intracerebral hemorrhage (33.3% vs. 5.3%, p = 0.026) were associated with 3-month mortality. Multivariate analyses found that low rates of successful recanalization (OR 0.081; 95% CI 0.009–0.780, p = 0.030) remained significant independent predictive factor of 3-month mortality.

Conclusion

Successful recanalization was an independent predictor of 3-month mortality after MT.

Diagnostic test accuracy of pretreatment collateral score in predicting stroke outcomes after intra-arterial endovascular thrombectomy: a meta-analysis in DSA and CTA

OBJECTIVES

This study compared the diagnostic accuracy of pretreatment circulation collateral scoring (CS) system using digital subtraction angiography (DSA) and computed tomography angiography (CTA) in predicting favorable functional outcome (FFO) after intra-arterial endovascular thrombectomy (IA-EVT). Subgroup analysis characterizing scoring systems within each category was additionally conducted.

MATERIALS AND METHODS

We performed a diagnostic meta-analysis to assess the sensitivity and specificity of each CS system by using DSA and CTA, respectively. The hierarchical summary receiver operating characteristic curve (HSROC) models were used to estimate the diagnostic odds ratio (DOR) and area under the curve (AUC). The Bayes theorem was employed to determine posttest probability (PTP).

RESULTS

In total, 14 and 21 studies were assessed with DSA and CTA, respectively. In DSA, the pooled sensitivity and specificity were 0.72 (95% CI, 0.63-0.79) and 0.61 (0.53-0.68), respectively, and in the HSROC model, the DOR was 3.94 (2.71-5.73), and the AUC was 0.71 (90.67-0.75). CTA revealed a pooled sensitivity and specificity of 0.74 (0.64-0.82) and 0.53 (0.44-0.62), respectively, and in the HSROC model, the DOR was 3.17 (2.34-4.50), and the AUC was 0.67 (0.63-0.71). With a pretest probability of 26.3%, the CS in DSA and CTA exhibited limited increase of PTPs of 39% and 36%, respectively, in detecting the FFO on day 90.

CONCLUSION

DSA and CTA have comparable accuracy and are limited in predicting the functional outcome. The collateral score systems assessed with DSA and CTA were more suitable for screening than diagnosis for patients before IA-EVT.

KEY POINTS

• Our study revealed the differences of various scoring systems for assessing collateral status. • DSA and CTA have comparable accuracy, but both imaging modalities played relatively limited roles in predicting functional outcome on day 90. • The collateral score systems assessed with DSA and CTA were more suitable for screening than diagnosis for patients before IA-EVT.

Collateral Status and Clinical Outcomes after Mechanical Thrombectomy in Patients with Anterior Circulation Occlusion

Background. Successful mechanical thrombectomy (MT) requires reliable, noninvasive selection criteria. We aimed to investigate the association of collateral status and clinical outcomes after MT in patients with ischemic stroke due to anterior circulation occlusion. Methods. 109 patients with poor collaterals and 110 aged, sex-matched patients with good collaterals were enrolled in the study. Collateral circulation was estimated by the CT angiography with a 0–3 scale. The collateral status was categorized as poor collaterals (scores 0–1) and good collaterals (scores 2-3). The reperfusion was assessed by the modified Treatment in Cerebral Infarction scale (mTICI, score 0/1/2a/2b/3). The clinical outcomes included the scores on the modified Rankin scale (mRS, ranging from 0 to 6) and death 90 days after mechanical thrombectomy. Results. Patients with greater scores of collateral status were more likely to achieve successful reperfusion (mTICI 2b/3). Patients with good collaterals were significantly associated with a higher chance of achieving mRS of 0–1 at 90 days (adjusted ORs: 4.55; 95% CI: 3.17–7.24; and $P$  < 0.001) and a lower risk of death at 90 days (adjusted ORs: 0.87; 95% CI: 4.0%–28.0%; and $P$  = 0.012) compared to patients with poor collaterals. In subgroup analyses, patients with statin use seem to benefit more from the effect of collateral status on good mRS (≤2). Conclusion. Among patients with acute ischemic stroke caused by anterior circulation occlusion, better collateral status is associated with higher scores on mRS and lower mortality after mechanical thrombectomy. Statin use might have an interaction with the effect of collateral status.

Volumetric Flow Assessment in Doppler Ultrasonography in Risk Stratification of Patients with Internal Carotid Stenosis and Occlusion

