Advanced Neuroimaging of Acute Ischemic Stroke: Penumbra and Collateral Assessment

Automated advanced imaging in acute ischemic stroke. Certainties and uncertainties

The purpose of this is study was to review pearls and pitfalls of advanced imaging, such as computed tomography perfusion and diffusion-weighed imaging and perfusion-weighted imaging in the selection of acute ischemic stroke (AIS) patients suitable for endovascular treatment (EVT) in the late time window (6-24 h from symptom onset). Advanced imaging can quantify infarct core and ischemic penumbra using specific threshold values and provides optimal selection parameters, collectively called target mismatch. More precisely, target mismatch criteria consist of core volume and/or penumbra volume and mismatch ratio (the ratio between total hypoperfusion and core volumes) with precise cut-off values. The parameters of target mismatch are automatically calculated with dedicated software packages that allow a quick and standardized interpretation of advanced imaging. However, this approach has several limitations leading to a misclassification of core and penumbra volumes. In fact, automatic software platforms are affected by technical artifacts and are not interchangeable due to a remarkable vendor-dependent variability, resulting in different estimate of target mismatch parameters. In addition, advanced imaging is not completely accurate in detecting infarct core, that can be under- or overestimated. Finally, the selection of candidates for EVT remains currently suboptimal due to the high rates of futile reperfusion and overselection caused by the use of very stringent inclusion criteria. For these reasons, some investigators recently proposed to replace advanced with conventional imaging in the selection for EVT, after the demonstration that non-contrast CT ASPECTS and computed tomography angiography collateral evaluation are not inferior to advanced images in predicting outcome in AIS patients treated with EVT. However, other authors confirmed that CTP and PWI/DWI postprocessed images are superior to conventional imaging in establishing the eligibility of patients for EVT. Therefore, the routine application of automatic assessment of advanced imaging remains a matter of debate. Recent findings suggest that the combination of conventional and advanced imaging might improving our selection criteria.

Neuroimaging in Patient Selection for Thrombectomy, From the AJR Special Series on Emergency Radiology

Endovascular thrombectomy has become the standard-of-care treatment for carefully selected patients with acute ischemic stroke due to a large-vessel occlusion of the anterior circulation. Neuroimaging plays a vital role in determining patient eligibility for thrombectomy, both in the early (0-6 hours from symptom onset) and late (> 6 to 24 hours from symptom onset) time windows. Various neuroimaging algorithms are used to determine thrombectomy eligibility, and each algorithm must be optimized for institutional workflow. In this review, we describe common imaging modalities and recommended algorithms for the evaluation of patients for endovascular thrombectomy. We also discuss emerging patient populations who might qualify for thrombectomy in the coming years.

Advancements in the management of acute ischemic stroke: A narrative review

Primary literature detailing updated management principles of acute ischemic stroke outpaces current guidelines, resulting in heterogenous practices. Recent advancements in neuroimaging have shifted treatment from a time-based approach to an individualized, image-guided appraisal directed by the presence or absence of salvageable brain tissue. In addition, tenecteplase appears to be a safe and effective for the treatment of acute ischemic stroke and is becoming an attractive agent due to its practical administration. Several factors must be accounted for when implementing tenecteplase into the health-system including cost, education, and changes in clinician workflows. Larger studies with broad patient populations are needed to more definitively evaluate whether intravenous thrombolytics should be used in combination with endovascular thrombectomy in patients with anterior large-vessel occlusions. Although debate regarding the safety and efficacy of various endovascular therapies, delays encountered in the identification, triage, and care of acute ischemic stroke patients increase the likelihood of necrotic core lesion development and loss of salvageable penumbra.

Radiation Dose Reduction Opportunities in Vascular Imaging

Computed tomography angiography (CTA) has been the gold standard imaging modality for vascular imaging due to a variety of factors, including the widespread availability of computed tomography (CT) scanners, the ease and speed of image acquisition, and the high sensitivity of CTA for vascular pathology. However, the radiation dose experienced by the patient during imaging has long been a concern of this image acquisition method. Advancements in CT image acquisition techniques in combination with advancements in non-ionizing radiation imaging techniques including magnetic resonance angiography (MRA) and contrast-enhanced ultrasound (CEUS) present growing opportunities to reduce total radiation dose to patients. This review provides an overview of advancements in imaging technology and acquisition techniques that are helping to minimize radiation dose associated with vascular imaging.

The Cerebral Collateral Cascade: Comprehensive Blood Flow in Ischemic Stroke

BACKGROUND AND OBJECTIVES

Robust cerebral collaterals are associated with favorable outcomes in patients with acute ischemic stroke due to large vessel occlusion treated by thrombectomy. However, collateral status assessment mostly relies on single imaging biomarkers and a more comprehensive holistic approach may provide deeper insights into the biology of collateral perfusion on medical imaging. Comprehensive collateralization is defined as blood flow of cerebral arteries through the brain tissue and into draining veins. We hypothesized that a comprehensive analysis of the cerebral collateral cascade (CCC) on an arterial, tissue, and venous level would predict clinical and radiologic outcomes.

METHODS

This was a multicenter retrospective cohort study of patients with acute stroke undergoing thrombectomy triage. CCC was determined by quantifying pial arterial collaterals, tissue-level collaterals, and venous outflow (VO). Pial arterial collaterals were determined by CT angiography; tissue-level collaterals were assessed on CT perfusion. VO was assessed on CT angiography using the cortical vein opacification score. Three groups were defined: CCC+ (good pial collaterals, tissue-level collaterals, and VO), CCC- (poor pial collaterals, tissue-level collaterals, and VO), and CCCmixed (the remainder of the patients). Primary outcome was functional independence (modified Rankin Scale score 0-2) at 90 days. Secondary outcome was final infarct volume.

