Mechanical Thrombectomy in Patients with Acute Ischemic Stroke and Lower NIHSS Scores: Recanalization Rates,Periprocedural Complications,and Clinical Outcome

BACKGROUND AND PURPOSE:Mechanical thrombectomy, in addition to intravenous thrombolysis, has become standard in acute ischemic stroke treatment in patients with large-vessel occlusion in the anterior circulation. However, previous randomized controlled stroke trials were not focused on patients with mild-to-moderate symptoms. Thus, there are limited data for patient selection, prediction of clinical outcome, and occurrence of complications in this patient population. The purpose of this analysis was to assess clinical and interventional data in patients treated with mechanical thrombectomy in case of ischemic stroke with mild-to-moderate symptoms.MATERIALS AND METHODS:We performed a retrospective analysis of a prospectively collected stroke data base. Inclusion criteria were anterior circulation ischemic stroke treated with mechanical thrombectomy at our institution between September 2010 and October 2015 with an NIHSS score of ≤8.RESULTS:Of 484 patients, we identified 33 (6.8%) with the following characteristics: median NIHSS = 5 (interquartile range, 4–7), median onset-to-groin puncture time = 320 minutes (interquartile range, 237–528 minutes). Recanalization (TICI = 2b–3) was achieved in 26 (78.7%) patients. Two cases of symptomatic intracranial hemorrhage were observed. Favorable (mRS 0–2) and moderate (mRS 0–3) clinical outcome at 90 days was achieved in 21 (63.6%) and 30 (90.9%) patients, respectively.CONCLUSIONS:The clinical outcome of patients undergoing mechanical thrombectomy for acute ischemic stroke with mild stroke due to large-vessel occlusion appears to be predominately favorable, even in a prolonged time window. However, although infrequent, angiographic complications could impair clinical outcome. Future randomized controlled trials should assess the benefit compared with the best medical treatment.

In several randomized multicenter stroke trials, mechanical thrombectomy has proved to be an effective treatment for large intracranial vessel occlusion in patients with acute ischemic stroke in the anterior circulation.^1–5 With the exception of the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN) trial⁴ and Extending the Time for Thrombolysis in Emergency Neurological Deficits–Intra-Arterial (EXTEND-IA),¹ all of those stroke trials did not include patients with minor-to-moderate stroke symptoms but focused on patients with a moderate or severe stroke with a score of at least 6–8 or higher on the National Institutes of Health Stroke Scale. Consequently, the median NIHSS score for patients who underwent mechanical thrombectomy was about 15–17 in all trials; including the MR CLEAN und EXTEND-IA trials.Large intracranial vessel occlusions are not necessarily associated with a high baseline NIHSS score and could be missed in patients with low NIHSS scores.⁶ In a large single-center cohort, 72% of the patients presenting with mild stroke symptoms did not undergo advanced stroke imaging (eg, CT angiography or CT perfusion) before intravenous thrombolysis. However, visualization of a possible proximal occlusion is essential for further treatment decisions. If thrombus length exceeds 8 mm, intravenous thrombolysis has almost no potential to recanalize the occluded vessel.^7,8 The chance for a good clinical outcome (mRS 0–2) is only 7.7% in such cases.⁷ Furthermore, despite intravenous thrombolysis, mortality is 1.3%, and 30.3% of the patients who presented with mild initial stroke symptoms could not ambulate independently at discharge.⁹Even though the complication rate in mechanical thrombectomy is low, the clinical benefit for the patient has to outperform the cost and potential risks. Here, we assessed the outcome of patients with acute ischemic minor-to-moderate stroke who underwent mechanical thrombectomy at our institution. We present data on the location of occlusions, thrombus length, collateral status, recanalization rates, periprocedural complications, and clinical outcome.     

Relative Filling Time Delay Based on CT Perfusion Source Imaging: A Simple Method to Predict Outcome in Acute Ischemic Stroke

BACKGROUND AND PURPOSE:Collateral vessel status is strongly associated with clinical outcome in ischemic stroke but can be challenging to assess. The aim of this study was to develop a tomography perfusion source imaging–based assessment of collateral vessel status.MATERIALS AND METHODS:Consecutive patients with ischemic stroke who received intravenous thrombolysis or intra-arterial reperfusion therapy after CTP were retrospectively analyzed. In those with middle cerebral artery or internal carotid artery occlusion, CT perfusion source imaging was used to identify the relative filling time delay between the normal MCA Sylvian branches and those in the affected hemisphere. Receiver operating characteristic analysis and logistic regression were used to assess the association of the relative filling time delay with the 24-hour Alberta Stroke Program Early CT Score based on noncontrast CT and the 90-day modified Rankin Scale score.RESULTS:There were 217 patients treated in 2009–2011 who had CTP data, of whom 60 had MCA or ICA occlusion and 55 had 90-day mRS data. The intraclass correlation coefficient for relative filling time delay was 0.95. Relative filling time delay was correlated with 24-hour ASPECTS (Spearman ρ = −0.674; P < .001) and 90-day mRS score (ρ = 0.516, P < .01). Increased relative filling time delay was associated with poor radiologic outcome (ASPECTS, 0–7) (area under the curve = 0.79, P < .001) and poor functional outcome (mRS score, 3–6) (area under the curve = 0.77, P = .001). In multivariate logistic regression, the association of longer relative filling time delay with poor outcome remained significant, independent of age, sex, and baseline National Institutes of Health Stroke Scale score.CONCLUSIONS:Relative filling time delay is a useful independent predictor of clinical outcome after ischemic stroke.

Leptomeningeal collateral flow has an important role in maintaining blood flow to brain regions distal to an arterial occlusion.^1–5 Imaging assessment of leptomeningeal collaterals in humans does not depict the small interarteriolar connections directly but, instead, relies on an indirect assessment of the extent and rate of backfilling of pial arteries receiving blood flow through these collateral vessels.^1,4,6,7 Many leptomeningeal collateral flow studies, most of which were CT angiography studies, used various grading methods to assess the vessel filling status in the Sylvian fissure by observers.^3,8–11 Traditional assessment of leptomeningeal collateral flow by using static CTA images lacks temporal resolution. Although newer scanners offer whole-brain perfusion acquisitions that can be reconstructed to provide dynamic CTA by using advanced software,¹² this technology is not yet widely available.CT perfusion expands the role of CT in the evaluation of acute stroke by providing physiologic insights into cerebral hemodynamics and, in so doing, complements the strength of CTA by determining the consequences of vessel occlusions and stenosis.^9,12,13 Although 1 study used CTP source data to confirm that contrast opacification was indeed retrograde collateral flow, no prior studies have graded collateral status by rating CTP source imaging (CTP-SI). We investigated a simple, time-resolved scale of collateral-derived contrast opacification in the Sylvian fissure as a predictor of radiologic and functional outcome. We hypothesized that delayed filling of the middle cerebral artery in the Sylvian fissure due to poor collateral flow would be associated with worse radiologic and functional outcome after ischemic stroke.     

