Younger Stroke Patients With Large Pretreatment Diffusion-Weighted Imaging Lesions May Benefit From Endovascular Treatment

Usefulness of additional diffusion MRI acquisition prior to mechanical thrombectomy for acute large vessel occlusion in the early time period at a CT-based stroke center

OBJECTIVE

This study aimed to investigate whether evaluating the infarction core using additionally acquired diffusion magnetic resonance imaging (MRI) could help improve the assessment of prognosis including complication rates and modify the strategy for mechanical thrombectomy in endovascular procedures at a computed tomography (CT)-based stroke center.

METHODS

Single-center data from patients with acute large-vessel occlusion in the anterior circulation who underwent mechanical thrombectomy between May 2018 and January 2021 were analyzed. Diffusion MRI sequences were performed during the preparation period for mechanical thrombectomy after CT angiography. We set the infarction core reference volume on diffusion MRI to 60 cc and divided the patients into two groups: a small infarction core group (less than 60 cc) and a large infarction core group (more than 60 cc). The baseline characteristics, radiological and clinical outcomes of the patients were investigated and compared between the two groups.

RESULTS

The difference in numbers between the two groups was not significant in the Alberta Stroke Program Early Computed Tomography (ASPECT) score; however, the ASPECT score on diffusion MRI showed a remarkable difference between the two groups. The large infarction core volume group on diffusion MRI had a poor prognosis, with the modified Rankin score at 90 days showing a statistically significant difference (p = 0.011). Complications after the procedure, such as hemorrhagic transformation, that can occur after reperfusion, symptomatic intracerebral hemorrhage, decompressive craniectomy for increased intracranial pressure, and mortality, were significantly more frequent in the large infarction core volume group.

CONCLUSION

At a CT-based stroke center, additionally acquired diffusion MRI without a time delay for reperfusion would improve the assessment of prognosis including complication rate, and could help neurointerventionists determine the extent of recanalization of occluded vessels during mechanical thrombectomy.

Mechanical thrombectomy in low Alberta Stroke Program Early Computed Tomographic Score: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Due to their poor natural history and lack in level-I evidence, patients with large vessel occlusion and large core infarcts (Alberta Stroke Program Early Computed Tomographic Score <6) have been excluded from receiving mechanical thrombectomy. This systematic review and meta-analysis seeks to summarize current evidence from published randomized controlled trials to compare the safety and efficacy of mechanical thrombectomy with optimal medical therapy in treating stroke patients with large core infarcts.

METHODS

We searched PubMed and EMBASE for randomized controlled trials investigating the safety and efficacy of mechanical thrombectomy vs optimal medical therapy in patients presenting with large vessel occlusion and large infarcts. Basic demographic and comorbidities were assessed, and clinical outcomes were compared, including modified Rankin scale 0-3, and 0-2 at 3 months, symptomatic intracranial hemorrhage, decompressive hemicortectomy, and 90-day mortality.

RESULTS

Three randomized controlled trials totaling 1011 patients (501 and 510 in the medical management and mechanical thrombectomy arm, respectively) were included. Patients undergoing mechanical thrombectomy had significantly higher odds of achieving better functional outcomes at 3 months: Modified Rankin scale 0-2 (OR = 3.05, 95% CI = 2.101-4.4021, p < 0.0001) and modified Rankin scale 0-3 (OR = 2.20, 95% CI = 1.67-2.89, p < 0.0001) as compared to those receiving optimal medical management. There were no differences between groups in 90-day mortality (OR = 0.93, 95% CI = 0.70-1.23, p = 0.60), symptomatic intracranial hemorrhage (OR = 1.89, 95% = CI 0.95-3.77, p = 0.07) or decompressive hemicraniectomy (OR = 1.25, 95% CI = 0.69-2.25, p = 0.46).

CONCLUSION

Mechanical thrombectomy for patients with large infarcts is associated with improved functional outcomes and a similar safety profile compared to optimal medical management. Ongoing trials will help better refine the target population that benefits the most from treatment.

Nomogram to predict unfavorable outcome of endovascular thrombectomy for large ischemic core

OBJECTIVE

The prognosis for patients presenting with a large ischemic core (LIC) following endovascular thrombectomy is relatively poor. This study aimed to construct and validate a nomogram for predicting 3-month unfavorable outcome in patients with anterior circulation occlusion-related LIC who underwent endovascular thrombectomy.

METHODS

A retrospective training cohort and a prospective validation cohort of patients with a large ischemic core were studied. The diffusion weighted imaging related radiomic features and pre-thrombectomy clinical features were collected. After the selection of relevant features, a nomogram predicting modified Rankin Scale score of 3-6 as an unfavorable outcome was established. The discriminatory value of the nomogram was evaluated with a receiver operating characteristic curve.

RESULTS

A total of 140 patients (mean age 66.3 ± 13.4 years, 35% female) were included in this study, consisting of a training cohort (n = 95) and a validation cohort (n = 45). The percentage of patients with an mRS scores of 0-2 was 30%, 0-3 was 40.7%, and 32.9% were dead. Age, National Institute of Health Stroke Scale (NIHSS) score, and two radiomic features, Maximum2DDiameterColumn and Maximum2DDiameterSlice, were identified as factors associated with unfavorable outcome in the nomogram. The nomogram demonstrated an area under the curve of 0.892 (95% confidence interval [CI], 0.812-0.947) in the training dataset and 0.872 (95% CI, 0.739-0.953) in the validation dataset.

INTERPRETATION

This nomogram, which includes age, NIHSS score, Maximum2DDiameterColumn, and Maximum2DDiameterSlice, may predict the risk of unfavorable outcome in patients with LIC caused by anterior circulation occlusion.

Neurological Functional Independence After Endovascular Thrombectomy and Different Imaging Modalities for Large Infarct Core Assessment : A Systematic Review and Meta-analysis

PURPOSE

To investigate the rate of neurological functional independence (NFI) at 90 days in patients with large infarct core (LIC), which was evaluated by different imaging modalities before endovascular thrombectomy (EVT).

METHODS

PubMed and EMBASE were searched for original studies on clinical functional outcomes at 90 days in LIC patients who received EVT treatment from inception to 28 September 2021. The pooled NFI rates were calculated using random effects model according to different imaging modalities and criteria.

RESULTS

We included 34 studies enrolling 2997 LIC patients. The NFI rates were 23% (95% confidence interval, CI 15-32%) and 24% (95% CI 10-38%) when LIC was defined as core volume ≥50 ml and ≥ 70 ml separately on computed tomography perfusion, 36% (95% CI 23-48%) and 21% (95% CI 17-25%) when LIC was defined as core volume ≥ 50 ml and ≥ 70 ml separately on magnetic resonance diffusion-weighted imaging (DWI), 28% (95% CI 24-32%) and 37% (95% CI 21-53%) when LIC was defined as DWI-ASPECTS ≤ 5 and ≤ 6 separately, 23% (95% CI 19-27%) and 32% (95% CI 18-46%) when LIC was defined as NCCT-ASPECTS ≤ 5 and ≤ 6 separately.

CONCLUSION

Similar NFI rates could be obtained after EVT in LIC patients if proper LIC criteria were select according to the imaging modality.

Smaller baseline subcortical infarct volume predicts good outcomes in patients with a large core in early acute ischemic stroke after endovascular treatment

Background

Patients with acute ischemic stroke (AIS) and a large core may benefit from endovascular treatment (EVT) in the early time window.

Purpose

To examine the prognostic factors for good outcomes in patients with a large core (70-130 ml) after EVT.

Materials and methods

We retrospectively reviewed 40 patients who met the criteria from October 2019 to April 2021. Based on the modified Rankin Score (mRS) at 90 days, the patients were divided into a good outcome group (mRS 0-2) and a poor outcome group (mRS 3-6). Baseline and procedural characteristics were collected for unilateral and multivariate regression analyses to explore the factors that influence good outcomes. In particular, the infarct territories were quantified as subcortical infarct volume (SIV) and cortical infarct volume (CIV).

Results

Of the 40 patients included, good outcomes were observed in 11 (27.5%) patients. Younger age, smaller SIV and larger mismatch volume were noted in the good outcome group than in the poor outcome group (all P < 0.05). Multivariate logistic regression analysis showed that only a smaller SIV [odds ratio (OR) 0.801; 95% CI 0.644-0.996; P = 0.046] was an independent predictor for good outcomes. The receiver operating characteristic curve indicated a moderate value of SIV for predicting good outcomes, with an area under the receiver operating characteristic curve of 0.735 (95% CI 0.572-0.862; P = 0.007).

Conclusion

Subcortical infarct volume was a potential useful predictor of good outcomes in patients with a large core after EVT in the early time window.