(1) Background: Alterations of blood flow volume in extracranial arteries may be related to the risk of occurrence of neurological symptoms. The aim of this study was the estimation of cerebral blood flow (CBF) in Doppler ultrasonography, as well as comparison of the flow volume in asymptomatic patients over 65 years old with ≥50%, and symptomatic patients with ≥70% internal carotid artery (ICA) stenosis, in order to assess whether the changes in the CBF correlates with the presence of neurological symptoms. (2) Methods: 308 patients over 65 years old were included in the retrospective cohort observational study: 154 asymptomatic with ≥50% ICA stenosis, 123 healthy volunteers, and 31 symptomatic referred for surgical treatment. The study group was split according to ICA stenosis (50–69%, 70–99% and occlusion). In all patients an extensive Doppler ultrasound examination with measurements of flow volume in common, internal, external carotid (ECA) and vertebral arteries (VA) was performed. (3) Results: Among asymptomatic (A) and symptomatic (S) patients with carotid stenosis 3 subgroups were identified: 57/154—37% (A) and 8/31—25.5% (S)—with significantly increased flow volume (CBF higher than reference range: average CBF + std. dev in the group of healthy volunteers), 67/154—43.5% (A) and 12/31—39% (S)—with similar to reference group flow volume (CBF within range average ± std.dev), and 30/154—19.5% (A) and 11/31—35.5% (S)—with decreased flow volume in extracranial arteries (flow lower than average-std.dev. in healthy volunteers). In symptomatic patients the percentage of patients with significant compensatory increased flow tends to raise with the severity of the stenosis, while simultaneous decline of number of patients with mild compensation (unchanged total CBF) is observed. The percentage of patients without compensation remains unchanged. In the group referred for surgical treatment (symptomatic, ≥70% ICA stenosis) the percentage of patients with flow compensation is twice as low as in the asymptomatic ones with similar degree of the ICA stenosis (8/31—25.8% vs. 26/53—49%, p = 0.04). Compensatory elevated flow was observed most frequently in ECA. (4) Conclusions: The presence of significant volumetric flow compensation has protective influence on developing ischaemic symptoms, including TIA or stroke. The assessment of cerebral inflow in Doppler ultrasonography may provide novel and easily accessible tool of identifying patients prone to cerebral ischaemia. The multivessel character of compensation with enhanced role of ECA justifies the importance of including this artery in the estimation of CBF.

Stroke Aetiology and Collateral Status in Acute Ischemic Stroke Patients Receiving Reperfusion Therapy-A Meta-Analysis

BACKGROUND

The interplay between collateral status and stroke aetiology may be crucial in the evaluation and management of acute ischemic stroke (AIS). Our understanding of this relationship and its level of association remains sub-optimal. This study sought to examine the association of pre-intervention collateral status with stroke aetiology, specifically large artery atherosclerosis (LAA) and cardio-embolism (CE), in AIS patients receiving reperfusion therapy, by performing a meta-analysis.

METHODS

Relevant search terms were explored on Medline/PubMed, Embase and Cochrane databases. Studies were included using the following inclusion criteria: (a) patients aged 18 or above; (b) AIS patients; (c) patients receiving reperfusion therapy; (d) total cohort size of >20, and (e) qualitative or quantitative assessment of pre-intervention collateral status on imaging using a grading scale. Random-effects meta-analysis was performed to investigate the association of aetiology with pre-intervention collateral status, and forest plots of risk ratio (RR) were generated.

RESULTS

A meta-analysis was conducted on seven studies, with a cumulative cohort of 1235 patients, to assess the association of pre-intervention collateral status with stroke aetiology. Patients with LAA were associated significantly with an increased rate of good collaterals (RR 1.24; 95% CI 1.04-1.50; p = 0.020, z = 2.33). Contrarily, CE aetiology was associated significantly with a decreased rate of good collaterals (RR 0.83; 95% CI 0.71-0.98; p = 0.027, z = -2.213).

CONCLUSIONS

This study demonstrates that, in AIS patients receiving reperfusion therapy, LAA and CE aetiologies are associated significantly with collateral status.

Radiographic Characteristics of Mild Ischemic Stroke Patients With Visible Intracranial Occlusion: The INTERRSeCT Study

BACKGROUND AND PURPOSE

Early neurological deterioration occurs in one-third of mild strokes primarily due to the presence of a relevant intracranial occlusion. We studied vascular occlusive patterns, thrombus characteristics, and recanalization rates in these patients.

METHODS

Among patients enrolled in INTERRSeCT (Identifying New Approaches to Optimize Thrombus Characterization for Predicting Early Recanalization and Reperfusion With IV Alteplase and Other Treatments Using Serial CT Angiography), a multicenter prospective study of acute ischemic strokes with a visible intracranial occlusion, we compared characteristics of mild (National Institutes of Health Stroke Scale score, ≤5) to moderate/severe strokes.

RESULTS

Among 575 patients, 12.9% had a National Institutes of Health Stroke Scale score ≤5 (median age, 70.5 [63-79]; 58% male; median National Institutes of Health Stroke Scale score, 4 [2-4]). Demographics and vascular risk factors were similar between the two groups. As compared with those with a National Institutes of Health Stroke Scale score >5, mild patients had longer symptom onset to assessment times (onset to computed tomography [240 versus 167 minutes] and computed tomography angiography [246 versus 172 minutes]), more distal occlusions (M3, anterior cerebral artery and posterior cerebral artery; 22% versus 6%), higher clot burden score (median, 9 [6-9] versus 6 [4-9]), similar favorable thrombus permeability (residual flow grades I-II, 21% versus 19%), higher collateral flow (9.1 versus 7.6), and lower intravenous alteplase treatment rates (55% versus 85%). Mild patients were more likely to recanalize (revised arterial occlusion scale score 2b/3, 45%; 49% with alteplase) compared with moderate/severe strokes (26%; 29% with alteplase). In an adjusted model for sex, alteplase, residual flow, and time between the two vessel imagings, intravenous alteplase use (odds ratio, 3.80 [95% CI, 1.11-13.00]) and residual flow grade (odds ratio, 8.70 [95% CI, 1.26-60.13]) were associated with successful recanalization among mild patients.