Feasibility of a Clinical-Radiomics Model to Predict the Outcomes of Acute Ischemic Stroke

ObjectiveTo develop a model incorporating radiomic features and clinical factors to accurately predict acute ischemic stroke (AIS) outcomes.Materials and MethodsData from 522 AIS patients (382 male [73.2%]; mean age ± standard deviation, 58.9 ± 11.5 years) were randomly divided into the training (n = 311) and validation cohorts (n = 211). According to the modified Rankin Scale (mRS) at 6 months after hospital discharge, prognosis was dichotomized into good (mRS ≤ 2) and poor (mRS > 2); 1310 radiomics features were extracted from diffusion-weighted imaging and apparent diffusion coefficient maps. The minimum redundancy maximum relevance algorithm and the least absolute shrinkage and selection operator logistic regression method were implemented to select the features and establish a radiomics model. Univariable and multivariable logistic regression analyses were performed to identify the clinical factors and construct a clinical model. Ultimately, a multivariable logistic regression analysis incorporating independent clinical factors and radiomics score was implemented to establish the final combined prediction model using a backward step-down selection procedure, and a clinical-radiomics nomogram was developed. The models were evaluated using calibration, receiver operating characteristic (ROC), and decision curve analyses.ResultsAge, sex, stroke history, diabetes, baseline mRS, baseline National Institutes of Health Stroke Scale score, and radiomics score were independent predictors of AIS outcomes. The area under the ROC curve of the clinical-radiomics model was 0.868 (95% confidence interval, 0.825–0.910) in the training cohort and 0.890 (0.844–0.936) in the validation cohort, which was significantly larger than that of the clinical or radiomics models. The clinical radiomics nomogram was well calibrated (p > 0.05). The decision curve analysis indicated its clinical usefulness.ConclusionThe clinical-radiomics model outperformed individual clinical or radiomics models and achieved satisfactory performance in predicting AIS outcomes.     

Differential Contribution of ASPECTS Regions to Clinical Outcome after Thrombectomy for Acute Ischemic Stroke

BACKGROUND AND PURPOSE:Ischemic stroke is the leading cause of long-term disability in adults, but our ability to prognosticate from baseline imaging data is limited. The ASPECTS measures ischemic change in the middle cerebral artery territory on noncontrast CT based on 10 anatomic regions. Here, we investigated whether infarction in particular regions was associated with worse long-term outcome.MATERIALS AND METHODS:We identified consecutive patients receiving mechanical thrombectomy for ICA/MCA occlusion at 2 comprehensive stroke centers. Pretreatment ASPECTS was assessed by 2 blinded reviewers. Clinical data including demographics, baseline NIHSS score, and 90-day mRS were collected. The relationship between individual ASPECTS regions and the mRS score (0–2 versus 3–6) was assessed using multivariable logistic regression.RESULTS:Three hundred fifty-three patients were included (mean age, 70 years; 46% men), of whom 214 had poor outcome (mRS = 3–6). Caudate (OR = 3.26; 95% CI, 1.33–8.82), M4 region (OR = 2.94; 95% CI, 1.09–9.46), and insula (OR = 1.75; 95% CI, 1.08–2.85) infarcts were associated with significantly greater odds of poor outcome, whereas M1 region infarction reduced the odds of poor outcome (OR = 0.38; 95% CI, 0.14–0.99). This finding remained unchanged when restricted to only patients with good recanalization. No significant associations were found by laterality. Similarly, no region was predictive of neurologic improvement during the first 24 hours or of symptomatic intracerebral hemorrhage.CONCLUSIONS:Our results indicate that ASPECTS regions are not equal in their contribution to functional outcome. This finding suggests that patient selection based on total ASPECTS alone might be insufficient, and infarct topography should be considered when deciding eligibility for thrombectomy.

Recent advances in the field of endovascular thrombectomy have led to a sea change in the management of large-vessel-occlusion acute ischemic stroke, with several initial trials showing benefit with new-generation endovascular approaches.^1-6 The time window for thrombectomy has subsequently expanded to up to 24 hours from onset.^7,8 In all these trials, imaging was crucial to identify patients likely to benefit. Most trials in 2015 used lesion size on CT as part of their selection criteria, quantified as the ASPECTS. ASPECTS was first described in 2000 and separates the middle cerebral artery territory into 10 regions (6 superficial, 4 deep; Figure). These are then assigned a value of 0 if there are early ischemic changes—parenchymal hypoattenuation, loss of gray-white differentiation, and focal swelling—and a value of 2 if the region is normal in appearance.⁹ Correspondingly, lower scores imply more extensive ischemia and intuitively suggest that the outcome is more likely to be poor; indeed, the ASPECTS is known to have value in long-term prognostication after stroke,¹⁰ and has previously been shown to correlate with functional independence in intra-arterial thrombolysis.¹¹ Thus, low ASPECTS values continue to be used as an exclusion criterion for thrombectomy because these patients are assumed to have a low likelihood of meaningful improvement.Open in a separate windowFIGURE.Illustration of ASPECTS, showing 10 regions in 1 hemisphere. C indicates caudate; IC, internal capsule; L, lentiform; I, insula. Reproduced from Neuhaus et al²⁵ with permission from BMJ Publishing Group Ltd.However, there are a number of disadvantages in using ASPECTS. First, although it significantly correlates with long-term function on a group level, individual outcomes are discriminated less accurately, particularly when the ASPECTS is moderate to high (eg, 6–10, implying limited ischemic change).¹² Second, it is known that involvement of specific regions leads to particular functional deficits, eg, the angular gyrus in language¹³ and multiple cortical and subcortical areas in motor function.¹⁴ The ASPECTS treats all 10 areas equally; therefore, a composite ASPECTS of 7 may reflect very different lesion patterns, and there is no a priori reason to think these would be equivalent in terms of functional consequences. Third, the volumes of ASPECTS regions are not equal, and the loss of a single point can reflect a wide range of ischemic volumes, depending on which areas are affected. Indeed, it has been previously reported that some regions confer a greater risk of poor long-term outcome.¹⁵ Variation in outcome based on the affected area has also been described with ASPECTS regions from baseline CT,^15-18 though with inconsistent findings.The implication of this finding is that a significant number of patients with a poor composite ASPECTS might, in fact, have a greater likelihood of good outcome than the total score would suggest, which may influence treatment decisions. In this study, we sought to estimate regional contributions to long-term function using pretreatment ASPECTS data in a thrombectomy cohort.     