Endovascular thrombectomy versus standard bridging thrombolytic with endovascular thrombectomy within 4·5 h of stroke onset: an open-label, blinded-endpoint, randomised non-inferiority trial

BACKGROUND

The benefit of combined treatment with intravenous thrombolysis before endovascular thrombectomy in patients with acute ischaemic stroke caused by large vessel occlusion remains unclear. We hypothesised that the clinical outcomes of patients with stroke with large vessel occlusion treated with direct endovascular thrombectomy within 4·5 h would be non-inferior compared with the outcomes of those treated with standard bridging therapy (intravenous thrombolysis before endovascular thrombectomy).

METHODS

DIRECT-SAFE was an international, multicentre, prospective, randomised, open-label, blinded-endpoint trial. Adult patients with stroke and large vessel occlusion in the intracranial internal carotid artery, middle cerebral artery (M1 or M2), or basilar artery, confirmed by non-contrast CT and vascular imaging, and who presented within 4·5 h of stroke onset were recruited from 25 acute-care hospitals in Australia, New Zealand, China, and Vietnam. Eligible patients were randomly assigned (1:1) via a web-based, computer-generated randomisation procedure stratified by site of baseline arterial occlusion and by geographic region to direct endovascular thrombectomy or bridging therapy. Patients assigned to bridging therapy received intravenous thrombolytic (alteplase or tenecteplase) as per standard care at each site; endovascular thrombectomy was also per standard of care, using the Trevo device (Stryker Neurovascular, Fremont, CA, USA) as first-line intervention. Personnel assessing outcomes were masked to group allocation; patients and treating physicians were not. The primary efficacy endpoint was functional independence defined as modified Rankin Scale score 0-2 or return to baseline at 90 days, with a non-inferiority margin of -0·1, analysed by intention to treat (including all randomly assigned and consenting patients) and per protocol. The intention-to-treat population was included in the safety analyses. The trial is registered with ClinicalTrials.gov, NCT03494920, and is closed to new participants.

FINDINGS

Between June 2, 2018, and July 8, 2021, 295 patients were randomly assigned to direct endovascular thrombectomy (n=148) or bridging therapy (n=147). Functional independence occurred in 80 (55%) of 146 patients in the direct thrombectomy group and 89 (61%) of 147 patients in the bridging therapy group (intention-to-treat risk difference -0·051, two-sided 95% CI -0·160 to 0·059; per-protocol risk difference -0·062, two-sided 95% CI -0·173 to 0·049). Safety outcomes were similar between groups, with symptomatic intracerebral haemorrhage occurring in two (1%) of 146 patients in the direct group and one (1%) of 147 patients in the bridging group (adjusted odds ratio 1·70, 95% CI 0·22-13·04) and death in 22 (15%) of 146 patients in the direct group and 24 (16%) of 147 patients in the bridging group (adjusted odds ratio 0·92, 95% CI 0·46-1·84).

INTERPRETATION

We did not show non-inferiority of direct endovascular thrombectomy compared with bridging therapy. The additional information from our study should inform guidelines to recommend bridging therapy as standard treatment.

FUNDING

Australian National Health and Medical Research Council and Stryker USA.

Outcomes and CT Perfusion Thresholds of Mechanical Thrombectomy for Patients With Large Ischemic Core Lesions

Objective

To explore the clinical prognosis and factors after mechanical thrombectomy (MT) in patients with large cerebral infarction assessed by computed tomographic perfusion (CTP)and the optimal threshold of cerebral blood flow (CBF) for estimating ischemic core.

Methods

We analyzed data from the anterior circulation database of our hospital (August 2018-June 2021). Multivariate logistic regression analyses identified the predictors of clinical outcomes for patients with large baseline infarcts (>50 ml) assessed by the MIStar software. The receiver operating characteristic (ROC) analysis was used to explore the cutoff value of factors.

Results

The present study included one hundred thirty-seven patients with large baseline infarcts. Moreover, 23 (16.8%) patients achieved functionally independent outcomes, and 50 (36.5%) patients died at 90 days. A total of 20 (14.7%) patients had symptomatic intracranial hemorrhage (sICH). The multivariable analysis showed that higher age and larger core volume were independent of poor outcomes. The cutoff value of core volume was 90 ml, and the age was 76 years. Hypertension and rt-PA treatment were independent factors of sICH. Higher age and larger ischemic volume were independent risk factors of mortality.

Conclusions

Mechanical thrombectomy can be applied in patients with large ischemic core volumes. Patients older than 76 years with large cores (>90 ml) are unlikely to benefit from MT. These findings may be helpful in selecting patients with large baseline infarcts to be treated by MT. The threshold of CBF < 30% is the independent factor, and this is worth evaluating in future studies to find the optimal threshold of CBF.

Clinical protocol of the ischemic stroke patients treatment

Today in Ukraine there is no single standardized protocol for the treatment of patients in the acute period of ischemic stroke using modern methods of diagnosis and treatment, which include thrombolytic therapy and endovascular treatment. This protocol was created and implemented in Scientific-practical Center of endovascular neuroradiology, NAMS of Ukraine and is based on the latest recommendations of AHA/ASA and ESO, as well as registers of patients with ischemic stroke. The main purpose of this publication is the creation and implementation of «instructions» for the diagnosis and selection of objective tactics for treating patients in the acute period of ischemic stroke.

DIRECT-SAFE: A Randomized Controlled Trial of DIRECT Endovascular Clot Retrieval versus Standard Bridging Therapy

Background and Purpose

The benefit regarding co-treatment with intravenous (IV) thrombolysis before mechanical thrombectomy in acute ischemic stroke with large vessel occlusion remains unclear. To test the hypothesis that clinical outcome of ischemic stroke patients with intracranial internal carotid artery, middle cerebral artery or basilar artery occlusion treated with direct endovascular thrombectomy within 4.5 hours will be non-inferior compared with that of standard bridging IV thrombolysis followed by endovascular thrombectomy.

Methods

To randomize 780 patients 1:1 to direct thrombectomy or bridging IV thrombolysis with thrombectomy. An international-multicenter prospective randomized open label blinded endpoint trial (PROBE) (ClincalTrials.gov identifier: NCT03494920).

Results

Primary endpoint is functional independence defined as modified Rankin Scale (mRS) 0–2 or return to baseline at 90 days. Secondary end points include ordinal mRS analysis, good angiographic reperfusion (modified Thrombolysis in Cerebral Infarction score [mTICI] 2b–3), safety endpoints include symptomatic intracerebral hemorrhage and death.

Conclusions

DIRECT-SAFE will provide unique information regarding the impact of direct thrombectomy in patients with large vessel occlusion, including patients with basilar artery occlusion, with comparison across different ethnic groups.

Outcomes of Mechanical Thrombectomy in Patients with Large Diffusion-Weighted Imaging Lesions

Objective

Despite many advancements in endovascular treatment, the benefits of mechanical thrombectomy (MT) in patients with large infarctions remain uncertain due to hemorrhagic complications. Therefore, we aimed to investigate the efficacy and safety of recanalization via MT within 6 hours after stroke in patients with large cerebral infarction volumes (>70 mL).

Methods

We retrospectively reviewed the medical data of 30 patients with large lesions on initial diffusion-weighted imaging (>70 mL) who underwent MT at our institution within 6 hours after stroke onset. Baseline data, recanalization rate, and 3-month clinical outcomes were analyzed. Successful recanalization was defined as a modified treatment in cerebral ischemia score of 2b or 3.

Results

The recanalization rate was 63.3%, and symptomatic intracerebral hemorrhage occurred in six patients (20%). The proportion of patients with modified Rankin Scale (mRS) scores of 0-3 was significantly higher in the recanalization group than in the non-recanalization group (47.4% vs. 9.1%, p=0.049). The mortality rate was higher in the non-recanalization group, this difference was not significant (15.8% vs. 36.4%, p=0.372). In the analysis of 3-month clinical outcomes, only successful recanalization was significantly associated with mRS scores of 0-3 (90% vs. 50%, p=0.049). The odds ratio of recanalization for favorable outcomes (mRS 0-3) was 9.00 (95% confidence interval, 0.95-84.90; p=0.055).

Conclusion

Despite the risk of symptomatic intracerebral hemorrhage, successful recanalization via MT 6 hours after stroke may improve clinical outcomes in patients with large vessel occlusion.