RESULTS

A total of 647 patients met inclusion criteria: 176 CCC+, 345 CCCmixed, and 126 CCC-. Multivariable ordinal logistic regression showed that CCC+ predicted good functional outcomes (odds ratio [OR] 18.9 [95% CI 8-44.5]; p < 0.001) compared with CCC- and CCCmixed. CCCmixed patients likely had better functional outcomes compared with CCC- patients (OR 2.5 [95% CI 1.2-5.4]; p = 0.014). Quantile regression analysis (50th percentile) showed that CCC+ (β -78.5, 95% CI -96.0 to -61.1; p < 0.001) and CCCmixed (β -64.0, 95% CI -82.4 to -45.6; p < 0.001) profiles were associated with considerably lower final infarct volumes compared with CCC- profiles.

DISCUSSION

Comprehensive assessment of the collateral blood flow cascade in patients with acute stroke is a strong predictor of clinical and radiologic outcomes in patients treated by thrombectomy.

Optimized Deconvolutional Algorithm-based CT Perfusion Imaging in Diagnosis of Acute Cerebral Infarction

To apply deconvolution algorithm in computer tomography (CT) perfusion imaging of acute cerebral infarction (ACI), a convolutional neural network (CNN) algorithm was optimized first. RIU-Net was applied to segment CT image, and then equipped with SE module to enhance the feature extraction ability. Next, the BM3D algorithm, Dn CNN, and Cascaded CNN were compared for denoising effects. 80 patients with ACI were recruited and grouped for a retrospective analysis. The control group utilized the ordinary method, and the observation group utilized the algorithm proposed. The optimized model was utilized to extract the feature information of the patient's CT images. The results showed that after the SE module pooling was added to the RIU-Net network, the utilization rate of the key features was raised. The specificity of patients in observation group was 98.7%, the accuracy was 93.7%, and the detected number was (1.6 ± 0.2). The specificity of patients in the control group was 93.2%, the accuracy was 87.6%, and the detected number was (1.3 ± 0.4). Obviously, the observation group was superior to the control group in all respects (P < 0.05). In conclusion, the optimized model demonstrates superb capabilities in image denoising and image segmentation. It can accurately extract the information to diagnose ACI, which is suggested clinically.

Longitudinal Variations of CDC42 in Patients With Acute Ischemic Stroke During 3-Year Period: Correlation With CD4+ T Cells, Disease Severity, and Prognosis

Objective

Cell division cycle 42 (CDC42) modulates CD4⁺ T-cell differentiation, blood lipids, and neuronal apoptosis and is involved in the pathogenesis of acute ischemic stroke (AIS); however, the clinical role of CDC42 in AIS remains unanswered. This study aimed to evaluate the expression of CDC42 in a 3-year follow-up and its correlation with disease severity, T helper (Th)1/2/17 cells, and the prognosis in patients with AIS.

Methods

Blood CDC42 was detected in 143 patients with AIS at multiple time points during the 3-year follow-up period and in 70 controls at admission by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In addition, blood Th1, Th2, and Th17 cells and their secreted cytokines (interferon-γ (IFN-γ), interleukin-4 (IL-4), and interleukin-17A (IL-17A)) in patients with AIS were detected by flow cytometry and enzyme-linked immunosorbent assay (ELISA), respectively.

Results

Compared with controls (p < 0.001), CDC42 was reduced in patients with AIS. CDC42 was negatively correlated with the National Institutes of Health Stroke Scale (NIHSS) score (p < 0.001), whereas, in patients with AIS (all p < 0.050), it was positively associated with Th2 cells and IL-4 but negatively correlated with Th17 cells and IL-17A. CDC42 was decreased from admission to 3 days and gradually increased from 3 days to 3 years in patients with AIS (P<0.001). In a 3-year follow-up, 24 patients with AIS recurred and 8 patients died. On the 3rd day, 7th day, 1st month, 3rd month, 6th month, 1st year, 2nd year, and 3rd year, CDC42 was decreased in recurrent patients than that in non-recurrent patients (all p < 0.050). CDC42 at 7 days (p = 0.033) and 3 months (p = 0.023) was declined in reported deceased patients than in survived patients.

Conclusion

CDC42 is used as a biomarker to constantly monitor disease progression and recurrence risk of patients with AIS.

Role of Magnetic Resonance Perfusion Imaging in Acute Stroke: Arterial Spin Labeling Versus Dynamic Susceptibility Contrast-Enhanced Perfusion

Introduction: The role of perfusion neuroimaging in managing cases of acute ischemic stroke (AIS) is to identify ischemic penumbra and regions of hypo-perfusion, which can be salvaged. Dynamic susceptibility contrast (DSC) perfusion imaging techniques have been the main magnetic resonance imaging (MRI) perfusion techniques used to identify AIS. Arterial spin labelling (ASL) is an alternative non-invasive perfusion technique, which permits tissue perfusion measurement without any need for administration of exogenous contrast agents. The objective was to compare the diagnostic accuracy of ASL perfusion MRI versus DSC enhanced perfusion MRI in detecting perfusion-diffusion mismatch of varying volumes in acute ischemic stroke.

Materials and methods: A hospital-based observational cross-sectional study was done in a tertiary care institute in Tamil Nadu between December 2018 to October 2019. Fifty-five subjects aged more than 18 years referred to the Radio-diagnosis department (less than 24 hours since the onset of weakness) for emergency assessment of suspected acute stroke were subjected to MRI stroke scan protocol. Then AIS cases were evaluated with ASL and DSC perfusion-weighted imaging. The collected data was entered in Excel (Microsoft, Redmond, WA, USA). IBM SPSS version 22 (IBM Corp., Armonk, NY, USA) was used for statistical analysis. Receiver operating characteristic (ROC) analysis was done to assess the predictive validity of ASL in predicting DSC mismatch. The diagnostic accuracy of ASL was the primary outcome variable. P-value < 0.05 was considered statistically significant.