CONCLUSIONS

Mild strokes with visible intracranial occlusions have different vascular occlusive patterns but similar thrombus permeability compared with moderate/severe strokes. Higher thrombus permeability and alteplase use were associated with successful recanalization, although the majority do not recanalize. Randomized controlled trials are needed to assess the efficacy of new thrombolytics and endovascular therapy in this population.

Leptomeningeal collateral flow in patients with middle cerebral artery occlusion assessed by transcranial Doppler

BACKGROUND AND PURPOSE

To explore the application value and clinical significance of transcranial Doppler(TCD)in assessing leptomeningeal collateral flow (LMF) status in patients with unilateral middle cerebral artery (MCA) occlusion.

METHODS

Medical records of patients with unilateral MCA occlusion confirmed by digital subtraction angiography (DSA) were analyzed retrospectively. The patients were divided into three groups according to LMF status, and the laboratory and imaging results were collected. Cerebral blood flow velocity (CBFV) of MCA, anterior cerebral artery (ACA), and posterior cerebral artery (PCA) on the affected side (ipsilateral, i) and the healthy side (contralateral, c) were measured and recorded by TCD. The results of CBFV changes detected by TCD were compared with those of DSA, and the correlation between CBFV changes and LMF status was analyzed.

RESULTS

Eighty-four patients with unilateral MCA occlusion were included. CBFViACA and CBFViPCA were significantly faster than CBFVcACA and CBFVcPCA in patients with good LMF status (p<.05). There was a significant positive correlation between CBFViACA and LMF status (r = 0.697, p<.001). There was statistical significance in receiver operating characteristic curve analysis of CBFViACA and CBFViPCA (p<.05). The area under the curve of CBFViACA and CBFViPCA, respectively, was 0.879 and 0.678, and the best cutoff value was 82 and 60.5 cm/s.

CONCLUSIONS

TCD can assess LMF status by detecting the changes of flow velocity of intracranial vessels. CBFV of ACA and PCA in patients with MCA occlusion is significantly correlated with LMF status by DSA. Assessing LMF status, CBFViACA, CBFViACA/CBFVcACA, and CBFViACA/CBFViMCA has the great diagnostic value, which is of great significance in guiding MCA occlusion patients to choose individualized treatment.

Effects of Anterior Borderzone Angle Grading on Predicting the 90-Day Prognosis After Recanalization of Acute Middle Cerebral Artery Occlusion

Objective: This work explores collateral circulation metrics, such as the anterior borderzone angle grading (ABZA-grading), as a predictor of the prognosis in patients with acute middle cerebral artery occlusion (MCAO) following endovascular treatment (EVT).

Methods: Clinical data from 108 patients with acute MCAO, treated by EVT, were retrospectively analyzed. In patients with MCAO, ABZA is the angle between the median line of the sagittal sinus and the borderzone of the pial arterioles of ACA and MCA, and the ABZA/23.0° was rounded to obtain the corresponding collateral circulation score (ABZA-grading). In parallel, the primary outcome was defined as the 90-day clinical outcome by modified ranking scale score (mRS). Univariate analysis and logistic regression were used to analyze the independent predictors of the 90-day clinical outcome (mRS). Receiver operating characteristic curve (ROC) analysis was used to judge the predictive value of ABZA.

Results: Univariate analysis and logistic regression analysis showed that ABZA-grading > 2 and age were independent predictors of the 90-day clinical outcome after EVT in patients with acute MCAO. The ROC analysis showed that ABZA alone could predict a favorable 90-day clinical outcome with an area under the curve (AUC) of 0.868. Using an ABZA of >57.8° (the corresponding ABZA-grading of >2) as the cut-off value, the predictive sensitivity and specificity were 75.7 and 88.7%, respectively. Contingency table analysis showed a statistical difference in mRS score between ABZA-grading subgroups, and ABZA-grading between stroke caused by large artery atherosclerosis (LAA) and cardiogenic embolism (CE).

Conclusion: The ABZA-grading is an easy and objective assessment of collateral circulation that is independently associated with short-time clinical outcome after EVT in patients with acute MCAO. Therefore, it may guide selection of patients with acute ischemic stroke (AIS) suitable for EVT. The ABZA-grading of collateral circulation can be a supplemental metric to help differentiate stroke by LAA and CE.

Measuring Cerebrovascular Reactivity: Sixteen Avoidable Pitfalls

An increase in arterial PCO₂ is the most common stressor used to increase cerebral blood flow for assessing cerebral vascular reactivity (CVR). That CO₂ is readily obtained, inexpensive, easy to administer, and safe to inhale belies the difficulties in extracting scientifically and clinically relevant information from the resulting flow responses. Over the past two decades, we have studied more than 2,000 individuals, most with cervical and cerebral vascular pathology using CO₂ as the vasoactive agent and blood oxygen-level-dependent magnetic resonance imaging signal as the flow surrogate. The ability to deliver different forms of precise hypercapnic stimuli enabled systematic exploration of the blood flow-related signal changes. We learned the effect on CVR of particular aspects of the stimulus such as the arterial partial pressure of oxygen, the baseline PCO₂, and the magnitude, rate, and pattern of its change. Similarly, we learned to interpret aspects of the flow response such as its magnitude, and the speed and direction of change. Finally, we were able to test whether the response falls into a normal range. Here, we present a review of our accumulated insight as 16 “lessons learned.” We hope many of these insights are sufficiently general to apply to a range of types of CO₂-based vasoactive stimuli and perfusion metrics used for CVR.