Impact of Pretreatment Ischemic Location on Functional Outcome after Thrombectomy

Pretreatment ischemic location may be an important determinant for functional outcome prediction in acute ischemic stroke. In total, 143 anterior circulation ischemic stroke patients in the THRACE study were included. Ischemic lesions were semi-automatically segmented on pretreatment diffusion-weighted imaging and registered on brain atlases. The percentage of ischemic tissue in each atlas-segmented region was calculated. Statistical models with logistic regression and support vector machine were built to analyze the predictors of functional outcome. The investigated parameters included: age, baseline National Institutes of Health Stroke Scale score, and lesional volume (three-parameter model), together with the ischemic percentage in each atlas-segmented region (four-parameter model). The support vector machine with radial basis functions outperformed logistic regression in prediction accuracy. The support vector machine three-parameter model demonstrated an area under the curve of 0.77, while the four-parameter model achieved a higher area under the curve (0.82). Regions with marked impacts on outcome prediction were the uncinate fasciculus, postcentral gyrus, putamen, middle occipital gyrus, supramarginal gyrus, and posterior corona radiata in the left hemisphere; and the uncinate fasciculus, paracentral lobule, temporal pole, hippocampus, inferior occipital gyrus, middle temporal gyrus, pallidum, and anterior limb of the internal capsule in the right hemisphere. In conclusion, pretreatment ischemic location provided significant prognostic information for functional outcome in ischemic stroke.

Mechanical Thrombectomy in Patients with a Large Ischemic Volume at Presentation: Systematic Review and Meta-Analysis

The benefits of mechanical thrombectomy (MT) for patients with acute ischemic stroke (AIS) and a large ischemic core (LIC) at presentation are uncertain. We aimed to obtain up-to-date aggregate estimates of the outcomes following MT in patients with volumetrically assessed LIC. We conducted a Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA)-conformed, PROSPERO-registered, systematic review and meta-analysis of studies that included patients with AIS and a baseline LIC treated with MT, reported ischemic core volume quantitatively, and included patients with a LIC defined as a core volume ≥50 mL. The search was restricted to studies published between January 2015 and June 2020. Random-effects-meta-analysis was used to assess the effect of MT on 90-day unfavorable outcome (i.e., modified Rankin Scale [mRS] 3–6), mortality, and symptomatic intracranial hemorrhage (sICH) occurrence. Sensitivity analyses were performed for imaging-modality (computed tomography-perfusion or magnetic resonance-diffusion weighted imaging) and LIC-definition (≥50 or ≥70 mL). We analyzed 10 studies (954 patients), including six (682 patients) with a control group, allowing to compare 332 patients with MT to 350 who received best-medical-management alone. Overall, after MT the rate of patients with mRS 3–6 at 90 days was 74% (99% confidence interval [CI], 67 to 84; Z-value=7.04; I²=92.3%) and the rate of 90-day mortality was 36% (99% CI, 33 to 40; Z-value=–7.07; I²=74.5). Receiving MT was associated with a significant decrease in mRS 3–6 odds ratio (OR) 0.19 (99% CI, 0.11 to 0.33; P<0.01; Z-value=–5.92; I²=62.56) and in mortality OR 0.60 (99% CI, 0.34 to 1.06; P=0.02; Z-value=–2.30; I²=58.72). Treatment group did not influence the proportion of patients experiencing sICH, OR 0.96 (99% CI, 0.2 to 1.49; P=0.54; Z-value=–0.63; I²=64.74). Neither imaging modality for core assessment, nor LIC definition influenced the aggregated outcomes. Using aggregate estimates, MT appeared to decrease the risk of unfavorable functional outcome in patients with a LIC assessed volumetrically at baseline.

Role of Apparent Diffusion Coefficient Gradient Within Diffusion Lesions in Outcomes of Large Stroke After Thrombectomy

BACKGROUND AND PURPOSE

The outcome of endovascular treatment in stroke patients with a large ischemic core is not always satisfactory. We evaluated whether the severity of baseline diffusion-weighted imaging abnormalities, as assessed by different apparent diffusion coefficient (ADC) thresholds, correlates with the clinical outcome in these patients after successful endovascular treatment.

METHODS

In 82 consecutive patients with a large vessel occlusion in the anterior circulation admitted ≤24 hours after onset, a baseline diffusion lesion volume (ADC ≤620×10^-6 mm²/s [ADC₆₂₀]) ≥50 mL and successful recanalization by endovascular treatment were retrospectively investigated. Lesion volumes of 3 ADC thresholds (ADC₆₂₀, ADC ≤520×10^-6 mm²/s [ADC₅₂₀], and ADC ≤540×10^-6 mm²/s [ADC₅₄₀]) were measured using an automated Olea software program. The performance of the ADC₅₂₀/ADC₆₂₀ and ADC₅₄₀/ADC₆₂₀ ratios in predicting the functional outcome was assessed by receiver operating characteristic curve analysis. The ADC ratio with optimal threshold showing better receiver operating characteristic performance was dichotomized at its median value into low versus high subgroup and its association with the outcome subsequently evaluated in a multivariable logistic regression model.

RESULTS

The median baseline diffusion lesion volume was 80.8 mL (interquartile range, 64.4-105.4). A good functional outcome (modified Rankin Scale score, ≤2) was achieved in 35 patients (42.7%). The optimal threshold for predicting the functional outcome was identified as ADC₅₄₀/ADC₆₂₀ (area under the curve, 0.833) and dichotomized at 0.674. After adjusting for age, baseline National Institutes of Health Stroke Scale score, intravenous tissue-type plasminogen activator, baseline diffusion lesion volume, and onset-to-recanalization time, a low ADC₅₄₀/ADC₆₂₀ was independently associated with a good functional outcome (adjusted odds ratio, 10.72 [95% CI, 3.06-37.50]; P<0.001).

CONCLUSIONS

A low ADC₅₄₀/ADC₆₂₀, which may reflect less severe ischemic stress inside a diffusion lesion, may help to identify patients who would benefit from endovascular treatment despite having a large ischemic core.

Controversies in Imaging of Patients with Acute Ischemic Stroke: AJR Expert Panel Narrative Review

The development of reperfusion therapies has profoundly impacted stroke care, initially with the advent of IV thrombolytic (IVT) treatment and, more recently, with the development and refinement of endovascular treatment (EVT). Progress in neuroimaging has supported the paradigm shift of stroke care, and advanced neuroimaging now has a fundamental role in triaging patients for both IVT and EVT. As the standard of care for acute ischemic stroke (AIS) evolves, controversies remain in certain clinical scenarios. This article explores the use of multimodality imaging for treatment selection of AIS in the context of recent guidelines, highlighting controversial topics and providing guidance for clinical practice. Results of major randomized trials supporting EVT are reviewed. Advantages and disadvantages of CT, CTA, MRI, and MRA in stroke diagnosis are summarized, with attention to level 1 evidence supporting the role of vascular imaging and perfusion imaging. Patient selection is compared between approaches based on time thresholds and physiologic approaches based on infarct core measurement using imaging. Moreover, various imaging approaches to core measurement are described. As ongoing studies push treatment boundaries, advanced imaging is expected to help identify a widening range of patients who may benefit from therapy.

Acute reperfusion therapies for acute ischemic stroke patients with unknown time of symptom onset or in extended time windows: an individualized approach

Recent randomized controlled clinical trials (RCTs) have revolutionized acute ischemic stroke care by extending the use of intravenous thrombolysis and endovascular reperfusion therapies in time windows that have been originally considered futile or even unsafe. Both systemic and endovascular reperfusion therapies have been shown to improve outcome in patients with wake-up strokes or symptom onset beyond 4.5 h for intravenous thrombolysis and beyond 6 h for endovascular treatment; however, they require advanced neuroimaging to select stroke patients safely. Experts have proposed simpler imaging algorithms but high-quality data on safety and efficacy are currently missing. RCTs used diverse imaging and clinical inclusion criteria for patient selection during the dawn of this novel stroke treatment paradigm. After taking into consideration the dismal prognosis of nonrecanalized ischemic stroke patients and the substantial clinical benefit of reperfusion therapies in selected late presenters, we propose rescue reperfusion therapies for acute ischemic stroke patients not fulfilling all clinical and imaging inclusion criteria as an option in a subgroup of patients with clinical and radiological profiles suggesting low risk for complications, notably hemorrhagic transformation as well as local or remote parenchymal hemorrhage. Incorporating new data to treatment algorithms may seem perplexing to stroke physicians, since treatment and imaging capabilities of each stroke center may dictate diverse treatment pathways. This narrative review will summarize current data that will assist clinicians in the selection of those late presenters that will most likely benefit from acute reperfusion therapies. Different treatment algorithms are provided according to available neuroimaging and endovascular treatment capabilities.

Identifying large ischemic core volume ranges in acute stroke that can benefit from mechanical thrombectomy

BACKGROUND

We aimed to identify the large ischemic core (LIC) volume ranges in acute ischemic stroke patients that can benefit from mechanical thrombectomy (MT).