Results: Forty-four subjects confirmed as stroke were included in the final analysis. Their mean (±SD) age was 53.84 (±10.80) years. 72.7% were males. The majority (53.8%) presented during the acute stage of cerebral infarction (53.8%). The majority (45.5%) had hemiplegia followed by aphasia (27.3%). The major vascular territory involved was the middle cerebral artery (54.5%). The sensitivity, specificity, positive predictive value, and negative predictive value of ASL (non-contrast) in predicting DSC (contrast) mismatch was found to be 71.43%, 78.57%, 83.33%, and 64.71% respectively.

Conclusion: ASL MR has the potential to replace MRI DSC perfusion in the future imaging diagnostic work-up for stroke. However, further studies are required to validate its role as the first-line imaging for stroke therapy.

Anomalous location of intracranial vessels in adults

Anomalous intracranial vessels are not uncommon, and this finding is not always associated with arteriovenous malformations. Other conditions such as anomalous connections between arteries or phlebitc patterns can also present as vessels with abnormal intracranial locations. Noninvasive diagnosis is important to determine whether to do more invasive tests such as cerebral digital subtraction angiography or to estimate the risk of bleeding in arteriovenous malformations and therefore to evaluate the need for endovascular/surgical treatment. In this paper, we present an algorithm for the differential diagnosis of anomalous intracranial vessels according to their location (intra/extra-axial) and function (whether the vessels are arterialized). Moreover, we analyze the important points of the angioarchitecture of the principal arteriovenous malformations with risk of intracranial bleeding, such as pial arteriovenous malformations and dural fistulas.

Clinical Implications of Prominent Cortical Vessels on Susceptibility-Weighted Imaging in Acute Ischemic Stroke Patients Treated with Recanalization Therapy

Prominent cortical vessels on susceptibility-weighted imaging (PCV–SWI) correlate with poor leptomeningeal collaterals. However, little is known about PCV–SWI in recanalization therapy-treated patients with anterior circulation large vessel occlusions (LVO). We investigated PCV–SWI-based assessment of leptomeningeal collaterals and outcome predictions in 100 such patients in an observational study. We assessed PCV–SWI using the Alberta Stroke Program Early CT Score and evaluated leptomeningeal collaterals on multiphase CT angiography (mCTA). Predictive abilities were analyzed using multivariable logistic regression and area of receiver operating curves (AUCs). The extent of PCV–SWI correlated with leptomeningeal collaterals on mCTA (Spearman test, r = 0.77; p < 0.001); their presence was associated with worse functional outcomes and a lower successful recanalization rate (adjusted odds ratios = 0.24 and 0.23, 95% CIs = 0.08–0.65 and 0.08–0.65, respectively). The presence of PCV–SWI predicted outcomes better than good collaterals on mCTA did (C-statistic = 0.84 vs. 0.80; 3-month modified Rankin Scale (mRS) 0–2 = 0.75 vs. 0.67 for successful recanalization). Comparison of AUCs showed that they had similar abilities for predicting outcomes (p = 0.68 for 3-month mRS 0–2; p = 0.23 for successful recanalization). These results suggest that PCV–SWI is a useful feature for assessing leptomeningeal collaterals in acute ischemic stroke patients with anterior circulation LVO and predicting outcomes after recanalization therapy.

Collateral estimation by susceptibility-weighted imaging and prediction of functional outcomes after acute anterior circulation ischemic stroke

To determine the value of susceptibility-weighted imaging (SWI) for collateral estimation and for predicting functional outcomes after acute ischemic stroke. To identify independent predictors of favorable functional outcomes, age, sex, risk factors, baseline National Institutes of Health Stroke Scale (NIHSS) score, baseline diffusion-weighted imaging (DWI) lesion volume, site of steno-occlusion, SWI collateral grade, mode of treatment, and successful reperfusion were evaluated by multiple logistic regression analyses. A total of 152 participants were evaluated. A younger age (adjusted odds ratio (aOR), 0.42; 95% confidence interval (CI) 0.34 to 0.77; P < 0.001), a lower baseline NIHSS score (aOR 0.90; 95% CI 0.82 to 0.98; P = 0.02), a smaller baseline DWI lesion volume (aOR 0.83; 95% CI 0.73 to 0.96; P = 0.01), an intermediate collateral grade (aOR 9.49; 95% CI 1.36 to 66.38; P = 0.02), a good collateral grade (aOR 6.22; 95% CI 1.16 to 33.24; P = 0.03), and successful reperfusion (aOR 5.84; 95% CI 2.08 to 16.42; P = 0.001) were independently associated with a favorable functional outcome. There was a linear association between the SWI collateral grades and functional outcome (P = 0.008). Collateral estimation using the prominent vessel sign on SWI is clinically reliable, as it has prognostic value.

Refined Ischemic Penumbra Imaging with Tissue pH and Diffusion Kurtosis Magnetic Resonance Imaging

Imaging has played a vital role in our mechanistic understanding of acute ischemia and the management of acute stroke patients. The most recent DAWN and DEFUSE-3 trials showed that endovascular therapy could be extended to a selected group of late-presenting stroke patients with the aid of imaging. Although perfusion and diffusion MRI have been commonly used in stroke imaging, the approximation of their mismatch as the penumbra is oversimplified, particularly in the era of endovascular therapy. Briefly, the hypoperfusion lesion includes the benign oligemia that does not proceed to infarction. Also, with prompt and effective reperfusion therapy, a portion of the diffusion lesion is potentially reversible. Therefore, advanced imaging that provides improved ischemic tissue characterization may enable new experimental stroke therapeutics and eventually further individualize stroke treatment upon translation to the clinical setting. Specifically, pH imaging captures tissue of altered metabolic state that demarcates the hypoperfused lesion into ischemic penumbra and benign oligemia, which remains promising to define the ischemic penumbra's outer boundary. On the other hand, diffusion kurtosis imaging (DKI) differentiates the most severely damaged and irreversibly injured diffusion lesion from the portion of diffusion lesion that is potentially reversible, refining the inner boundary of the penumbra. Altogether, the development of advanced imaging has the potential to not only transform the experimental stroke research but also aid clinical translation and patient management.