Histologic Analysis of Retrieved Clots in Acute Ischemic Stroke: Correlation with Stroke Etiology and Gradient-Echo MRI

BACKGROUND AND PURPOSE:It is unclear whether clot composition analysis is helpful to predict a stroke mechanism in acute large vessel occlusion. In addition, the relationship between early vessel signs on imaging studies and clot compositions has been poorly understood. The purpose of this study was to elucidate the relationship between clot composition and stroke etiology following mechanical thrombectomy and to investigate the effect of varied clot compositions on gradient-echo MR imaging of clots.MATERIALS AND METHODS:Histopathologic analysis of retrieved clots from 37 patients with acute MCA occlusion was performed. Patients underwent gradient-echo imaging before endovascular therapy. Retrieved clots underwent semiquantitative proportion analysis to quantify red blood cells, fibrin, platelets, and white blood cells by area. Correlations between clot compositions and stroke subtypes and susceptibility vessel signs on gradient-echo imaging were assessed.RESULTS:Stroke etiology was classified as cardioembolism in 22 patients (59.4%), large-artery atherosclerosis in 8 (21.6%), and undetermined in 7 (18.9%). The clots from cardioembolism had a significantly higher proportion of red blood cells (37.8% versus 16.9%, P = .031) and a lower proportion of fibrin (32.3% versus 48.5%, P = .044) compared with those from large-artery atherosclerosis. The proportion of red blood cells was significantly higher in clots with a susceptibility vessel sign than in those without it (48.0% versus 1.9%, P < .001), whereas the proportions of fibrin (26.4% versus 57.0%, P < .001) and platelets (22.6% versus 36.9%, P = .011) were significantly higher in clots without a susceptibility vessel sign than those with it.CONCLUSIONS:The histologic composition of clots retrieved from cerebral arteries in patients with acute stroke differs between those with cardioembolism and large-artery atherosclerosis. In addition, a susceptibility vessel sign on gradient-echo imaging is strongly associated with a high proportion of red blood cells and a low proportion of fibrin and platelets in retrieved clots.

Endovascular therapy is increasingly used for treating acute ischemic stroke due to intracranial large-vessel occlusion. Among various endovascular therapies, mechanical thrombectomy is now accepted as the first-line endovascular therapy for acute large-vessel occlusion. Recent studies have shown that thrombectomies with a retrievable stent or flexible aspiration catheter were associated with high-recanalization and low-complication rates.^1–5 One of the striking features of mechanical thrombectomy is that it enables physicians to perform histopathologic examination of clots retrieved from human intracranial arteries. Recent studies suggested that histologic examination of retrieved clots can offer new insights into the pathogenesis of acute stroke due to intracranial large-vessel occlusion.^6–9 However, it is currently unclear whether clot-composition analysis is helpful to predict a stroke mechanism in acute large-vessel occlusion. Only a few studies have been conducted on this topic, and prior studies have yielded only vague and contradictory results.^8–10In addition, histopathologic analysis of retrieved clots allows understanding of the pathologic basis of early vessel signs on imaging studies in patients with acute ischemic stroke. Several studies have shown that the hyperattenuated vessel sign on CT and the susceptibility vessel sign on gradient-echo (GRE) MR imaging were more often associated with erythrocyte-rich thrombi (red thrombi) than fibrin-rich thrombi (white thrombi).^8,10,11 Platelets play an important role in the pathogenesis of white thrombi associated with atherosclerotic plaque rupture.¹² However, the relationship between early vessel signs on imaging studies and the proportion of platelets within the retrieved clots has been poorly understood. Thus, we performed histopathologic analysis on retrieved clots from patients with acute MCA occlusion to further elucidate the relationship between clot composition and stroke etiology and to investigate the effect of platelet levels on GRE MR imaging of clots.     

Procedural Predictors of Outcome in Patients Undergoing Endovascular Therapy for Acute Ischemic Stroke

Purpose

To identify factors impacting outcome in patients undergoing interventions for acute ischemic stroke (AIS).

Materials and Methods

This was a retrospective analysis of patients undergoing endovascular therapy for AIS secondary during a 30?month period. Outcome was based on modified Rankin score at 3- to 6-month follow-up. Recanalization was defined as Thrombolysis in myocardial infarction score 2 to 3. Collaterals were graded based on pial circulation from the anterior cerebral artery either from an ipsilateral injection in cases of middle cerebral artery (MCA) occlusion or contralateral injection for internal carotid artery terminus (ICA) occlusion as follows: no collaterals (grade 0), some collaterals with retrograde opacification of the distal MCA territory (grade 1), and good collaterals with filling of the proximal MCA (M2) branches or retrograde opacification up to the occlusion site (grade 2). Occlusion site was divided into group 1 (ICA), group 2 (MCA with or without contiguous M2 involvement), and group 3 (isolated M2 or M3 branch occlusion).

Results

A total of 89 patients were studied. Median age and National Institutes of health stroke scale (NIHSS) score was 71 and 15?years, respectively. Favorable outcome was seen in 49.4% of patients and mortality in 25.8% of patients. Younger age (P?=?0.006), lower baseline NIHSS score (P?=?0.001), successful recanalization (P?<?0.0001), collateral support (P?=?0.0008), distal occlusion (P?=?0.001), and shorter procedure duration (P?=?0.01) were associated with a favorable outcome. Factors affecting successful recanalization included younger age (P?=?0.01), lower baseline NIHSS score (P?=?0.05), collateral support (P?=?0.01), and shorter procedure duration (P?=?0.03). An ICA terminus occlusion (P?<?0.0001), lack of collaterals (P?=?0.0003), and unsuccessful recanalization (P?=?0.005) were significantly associated with mortality.

Conclusion

Angiographic findings and preprocedure variables can help prognosticate procedure outcomes in patients undergoing endovascular therapy for AIS.     