METHODS

Consecutive patients within 24 hours of onset of anterior circulation ischemic stroke with large vessel occlusion and ischemic core volumes of 70-300 mL were included from our single-center prospective database from March 2014 to December 2019. Subjects were divided into three groups by baseline ischemic core volume (A: 70-100 mL; B: 101-130 mL; C: >130 mL). We compared modified Rankin Scale (mRS) score 0-2 at 3 months and parenchymal hematoma between patients receiving MT and standard medical treatment (SMT), and determined clinically treatable core volume ranges for MT.

RESULTS

Of 157 patients (86 women; median age, 81 years; median ischemic core volume, 123 mL), 49 patients underwent MT. In Group A (n=52), MT patients (n=31) showed a higher proportion of mRS 0-2 at 3 months (52% vs 5%, P<0.05) versus SMT, respectively. Group B (n=36) MT patients (n=14) also had a higher proportion of mRS 0-2 at 3 months (29% vs 9%, P=0.13) versus SMT, respectively. In Group C (n=69), only four patients received MT. The 95% confidence intervals for the probability of mRS 0-2 at 3 months in patients with MT (n=49) versus SMT (n=108) intersected at 120-130 mL.

CONCLUSIONS

Ischemic core volumes between 70 and 100 mL may benefit from MT. The treatable upper core limit is approximately 120 mL in selected patients with LIC of 70-300 mL.

The role of infarct location in patients with DWI-ASPECTS 0-5 acute stroke treated with thrombectomy

OBJECTIVE

To determine whether hemisphere involvement and infarct location on the Alberta Stroke Program CT Score (ASPECTS) template should serve as predictors of 90-day clinical outcome in patients with acute ischemic stroke with pretreatment diffusion-weighted imaging (DWI)-ASPECTS 0-5 treated with mechanical thrombectomy (MT).

METHODS

We analyzed data of all consecutive patients included in the Endovascular Treatment in Ischemic Stroke registry between January 1, 2012, and August 31, 2018, who presented with a pretreatment DWI-ASPECTS 0-5 and underwent MT. Multivariable analyses were performed in order to identify the role of infarct location and hemisphere involvement on good outcome defined by a modified Rankin Scale (mRS) score 0-2 at 90 days and on the whole distribution of mRS (shift analysis).

RESULTS

A total of 344 patients with a DWI-ASPECTS 0-5 (median 4, IQR 3-5) were included. Neither infarct location nor hemisphere involvement was found to be an independent predictor of good outcome. Involvement of the M6 region in right-sided strokes (adjusted odds ratio [aOR] 2.6, 99% confidence interval [CI] 1.14-5.8; p = 0.003) and the internal capsule in left-sided strokes (aOR 2.6, 99% CI 0.8-7.9; p < 0.020) independently predicted increased disability on the mRS distribution in the affected subpopulations.

CONCLUSION

Our study suggests that neither hemisphere nor infarct location should be considered as an exclusion criterion for MT in patients with stroke with pretreatment DWI-ASPECTS 0-5. The involvement of specific regions of interest was associated with increased disability. These may provide valuable information regarding stroke management options and neurologic recovery for use of caregivers in the postacute phase.

The impact of position-orientation adaptive smoothing in diffusion weighted imaging-From diffusion metrics to fiber tractography

In contrast to commonly used approaches to improve data quality in diffusion weighted imaging, position-orientation adaptive smoothing (POAS) provides an edge-preserving post-processing approach. This study aims to investigate its potential and effects on image quality, diffusion metrics, and fiber tractography of the corticospinal tract in relation to non-post-processed and averaged data. 22 healthy volunteers were included in this study. For each volunteer five clinically applicable diffusion weighted imaging data sets were acquired and post-processed by standard averaging and POAS. POAS post-processing led to significantly higher signal-to-noise-ratios (p < 0.001), lower fractional anisotropy across the whole brain (p < 0.05) and reduced intra-subject variability of diffusion weighted imaging signal intensity and fractional anisotropy (p < 0.001, p = 0.006). Fiber tractography of the corticospinal tract resulted in significantly (p = 0.027, p = 0.014) larger tract volumes while fiber density was the lowest. Similarity across tractography results was highest for POAS post-processed data (p < 0.001). POAS post-processing enhances image quality, decreases the intra-subject variability of signal intensity and fractional anisotropy, increases fiber tract volume of the corticospinal tract, and leads to higher reproducibility of tractography results. Thus, POAS post-processing supports a reliable and more accurate fiber tractography of the corticospinal tract, being mandatory for the clinical use.

Diffusion MRI Reversibility in Ischemic Stroke Following Thrombolysis: A Meta-Analysis

BACKGROUND AND PURPOSE

Diffusion-weighted magnetic resonance imaging (DWI) detects early infarction in acute stroke. With the substantial progress in stroke therapies, the frequency of posttreatment DWI reversibility in modern stroke cohorts is currently unknown. The purpose of this study was to perform a systematic literature review examining the relationship between characteristics of patients with ischemic stroke and DWI reversibility following treatment with lytic therapy.

METHODS

A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, yielding a total of 422 unique articles. Studies that were nonclinical or did not report data pertaining to DWI reversibility in the context of an acute stroke series were excluded. Characteristics regarding presentation, diagnosis, intervention, and the timing of DWI reversibility were collected for each study.

RESULTS

After full-text review, 10 studies were identified as meeting inclusion criteria. The number of patients with DWI reversal ranged from .9% to 50%, whereas the extent of reversal ranged from 1.8% to 72.7%. Studies reporting on younger patients describe greater rates of reversibility following stroke treatment.

CONCLUSIONS

These data suggest that early DWI signal may not represent the definitive DWI burden in recanalized populations. However, substantial heterogeneity exists regarding the rate of DWI reversal following recanalization. Additional studies are needed to elucidate the relationship among time to treatment, early reversal rates, and clinical outcomes. Physicians should use caution when basing clinical decisions on DWI lesion volumes, as these likely change to some degree with recanalization.

Deep Learning–Derived High-Level Neuroimaging Features Predict Clinical Outcomes for Large Vessel Occlusion

Background and Purpose—

For patients with large vessel occlusion, neuroimaging biomarkers that evaluate the changes in brain tissue are important for determining the indications for mechanical thrombectomy. In this study, we applied deep learning to derive imaging features from pretreatment diffusion-weighted image data and evaluated the ability of these features in predicting clinical outcomes for patients with large vessel occlusion.

Methods—

This multicenter retrospective study included patients with anterior circulation large vessel occlusion treated with mechanical thrombectomy between 2013 and 2018. We designed a 2-output deep learning model based on convolutional neural networks (the convolutional neural network model). This model employed encoder-decoder architecture for the ischemic lesion segmentation, which automatically extracted high-level feature maps in its middle layers, and used its information to predict the clinical outcome. Its performance was internally validated with 5-fold cross-validation, externally validated, and the results compared with those from the standard neuroimaging biomarkers Alberta Stroke Program Early CT Score and ischemic core volume. The prediction target was a good clinical outcome, defined as a modified Rankin Scale score at 90-day follow-up of 0 to 2.

Results—

The derivation cohort included 250 patients, and the validation cohort included 74 patients. The convolutional neural network model showed the highest area under the receiver operating characteristic curve: 0.81±0.06 compared with 0.63±0.05 and 0.64±0.05 for the Alberta Stroke Program Early CT Score and ischemic core volume models, respectively. In the external validation, the area under the curve for the convolutional neural network model was significantly superior to those for the other 2 models.

Conclusions—

Compared with the standard neuroimaging biomarkers, our deep learning model derived a greater amount of prognostic information from pretreatment neuroimaging data. Although a confirmatory prospective evaluation is needed, the high-level imaging features derived by deep learning may offer an effective prognostic imaging biomarker.

Perfusion Imaging to Select Patients with Large Ischemic Core for Mechanical Thrombectomy

BACKGROUND AND PURPOSE

Patients with acute ischemic stroke, proximal vessel occlusion and a large ischemic core at presentation are commonly not considered for mechanical thrombectomy (MT). We tested the hypothesis that in patients with baseline large infarct cores, identification of remaining penumbral tissue using perfusion imaging would translate to better outcomes after MT.

METHODS

This was a multicenter, retrospective, core lab adjudicated, cohort study of adult patients with proximal vessel occlusion, a large ischemic core volume (diffusion weighted imaging volume ≥70 mL), with pre-treatment magnetic resonance imaging perfusion, treated with MT (2015 to 2018) or medical care alone (controls; before 2015). Primary outcome measure was 3-month favorable outcome (defined as a modified Rankin Scale of 0-3). Core perfusion mismatch ratio (CPMR) was defined as the volume of critically hypo-perfused tissue (Tmax >6 seconds) divided by the core volume. Multivariable logistic regression models were used to determine factors that were independently associated with clinical outcomes. Outputs are displayed as adjusted odds ratio (aOR) and 95% confidence interval (CI).