Dengzhanxixin Injection Ameliorates Cognitive Impairment Through a Neuroprotective Mechanism Based on Mitochondrial Preservation in Patients With Acute Ischemic Stroke

Acute ischemic stroke (AIS) is a global health burden and cognitive impairment is one of its most serious complication. Adequate interventions for AIS may have the potential to improve cognitive outcomes. In the present study, we selected Erigeron breviscapus (Vaniot) Hand.-Mazz. injection (Dengzhanxixin injection, DZXI), a widely used Chinese herbal injection, in contrast to edaravone as the positive control drug to test its potential to ameliorates neurological and cognitive impairments caused by AIS. We performed a 2-week randomized trial with these two drugs in AIS patients presenting mild to moderate cognitive impairments. Neuropsychological tests and MRI examinations showed that DZXI attenuated the neurological and cognitive impairments of patients and protected the grey matter in specific regions from ischemic damage. Notably, DZXI exerted better effects than edaravone in some neuropsychological tests, probably due to the protective effect of DZXI on grey matter. To explore the therapeutic mechanisms, we carried out an experiment with a middle cerebral artery occlusion rat model. We found that DZXI decreased the infarct volume and increased the survival of neuronal cells in the ischemic penumbra; furthermore, DZXI modulated the mitochondrial respiratory chain process and preserved the mitochondrial structure in the brain tissue. Overall, our data suggested that the administration of DZXI is effective at ameliorating neurological and cognitive impairments in AIS, and the underlying mechanisms are related to the protective effects of DZXI on cerebral neurons and neuronal mitochondria.

Rethinking the Collateral Vasculature Assessment in Acute Ischemic Stroke: The Comprehensive Collateral Cascade

ABSTRACT

Occlusion of a cervical or cerebral artery results in disruption of blood flow to the brain and may result in irreversible infarction. Intracranial pial collaterals are a network of arteries that may preserve blood flow to otherwise critically hypoperfused brain areas until vessel recanalization is achieved. The robustness of these arterial collaterals is pivotal for the survivability of ischemic brain tissue and is associated with treatment success and long-term clinical outcome. More recently, the importance of venous outflow from ischemic brain tissue has been appreciated. Arterial collaterals and venous outflow are evaluated by neuroimaging parameters, and recent imaging advances have enabled a more comprehensive assessment of the entire collateral cascade in patients with acute ischemic stroke. Here we review novel imaging biomarkers for the assessment of arterial collaterals, tissue-level collateral blood flow, and venous outflow. We also summarize how a more comprehensive assessment of the cerebral blood flow leads to a better prediction of treatment efficacy and improved clinical outcomes.

Perfusion imaging-based tissue-level collaterals predict ischemic lesion net water uptake in patients with acute ischemic stroke and large vessel occlusion

Ischemic lesion Net Water Uptake (NWU) quantifies cerebral edema formation and likely correlates with the microvascular perfusion status of patients with acute ischemic stroke due to large vessel occlusion (AIS-LVO). We hypothesized that favorable tissue-level collaterals (TLC) predict less NWU and good functional outcomes. We performed a retrospective multicenter analysis of AIS-LVO patients who underwent thrombectomy triage. TLC were measured on cerebral perfusion studies using the hypoperfusion intensity ratio (HIR; volume ratio of brain tissue with [Tmax > 10 sec/Tmax > 6 sec]); favorable TLC were regarded as HIR ≤ 0.4. NWU was determined using a quantitative densitometry approach on follow-up CT. Primary outcome was NWU. Secondary outcome was a good functional outcome (modified Rankin Scale [mRS] 0-2).580 patients met inclusion criteria. Favorable TLC (β: 4.23, SE: 0.65; p < 0.001) predicted smaller NWU after treatment. Favorable TLC (OR: 2.35, [95% CI: 1.31-4.21]; p < 0.001), and decreased NWU (OR: 0.75, [95% CI: 0.70-0.79]; p < 0.001) predicted good functional outcome, while controlling for age, glucose, CTA collaterals, baseline NIHSS and good vessel reperfusion status.We conclude that favorable TLC predict less ischemic lesion NWU after treatment in AIS-LVO patients. Favorable TLC and decreased NWU were independent predictors of good functional outcome.

First-Pass Reperfusion by Mechanical Thrombectomy in Acute M1 Occlusion: The Size of Retriever Matters

Introduction: Single-pass complete reperfusion using stent retrievers has been shown to improve functional outcome in patients with large vessel occlusion strokes. The aim of this study was to investigate the optimal size of stent retrievers to achieve one-pass complete reperfusion by mechanical thrombectomy. Methods: The study evaluated the results of aspiration-assisted mechanical thrombectomy of acute isolated occlusion of the middle cerebral artery in the M1 segment with a novel 5 × 40-mm stent retriever compared to the usual 4 × 20-mm device. Reperfusion status was quantified using the Thrombolysis In Cerebral Infarction (TICI) scale. We hypothesized that thrombectomy of M1 occlusions with 5 × 40-mm stent retriever yields higher rates of complete first-pass reperfusion (FP) (TICI ≥2c after one pass) and successful or modified FP (mFP) (TICI ≥2b after one pass) than thrombectomy with 4 × 20. We included isolated M1 occlusions treated with pRESET 5 × 40 (phenox) as first-choice device for thrombectomy and compared with M1 occlusions treated with pRESET 4 × 20. We excluded patients with additional occlusions or tandem stenosis or who received an intracranial stent or angioplasty as a part of the endovascular treatment. Results: One hundred thirteen patients were included in the 4 × 20 group and 57 patients in the 5 × 40 group. The 5 × 40 group achieved higher FP compared to 4 × 20 group [61.4% (35 of 57 patients) vs. 40.7% (46 of 113), respectively; adjusted odds ratio (OR) and 95% confidence interval (95% CI) = 2.20 (1.08-4.48), p = 0.030] and a higher mFP [68.4%, 39 of 57 patients vs. 48.7%, 55 of 113; adjusted OR (95% CI) = 2.11 (1.04-4.28), p = 0.037]. Frequency of successful reperfusion (TICI ≥2b) was similar in both groups (100 vs. 97.3%), but frequency of complete reperfusion (TICI ≥2c) was higher in the 5 × 40 group [82.5 vs. 61.9%, adjusted OR (95% CI) = 2.47 (1.01-6.04), p = 0.047]. Number of passes to achieve reperfusion was lower in the 5 × 40 group than in the 4 × 20 group [1.6 ± 1.1 vs. 2 ± 1.4, p = 0.033; adjusted incidence rate ratio (95% CI) = 0.84 (0.69-1.03), p = 0.096]. Modified Rankin scale at 90 days was similar in 5 × 40 and 4 × 20 groups. Conclusions: The size of stent retriever matters in acute M1 occlusions treated with aspiration-assisted mechanical thrombectomy. A longer stent retriever with a larger nominal diameter achieves a higher complete and successful FP and higher successful reperfusion compared to a shorter stent retriever.