Hemodynamics in acute stroke: Cerebral and cardiac complications

Hemodynamics is the study of blood flow, where parameters have been defined to quantify blood flow and the relationship with systemic circulatory changes. Understanding these perfusion parameters, the relationship between different blood flow variables and the implications for ischemic injury are outlined in the ensuing discussion. This chapter focuses on the hemodynamic changes that occur in ischemic stroke, and their contribution to ischemic stroke pathophysiology. We discuss the interaction between cardiovascular response and hemodynamic changes in stroke. Studying hemodynamic changes has a key role in stroke prevention, therapeutic implications and prognostic importance in acute ischemic stroke: preexisting hemodynamic and autoregulatory impairments predict the occurrence of stroke. Hemodynamic failure predisposes to the formation of thromboemboli and accelerates infarction due to impairing compensatory mechanisms. In ischemic stroke involving occlusion of a large vessel, persistent collateral circulation leads to preservation of ischemic penumbra and therefore justifying endovascular thrombectomy. Following thrombectomy, impaired autoregulation may lead to reperfusion injury and hemorrhage.

Association between flat-panel computed tomography hyperattenuation and clinical outcome after successful recanalization by endovascular treatment

OBJECTIVE

Hyperattenuation on CT scanning performed immediately after endovascular treatment (EVT) is known to be associated with the final infarct. As flat-panel CT (FPCT) scanning is readily accessible within their angiography suite, the authors evaluated the ability of the extent of hyperattenuation on FPCT to predict clinical outcomes after EVT.

METHODS

Patients with successful recanalization (modified Thrombolysis in Cerebral Infarction grade 2b or 3) were reviewed retrospectively. The extent of hyperattenuation was assessed by the Alberta Stroke Program Early CT Score on FPCT (FPCT-ASPECTS). FPCT-ASPECTS findings were compared according to functional outcome and malignant infarction. The predictive power of the FPCT-ASPECTS with initial CT images before EVT (CT-ASPECTS) and follow-up diffusion-weighted images (MR-ASPECTS) was also compared.

RESULTS

A total of 235 patients were included. All patients were treated with mechanical thrombectomy, and 45.5% of the patients received intravenous tissue plasminogen activator. The mean (± SD) time from stroke onset to recanalization was 383 ± 290 minutes. The FPCT-ASPECTS was significantly different between patients with a favorable outcome and those without (mean 9.3 ± 0.9 vs 6.7 ± 2.6) and between patients with malignant infarction and those without (3.4 ± 2.9 vs 8.8 ± 1.4). The FPCT-ASPECTS was an independent factor for a favorable outcome (adjusted OR 3.28, 95% CI 2.12-5.01) and malignant infarction (adjusted OR 0.42, 95% CI 0.31-0.57). The area under the curve (AUC) of the FPCT-ASPECTS for a favorable outcome (0.862, cutoff ≥ 8) was significantly greater than that of the CT-ASPECTS (0.637) (p < 0.001) and comparable to that of the MR-ASPECTS (0.853) (p = 0.983). For malignant infarction, the FPCT-ASPECTS was also more predictive than the CT-ASPECTS (AUC 0.906 vs 0.552; p = 0.001) with a cutoff of ≤ 5.

CONCLUSIONS

The FPCT-ASPECTS was highly predictive of clinical outcomes in patients with successful recanalization. FPCT could be a practical method to immediately predict clinical outcomes and thereby aid in acute management after EVT.

Cerebrovascular Reactivity Assays Collateral Function in Carotid Stenosis

In patients with carotid artery stenosis (CAS), the risk of stroke, its severity, and response to revascularization are strongly related to the availability of collateral blood flow. Unfortunately, there is poor agreement between observers in assessing collateral flow using flow-based imaging. We used changes in blood-oxygen-level-dependent (BOLD) MRI as a surrogate of changes in regional cerebral blood flow in response to a hypercapnic stimulus [i.e., cerebrovascular reactivity (CVR)] as indicating flow reserve ipsilateral to CAS. We hypothesized that some patients with hemodynamically significant CAS develop functional collateral flow as indicated by normalization of ipsilateral CVR. We identified 55 patients in our CVR database with various degrees of CAS assessed by angiography and classed them as <50% stenosis, 50–69% stenosis, 70–90% stenosis, >90% stenosis, and full occlusion. CVR was measured as the change in BOLD signal in response to changes in end-tidal partial pressure of CO₂ (Δ BOLD/Δ PETCO₂) and normalized voxel-wise relative to the mean and standard deviation of the CVR in the corresponding voxels of an atlas of 46 healthy controls (CVR z scores). CVR and z scores were then averaged over gray matter (GM) and white matter (WM) on each side of the middle cerebral artery (MCA) territory. As hypothesized, CVR varied for each severity of CAS. Ipsilateral MCA territory CVR was less than normal in each class, including that with <50% stenosis (Student t-test, two-tailed; p = 0.0014 for GM and p = 0.030 for WM), with a trend of decreasing average CVR with increasing stenosis. Remarkably, the considerable individual variability in MCA CVR included some patients with normal CVR in each class – including that with complete occlusion. We conclude that, in general, CAS depresses downstream vascular reserve, but the extent of collateralization is highly variable and not predictable from the degree of stenosis, including both <50% stenosis and complete occlusion. CVR may be the more reliable marker for recruitable collateral blood flow than degree of CAS.