RESULTS

A total of 172 patients were included (MT n=130; Control n=42; mean age 69.0±15.4 years; 36% females). Mean core-volume and CPMR were 102.3±36.7 and 1.8±0.7 mL, respectively. As hypothesized, receiving MT was associated with increased probability of favorable outcome and functional independence, as CPMR increased, a difference becoming statistically significant above a mismatch-ratio of 1.72. Similarly, receiving MT was also associated with favorable outcome in the subgroup of 74 patients with CPMR >1.7 (aOR, 8.12; 95% CI, 1.24 to 53.11; P=0.028). Overall (prior to stratification by CPMR) 73 (42.4%) patients had a favorable outcome at 3 months, with no difference amongst groups.

CONCLUSION

s In patients currently deemed ineligible for MT due to large infarct ischemic cores at baseline, CPMR identifies a subgroup strongly benefiting from MT. Prospective studies are warranted.

[Diffusion-weighted imaging hyperintensity is reversible in large middle cerebral artery infarction following thrombectomy:a case report]

Diffusion-weighted imaging (DWI) is currently the most sensitive technique to diagnose early ischemic stroke. DWI signal hyperintensity is usually considered to suggest irreversible infarct core, but recent studies demonstrated that DWI hyperintensity signal could be reversible on small embolic lesions. Herein we present a case in a 63-year-old male patient, who was admitted to the emergency department with altered mental status and complaint of weakness in the left arm and leg 6.8 h prior to the admission. Emergency cranial magnetic resonance imaging (MRI) and angiography (MRA) revealed occlusion of his right middle cerebral artery (MCA) and large lesions on DWI. The patient underwent intra-artery thrombectomy after evaluation in spite of the large volume of the DWI lesions up to 91.5 mL at the baseline. His right MCA was recanalized at 8.5 h from symptom onset. One week after the procedure, the patient showed reduced DWI lesion volume to 11.58 mL. In this case we observed the reversibility of a large lesion of the anterior artery circulation presenting with hyperintensity on DWI, suggesting that the clinical implication of DWI hyperintensity should be interpreted with caution, and a large volume of baseline DWI hyperintensity may not be a contraindication to thrombectomy. This conclusion, however, awaits further validation by future large-scale randomized controlled trials.

Large Infarct Volume Post Thrombectomy: Characteristics, Outcomes, and Predictors

BACKGROUND

Despite increasing interest in endovascular therapy (EVT) for large-core strokes, little is known about the predictors of good outcome in these patients. The aim of this study was to analyze patients with large-core strokes post-EVT and to define the predictors of favorable outcome in this population.

METHODS

A retrospective analysis of prospectively collected data on anterior circulation strokes undergoing EVT between January 2015 and February 2018 was performed. Patients with good baseline functional status who underwent EVT for occlusion of an anterior circulation artery and achieved successful recanalization (modified Treatment in Cerebral Ischemia score ≥2b) but had large follow-up infarct volume (FIV ≥70 cm³) were included in the study. Demographic characteristics, clinical and radiologic data, treatment and postprocedural outcomes were extracted and analyzed. The primary outcome was 90-day modified Rankin Scale (mRS) score, stratified by favorable (mRS 0-3) versus unfavorable (mRS 4-6).

RESULTS

Of 355 patients meeting inclusion criteria, 85 (24%) had large FIV on follow-up imaging after EVT and constituted the study cohort. No patients achieved mRS score 0-2 at hospital discharge; 32% had 90-day mRS score 0-3. On multivariate logistic regression analysis, lower FIV (OR, -0.96 [0.95-0.99]; P = 0.007), male sex (OR, -1.29 [1.07-12.3]; P = 0.026), and intravenous tissue plasminogen activator use (OR, 3.6 [2.01-8.9]; P = 0.003) were independent predictors of favorable outcome. Independent predictors of mortality on multivariate analysis were higher FIV (OR, -1.01 [1.007-1.02]; P = 0.001) and female sex (OR, 4.08 [1.25-13.3]; P = 0.02).

CONCLUSIONS

For patients with large-core strokes (≥70 cm³) after EVT, approximately one third have favorable outcome at 90 days. Independent predictors of favorable 90-day outcomes include male sex, intravenous tissue plasminogen activator use, and lower FIV.

Clinical benefit of thrombectomy in stroke patients with low ASPECTS is mediated by oedema reduction

The impact of endovascular vessel recanalization on patients with a low initial Alberta Stroke Program Early Computer Tomography Score (ASPECTS) is still uncertain. We hypothesized that vessel recanalization leads to an improvement in mortality and degree of disability by reducing brain oedema and malignant mass effect. In this multicentre observational study, patients with acute ischaemic stroke due to large vessel occlusion in the anterior circulation and an ASPECTS of ≤ 5 were analysed. Patients were assembled into two groups: successful vessel recanalization (thrombolysis in cerebral infarctions, TICI scale 2b/3) or persistent vessel occlusion (no endovascular procedure or TICI scale 0-2a). Observers were blinded to clinical data. Net water uptake within brain infarct, a quantitative biomarker based on CT densitometry, was used to quantify oedema in admission and follow-up CT and Δ-water uptake was calculated as difference between water uptake at both time points. Occurrence of malignant infarctions and secondary parenchymal haemorrhage was documented. Furthermore, modified Rankin scale score at 90 days was used for functional outcome. We included 117 patients admitted between March 2015 and August 2017 in three German stroke centres: 71 with persistent vessel occlusion and 46 with successful recanalization. The mean water uptake in the admission imaging was not different between both groups: 10.0% (±4.8) in patients with persistent vessel occlusion and 9.0% (±4.8) in patients with vessel recanalization (P = 0.4). After follow-up CT, the mean Δ-water uptake was 16.0% (±7.5) in patients with persistent vessel occlusion and 8.0% (±5.7) in patients with vessel recanalization (P < 0.001). Successful reperfusion was independently associated with a lowered Δ-water uptake of 8.0% (95% confidence interval, CI: -10.5 to -5.3%; P < 0.001) and lowered modifed Rankin scale score after 90 days of 1.5 (95% CI: -2.2 to -0.8; P < 0.001). The prevalence of malignant infarctions was 44.3% in patients with persistent vessel occlusion and 26.1% in patients with vessel recanalization. There was no significant difference for secondary haemorrhage in both groups (P = 0.7). In conclusion, successful recanalization in patients with low initial ASPECTS resulted in a significant reduction of oedema formation and was associated with a decreased prevalence of malignant infarctions and an improvement of clinical outcome.

Predictors of independent outcome of thrombectomy in stroke patients with large baseline infarcts in clinical practice: a multicenter analysis

Objective

To analyze outcome and its predictors after endovascular treatment (ET) in stroke patients suffering from large vessel occlusion with large pre-treatment infarct cores defined by an Alberta Stroke Program Early CT Score (ASPECTS) <6.

Methods

We analyzed data from an industry-independent, multicenter, prospective registry (German Stroke Registry – Endovascular Treatment) which enrolled consecutive patients treated by ET (June 2015–April 2018) with different devices. Multivariate logistic regression analyses identified predictors of independent outcome (IO) defined as a modified Rankin Scale (mRS) 0–2, and mortality at 90 days in patients with ASPECTS <6.

Results

Of 1700 patients included in the analysis, 152 (8.9%) had a baseline ASPECTS <6. Of these, 33 patients (21.6%) achieved IO, and 68 (44.7%) were dead at 90 days. A lower age, lower baseline National Institutes of Health Stroke Scale (NIHSS) score, and successful recanalization (defined as modified Thrombolysis in Cerebral Infarction Score, mTICI 2b/3) were predictors of IO. Successful recanalization had the strongest association with IO (OR 7.0, 95% CI 1.8 to 26.8). Pre-treatment parameters predicting IO were age <70 years (sensitivity 0.79, specificity 0.69) and NIHSS <12 (0.57 and 0.94). A higher age, a pre-stroke mRS score >1, and failed recanalization were predictors of death.

Conclusions

A substantial proportion of stroke patients with an ASPECTS <6 can achieve independence after thrombectomy, in particular, if they are younger, have only moderate baseline stroke symptoms, and no relevant pre-stroke disability. These results may encourage considering thrombectomy in low ASPECTS patients in clinical practice until randomized trials are available.