Association of Venous Outflow Profiles and Successful Vessel Reperfusion After Thrombectomy

OBJECTIVE

Robust arterial collaterals are associated with successful reperfusion after thrombectomy treatment of acute ischemic stroke due to large vessel occlusion (AIS-LVO). Excellent venous outflow (VO) reflects excellent tissue perfusion and collateral status in patients with AIS-LVO. The goal of this study was to determine whether favorable VO profiles assessed on pretreatment CT angiography (CTA) images correlate with successful vessel reperfusion after thrombectomy in patients with AIS-LVO.

METHODS

This was a multicenter retrospective cohort study of consecutive patients with AIS-LVO treated by thrombectomy. Baseline CTA was used to assess collateral status (Tan scale) and VO using the Cortical Vein Opacification Score (COVES). Favorable VO was defined as COVES ≥3. Primary outcome was excellent vessel reperfusion status (modified Thrombolysis in Cerebral Infarction 2c/3). Secondary outcome was good functional outcome defined as a score of 0 to 2 on the modified Rankin Scale after 90 days.

RESULTS

Five hundred sixty-five patients met the inclusion criteria. Multivariable logistic regression analysis showed that favorable VO (odds ratio [OR] 2.10 [95% confidence interval (CI) 1.39-3.16]; p < 0.001) was associated with excellent vessel reperfusion during thrombectomy, regardless of good CTA collateral status (OR 0.87 [95% CI 0.58-1.34]; p = 0.48). A favorable VO profile (OR 8.9 [95%CI 5.3-14.9]; p < 0.001) and excellent vessel reperfusion status (OR 2.7 [95%CI 1.7-4.4]; p < 0.001) were independently associated with good functional outcome adjusted for age, sex, glucose, tissue plasminogen activator administration, good CTA collateral status, and presentation NIH Stroke Scale score.

CONCLUSION

A favorable VO profile is associated with reperfusion success and good functional outcomes in patients with AIS-LVO treated by endovascular thrombectomy.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that a favorable VO profile is associated with reperfusion success and good functional outcomes in patients with AIS-LVO treated by endovascular thrombectomy.

Measuring Perfusion: Intravoxel Incoherent Motion MR Imaging

The signal acquired in vivo using a diffusion-weighted MR imaging (DWI) sequence is influenced by blood motion in the tissue. This means that perfusion information from a DWI sequence can be obtained in addition to thermal diffusion, if the appropriate sequence parameters and postprocessing methods are applied. This is commonly regrouped under the denomination intravoxel incoherent motion (IVIM) perfusion MR imaging. Of relevance, the perfusion information acquired with IVIM is essentially local, quantitative and acquired without intravenous injection of contrast media. The aim of this work is to review the IVIM method and its clinical applications.

Venous Outflow Profiles Are Linked to Cerebral Edema Formation at Noncontrast Head CT after Treatment in Acute Ischemic Stroke Regardless of Collateral Vessel Status at CT Angiography

Background Ischemic lesion net water uptake (NWU) at noncontrast head CT enables quantification of cerebral edema in patients with acute ischemic stroke (AIS) due to large vessel occlusion (LVO). Purpose To assess whether favorable venous outflow (VO) profiles at CT angiography are associated with reduced NWU and good functional outcomes in patients with AIS due to LVO. Materials and Methods This multicenter retrospective cohort study evaluated consecutive patients with AIS due to LVO who underwent thrombectomy triage between January 2013 and December 2019. Arterial collateral vessel status (Tan scale) and venous output were measured at CT angiography. Venous outflow was graded with use of the cortical vein opacification score, which quantifies opacification of the vein of Labbé, sphenoparietal sinus, and superficial middle cerebral vein. Favorable VO was regarded as a score of 3-6 and unfavorable VO as a score of 0-2. NWU was determined at follow-up noncontrast CT. Multivariable regression analyses were performed to determine the association between favorable VO profiles and NWU after treatment and good functional outcome (modified Rankin Scale, ≤2). Results A total of 580 patients were included. Of the 580 patients, 231 had favorable VO (104 women; median age, 73 years [interquartile range {IQR}, 62-81 years]) and 349 had unfavorable VO (190 women; median age, 77 years [IQR, 66-84 years]). Compared with patients with unfavorable VO, those with favorable VO exhibited lower baseline National Institutes of Health Stroke Scale score (median, 12.5 [IQR, 7-17] vs 17 [IQR, 13-21]), higher Alberta Stroke Program Early CT Score (median, 9 [IQR, 7-10] vs 7 [IQR, 6-8]), and less NWU after treatment (median, 7% [IQR, 4.6%-11.5%] vs 17.9% [IQR, 12.3%-22.2%]). In a multivariable regression analysis, NWU mean difference between patients with unfavorable VO and those with favorable VO was 6.1% (95% CI: 4.9, 7.3; P < .001) regardless of arterial CT angiography collateral vessel status (b coefficient, 0.72 [95% CI: -0.59, 2.03; P = .28]). Favorable VO (odds ratio [OR]: 4.1 [95% CI: 2.2, 7.7]; P < .001) and reduced NWU after treatment (OR: 0.77 [95% CI: 0.73, 0.83]; P < .001) were independently associated with good functional outcomes. Conclusion Favorable venous outflow (VO) correlated with reduced ischemic net water uptake (NWU) after treatment. Reduced NWU and favorable VO were associated with good functional outcomes regardless of CT angiography arterial collateral vessel status. © RSNA, 2021 Online supplemental material is available for this article.