Perfusion-Based Selection for Endovascular Reperfusion Therapy in Anterior Circulation Acute Ischemic Stroke

BACKGROUND AND PURPOSE:Controversy exists about the role of perfusion imaging in patient selection for endovascular reperfusion therapy in acute ischemic stroke. We hypothesized that perfusion imaging versus noncontrast CT- based selection would be associated with improved functional outcomes at 3 months.MATERIALS AND METHODS:We reviewed consecutive patients with anterior circulation strokes treated with endovascular reperfusion therapy within 8 hours and with baseline NIHSS score of ≥8. Baseline clinical data, selection mode (perfusion versus NCCT), angiographic data, complications, and modified Rankin Scale score at 3 months were collected. Using multivariable logistic regression, we assessed whether the mode of selection for endovascular reperfusion therapy (perfusion-based versus NCCT-based) was independently associated with good outcome.RESULTS:Two-hundred fourteen patients (mean age, 67.2 years; median NIHSS score, 18; MCA occlusion 74% and ICA occlusion 26%) were included. Perfusion imaging was used in 76 (35.5%) patients (39 CT and 37 MR imaging). Perfusion imaging–selected patients were more likely to have good outcomes compared with NCCT-selected patients (55.3 versus 33.3%, P = .002); perfusion selection by CT was associated with similar outcomes as that by MR imaging (CTP, 56.; MR perfusion, 54.1%; P = .836). In multivariable analysis, CT or MR perfusion imaging selection remained strongly associated with good outcome (adjusted OR, 2.34; 95% CI, 1.22–4.47), independent of baseline severity and reperfusion.CONCLUSIONS:In this multicenter study, patients with acute ischemic stroke who underwent perfusion imaging were more than 2-fold more likely to have good outcomes following endovascular reperfusion therapy. Randomized studies should compare perfusion imaging with NCCT imaging for patient selection for endovascular reperfusion therapy.

Endovascular reperfusion therapy (ERT) for acute ischemic stroke has been associated with mixed results. In trials of carefully selected patients with middle cerebral artery occlusion, a benefit of intra-arterial thrombolysis over placebo was seen when patients were treated within 6 hours.^1,2 However, subsequent single-arm studies of mechanical embolectomy have observed less impressive results^3,4 and suggest that outcomes are related to several key factors, including patient characteristics (age, co-morbidities, and stroke severity) and treatment factors (time to reperfusion).^5–10 Radiographic features, including pretreatment tissue status by NCCT of the head, brain MR imaging, and perfusion imaging (CTP or MR perfusion [MRP]), may improve patient selection.^5,8,9,11 Few studies have compared NCCT-based selection with perfusion imaging–based selection of patients for ERT following acute ischemic stroke.^12,13 We, therefore, sought to compare NCCT selection with perfusion imaging selection as a predictor of good outcome following ERT. We hypothesized that perfusion imaging–based selection would be associated with better functional outcomes at 3 months compared with NCCT-based selection alone.     

关急性缺血性脑卒中患者阻塞部位与功能恢复相

目的：探讨重组组织型纤溶酶原激活剂（ rt－PA）治疗急性缺血性脑卒中后临床症状轻度改善时间是否可以预测1年后功能恢复情况。方法186例急性大脑前循环梗塞患者,且发病3 h内接受rt－PA治疗,作为研究对象。患者根据临床症状轻度改善时间可以分为：早期见效者（ ER）,即rt－PA治疗2 h内NIHSS评分改善≥4或其中一项NIHSS评分为0;晚期见效者（ LR）, rt－PA治疗2 h－24 h内,NIHSS评分改善≥4或其中一项NIHSS评分为0;无效果者（ NR）。此外,根据患者动脉阻塞部位分为：颈内动脉和大脑中动脉M1段近端（ P组）;大脑中动脉M1、M2段远端（ D组）。结果 P组包括96例（52％）患者, D组包括90例（48％）患者。76例（41％）患者属于ER,40例（22％）患者是LR,70例（38％）患者为NR。多元线性回归分析显示,P组（OR：3.04;95％CI：1.18－10.45; P＝0.031）和NR （OR：4.14;95％ CI,1.29－14.27; P＝0.014）是1年后临床功能恢复较差的独立预测因素。 ER （53％, P＝0.01）和LR （55％, P＝0.01）患者临床功能恢复比例高于NR （23％）患者,ER和LR临床功能恢复率无显著统计学意义。结论早期轻度临床症状改善不能预测脑梗塞后1年功能恢复,但是阻塞部位是rt－PA治疗后功能恢复的有效预测因素。     

Comparison of Imaging Selection Criteria for Intra-Arterial Thrombectomy in Acute Ischemic Stroke with Advanced CT

Objectives

To compare two selection criteria (noncontrast CT [NCCT] with multi-phase CT Angiography [MPCTA] and CT perfusion [CTP]) for the determination of eligibility for thrombectomy.

Methods

We retrospectively enrolled 71 patients who underwent head NCCT, 9.6-cm CTP, and craniocervical single-phase CTA (SPCTA) within 6 hours of onset. The simulated MPCTA was reconstructed from 1-mm CTP images for assessment of collateral circulation. Infarct core (relative CBF <?30 %) and penumbra (Tmax > 6 seconds) volumes were measured. The infarct core?<?70 mL with a mismatch ratio?>?1.2 (CTP-A), infarct core?≤?40 mL with a mismatch ratio?>?1.8 (CTP-B), and ASPECTS?>?5 with good collaterals (50 %?≥?MCA territory) were used to determine eligibility for thrombectomy. SPCTA was compared with the simulated MPCTA for assessment of collaterals.

Results

CTP-B determined that 11 patients were ineligible for thrombectomy, of which three were eligible by NCCT with MPCTA and 6 by CTP-A. CTP-A and CTP-B showed discrepancy in determining eligibility for thrombectomy between NCCT with MPCTA in three patients each, rendering no significant statistical difference (P?>?0.05). The number of patients with poor collaterals was significantly higher on SPCTA than MPCTA (n?=?22 and 6 respectively; P?<?0.0001).

Conclusion

The two imaging selection criteria (NCCT with MPCTA and CTP) were statistically comparable for determining eligibility for thrombectomy.

Key Points

? Early mechanical thrombectomy improves clinical outcomes. ? Noncontrast CT–multi-phase CTA is used for determining eligibility for thrombectomy. ? CTP can help to select patients who are eligible for thrombectomy. ? Noncontrast CT–multi-phase CTA and CTP are comparable for patient selection. ? Multi-phase CTA is more accurate than single-phase CTA for assessment of collaterals.