Multiphase MR Angiography Collateral Map: Functional Outcome after Acute Anterior Circulation Ischemic Stroke

Background Collateral circulation determines tissue fate and affects treatment result in acute ischemic stroke. A precise method for collateral estimation in an optimal imaging protocol is necessary to make an appropriate treatment decision for acute ischemic stroke. Purpose To verify the value of multiphase collateral imaging data sets (MR angiography collateral map) derived from dynamic contrast material-enhanced MR angiography for predicting functional outcomes after acute ischemic stroke. Materials and Methods This secondary analysis of an ongoing prospective observational study included data from participants with acute ischemic stroke due to occlusion or stenosis of the unilateral internal carotid artery and/or M1 segment of the middle cerebral artery who were evaluated within 8 hours of symptom onset. Data were obtained from March 2016 through August 2018. The collateral grading based on the MR angiography collateral map was estimated by using six-scale MR acute ischemic stroke collateral (MAC) scores. 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, collateral grade, mode of treatment, and early reperfusion were evaluated with multiple logistic regression analyses. Results One hundred fifty-four participants (mean age ± standard deviation, 69 years ± 13; 99 men) were evaluated. Younger age (odds ratio [OR], 0.45; 95% confidence interval [CI]: 0.29, 0.70; P < .001), lower baseline NIHSS score (OR, 0.85; 95% CI: 0.78, 0.94; P < .001), MAC score of 3 (OR, 27; 95% CI: 4.0, 179; P < .001), MAC score of 4 (OR, 17; 95% CI: 2.1, 134; P = .007), MAC score of 5 (OR, 27; 95% CI: 2.5, 306; P = .007), and successful early reperfusion (OR, 7.5; 95% CI: 2.6, 22; P < .001) were independently associated with favorable functional outcomes in multivariable analysis. There was a linear negative association between collateral perfusion grades and functional outcomes (P < .001). Conclusion An MR angiography collateral map was clinically reliable for collateral estimation in patients with acute ischemic stroke. This map provided patient-specific pacing information for ischemic progression. © RSNA, 2020.

Impact of endovascular recanalization on quantitative lesion water uptake in ischemic anterior circulation strokes

Studies evaluating the effect of reperfusion on ischemic edema in acute stroke described conflicting results. Net water uptake (NWU) per brain volume is a new quantitative imaging biomarker of space-occupying ischemic edema, which can be measured in computed tomography (CT). We sought to investigate the effects of vessel recanalization on the formation of ischemic brain edema using quantitative NWU. In this multicenter observational study, acute ischemic stroke patients with a large vessel occlusion (LVO) in the anterior circulation were consecutively screened. Patients with vessel recanalization (thrombolysis in cerebral infarction (TICI) 2 b or 3) versus persistent vessel occlusion (no thrombectomy, TICI 0-1) were compared. Lesion-NWU was quantified in multimodal admission CT and follow-up CT (FCT), and ΔNWU was calculated as difference. Of 194 included patients, 150 had successful endovascular recanalization and 44 persistent LVO. In FCT after treatment, the mean (standard deviation) ΔNWU was 15.8% (5.7) in patients with persistent LVO and 9.8% (5.8) with vessel recanalization (p < 0.001). In multivariate regression analysis, vessel recanalization was independently associated with a lowered ΔNWU by 6.3% compared to LVO (95% confidence interval: 3.7-9.0, p < 0.001). Successful vessel recanalization was associated with a significantly reduced formation of ischemic brain edema. Quantitative NWU may be used to compare the treatment effects in acute stroke.

Effect of workflow metrics on clinical outcomes of low diffusion-weighted imaging Alberta Stroke Program Early Computed Tomography Score (DWI-ASPECTS) patients subjected to mechanical thrombectomy

BACKGROUND

Although accumulating evidence has demonstrated the benefit of mechanical thrombectomy (MT) in patients with low Alberta Stroke Program Early Computed Tomography Score (ASPECTS), it is still unclear how workflow metrics impact the clinical outcomes of this subgroup of patients.

METHODS

Patients with acute stroke and diffusion-weighted imaging (DWI) ASPECTS ≤5 at baseline, who underwent MT within 6 hours of symptoms onset, were included from a prospectively maintained national multicentric registry between January 1, 2012 to August 31, 2017. The degree of disability was assessed by the modified Rankin Scale (mRS) at 90 days. The primary outcome was functional independence defined as mRS 0 to 2 at 90 days.

RESULTS

The study included 291 patients with baseline DWI-ASPECTS ≤5. Good outcome was achieved in 82 (28.2%) patients, and 104 (35.7%) patients died within 90 days. Successful reperfusion (modified Thrombolysis In Cerebral Infarction (mTICI) 2b-3) rate was 75.3%, and median onset to recanalization (OTR) time was 2 268min. Among time-related variables, OTR emerged as the strongest predictor of primary outcome (adjusted OR for every 60 min 0.59, 95% CI 0.44 to 0.77; p<0.001). mTICI 2c-3 independently predicted a good outcome (adjusted OR 1.91, 95% CI 1.004 to 3.6; p=0.049) along with age and baseline DWI-ASPECTS. Recanalization status failed to significantly impact outcome in the DWI-ASPECTS 0-3 subpopulation.

CONCLUSIONS

Near complete reperfusion (mTICI 2c-3) and OTR are the strongest modifiable outcome predictors in patients with DWI-ASPECTS ≤5 treated with MT.

Outcomes of Endovascular Thrombectomy vs Medical Management Alone in Patients With Large Ischemic Cores: A Secondary Analysis of the Optimizing Patient's Selection for Endovascular Treatment in Acute Ischemic Stroke (SELECT) Study

Importance

The efficacy and safety of endovascular thrombectomy (EVT) in patients with large ischemic cores remains unknown, to our knowledge.

Objective

To compare outcomes in patients with large ischemic cores treated with EVT and medical management vs medical management alone.

Design, Setting, and Participants

This prespecified analysis of the Optimizing Patient's Selection for Endovascular Treatment in Acute Ischemic Stroke (SELECT) trial, a prospective cohort study of imaging selection that was conducted in 9 US comprehensive stroke centers, enrolled patients between January 2016 and February 2018, and followed them up for 90 days. Patients with moderate to severe stroke and anterior circulation large-vessel occlusion presenting up to 24 hours from the time they were last known to be well were eligible for the cohort. Of these, patients with large ischemic cores on computed tomography (CT) (Alberta Stroke Program Early CT Score <6) or CT perfusion scanning (a volume with a relative cerebral blood flow <30% of ≥50 cm3) were included in analyses.

Exposures

Endovascular thrombectomy with medical management (MM) or MM only.

Main Outcomes and Measures

Functional outcomes at 90 days per modified Rankin scale; safety outcomes (mortality, symptomatic intracerebral hemorrhage, and neurological worsening).

Results

A total of 105 patients with large ischemic cores on either CT or CT perfusion images were included: 71 with Alberta Stroke Program Early CT Scores of 5 or less (EVT, 37; MM, 34), 74 with cores of 50 cm3 or greater on CT perfusion images (EVT, 39; MM, 35), and 40 who had large cores on both CT and CT perfusion images (EVT, 14; MM, 26). The median (interquartile range) age was 66 (60-75) years; 45 patients (43%) were female. Nineteen of 62 patients (31%) who were treated with EVT achieved functional independence (modified Rankin Scale scores, 0-2) vs 6 of 43 patients (14%) treated with MM only (odds ratio [OR], 3.27 [95% CI, 1.11-9.62]; P = .03). Also, EVT was associated with better functional outcomes (common OR, 2.12 [95% CI, 1.05-4.31]; P = .04), less infarct growth (44 vs 98 mL; P = .006), and smaller final infarct volume (97 vs 190 mL; P = .001) than MM. In the odds of functional independence, there was a 42% reduction per 10-cm3 increase in core volume (adjusted OR, 0.58 [95% CI, 0.39-0.87]; P = .007) and a 40% reduction per hour of treatment delay (adjusted OR, 0.60 [95% CI, 0.36-0.99]; P = .045). Of 10 patients who had EVT with core volumes greater than 100 cm3, none had a favorable outcome.

Conclusions and Relevance

Although the odds of good outcomes for patients with large cores who receive EVT markedly decline with increasing core size and time to treatment, these data suggest potential benefits. Randomized clinical trials are needed.

Mechanical Recanalization after Transfer from a Distant Primary Stroke Center: Effectiveness and Future Directions

INTRODUCTION

Little is known about the effectiveness of endovascular treatment (EVT) in patients with acute ischemic stroke (AIS) due to large vessel occlusion (LVO) admitted to a primary stroke center (PSC). The aim of this study was to assess EVT effectiveness after transfer from a PSC to a distant (156 km apart; 1.5 hour by car) comprehensive stroke center (CSC), and to discuss perspectives to improve access to EVT, if indicated.