Favorable Venous Outflow Profiles Correlate With Favorable Tissue-Level Collaterals and Clinical Outcome

BACKGROUND AND PURPOSE

Patients with acute ischemic stroke due to large vessel occlusion and favorable tissue-level collaterals (TLCs) likely have robust cortical venous outflow (VO). We hypothesized that favorable VO predicts robust TLC and good clinical outcomes.

METHODS

Multicenter retrospective cohort study of consecutive acute ischemic stroke due to large vessel occlusion patients who underwent thrombectomy triage. Included patients had interpretable prethrombectomy computed tomography, computed tomography angiography, and cerebral perfusion imaging. TLCs were measured on cerebral perfusion studies using the hypoperfusion intensity ratio (volume ratio of brain tissue with [Tmax >10 s/Tmax >6 s]). VO was determined by opacification of the vein of Labbé, sphenoparietal sinus, and superficial middle cerebral vein on computed tomography angiography as 0, not visible; 1, moderate opacification; and 2, full. Clinical and demographic data were determined from the electronic medical record. Using multivariable regression analyses, we determined the association between VO and (1) favorable TLC status (defined as hypoperfusion intensity ratio ≤0.4) and (2) good functional outcome (modified Rankin Scale score, 0-2).

RESULTS

Six hundred forty-nine patients met inclusion criteria. Patients with favorable VO were younger (median age, 72 [interquartile range (IQR), 62-80] versus 77 [IQR, 66-84] years), had a lower baseline National Institutes of Health Stroke Scale (median, 12 [IQR, 7-17] versus 19 [IQR, 13-20]), and had a higher Alberta Stroke Program Early Computed Tomography Score (median, 9 [IQR, 7-10] versus 7 [IQR, 6-9]). Favorable VO strongly predicted favorable TLC (odds ratio, 4.5 [95% CI, 3.1-6.5]; P<0.001) in an adjusted regression analysis. Favorable VO also predicted good clinical outcome (odds ratio, 10 [95% CI, 6.2-16.0]; P<0.001), while controlling for favorable TLC, age, glucose, baseline National Institutes of Health Stroke Scale, and good vessel reperfusion status.

CONCLUSIONS

In this selective retrospective cohort study of acute ischemic stroke due to large vessel occlusion patients undergoing thrombectomy triage, favorable VO profiles correlated with favorable TLC and were associated with good functional outcomes after treatment. Future prospective studies should independently validate our findings.

Silver Jubilee of Stroke Thrombolysis With Alteplase: Evolution of the Therapeutic Window

In 1995, the results of a landmark clinical trial by National Institute of Neurological Disorders and Stroke (NINDS) made a paradigm shift in managing acute cerebral ischemic stroke (AIS) patients at critical care centers. The study demonstrated the efficacy of tissue-type plasminogen activator (tPA), alteplase in improving neurological and functional outcome in AIS patients when administered within 3 h of stroke onset. After about 12 years of efforts and the results of the ECASS-III trial, it was possible to expand the therapeutic window to 4.5 h, which still represents a major logistic issue, depriving many AIS patients from the benefits of tPA therapy. Constant efforts in this regards are directed toward either speeding up the patient recruitment for tPA therapy or expanding the current tPA window. Efficient protocols to reduce the door-to-needle time and advanced technologies like telestroke services and mobile stroke units are being deployed for early management of AIS patients. Studies have demonstrated benefit of thrombolysis guided by perfusion imaging in AIS patients at up to 9 h of stroke onset, signifying “tissue window.” Several promising pharmacological and non-pharmacological approaches are being explored to mitigate the adverse effects of delayed tPA therapy, thus hoping to further expand the current tPA therapeutic window without compromising safety. With accumulation of scientific data, stroke organizations across the world are amending/updating the clinical recommendations of tPA, the only US-FDA approved drug for managing AIS patients. Alteplase has been a part of our neurocritical care and we intend to celebrate its silver jubilee by dedicating this review article discussing its journey so far and possible future evolution.

Endovascular Treatment of Acute Ischemic Stroke

PURPOSE OF REVIEW

This article reviews the actual indications for mechanical thrombectomy in patients with acute ischemic stroke and how the opportunities for endovascular therapy can be expanded by using the concept of clinical-imaging or perfusion-imaging mismatch (as a surrogate for salvageable tissue) rather than time of ischemia.

RECENT FINDINGS

Six randomized controlled trials undoubtedly confirmed the benefits of using endovascular thrombectomy on the clinical outcome of patients with stroke with large vessel occlusion within 6 hours from symptom onset compared with those receiving only standard medical care. In a meta-analysis of individual patient data, the number needed to treat with endovascular thrombectomy to reduce disability by at least one level on the modified Rankin Scale for one patient was 2.6. Recently, the concept of "tissue window" versus time window has proved useful for selecting patients for mechanical thrombectomy up to 24 hours from symptom onset. The DAWN (DWI or CTP Assessment With Clinical Mismatch in the Triage of Wake-Up and Late Presenting Strokes Undergoing Neurointervention) trial included patients at a median of 12.5 hours from onset and showed the largest effect in functional outcome ever described in any acute stroke treatment trial (35.5% increase in functional independence). In DEFUSE 3 (Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution 3), patients treated with mechanical thrombectomy at a median of 11 hours after onset had a 28% increase in functional independence and an additional 20% absolute reduction in death or severe disability.