     

Cost-Effectiveness Study of Initial Imaging Selection in Acute Ischemic Stroke Care

PurposeNational guidelines recommend prompt identification of candidates for acute ischemic stroke (AIS) treatment, requiring timely neuroimaging with CT and/or MRI. CT is often preferred because of its widespread availability and rapid acquisition. Despite higher diagnostic accuracy of MRI, it commonly involves complex workflows that could potentially cause treatment time delays. The purpose of this study was to analyze the impact on outcomes of imaging utilization before treatment decisions at comprehensive stroke centers for patients presenting with suspected AIS in the anterior circulation with last-known-well-to-arrival time 0 to 24 hours.MethodsA decision simulation model based on the American Heart Association’s recommendations for AIS care pathways was developed from a health care perspective to compare initial imaging strategies: (1) stepwise-CT: noncontrast CT (NCCT) at the time of presentation, with CT angiography (CTA) ± CT perfusion (CTP) only in select patients (initial imaging to exclude hemorrhage and extensive ischemia) for mechanical thrombectomy (MT) evaluation; (2) stepwise-hybrid: NCCT at the time of presentation, with MR angiography (MRA) ± MR perfusion (MRP) only for MT evaluation; (3) stepwise-advanced: NCCT + CTA at presentation, with MR diffusion-weighted imaging (MR DWI) + MRP only for MT evaluation; (4) comprehensive-CT: NCCT + CTA + CTP at the time of presentation; and (5) comprehensive-MR: MR DWI + MRA + MRP at the time of presentation. Model parameters were defined using evidence-based data. Cost-effectiveness and sensitivity analyses were performed.ResultsThe cost-effectiveness analyses revealed that comprehensive-CT and comprehensive-MR yield the highest lifetime quality-adjusted life-years (QALYs) (4.81 and 4.82, respectively). However, the incremental cost-effectiveness ratio of comprehensive-MR is $233,000/QALY compared with comprehensive-CT. Stepwise-CT, stepwise-hybrid, and stepwise-advanced strategies are dominated, yielding lower QALYs and higher costs compared with comprehensive-CT.ConclusionsPerforming comprehensive-CT at presentation is the most cost-effective initial imaging strategy at comprehensive stroke centers.     

The Impact of Arterial Collateralization on Outcome after Intra-Arterial Therapy for Acute Ischemic Stroke

BACKGROUND AND PURPOSE:Although intra-arterial therapy for acute ischemic stroke is associated with superior recanalization rates, improved clinical outcomes are inconsistently observed following successful recanalization. There is emerging concern that unfavorable arterial collateralization, though unproven, predetermines poor outcome. We hypothesized that poor leptomeningeal collateralization, assessed by preprocedural CTA, is associated with poor outcome in patients with acute ischemic stroke undergoing intra-arterial therapy.MATERIALS AND METHODS:We retrospectively analyzed patients with acute ischemic stroke with intracranial ICA and/or MCA occlusions who received intra-arterial therapy. The collaterals were graded on CTA. Univariate and multivariate analyses were used to investigate the association between the dichotomized leptomeningeal collateral score and functional outcomes at 3-months mRS ≤2, mortality, and intracranial hemorrhages.RESULTS:Eighty-seven patients were included. The median age was 66 years (interquartile range, 54–76 years) and the median NIHSS score at admission was 18 (interquartile range, 14–20). The leptomeningeal collateral score 3 was found to have significant association with the good functional outcome at 3 months: OR = 3.13; 95% CI, 1.25–7.825; P = .016. This association remained significant when adjusted for the use of IV tissue plasminogen activator: alone, OR = 2.998; 95% CI, 1.154–7.786; P = .024; and for IV tissue plasminogen activator and other confounders (age, baseline NIHSS score, and Thrombolysis in Cerebral Infarction grades), OR = 2.985; 95% CI, 1.027–8.673; P = .045.CONCLUSIONS:We found that poor arterial collateralization, defined as a collateral score of <3, was associated with poor outcome, after adjustment for recanalization success. We recommend that future studies include collateral scores as one of the predictors of functional outcome.

Intravenous tissue plasminogen activator is the only proved reperfusion therapy for acute ischemic stroke. However, a narrow therapeutic time window (<4.5 hours) limits its use because the clinical effectiveness is critically time-dependent.^1–3 In addition, recanalization rates with IV-tPA are low in the setting of large-artery occlusion, (eg, ICA occlusion <10%).^4–6 Intra-arterial therapy (IAT) has higher recanalization rates than intravenous thrombolysis, but this result has not been matched by concordant improvement in clinical outcomes.^7–9 Two recent randomized trials comparing IAT with IV-tPA, the Interventional Management of Stroke III trial and the Local versus Systemic Thrombolysis for Acute Ischemic Stroke trial, did not demonstrate superiority.^10,11Inadequate arterial collateralization is a possible mechanism to explain the mismatch between recanalization success and clinical outcome, apart from the presence of an already infarcted ischemic core and an incomplete microcirculatory reperfusion after focal cerebral ischemia.^12,13 A favorable arterial collateralization as determined by a robust leptomeningeal anastomoses profile may enhance recanalization, improve downstream reperfusion, reduce the extent of infarct core and ischemic lesion growth, decrease hemorrhagic transformation, and improve outcome postrevascularization.^14–16The leptomeningeal collateral scoring system based on CTA correlates with clinical outcome.^17–21 However, its role in IAT is unclear. We hypothesized that a poor leptomeningeal CTA score predicts clinical futility in patients undergoing IAT independent of recanalization status.     

Predictors of Reperfusion in Patients with Acute Ischemic Stroke

BACKGROUND AND PURPOSE:Ischemic stroke studies emphasize a difference between reperfusion and recanalization, but predictors of reperfusion have not been elucidated. The aim of this study was to evaluate the relationship between reperfusion and recanalization and identify predictors of reperfusion.MATERIALS AND METHODS:From the Dutch Acute Stroke Study, 178 patients were selected with an MCA territory deficit on admission CTP and day 3 follow-up CTP and CTA. Reperfusion was evaluated on CTP, and recanalization on CTA, follow-up imaging. Reperfusion percentages were calculated in patients with and without recanalization. Patient admission and treatment characteristics and admission CT imaging parameters were collected. Their association with complete reperfusion was analyzed by using univariate and multivariate logistic regression.RESULTS:Sixty percent of patients with complete recanalization showed complete reperfusion (relative risk, 2.60; 95% CI, 1.63–4.13). Approximately one-third of patients showed some discrepancy between recanalization and reperfusion status. Lower NIHSS score (OR, 1.06; 95% CI, 1.01–1.11), smaller infarct core size (OR, 3.11; 95% CI, 1.46–6.66; and OR, 2.40; 95% CI, 1.14–5.02), smaller total ischemic area (OR, 4.20; 95% CI, 1.91–9.22; and OR, 2.35; 95% CI, 1.12–4.91), lower clot burden (OR, 1.35; 95% CI, 1.14–1.58), distal thrombus location (OR, 3.02; 95% CI, 1.76–5.20), and good collateral score (OR, 2.84; 95% CI, 1.34–6.02) significantly increased the odds of complete reperfusion. In multivariate analysis, only total ischemic area (OR, 6.12; 95% CI, 2.69–13.93; and OR, 1.91; 95% CI, 0.91–4.02) was an independent predictor of complete reperfusion.CONCLUSIONS:Recanalization and reperfusion are strongly associated but not always equivalent in ischemic stroke. A smaller total ischemic area is the only independent predictor of complete reperfusion.