A meta-analysis of collateral status and outcomes of mechanical thrombectomy

OBJECTIVES

To perform a systematic review and meta-analysis to investigate pretreatment collaterals and outcomes of mechanical thrombectomy in patients with acute ischemic stroke of large-vessel occlusion in anterior circulation.

METHODS

We systematically searched Embase, PubMed, and the Cochrane Library from their dates of inception to March 5, 2020, and also manually searched reference lists of relevant articles. Pooled relative risk with 95% confidence interval on the association between good collaterals and functional independence (in terms of mRS 0-2), symptomatic intracranial hemorrhage, mortality, and successful reperfusion were synthesized using a random-effects model.

RESULTS

Thirty-four studies enrolling 5768 patients were included in analysis. Good collaterals were significantly associated with functional independence (RR 1.93, 95%CI 1.64-2.27, P < .0001), successful reperfusion (RR 1.23, 95%CI 1.12-1.35, P < .0001), decreased rate of symptomatic intracranial hemorrhage (RR 0.68, 95%CI 0.47-0.97, P = .032), and mortality (RR 0.37, 95%CI 0.27-0.52, P < .0001). The results were consistent in sensitivity analysis. The associations between good collaterals and reperfusion remained stable after adjusting for publication bias.

CONCLUSIONS

Good pretreatment collaterals were associated with functional independence, successful reperfusion, and decreased rate of sICH and mortality after receiving mechanical thrombectomy in patients with acute ischemic stroke of large-vessel occlusion.

Telemedicine in Prehospital Acute Stroke Care: An Expanding Infrastructure for Treatment and Research

See Article by Geisler et al.

Risk Stratification for Endovascular Treatment in Acute Anterior Circulation Occlusive Stroke

OBJECTIVE

To develop and validate a novel scoring system for risk stratification in acute anterior circulation large vessel occlusion stroke patients undergoing endovascular treatment.

METHODS

Subjects were included from a multicenter registry on acute ischemic stroke undergoing thrombectomy in China. Two thirds of the patients were used as the derivation group and the other one third of the patients as the validation group. Multivariable logistic regression was used to generate the scoring system. The area under the receiver operating characteristic curve and Hosmer-Lemeshow goodness-of-fit test were used to assess model discrimination and calibration, respectively.

RESULTS

The Risk strAtification for eNdovascular treatment in acute anterior circulation occlusive stroKe (RANK) scale (total score ranges from -11 to 14) showed good discrimination in the derivation cohort (AUC = .79; 95% confidence interval [CI], .74-.84) and validation cohorts (AUC = .74; 95% CI, .68-.81), as well as good calibration (Hosmer-Lemeshow test) in the validation cohort (P = .54). We categorized the RANK score into 5 predictive groups for an unfavorable functional outcome, less than or equal to -8 (very low risk), -7 to -4 (low risk), -3 to 0 (intermediate), 1-5 (high risk), and greater than or equal to 6 (very high risk). In the very high risk group, only 3.3% (1 of 30, 95% CI: .08%-.2%) of patients in the derivation group and 5.5% (1 of 18, 95% CI: .1%-.3%) of patients in the validation group achieved a good functional outcome at day 90.

CONCLUSIONS

The novel scale is a valid tool for risk stratification for endovascular stroke treatment in anterior circulation large vessel occlusions.

Sex Differences in Outcome After Endovascular Stroke Therapy for Acute Ischemic Stroke

Background and Purpose- We determined the effect of sex on outcome after endovascular stroke thrombectomy in acute ischemic stroke, including lifelong disability outcomes. Methods- We analyzed patients treated with the Solitaire stent retriever in the combined SWIFT (Solitaire FR With the Intention for Thrombectomy), STAR (Solitaire FR Thrombectomy for Acute Revascularization), and SWIFT PRIME (Solitaire FR With the Intention for Thrombectomy as Primary Endovascular Treatment) cohorts. Ordinal and logistic regression were used to examine known factors influencing outcome after endovascular stroke thrombectomy and study the effect of sex on the association between these factors and outcomes, including age and time to reperfusion. Years of optimal life after thrombectomy were defined as disability-adjusted life years and calculated by projecting disability through adjusted poststroke life expectancy by sex. Results- Among 389 patients treated with endovascular stroke thrombectomy, 55% were females, and median National Institutes of Health Stroke Scale was 17 (interquartile range, 8-28). There were no differences between females versus males in presenting deficit severity (National Institutes of Health Stroke Scale score, 17 versus 17, P=0.21), occlusion location (69% versus 64% M1, P=0.62), presenting infarct extent (Alberta Stroke Program Early CT Score 8 versus 8, P=0.24), rate of substantial reperfusion (Thrombolysis in Cerebral Infarction 2b/3, 87% versus 83%, P=0.37), onset to reperfusion time (294 versus 302 minutes, P=0.46). Despite older ages (69 versus 64, P<0.001) and higher rate of atrial fibrillation (45% versus 30%, P=0.002) for females compared with males, adjusted rates of functional independence at 90 days were similar (odds ratio, 1.0; 95% CI, 0.6-1.6). After adjusting for age at presentation and stroke severity, females had more years of optimal life (disability-adjusted life year) after endovascular stroke thrombectomy, 10.6 versus 8.5 years (P<0.001). Conclusions- Despite greater age and higher rate of atrial fibrillation, females experienced comparable functional outcomes and greater years of optimal life after intervention compared with males.