SUMMARY

For patients with acute ischemic stroke and a large vessel occlusion in the proximal anterior circulation who can be treated within 6 hours of stroke symptom onset, mechanical thrombectomy with a second-generation stent retriever or a catheter aspiration device should be indicated regardless of whether the patient received treatment with intravenous (IV) recombinant tissue plasminogen activator (rtPA) in patients with limited signs of early ischemic changes on neuroimaging. Two clinical trials completely disrupted the time window concept in acute ischemic stroke, showing excellent clinical outcomes in patients treated up to 24 hours from symptom onset. Time of ischemia is, on average, a good biomarker for tissue viability; however, the window of opportunity for treatment varies across different individuals because of a range of compensatory mechanisms. Adjusting time to the adequacy of collateral flow leads to the concept of tissue window, a paradigm shift in stroke reperfusion therapy.

Association of circulating long non-coding RNA MALAT1 in diagnosis, disease surveillance, and prognosis of acute ischemic stroke

We aimed to investigate the association of long non-coding RNA metastasis-associated lung adenocarcinoma transcript 1 (lnc-MALAT1) with acute ischemic stroke (AIS), and its association with disease severity, inflammation, and recurrence-free survival (RFS) in AIS patients. One hundred and twenty AIS patients and 120 controls were recruited. Venous blood samples from AIS patients (within 24 h after symptoms onset) and controls (at entry to study) were collected to detect plasma lnc-MALAT1 expression by real-time quantitative polymerase chain reaction. AIS severity was assessed by the National Institutes of Health Stroke Scale (NIHSS) score. Plasma concentrations of inflammation factors (including C-reactive protein (CRP), tumor necrosis factor α (TNF-α), interleukin (IL)-6, IL-8, IL-10, IL-17, and IL-22) were measured and RFS was calculated. lnc-MALAT1 expression was decreased in AIS patients compared to controls, and it had a close correlation with AIS (AUC=0.791, 95% CI: 0.735-0.846). For disease condition, lnc-MALAT1 expression negatively correlated with NIHSS score and pro-inflammatory factor expression (including CRP, TNF-α, IL-6, IL-8, and IL-22), while it positively correlated with anti-inflammatory factor IL-10 expression. Furthermore, lnc-MALAT1 expression was elevated in AIS patients with diabetes. For prognosis, no statistical correlation of lnc-MALAT1 expression with RFS was found, while a trend for longer RFS was observed in patients with lnc-MALAT1 high expression compared to those with lnc-MALAT1 low expression.

Multiparametric classification of sub-acute ischemic stroke recovery with ultrafast diffusion, 23 Na, and MPIO-labeled stem cell MRI at 21.1 T

MRI leverages multiple modes of contrast to characterize stroke. High-magnetic-field systems enhance the performance of these MRI measurements. Previously, we have demonstrated that individually sodium and stem cell tracking metrics are enhanced at ultrahigh field in a rat model of stroke, and we have developed robust single-scan diffusion-weighted imaging approaches that utilize spatiotemporal encoding (SPEN) of the apparent diffusion coefficient (ADC) for these challenging field strengths. Here, we performed a multiparametric study of middle cerebral artery occlusion (MCAO) biomarker evolution focusing on comparison of these MRI biomarkers for stroke assessment during sub-acute recovery in rat MCAO models at 21.1 T. T₂ -weighted MRI was used as the benchmark for identification of the ischemic lesion over the course of the study. The number of MPIO-induced voids measured by gradient-recalled echo, the SPEN measurement of ADC, and ²³ Na MRI values were determined in the ischemic area and contralateral hemisphere, and relative performances for stroke classification were compared by receiver operator characteristic analysis. These measurements were associated with unique time-dependent trajectories during stroke recovery that changed the sensitivity and specificity for stroke monitoring during its evolution. Advantages and limitations of these contrasts, and the use of ultrahigh field for multiparametric stroke assessment, are discussed.

Long noncoding RNA NEAT1 correlates with higher disease risk, worse disease condition, decreased miR-124 and miR-125a and predicts poor recurrence-free survival of acute ischemic stroke

Objective

This study aimed to investigate the predictive value of long noncoding RNA nuclear enriched abundant transcript 1 (lncRNA NEAT1) for acute ischemic stroke (AIS) risk and to explore the correlation of lncRNA NEAT1 with disease severity, inflammation, recurrence and target microRNAs in patients with AIS.

Methods

210 patients with AIS and 210 controls were enrolled, and their peripheral blood samples were collected within 24 hours after admission and collected on the enrollment, respectively. lncRNA NEAT1 expression was detected by quantitative polymerase chain reaction (qPCR). For patients with AIS, disease severity was evaluated by National Institute of Health Stroke Scale (NIHSS) score; plasma concentrations of inflammatory factors and lncRNA NEAT1 target microRNAs were measured by enzyme‐linked immune sorbent assay and qPCR, respectively; stroke recurrence and death were recorded; and recurrence‐free survival (RFS) was calculated.

Results

lncRNA NEAT1 expression was elevated in patients with AIS compared with controls, and it had a good predictive value for AIS risk (area under the curve [AUC]: 0.804 [95% confidence interval [CI]: 0.763‐0.845]). In patients with AIS, lncRNA NEAT1 expression positively correlated with NIHSS score and inflammatory factor levels including C‐reactive protein (CRP), tumor necrosis factor (TNF)‐α, interleukin (IL)‐6, IL‐8, and IL‐22, while it negatively correlated with anti‐inflammatory cytokine IL‐10 level. Besides, lncRNA NEAT1 predicted increased recurrence/death risk (AUC: 0.641 [95% CI: 0.541‐0.741]), and its high expression correlated with worse RFS. Additionally, lncRNA NEAT1 expression negatively correlated with microRNA‐124 and microRNA‐125a expressions.