Patients with acute ischemic stroke presenting within 4.5 hours are treated with IV-rtPA to dissolve the thrombus and achieve revascularization.¹ A recent consensus meeting on stroke imaging research (Acute Stroke Imaging Research Roadmap II) suggests that revascularization is a combination of 3 different mechanisms: 1) recanalization, referring to arterial patency; 2) reperfusion, which refers to antegrade microvascular perfusion; and 3) collateralization, which refers to microvascular perfusion via pial arteries or other anastomotic arterial channels that bypass the primary site of vessel occlusion.² Recanalization, reperfusion, and collateralization can be evaluated by CTA and CTP, which are frequently used in dedicated stroke imaging protocols. An important reason to look at the revascularization mechanisms separately is the concept that recanalization of an arterial occlusion, as visualized on CTA, does not necessarily lead to complete reperfusion and improved clinical outcome.^3,4 Furthermore, reperfusion can also occur without afferent vessel recanalization through collateralization of the ischemic area by collateral flow.^5,6Many previous studies, including those investigating intra-arterial therapy, consider recanalization to be synonymous with reperfusion.^7–10 Other articles suggest that this assumption is not justified and found reperfusion to be a better predictor of follow-up infarct volume and clinical outcome than recanalization.^{5,8,9,11–15}Although recanalization correlates well with improved reperfusion rates, it is unclear which other clinical and imaging factors influence reperfusion.^5,6,11,12,16 Knowing which factors, available before treatment decisions, predict complete reperfusion could aid in decision-making. Treatment with IV-rtPA, good collateral scores and lesion geography (location of the infarct relative to penumbra), and structure (solitary or multiple infarct areas) have been related to reperfusion status assessed with CT or MR imaging.^5,15,17–19The aim of this study was to evaluate the relationship between reperfusion and recanalization and to investigate which clinical and CT imaging parameters, available on admission, can help predict complete reperfusion in patients with acute ischemic stroke.     

Mechanical Thrombectomy with Stent Retrievers in Acute Ischemic Stroke

Mechanical thrombectomy (MTE) in patients with acute ischemic infarct caused by large-vessel occlusion is becoming used with increasing frequency in many stroke centers. With the introduction of stent retrievers, recanalization rates >80 % are reached by most operators. However, although the technical success rate of MTE has been increased, clinical results have not improved to the same degree. In this review, the indications for MTE, the technique, and the technical and clinical outcomes are discussed. Complications and predictors for good clinical outcome are described based on recent data from the literature.     

Performance and Predictive Value of a User-Independent Platform for CT Perfusion Analysis: Threshold-Derived Automated Systems Outperform Examiner-Driven Approaches in Outcome Prediction of Acute Ischemic Stroke

BACKGROUND AND PURPOSE:Treatment strategies in acute ischemic stroke aim to curtail ischemic progression. Emerging paradigms propose patient subselection using imaging biomarkers derived from CT, CTA, and CT perfusion. We evaluated the performance of a fully-automated computational tool, hypothesizing enhancements compared with qualitative approaches. The correlation between imaging variables and clinical outcomes in a cohort of patients with acute ischemic stroke is reported.MATERIALS AND METHODS:Sixty-two patients with acute ischemic stroke and MCA or ICA occlusion undergoing multidetector CT, CTA, and CTP were retrospectively evaluated. CTP was processed on a fully operator-independent platform (RApid processing of PerfusIon and Diffusion [RAPID]) computing automated core estimates based on relative cerebral blood flow and relative cerebral blood volume and hypoperfused tissue volumes at varying thresholds of time-to-maximum. Qualitative analysis was assigned by 2 independent reviewers for each variable, including CT-ASPECTS, CBV-ASPECTS, CBF-ASPECTS, CTA collateral score, and CTA clot burden score. Performance as predictors of favorable clinical outcome and final infarct volume was established for each variable.RESULTS:Both RAPID core estimates, CT-ASPECTS, CBV-ASPECTS, and clot burden score correlated with favorable clinical outcome (P < .05); CBF-ASPECTS and collateral score were not significantly associated with favorable outcome, while hypoperfusion estimates were variably associated, depending on the selected time-to-maximum thresholds. Receiver operating characteristic analysis demonstrated disparities among tested variables, with RAPID core and hypoperfusion estimates outperforming all qualitative approaches (area under the curve, relative CBV = 0.86, relative CBF = 0.81; P < .001).CONCLUSIONS:Qualitative approaches to acute ischemic stroke imaging are subject to limitations due to their subjective nature and lack of physiologic information. These findings support the benefits of high-speed automated analysis, outperforming conventional methodologies while limiting delays in clinical management.

Primary goals in the management of acute ischemic stroke (AIS) include timely pharmacologic or mechanical intervention, while avoiding untoward risks related to complications of treatment. Appropriate patient selection may thus prove paramount, and identification of a subpopulation most likely to benefit has been the subject of extensive inquiry.^1,2 While the precise profile of this target population remains to be conclusively defined, recent work has highlighted the potential strengths of stratification by using the ischemic penumbra formalism defining an irreversibly injured infarct core and putative penumbra of at-risk tissues.^1,3Despite promising results, penumbral imaging has met with skepticism and inconsistent outcomes, particularly because the broad array of imaging and computational approaches and interpretive parameters has precluded formulation of generalizable conclusions.^4–7 With studies further complicated by the time, materials, and expertise requisite to successfully undertake perfusion imaging, some investigators have focused on triage algorithms examining more readily attainable biomarkers derived from noncontrast CT (eg, Alberta Stroke Program Early CT Score) or CT angiography (eg, collateral score [CS], clot burden score [CBS]) common to stroke protocols.^8–11 While quickly attainable, the performance of ASPECTS in triaging patients to therapy or predicting outcome has been variable, and its use in prognostication of individual outcomes has been questioned.^12–14 Similarly, CS and CBS have shown promise as rapid approaches to assessment but may underperform when compared with perfusion imaging metrics.^9–11 Recently, the ASPECTS methodology was applied to CTP parametric maps in an effort to impart standardization and mitigate subjective elements of perfusion analysis; however, even in this context, the strengths of perfusion imaging may be attenuated by variability in postprocessing, computational analysis, selection of parametric maps, and the generally qualitative nature of such approaches.^10,11Expert consensus has emphasized the demand for standardization in the acquisition, processing, and analysis of perfusion imaging.^15,16 The potential for disparate results and the variability in accuracy among competing software platforms have been the subject of recent studies and were thoroughly expounded in a comparative analysis by Kudo et al.¹⁷ In light of recent reports, the primary objective of this study were to examine the predictive performance of several user-defined approaches to NCCT, CTA, and CTP analysis, by comparison with a fast, vendor- and operator-independent computational tool using fully automated lesion segmentation and pixel-wise parametric thresholding for semiquantitation (RApid processing of PerfusIon and Diffusion [RAPID]).¹⁸ The objective of our study was to evaluate these tools to determine their ability to predict 90-day favorable clinical outcome in patients with AIS.     