Differential Benefit of Collaterals for Stroke Patients Treated with Thrombolysis or Supportive Care : A Propensity Score Matched Analysis

PURPOSE

Leptomeningeal collaterals can slow down infarction growth; however, despite good collaterals in the DAWN and DEFUSE 3 trials, outcomes were devastating if reperfusion was not attempted. The aim of this study was to compare the influence of collaterals on morphological and functional outcome in patients with acute middle cerebral artery (MCA) stroke undergoing intravenous thrombolysis (IVT) vs. supportive care (non-IVT).

METHODS

Out of 1639 consecutive patients examined with multiparametric computed tomography (CT) for suspected ischemic stroke, all patients with confirmed MCA stroke who did not undergo endovascular thrombectomy were selected. Propensity score matching (PSM) was used to match IVT and non-IVT treated patients for potential confounders including age, sex, National Institutes of Health Stroke Scale (NIHSS) score on admission, Alberta Stroke Program Early CT Score (ASPECTS), and occlusion site. Regression analysis after PSM was performed to identify independent associations.

RESULTS

After PSM, 90 IVT patients were matched with 90 non-IVT patients. In multivariable regression analysis, a high regional leptomeningeal collateral (rLMC) score was independently associated with lower final infarction volume (FIV) in the IVT group (b = -0.472, p < 0.001) but not in the non-IVT group (b = -0.116, p = 0.327). The trichotomized rLMC scores predicted functional outcome in IVT treated patients (adjusted odds ratio, aOR = 4.57, 95% confidence interval, CI, 1.03-20.32, p = 0.046) but showed no independent association with outcome in the non-IVT group (aOR = 0.69, 95% CI 0.07-6.80, p = 0.753).

CONCLUSION

Good collaterals favored smaller FIV and good functional outcome in IVT treated patients but not in non-IVT treated patients. Good collateral flow may have limited prognostic value if IVT is not administered to attempt reperfusion.

What is the Role of Mechanical Thrombectomy in Childhood Stroke?

BACKGROUND

Like adults, most children have lifelong morbidity after stroke. Revascularization therapies such as intravenous tissue plasminogen activator and mechanical thrombectomy may be options to decrease this morbidity in selected children, although currently there are no evidence-based recommendations to guide treatment. The utility and safety of mechanical thrombectomy in childhood stroke is unknown because of the lack of safety trials, case-controlled trials, and comprehensive retrospective studies. As such, the current rationale for the use of mechanical thrombectomy in childhood is based on extrapolation from adult experience, as well as consensus at individual institutions with many centers deciding care on a case-by-case basis. Nevertheless, the increasing use of recanalization therapies in appropriately selected adults with acute arterial ischemic stroke has led to an increase in consideration and use in childhood, and there are enough case reports and series, as well as experience, to suggest that some children with large vessel occlusion will likely benefit.

METHODS

We reviewed current literature regarding mechanical thrombectomy in childhood.

RESULTS

There are differences between pediatric and adult stroke which may impact safety, efficacy, and individual decision-making, including patient size, pathophysiology of stroke, deficit, experience, and lack of data regarding natural history of stroke in children.

CONCLUSIONS

Hospitals planning to perform mechanical thrombectomy in children should establish local procedures and guidelines for considering thrombectomy. In our experience, care is best provided through multidisciplinary teams including a pediatric vascular neurologist, neurointerventionalist with pediatric experience, and pediatric neurocritical care.

Association of statin pretreatment with collateral circulation and final infarct volume in acute ischemic stroke patients: A meta-analysis

BACKGROUND AND AIMS

Statin pretreatment (SP) is associated with improved outcomes in acute ischemic stroke (AIS) patients. Collateral circulation status and final infarct volume (FIV) are independent predictors of functional outcome in AIS.

METHODS

We sought to evaluate the association of SP with collateral circulation and FIV in AIS patients. We used a random-effects model for all the analyses, and pooled standardized mean differences (SMDs) and odds ratios (OR) on the FIV and collateral status according to SP history, respectively.

RESULTS

We identified 9 eligible studies (1186 AIS patients). History of SP was associated with lower FIV (SMD = 0.25, 95%CI: 0.07-0.42, p = 0.005) compared to negative history of SP. A trend towards good collateral scores was observed in the SP group (OR = 1.45; 95% CI, 0.92-2.29, p = 0.11). Subgroup analysis demonstrated reduced FIV among atherosclerotic stroke patients with history of SP (SMD = 0.49; 95% CI, 0.19-0.80, p = 0.001).

CONCLUSIONS

SP appears to be associated with decreased FIV, especially in atherosclerotic AIS.

Current practice and future directions in the diagnosis and acute treatment of ischaemic stroke

Even though stroke presents as a variety of clinical syndromes, neuroimaging is the most important biomarker to help differentiate between stroke subtypes and assess treatment eligibility. Therapeutic advances have led to intravenous thrombolysis with tissue-type plasminogen activator and endovascular treatment for proximal vessel occlusion in the anterior cerebral circulation being standard care for acute ischaemic stroke. Providing access to this care has implications for existing systems of care for stroke and their organisation and has reintroduced the possibility of adjuvant and neuroprotective treatment strategies in acute ischaemic stroke. The use of neuroimaging for patient selection and speed of diagnosis and delivery of treatment are the dominant themes of modern ischaemic stroke care.