Conclusion

LncRNA NEAT1 may serve as a novel biomarker for assisting AIS management and prognosis.

The Yield of Multimodal Computed Tomography among Emergency Department Patients with Suspected Large Vessel Occlusion Stroke

OBJECTIVES

Endovascular therapy (EVT) improves outcomes for appropriately selected acute ischemic stroke patients. Guidelines suggest rapid acquisition of noninvasive vascular imaging to screen suspected ischemic stroke patients for large vessel occlusion (LVO) and candidacy for EVT. We sought to quantify the yield of an LVO stroke screening process in an undifferentiated emergency department (ED) suspected stroke population as well as identify predictors of successful EVT.

METHODS

We identified a cohort of consecutive ED patients who received CT angiography and brain perfusion (CTA/P) imaging to determine candidacy for EVT during 2016. In keeping with the guidelines at that time, hospital protocol directed physicians to obtain CTA/P studies if time from the onset of symptoms was less than or equal to 6 hours, and the National Institute of Health Stroke Scale (NIHSS) more than or equal to 6 or if recommended by the consulting stroke neurologist. Final discharge diagnoses, EVT attempts, and successful reperfusion (TICI 2b or better) were recorded. Yield of CTA/P was compared among patients based on NIHSS and duration of symptoms.

RESULTS

Over a 12-month period, 406 suspected stroke patients were screened with CTA/P; 273 (67%) received a final diagnosis of ischemic stroke. Among cases screened, 53 (13%) underwent attempted EVT; 35 (9%) achieved successful reperfusion. Only 1 of 113 (1%) patients with an NIHSS less than 6 was successfully treated with EVT compared to 34 of 285 (12%) with higher NIHSS (p = 0.001). The probability of successful EVT declined with increasing symptom duration (p = 0.009 for trend). In multivariable analysis, NIHSS more than or equal to 6 was associated with successful EVT (odds ratio [OR] 4.0 [1.6 to 9.9]) but presentation within 6 hours of onset was not (OR 2.3 [0.8 to 6.7]).

CONCLUSIONS

EVT candidates were common among suspected stroke patients screened with CTA/P in the ED, however, patients with NIHSS less than 6 rarely received successful EVT.

Hypoxic preconditioning relieved ischemic cerebral injury by promoting immunomodulation and microglia polarization after middle cerebral artery occlusion in rats

OBJECTIVES

This study was designed to investigate whether immunomodulation and Microglia polarization is involved in the anti-inflammatory and neuroprotective effect induced by hypoxic preconditioning (HPC) in the middle cerebral artery occlusion (MCAO) brain injury model.

METHODS

Longa method, (neurological disability status scale) NDSS method and TTC staining were used to evaluate the degree of cerebral infarction injury under different treatments (Sham, HPC, MCAO and co-treatment with HPC and MCAO). Western blot was used to detect expression profiles of apoptosis and related factors of neurological function. Flow cytometry was performed to analyze changes in the ratio of helper T cells, toxic T cells and NK cells in peripheral immune cells. And immunohistochemistry was used to examine the changes in microglial morphology. ELISA was used to evaluate the levels of nerve growth factors and neurogenesis conditions. Finally, RT-PCR was determined to analyze the transformation of microglia phenotype after HPC and MCAO treatment.

RESULTS

MCAO dramatically induced local formation of cerebral infarction. HPC relieved MCAO-induced cerebral infarction and increased rat cognition. HPC affected activation of microglia without significantly affecting in peripheral immune cell populations. After HPC co-treatment with MCAO, the M1 phenotype of microglia was changed and there was a transformation to M2.

CONCLUSION

The treatment of HPC remarkably affected the polarization of microglia cells in MCAO rats, and reduced the cerebral nerve injury and played a protective role in MCAO model.

Collateral blood flow measurement with intravoxel incoherent motion perfusion imaging in hyperacute brain stroke

Objective

To determine if intravoxel incoherent motion (IVIM) magnetic resonance perfusion can measure the quality of the collateral blood flow in the penumbra in hyperacute stroke.

Methods

A 6 b values IVIM MRI sequence was acquired in stroke patients with large vessel occlusion imaged <16 hours of last seen well. IVIM perfusion measures were evaluated in regions of interest drawn in the infarct core (D < 600 mm2/s), in the corresponding region in the contralateral hemisphere, and in the dynamic susceptibility contrast penumbra. In patients with a penumbra >15 mL, images were reviewed for the presence of a penumbra perfusion lesion on the IVIM f map, which was correlated with infarct size metrics. Statistical significance was tested using Student t test, Mann-Whitney U test, and Fisher exact test.

Results

A total of 34 patients were included. In the stroke core, IVIM f was significantly lower (4.6 ± 3.3%) compared to the healthy contralateral region (6.3 ± 2.2%, p < 0.001). In the 25 patients with a penumbra >15 mL, 9 patients had an IVIM penumbra perfusion lesion (56 ± 76 mL), and 16 did not. Patients with an IVIM penumbra perfusion lesion had a larger infarct core (82 ± 84 mL) at baseline, a larger infarct growth (68 ± 40 mL), and a larger final infarct size (126 ± 81 mL) on follow-up images compared to the patients without (resp. 20 ± 17 mL, p < 0.05; 13 ± 19 mL, p < 0.01; 29 ± 24 mL, p < 0.05). All IVIM penumbra perfusion lesions progressed to infarction despite thrombectomy treatment.

Conclusions

IVIM is a promising tool to assess the quality of the collateral blood flow in hyperacute stroke. IVIM penumbra perfusion lesion may be a marker of nonsalvageable tissue despite treatment with thrombectomy, suggesting that the IVIM penumbra perfusion lesion might be counted to the stroke core, together with the DWI lesion.