Patient Selection for Stroke Endovascular Therapy— DWI-ASPECTS Thresholds Should Vary among Age Groups: Insights from the RECOST Study

BACKGROUND AND PURPOSE:The purpose of this study was to evaluate the benefits of endovascular intervention in large-vessel occlusion strokes, depending on age class.MATERIALS AND METHODS:A clinical management protocol including intravenous treatment and mechanical thrombectomy was instigated in our center in 2009 (Prognostic Factors Related to Clinical Outcome Following Thrombectomy in Ischemic Stroke [RECOST] study). All patients with acute ischemic stroke with an anterior circulation major-vessel occlusion who presented within 6 hours were evaluated with an initial MR imaging examination and were analyzed according to age subgroups (younger than 50 years, 50–59 years, 60–69 years, 70–79 years; 80 years or older). The mRS score at 3 months was the study end point.RESULTS:One hundred sixty-five patients were included in the analysis. The mean age was 67.4 years (range, 29–90 years). The mean baseline NIHSS score was 17.24 (range, 3–27). The mean DWI-derived ASPECTS was 6.4. Recanalization of TICI 2b/3 was achieved in 80%. At 3 months, 41.72% of patients had a good outcome, with a gradation of prognosis depending on the age subgroup and a clear cutoff at 70 years. Only 19% of patients older than 80 years had a good outcome at 3 months (mean ASPECTS = 7.4) with 28% for 70–79 years (mean ASPECTS = 6.8), but 58% for 60–69 years (mean ASPECTS = 6), 52% for 50–59 years (mean ASPECTS = 5.91), and 72% for younger than 50 years (mean ASPECTS = 6.31). In contrast, the mortality rate was 35% for 80 years and older, and 26% for 70–79 versus 5%–9% for younger than 70 years.CONCLUSIONS:The elderly may benefit from thrombectomy when their ischemic core volume is low in comparison with younger patients who still benefit from acute recanalization despite larger infarcts. Stroke volume thresholds should, therefore, be related and adjusted to the patient''s age group.

Ischemic stroke is the third leading cause of death in France (fourth in the United States^1,2), leading to significant disability.³ The World Health Organization predicts an increasing number of strokes in Europe during the next 10 years.⁴ Intravenous recombinant tissue plasminogen activator for cerebral arterial occlusion is the established therapy to date for acute ischemic stroke. The odds ratio benefit is 1.28–1.7 for a favorable outcome versus a placebo^5,6 within 4.5 hours after stroke onset. Initially, being older than 80 years of age was established as a bad prognostic factor in intravenous treatment^7–10 and even considered an exclusion criterion.⁵ Today, this statement is seen as controversial, with recent studies having shown that elderly patients would still benefit from IV tPA.^11,12 In addition, new therapeutic strategies in stroke units are increasingly involving adjunctive endovascular techniques when fibrinolysis is contraindicated or has failed or when large and proximal intracranial vessels are occluded.^13–17 Previous studies have shown that mechanical thrombectomy by using Stentrievers (Trevo; Stryker, Kalamazoo, Michigan), in particular new stent retrievers,¹⁸ was successful in achieving a high rate of arterial recanalization and favorable clinical outcome in large-vessel occlusion.^19–21 Nevertheless, inclusion and exclusion criteria for these new invasive strategies are still being evaluated and may need to be optimized to avoid futile recanalization, particularly for fragile patients. The purpose of this study was to investigate the benefits and safety of these new recanalization devices according to age subgroups.     

Whole-Brain Susceptibility-Weighted Thrombus Imaging in Stroke: Fragmented Thrombi Predict Worse Outcome

BACKGROUND AND PURPOSE:The prevalence and clinical importance of primarily fragmented thrombi in patients with acute ischemic stroke remains elusive. Whole-brain SWI was used to detect multiple thrombus fragments, and their clinical significance was analyzed.MATERIALS AND METHODS:Pretreatment SWI was analyzed for the presence of a single intracranial thrombus or multiple intracranial thrombi. Associations with baseline clinical characteristics, complications, and clinical outcome were studied.RESULTS:Single intracranial thrombi were detected in 300 (92.6%), and multiple thrombi, in 24 of 324 patients (7.4%). In 23 patients with multiple thrombi, all thrombus fragments were located in the vascular territory distal to the primary occluding thrombus; in 1 patient, thrombi were found both in the anterior and posterior circulation. Only a minority of thrombus fragments were detected on TOF-MRA, first-pass gadolinium-enhanced MRA, or DSA. Patients with multiple intracranial thrombi presented with more severe symptoms (median NIHSS scores, 15 versus 11; P = .014) and larger ischemic areas (median DWI ASPECTS, 5 versus 7; P = .006); good collaterals, rated on DSA, were fewer than those in patients with a single thrombus (21.1% versus 44.2%, P = .051). The presence of multiple thrombi was a predictor of unfavorable outcome at 3 months (P = .040; OR, 0.251; 95% CI, 0.067–0.939).CONCLUSIONS:Patients with multiple intracranial thrombus fragments constitute a small subgroup of patients with stroke with a worse outcome than patients with single thrombi.