Advanced Neuroimaging of Acute Ischemic Stroke: Penumbra and Collateral Assessment

Acute ischemic stroke (AIS) occurs when there is a sudden loss in cerebral blood flow due to embolic or thromboembolic occlusion of a cerebral or cervical artery. Patients with AIS require emergent neuroimaging to guide treatment, which includes intravenous thrombolysis and endovascular mechanical thrombectomy (EMT). Recent advances in AIS treatment by EMT has been driven in part by advances in computed tomography (CT) and MR imaging neuroimaging evaluation of ischemic penumbra and pial collateral vessels. The authors review advanced noninvasive brain imaging by CT and MR imaging for the evaluation of AIS focusing on penumbral and collateral imaging.

Inter- and intraobserver reliability for angiographic leptomeningeal collateral flow assessment by the American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) scale

BACKGROUND

The adequacy of leptomeningeal collateral flow has a pivotal role in determining clinical outcome in acute ischemic stroke. The American Society of Interventional and Therapeutic Neuroradiology/Society of Interventional Radiology (ASITN/SIR) collateral score is among the most commonly used scales for measuring this flow. It is based on the extent and rate of retrograde collateral flow to the impaired territory on angiography.

OBJECTIVE

To evaluate inter- and intraobserver agreementin angiographic leptomeningeal collateral flow assessment.

MATERIALS AND METHODS

Thirty pretreatment angiogram video loops (frontal and lateral view), chosen from the randomized controlled trial THRombectomie des Artères CErebrales (THRACE), were sent for grading in an electronic file. 19 readers participated, including eight who had access to a training set before the first grading. 13 readers made a double evaluation, 3 months apart.

RESULTS

Overall agreement among the 19 observers was poor (κ = 0,16 ± 6,5.10 ^-3), and not improved with prior training (κ = 0,14 ± 0,016). Grade 4 showed the poorest interobserver agreement (κ=0.18±0.002) while grades 0 and 1 were associated with the best results (κ=0.52±0.001 and κ=0.43±0.004, respectively). Interobserver agreement increased (κ = 0,27± 0,014) when a dichotomized score, 'poor collaterals' (score of 0, 1 or 2) versus 'good collaterals' (score of 3 or 4) was used. The intraobserver agreements varied between slight (κ=0.18±0.13) and substantial (κ=0.74±0.1), and were slightly improved with the dichotomized score (from κ=0.19±0.2 to κ=0.79±0.11).

CONCLUSION

Inter- and intraobserver agreement of collateral circulation grading using the ASITN/SIR score was poor, raising concerns about comparisons among publications. A simplified dichotomized judgment may be a more reproducible assessment when images are rated by the same observer(s) in randomized trials.

Reperfusion therapy in acute ischemic stroke: dawn of a new era?

Following the success of recent endovascular trials, endovascular therapy has emerged as an exciting addition to the arsenal of clinical management of patients with acute ischemic stroke (AIS). In this paper, we present an extensive overview of intravenous and endovascular reperfusion strategies, recent advances in AIS neurointervention, limitations of various treatment paradigms, and provide insights on imaging-guided reperfusion therapies. A roadmap for imaging guided reperfusion treatment workflow in AIS is also proposed. Both systemic thrombolysis and endovascular treatment have been incorporated into the standard of care in stroke therapy. Further research on advanced imaging-based approaches to select appropriate patients, may widen the time-window for patient selection and would contribute immensely to early thrombolytic strategies, better recanalization rates, and improved clinical outcomes.

Mechanical Thrombectomy in Strokes with Large-Vessel Occlusion Beyond 6 Hours: A Pooled Analysis of Randomized Trials

Background and Purpose

Mechanical thrombectomy with or without intravenous thrombolysis is indicated in the acute treatment of ischemic strokes caused by an emergent large-vessel occlusion (ELVO) within 6 hours from symptom onset. However, a significant proportion of patients are referred to comprehensive stroke centers beyond this therapeutic time window. This study performed a pooled analysis of data from trials in which mechanical thrombectomy was performed beyond 6 hours from symptom onset.

Methods

We searched for randomized controlled trials that compared mechanical thrombectomy with the best medical treatment beyond 6 hours for ischemic strokes due to ELVO and reported on between 1990 and April 2018. The intervention group comprised patients treated with mechanical thrombectomy. Statistical analysis was conducted while pooling data and analyzing fixed- or random-effects models as appropriate.

Results

Four trials involving 518 stroke patients met the eligibility criteria. There were 267 strokes treated with mechanical thrombectomy, with a median time of 10.8 hours between when the patient was last known to be well to randomization. We observed a significant difference between groups concerning the rate of functional independence at 90 days from stroke, with an absolute difference of 27.5% (odds ratio=3.33, 95% CI=1.81–6.12, p<0.001) and good recanalization (odds ratio=13.17, 95% CI=4.17–41.60, p<0.001) favoring the intervention group.

Conclusions

This meta-analysis confirms the efficacy of mechanical thrombectomy in selected ischemic stroke patients beyond 6 hours from symptom onset. The selection is mainly based on the limited core infarct detected by emergent assessment using neuroimaging techniques.