PATIENTS AND METHOD

Analysis of the data collected in a 6-year prospective registry of patients admitted to a PSC for AIS due to LVO and selected for transfer to a distant CSC for EVT. The rate of transfer, futile transfer, EVT, reperfusion (thrombolysis in cerebral infarction score ≥2b-3), and relevant time measures were determined.

RESULTS

Among the 529 patients eligible, 278 (52.6%) were transferred and 153 received EVT (55% of transferred patients) followed by reperfusion in 115 (overall reperfusion rate: 21.7%). Median times (interquartile range) were: 90 minutes (76-110) for PSC-door-in to PSC-door-out, 88 minutes (65-104) for PSC-door-out to CSC-door-in, 262 minutes (239-316) for PSC-imaging to reperfusion, and 393 minutes (332-454) for symptom onset to reperfusion. At 3 months, rates of favorable outcome (modified Rankin Scale 0-2) were not significantly different between patients eligible for EVT (42.4%), transferred patients (49.1%) and patients who underwent EVT (34.1%).

DISCUSSION AND CONCLUSIONS

Our study suggests that transfer to a distant CSC is associated with reduced access to early EVT. These results argue in favor of on-site EVT at high volume PSCs that are distant from the CSC.

A New Era of Extended Time Window Acute Stroke Interventions Guided by Imaging

Ischemic stroke is one of the most debilitating and deadliest conditions worldwide. Intravenous t-PA is the current standard treatment within 4 hours after onset of symptoms. Recent randomized controlled trials have demonstrated the efficacy of neurointerventional intra-arterial treatment in acute ischemic stroke. About 20% of acute ischemic stroke are classified as wake-up strokes, which falls out of the conventional treatment time window. New evidence suggests that some patients with longer time from symptom onset (up to 24 hours) may benefit from thrombectomy, probably in part due to variations in collateral circulation among individual patients. Advanced imaging can play a crucial role in identifying patients who could benefit from endovascular intervention presenting within extended treatment time windows. In this article, we review the advanced imaging algorithm for ischemic stroke workup in the multiple studies published to date and summarize the results of the clinical trials for late ischemic stroke that can be clinically useful.

Dismantling the ability of CT and MRI to identify the target mismatch profile in patients with anterior circulation large vessel occlusion beyond six hours from symptom onset

PURPOSE

Patients with large vessel occlusion and target mismatch on imaging may be thrombectomy candidates in the extended time window. However, the ability of imaging modalities including non-contrast CT Alberta Stroke Program Early Computed Tomographic Scoring (CT ASPECTS), CT angiography collateral score (CTA-CS), diffusion-weighted MRI ASPECTS (DWI ASPECTS), DWI lesion volume, and DWI volume with clinical deficit (DWI + NIHSS), to identify mismatch is unknown.

METHODS

We defined target mismatch as core infarct (DWI volume) of < 70 mL, mismatch volume (tissue with TMax > 6 s) of ≥ 15 mL, and mismatch ratio of ≥ 1.8. Using experimental dismantling design, ability to identify this profile was determined for each imaging modality independently (phase 1) and then with knowledge from preceding modalities (phase 2). We used a generalized mixed model assuming binary distribution with PROC GLIMMIX/SAS for analysis.

RESULTS

We identified 32 patients with anterior circulation occlusions, presenting > 6 h from symptom onset, with National Institute of Health Stroke Scale of ≥ 6, who had CT and MR before thrombectomy. Sensitivities for identifying target mismatch increased modestly from 88% for NCCT to 91% with the addition of CTA-CS, and up to 100% for all MR-based modalities. Significant gains in specificity were observed from successive tests (29, 19, and 16% increase for DWI ASPECTS, DWI volume, and DWI + NIHSS, respectively).

CONCLUSIONS

The combination of NCCT ASPECTS and CTA-CS has high sensitivity for identifying the target mismatch in the extended time window. However, there are gains in specificity with MRI-based imaging, potentially identifying treatment candidates who may have been excluded based on CT imaging alone.

Leukoaraiosis Predicts Short-term Cognitive But not Motor Recovery in Ischemic Stroke Patients During Rehabilitation

BACKGROUND

Leukoaraiosis has been shown to impact functional outcomes after acute ischemic stroke. However, its association with domain specific recovery after ischemic stroke is uncertain. We sought to determine whether pre-existing leukoaraiosis is associated with short-term motor and cognitive recovery after stroke.

METHODS

We retrospectively studied ischemic stroke patients admitted to acute inpatient rehabilitation (AIR) between January 2013 and September 2015. Patient baseline characteristics, infarct volume, prestroke modified Rankin Scale, stroke cause, rehabilitation length of stay, and Functional Independence Measure (FIM) scores were recorded. Leukoaraiosis severity was graded on brain magnetic resonance imaging using the Fazekas scale. Multiple linear regression was used to determine factors independently associated with the total, cognitive, and motor FIM scores at AIR discharge, respectively.

RESULTS

Of 1600 ischemic stroke patients screened, 109 patients were included in the final analysis. After adjustment, the initial National Institute of Health Stroke Scale (β -0.541, confidence interval [CI] -0.993 to -0.888; P = 0.020) and pre-existing leukoaraiosis severity (β -1.448, CI -2.861 to -0.034; P = 0.045) independently predicted the total FIM score. Domain specific analysis showed that infarct volume (β -0.012, CI -0.019 to -0.005; P = 0.002) and leukoaraiosis severity (β -0.822, CI -1.223 to -0.410; P = 0.0001) independently predicted FIM cognitive scores at discharge from AIR. Leukoaraiosis did not predict FIM motor score (P = 0.17).

CONCLUSIONS

Leukoaraiosis severity is an independent predictor of total and cognitive, but not motor FIM scores after AIR for acute ischemic stroke. This highlights that leukoaraiosis affects poststroke recovery in a domain specific fashion, information that may aid counseling of patients and families as well as tailor rehabilitative efforts.

Acute ischemic stroke patients with diffusion-weighted imaging-Alberta Stroke Program Early Computed Tomography Score ≤ 5 can benefit from endovascular treatment: a single-center experience and literature review

PURPOSE

The recommendation strength of the guidelines for mechanical thrombectomy among patients with large pre-treatment core infarct is weak. We evaluated the safety and outcome of endovascular treatment for acute ischemic stroke with diffusion-weighted imaging-Alberta Stroke Program Early Computed Tomography Score (DWI-ASPECTS) ≤ 5.

METHODS

Data on acute ischemic stroke patients with DWI-ASPECTS ≤ 5 who underwent endovascular treatment within 6 h, or presented an arterial spin labeling-DWI (ASL-DWI) mismatch within 12 h, at our center were retrospectively collected. We report the clinical characteristics and outcome of every patient, and review the relevant literature.

RESULTS

Among the 19 patients who were enrolled, all experienced successful reperfusion, and 10 achieved a favorable outcome (modified Rankin scale (mRS) ≤ 2). Two patients presented with symptomatic intracranial hemorrhage (sICH); both of them had a poor outcome (mRS > 2).

CONCLUSION

Acute ischemic stroke patients with large DWI lesions caused by large vessel occlusion can achieve a favorable clinical outcome with endovascular treatment if recanalization is performed within 6 h, or after 6 h in case of an ASL-DWI mismatch.

Baseline Troponin T level in stroke and its association with stress cardiomyopathy

BACKGROUND

Differential diagnosis of elevated high sensitive Troponin T (hsTnT) in acute ischemic stroke includes myocardial infarction (MI) and neurogenic stunned myocardium (NSM). The aim of this study was to identify factors associated with baseline hsTnT levels and MI or NSM in acute ischemic stroke.

METHODS

We studied 204 consecutive patients of the prospective acquired Bern Stroke Database with acute ischemic stroke diagnosed by brain MR. All patient histories and cardiac examinations were reviewed retrospectively. Volumetry of lesions on diffusion and perfusion weighted brain imaging (circular singular value decomposition, Tmax >6sec) was performed. Voxel based analysis was performed to identify brain areas associated with hsTnT elevation. Linear regression analysis was used to identify predictors of baseline hsTnT levels and myocardial infarction.

RESULTS

Elevated hsTnT was observed in 58 of the 204 patients (28.4%). The mean age was 68.3 years in the normal hsTnT group and 69.7 years in the elevated hsTnT group. Creatinine (p<0.001, OR 6.735, 95% CI 58.734-107.423), baseline NIHSS score (p = 0.029, OR 2.207, 95% CI 0.675-12.096), ST segment depression (p = 0.025, OR 2.259, 95% CI 2.419-35.838), and negative T waves in baseline ECG (p = 0.002, OR 3.209, 95% CI 13.007-54.564) were associated with hsTnT elevation, while infarct location and size were not. Coronary angiography was performed in 30 of the 204 patients (14.7%) and myocardial infarction was diagnosed in 7 of them (23.3%). Predictive factors for myocardial infarction could not be identified.