Little is known about the proportion of acute ischemic strokes caused by multiple intracranial thrombi. Rarely, distal thrombus fragments that are separate from the primary occluding thrombus can be detected on DSA. Incomplete vessel occlusion by the primary thrombus with distal passage of contrast is required for this observation. Therefore, the true prevalence of multiple intracranial thrombi in the stroke population and the implications for clinical outcome remain unknown.Advanced gradient-echo-based MR imaging sequences, such as SWI, are highly sensitive in distinguishing structures that have different susceptibility values than their surroundings (eg, deoxygenated blood, hemosiderin, ferritin, or calcium).¹ SWI offers the possibility to directly visualize thrombotic material, commonly referred to as the susceptibility vessel sign (SVS), independent of the presence of blood flow or contrast media.^2–4 Recent studies confirmed that 1.5T and 3T SWI is a fast, robust, and highly sensitive imaging technique in acute stroke without relevant image interference following gadolinium application.^5,6 We performed SWI, covering the whole brain in patients with acute ischemic stroke of the anterior or posterior circulation to determine the prevalence of multiple intracranial thrombi before thrombolytic treatment and to study the associations between the presence of fragmented thrombi and baseline clinical and imaging characteristics, stroke etiology, and clinical outcome.     

Multiphasic Perfusion CT in Acute Middle Cerebral Artery Ischemic Stroke: Prediction of Final Infarct Volume and Correlation with Clinical Outcome

Objective

To assess the utility of multiphasic perfusion CT in the prediction of final infarct volume, and the relationship between lesion volume revealed by CT imaging and clinical outcome in acute ischemic stroke patients who have not undergone thrombolytic therapy.

Materials and Methods

Thirty-five patients underwent multiphasic perfusion CT within six hours of stroke onset. After baseline unenhanced helical CT scanning, contrast-enhanced CT scans were obtained 20, 34, 48, and 62 secs after the injection of 90 mL contrast medium at a rate of 3 mL/sec. CT peak and total perfusion maps were obtained from serial CT images, and the initial lesion volumes revealed by CT were compared with final infarct volumes and clinical scores.

Results

Overall, the lesion volumes seen on CT peak perfusion maps correlated most strongly with final infarct volumes (R²=0.819, p<0.001, slope of regression line=1.016), but individual data showed that they were less than final infarct volume in 31.4% of patients. In those who showed early clinical improvement (n=6), final infarct volume tended to be overestimated by CT peak perfusion mapping and only on total perfusion maps was there significant correlation between lesion volume and final infarct volume (R²=0.854, p=0.008). The lesion volumes depicted by CT maps showed moderate correlation with baseline clinical scores and clinical outcomes (R=0.445-0.706, p≤0.007).

Conclusion

CT peak perfusion maps demonstrate strong correlation between lesion volume and final infarct volume, and accurately predict final infarct volume in about two-thirds of the 35 patients. The lesion volume seen on CT maps shows moderate correlation with clinical outcome.     

Impact of Age and Baseline NIHSS Scores on Clinical Outcomes in the Mechanical Thrombectomy Using Solitaire FR in Acute Ischemic Stroke Study

BACKGROUND AND PURPOSE:Age and stroke severity are inversely correlated with the odds of favorable outcome after ischemic stroke. A previously proposed score for Stroke Prognostication Using Age and NIHSS Stroke Scale (SPAN) indicated that SPAN-100-positive patients (ie, age + NIHSS score = 100 or more) do not benefit from IV-tPA. If this finding holds true for endovascular therapy, this score can impact patient selection for such interventions. This study investigated whether a score combining age and NIHSS score can improve patients'' selection for endovascular stroke therapy.MATERIALS AND METHODS:The SPAN index was calculated for patients in the prospective Solitaire FR Thrombectomy for Acute Revascularization study: an international single-arm multicenter cohort for anterior circulation stroke treatment by using the Solitaire FR. The proportion with favorable outcome (90-day mRS score ≤2) was compared between SPAN-100-positive versus-negative patients.RESULTS:Of the 202 patients enrolled, 196 had baseline NIHSS scores. Fifteen (7.7%) patients were SPAN-100-positive. There was no difference in the rate of successful reperfusion (Thrombolysis In Cerebral Infarction 2b or 3) between SPAN-100-positive versus -negative groups (93.3% versus 82.8%, respectively; P = .3). Stroke SPAN-100-positive patients had a significantly lower proportion of favorable clinical outcomes (26.7% versus 60.8% in SPAN-100-negative, P = .01). In a multivariable analysis, SPAN-100-positive status was associated with lower odds of favorable outcome (OR, 0.3; 95% CI_, 0.1–0.9; P = .04). A higher baseline Alberta Stroke Program Early CT Score and a short onset to revascularization time also predicted favorable outcome in the multivariable analysis.CONCLUSIONS:A significantly lower proportion of patients with a positive SPAN-100 achieved favorable outcome in this cohort. SPAN-100 was an independent predictor of favorable outcome after adjusting for time to treatment and the extent of preintervention tissue damage according to the Alberta Stroke Program Early CT Score.

Stroke-related disability remains high at nearly 2 decades since the introduction of IV-tPA as an acute ischemic stroke therapy.¹ Three recent large randomized trials failed to demonstrate the efficacy of endovascular therapies in improving the 90-day functional outcomes over IV-tPA alone.^2–4 These trials are criticized for time delays in achieving reperfusion and for the use of dated devices in most patients. Stent retrievers have proved efficacy over the Merci retriever (Concentric Medical, Mountain View, California),^5,6 but they were used in <1% of patients in the recent neutral trials. Therefore, at least 4 multicenter randomized trials of acute stroke endovascular therapy by using stent retrievers are currently recruiting, and other trials are launching soon.The importance of patient selection for endovascular therapy of acute ischemic stroke cannot be overemphasized. While controversy exists regarding the optimal imaging technique for patient selection for endovascular therapy, there are proved and readily-available clinical indicators. Among the factors associated with poor functional recovery, age and NIHSS score are most relevant.⁷ This finding led to the derivation of the Stroke Prognostication Using Age and NIHSS Stroke Scale (SPAN) index by adding the patient age in years plus the baseline NIHSS score. Investigators reported that patients in the National Institute of Neurological Disorders and Stroke trial with a score of ≥100 (SPAN-100) did not benefit from IV-tPA therapy, with a higher rate of symptomatic intracranial hemorrhage and poor functional outcome compared with SPAN-100-negative patients.⁸ However, these findings do not take into account the rate of successful recanalization that has been consistently shown to be one of the strongest predictors of favorable stroke outcome.⁹ The National Institute of Neurological Disorders and Stroke trial,¹⁰ conducted between 1991 and 1994, does not reflect contemporary stroke care; this feature limits its generalizability.If the SPAN-100 index can identify patients who do not benefit from endovascular therapy, this simple and readily available index will have implications for patient eligibility for these interventions. We assessed the impact of the SPAN-100 index in the large multicenter prospective study for mechanical thrombectomy in acute ischemic stroke, Solitaire FR Thrombectomy for Acute Revascularization (STAR).¹¹