Leptomeningeal collateral status predicts outcome after middle cerebral artery occlusion

OBJECTIVES

Perfusion through leptomeningeal collateral vessels is a likely pivotal factor in the outcome of stroke patients. We aimed to investigate the effect of collateral status on outcome in a cohort of unselected, consecutive stroke patients with middle cerebral artery occlusion undergoing reperfusion therapy.

MATERIALS AND METHODS

This retrospectively planned analysis was passed on prospectively collected data from 187 consecutive patients with middle cerebral artery occlusion admitted within 4.5 hours to one center and treated with intravenous thrombolysis alone (N = 126), mechanical thrombectomy alone (N = 5), or both (N = 56) from May 2009 to April 2014. Non-contrast CT (NCCT) and computed tomography angiography (CTA) were provided on admission and NCCT repeated at 24 hours. Collateral status was assessed based on the initial CTA. Hemorrhagic transformation was evaluated on the 24-hour NCCT and according to European Cooperative Acute Stroke Study (ECASS) criteria. Modified Rankin Scale score was assessed at 90 days, and mortality at 1 year.

RESULTS

At 90 days, median (IQR) modified Rankin Scale score in patients with poor collateral status was 4 (3-6) compared to 2 (1-4) in patients with good collateral status (P < .0001). Patients with poor collateral status were less likely to achieve a good 90-day outcome (modified Rankin Scale score 0-2) (Adjusted odds ratio 0.27, 95% CI: 0.09-0.86). During the first year, 40.9% of patients with poor collateral status died vs 18.2% of the remaining population (P = .001).

CONCLUSIONS

Leptomeningeal collateral status predicts functional outcome, mortality, and hemorrhagic transformation following middle cerebral artery occlusion.

Minor stroke due to large artery occlusion. When is intravenous thrombolysis not enough? Results from the SITS International Stroke Thrombolysis Register

Purpose

Beyond intravenous thrombolysis, evidence is lacking on acute treatment of minor stroke caused by large artery occlusion. To identify candidates for additional endovascular therapy, we aimed to determine the frequency of non-haemorrhagic early neurological deterioration in patients with intravenous thrombolysis-treated minor stroke caused by occlusion of large proximal and distal cerebral arteries. Secondary aims were to establish risk factors for non-haemorrhagic early neurological deterioration and report three-month outcomes in patients with and without non-haemorrhagic early neurological deterioration.

Method

We analysed data from the SITS International Stroke Thrombolysis Register on 2553 patients with intravenous thrombolysis-treated minor stroke (NIH Stroke Scale scores 0-5) and available arterial occlusion data. Non-haemorrhagic early neurological deterioration was defined as an increase in NIH Stroke Scale score ≥4 at 24 h, without parenchymal hematoma on follow-up imaging within 22-36 h.

Findings

The highest frequency of non-haemorrhagic early neurological deterioration was seen in 30% of patients with terminal internal carotid artery or tandem occlusions (internal carotid artery + middle cerebral artery) (adjusted odds ratio: 10.3 (95% CI 4.3-24.9), p < 0.001) and 17% in extracranial carotid occlusions (adjusted odds ratio 4.3 (2.5-7.7), p < 0.001) versus 3.1% in those with no occlusion. Proximal middle cerebral artery-M1 occlusions had non-haemorrhagic early neurological deterioration in 9% (adjusted odds ratio 2.1 (0.97-4.4), p = 0.06). Among patients with any occlusion and non-haemorrhagic early neurological deterioration, 77% were dead or dependent at three months.

Conclusions

Patients with minor stroke caused by internal carotid artery occlusion, with or without tandem middle cerebral artery involvement, are at high risk of disabling deterioration, despite intravenous thrombolysis treatment. Acute vessel imaging contributes usefully even in minor stroke to identify and consider endovascular treatment, or intensive monitoring at a comprehensive stroke centre, for patients at high risk of neurological deterioration.

Impact of collateral circulation status on favorable outcomes in thrombolysis treatment: A systematic review and meta-analysis

Collateral circulation affects the prognosis of patients with acute ischemic stroke (AIS) treated by thrombolysis. The present study performed a systematic assessment of the impact of the collateral circulation status on the outcomes of patients receiving thrombolysis treatment. Relevant full-text articles from the Cochrane Library, Ovid, Medline, Embase and PubMed databases published from January 1, 2000 to November 1, 2016 were retrieved. The quality of the studies was assessed and data were extracted by 2 independent investigators. The random-effects model was used to estimate the impact of good vs. poor collateral circulation, as well as baseline characteristics, on the outcome within the series presented as risk ratios. Subgroup analyses explored the potential factors that may interfere with the effects of the collateral circulation status on the outcome. A total of 29 studies comprising 4,053 patients were included in the present meta-analysis. A good collateral circulation status was revealed to have a beneficial effect on favorable functional outcome (modified Rankin scale, 0–3 at 3–6 months; P<0.001) and a higher rate of recanalization (P<0.001) compared with poor collateral circulation. Good collateral circulation was also associated with a lower rate of symptomatic intracranial hemorrhage (P<0.01), a lower rate of mortality (P<0.01) and a smaller infarct size (P<0.01). In conclusion, good collateral circulation was demonstrated to have a favorable prognostic value regarding the outcome for patients with AIS receiving thrombolysis treatment. Assessment of collateral circulation and penumbra area during pre-treatment imaging within an appropriate time-window prior to thrombolytic therapy will therefore improve the identification of AIS patients who may benefit from thrombolysis treatment.