CONCLUSION

Elevated baseline baseline hsTnT was associated with NIHSS, creatinine, ST segment depression and inverted T waves, but not with stroke location or size. None of the factors was helpful to differentiate MI and NSM. Therefore, ancillary investigations such as coronary angiography, cardiac MRI or both may be needed to solve the differential diagnosis.

Endovascular stroke treatment's impact on malignant type of edema (ESTIMATE)

BACKGROUND AND PURPOSE

In patients with acute ischemic stroke and large vessel occlusion, the prognosis has improved tremendously since the implementation of endovascular thrombectomy (EVT). The effect of EVT on the incidence of malignant middle cerebral artery infarctions (MMI) has not been studied before.

METHODS

ESTIMATE, a multicenter retrospective study, evaluates data of ischemic stroke patients with occlusion in the anterior circulation in the years of 2007-2015 comparing three treatment options (no therapy; IV-TPA; IV-TPA plus EVT or EVT only). Primary endpoint of the study was the incidence of MMI on follow-up imaging and mortality rates. Secondary endpoints were functional outcome, further clinical and imaging data. Logistic and Cox-regression models with a propensity score weighting approach were applied to evaluate differences between treatment groups.

RESULTS

In 2161 patients over 9 years, EVT reduced the MMI rates significantly: patients without acute stroke treatment had increased odds for MMI of 1.57 [95% confidence interval (CI) 1.49-1.65]. In contrast, after treatment with IV-TPA, only we observed an OR of 0.88 (95% CI 0.83-0.94, p < 0.001), and after EVT an OR of 0.80 (95% CI 0.76-0.85, p < 0.001). This was more pronounced in larger pretreatment infarctions (ASPECTS < 5, p < 0.01). IV-TPA also lowers the MMI rates but not to the same extent. EVT-treated patients had increased survival rates (p < 0.05) and the best functional outcome at discharge.

CONCLUSIONS

The findings of this study illustrate that occurrence of MMI and mortality rates was significantly reduced in patients treated with EVT.

Penumbral imaging and functional outcome in patients with anterior circulation ischaemic stroke treated with endovascular thrombectomy versus medical therapy: a meta-analysis of individual patient-level data

BACKGROUND

CT perfusion (CTP) and diffusion or perfusion MRI might assist patient selection for endovascular thrombectomy. We aimed to establish whether imaging assessments of irreversibly injured ischaemic core and potentially salvageable penumbra volumes were associated with functional outcome and whether they interacted with the treatment effect of endovascular thrombectomy on functional outcome.

METHODS

In this systematic review and meta-analysis, the HERMES collaboration pooled patient-level data from all randomised controlled trials that compared endovascular thrombectomy (predominantly using stent retrievers) with standard medical therapy in patients with anterior circulation ischaemic stroke, published in PubMed from Jan 1, 2010, to May 31, 2017. The primary endpoint was functional outcome, assessed by the modified Rankin Scale (mRS) at 90 days after stroke. Ischaemic core was estimated, before treatment with either endovascular thrombectomy or standard medical therapy, by CTP as relative cerebral blood flow less than 30% of normal brain blood flow or by MRI as an apparent diffusion coefficient less than 620 μm²/s. Critically hypoperfused tissue was estimated as the volume of tissue with a CTP time to maximum longer than 6 s. Mismatch volume (ie, the estimated penumbral volume) was calculated as critically hypoperfused tissue volume minus ischaemic core volume. The association of ischaemic core and penumbral volumes with 90-day mRS score was analysed with multivariable logistic regression (functional independence, defined as mRS score 0-2) and ordinal logistic regression (functional improvement by at least one mRS category) in all patients and in a subset of those with more than 50% endovascular reperfusion, adjusted for baseline prognostic variables. The meta-analysis was prospectively designed by the HERMES executive committee, but not registered.

FINDINGS

We identified seven studies with 1764 patients, all of which were included in the meta-analysis. CTP was available and assessable for 591 (34%) patients and diffusion MRI for 309 (18%) patients. Functional independence was worse in patients who had CTP versus those who had diffusion MRI, after adjustment for ischaemic core volume (odds ratio [OR] 0·47 [95% CI 0·30-0·72], p=0·0007), so the imaging modalities were not pooled. Increasing ischaemic core volume was associated with reduced likelihood of functional independence (CTP OR 0·77 [0·69-0·86] per 10 mL, p_interaction=0·29; diffusion MRI OR 0·87 [0·81-0·94] per 10 mL, p_interaction=0·94). Mismatch volume, examined only in the CTP group because of the small numbers of patients who had perfusion MRI, was not associated with either functional independence or functional improvement. In patients with CTP with more than 50% endovascular reperfusion (n=186), age, ischaemic core volume, and imaging-to-reperfusion time were independently associated with functional improvement. Risk of bias between studies was generally low.

INTERPRETATION

Estimated ischaemic core volume was independently associated with functional independence and functional improvement but did not modify the treatment benefit of endovascular thrombectomy over standard medical therapy for improved functional outcome. Combining ischaemic core volume with age and expected imaging-to-reperfusion time will improve assessment of prognosis and might inform endovascular thrombectomy treatment decisions.

FUNDING

Medtronic.

Patients With Ischemic Core ≥70 ml Within 6 h of Symptom Onset May Still Benefit From Endovascular Treatment

Background: Large core is associated with poor outcome in acute ischemic stroke (AIS) patients. It is unclear whether endovascular treatment (EVT) could bring benefits to patients with core volume ≥70 ml before treatment. We aimed to compare the impact of EVT with intravenous thrombolysis (IVT) on the outcome in patients with core volume ≥70 ml. Methods: We included consecutive anterior circulation AIS patients who underwent MR or CT perfusion within 6 h post stroke onset, which revealed a core ≥70 ml before reperfusion therapy. Good outcome was defined by modified Rankin Scale of 0 to 2 at 90-day. Reperfusion was defined as a reduction in hypoperfusion volume of ≥70% between baseline and 24 h. Results: One hundred four patients were included. Among them, 76 received IVT only, and 28 received EVT. After adjusting for age, NIHSS score, baseline core volume and onset to imaging time, patients in EVT group were more likely to achieve good outcome compared to IVT patients (OR, 3.875; 95% Cl 1.068-14.055, p = 0.039). More patients in EVT group achieved recanalization (84.0 vs. 58.5%, p = 0.027) and reperfusion (66.7 vs. 33.3%, p = 0.010) than in IVT group. Reperfusion also independently predicted good outcome (OR, 7.718; 95% Cl 1.713-34.772, p = 0.008). All patients with good outcome achieved recanalization at 24 h. Conclusions: Our data indicated that patients with core volume ≥70 ml might still benefit from EVT, which was related to its high reperfusion rate.

Association of anemia and hemoglobin decrease during acute stroke treatment with infarct growth and clinical outcome

Background and purpose

Anemia is associated with worse outcome in stroke, but the impact of anemia with intravenous thrombolysis or endovascular therapy has hardly been delineated. The aim of this study was to analyze the role of anemia on infarct evolution and outcome after acute stroke treatment.

Methods

1158 patients from Bern and 321 from Los Angeles were included. Baseline data and 3 months outcome assessed with the modified Rankin Scale were recorded prospectively. Baseline DWI lesion volumes were measured in 345 patients and both baseline and final infarct volumes in 180 patients using CT or MRI. Multivariable and linear regression analysis were used to determine predictors of outcome and infarct growth.

Results

712 patients underwent endovascular treatment and 446 intravenous thrombolysis. Lower hemoglobin at baseline, at 24h, and nadir until day 5 predicted poor outcome (OR 1.150–1.279) and higher mortality (OR 1.131–1.237) independently of treatment. Decrease of hemoglobin after hospital arrival, mainly induced by hemodilution, predicted poor outcome and had a linear association with final infarct volumes and the amount and velocity of infarct growth. Infarcts of patients with newly observed anemia were twice as large as infarcts with normal hemoglobin levels.

Conclusion

Anemia at hospital admission and any hemoglobin decrease during acute stroke treatment affect outcome negatively, probably by enlarging and accelerating infarct growth. Our results indicate that hemodilution has an adverse effect on penumbral evolution. Whether hemoglobin decrease in acute stroke could be avoided and whether this would improve outcome would need to be studied prospectively.