Perfusion CT in patients with acute ischemic stroke treated with intra-arterial thrombolysis: predictive value of infarct core size on clinical outcome

Thrombectomy with and without computed tomography perfusion imaging for large-vessel occlusion stroke in the extended time window: a meta-analysis of randomized clinical trials

Objective

In recent years, several studies have used computed tomography perfusion (CTP) to assess whether mechanical thrombectomy can be performed in patients with large-vessel occlusion (LVO) stroke in an extended time window. However, it has the disadvantage of being time-consuming and expensive. This study aimed to compare the impact of the CTP group with the non-CTP group [non-contrast CT (NCCT) ± CT angiography (CTA)] on the prognosis of this patient population.

Methods

A search of PubMed, EMBASE, and the Cochrane Library databases was conducted to collect randomized controlled trials (RCTs) comparing the two strategies. Outcome indicators and factors influencing prognosis were summarized by standardized mean differences, ratios, and relative risks with 95% confidence intervals using a random-effects model.

Results

A total of two RCTs were included in the combined analysis. There were no significant differences in the main outcome indicators (modified Rankin Scale score at 90 days, successful postoperative reperfusion rate) or the incidence of adverse events (90-day mortality and symptomatic intracranial hemorrhage) between the NCCT ± CTA and CTP groups. The time from the last puncture appeared to be significantly shorter in the NCCT ± CTA group than in the CTP group (SMD: -0.14; 95% CI: -0.24, -0.04). Among them, age (OR: 0.96; 95% CI: 0.94, 0.98), ASPECTS (OR: 1.18; 95% CI: 1.12, 1.24), NIHSS score (OR: 0.90; 95% CI: 0.89, 0.91), and diabetes (OR: 0.69; 95% CI: 0.54, 0.88) were associated with a 90-day independent functional outcome.

Conclusion

These findings suggest that the choice of NCCT ± CTA (without CTP) for the assessment of mechanical thrombectomy within 6-24 h after LVO in the anterior circulation is not significantly different from CTP; instead, the choice of NCCT ± CTA significantly reduces the time from onset to arterial puncture.

Comparison of two computed tomography perfusion post-processing software to assess infarct volume in patients with acute ischemic stroke

Objectives

We used two automated software commonly employed in clinical practice-Olea Sphere (Olea) and Shukun-PerfusionGo (PerfusionGo)-to compare the diagnostic utility and volumetric agreement of computed tomography perfusion (CTP)-predicted final infarct volume (FIV) with true FIV in patients with anterior-circulation acute ischemic stroke (AIS).

Methods

In all, 122 patients with anterior-circulation AIS who met the inclusion and exclusion criteria were retrospectively enrolled and divided into two groups: intervention group (n = 52) and conservative group (n = 70), according to recanalization of blood vessels and clinical outcome (NIHSS) after different treatments. Patients in both groups underwent one-stop 4D-CT angiography (CTA)/CTP, and the raw CTP data were processed on a workstation using Olea and PerfusionGo post-processing software, to calculate and obtain the ischemic core (IC) and hypoperfusion (IC plus penumbra) volumes, hypoperfusion in the conservative group and IC in the intervention group were used to define the predicted FIV. The ITK-SNAP software was used to manually outline and measure true FIV on the follow-up non-enhanced CT or MRI-DWI images. Intraclass correlation coefficients (ICC), Bland-Altman, and Kappa analysis were used to compare the differences in IC and penumbra volumes calculated by the Olea and PerfusionGo software to investigate the relationship between their predicted FIV and true FIV.

Results

The IC and penumbra difference between Olea and PerfusionGo within the same group (p < 0.001) was statistically significant. Olea obtained larger IC and smaller penumbra than PerfusionGo. Both software partially overestimated the infarct volume, but Olea significantly overestimated it by a larger percentage. ICC analysis showed that Olea performed better than PerfusionGo (intervention-Olea: ICC 0.633, 95%CI 0.439-0.771; intervention-PerfusionGo: ICC 0.526, 95%CI 0.299-0.696; conservative-Olea: ICC 0.623, 95%CI 0.457-0.747; conservative-PerfusionGo: ICC 0.507, 95%CI 0.312-0.662). Olea and PerfusionGo had the same capacity in accurately diagnosing and classifying patients with infarct volume <70 ml.

Conclusion

Both software had differences in the evaluation of the IC and penumbra. Olea's predicted FIV was more closely correlated with the true FIV than PerfusionGo's prediction. Accurate assessment of infarction on CTP post-processing software remains challenging. Our results may have important practice implications for the clinical use of perfusion post-processing software.

Pooled blood volume measured by final flat-panel detector computed tomography predicts outcome after endovascular thrombectomy for acute ischemic stroke

Background

Pooled blood volume (PBV), measured in real-time in the angiography room using an angiography system, correlates with cerebral blood volume (CBV). We examined the usefulness of PBV in endovascular thrombectomy (EVT) for acute ischemic stroke (AIS).

Methods

EVT for AIS in the anterior circulation (internal carotid artery (ICA) and middle cerebral artery (MCA)) was performed in 31 cases (13 males, 18 females, average age 75.7 years). PBV was acquired using a biplane flat-panel detector (FD) angiographic system. Then, we measured the average PBV value in the M1-6 regions similar to the Alberta Stroke Program Early CT score (ASPECTS) before and after EVT. We investigated factors associated with favorable outcome at 90 days after EVT.

Results

There were 13 patients (41.9%) in the good outcome group (mRS (modified Rankin Scale) ≦2) and 18 patients (58.1%) in the poor outcome group (mRS>2). In univariate analysis, NIHSS (National Institutes of Health Stroke Scale) (odds ratio [OR] 0.74, 95% CI 0.57-0.87, p < 0.0001) and post PBV value (odds ratio [OR] 1.13, 95% CI 1.03-1.29, p = 0.0086) were significantly associated with good outcome. The good outcome group had significantly higher post-thrombectomy PBV value (3.69 ± 0.32 ml/100 g versus 2.78 ± 0.93 ml/100 g, P = 0.002) compared to that of the poor outcome group. The relationship between pre-thrombectomy PBV value and outcome at 90 days was not significant.

Conclusions

Post-operative PBV value measured by FD-CT (computed tomography) correlated with 90-day outcome after EVT for AIS. FD-CT-PBV would be one of the good predictors of clinical outcome.

Reduction in Radiation Exposure of CT Perfusion by Optimized Imaging Timing Using Temporal Information of the Preceding CT Angiography of the Carotid Artery in the Stroke Protocol

(1) Background: CT perfusion (CTP) is a fast, robust and widely available but dose-exposing imaging technique for infarct core and penumbra detection. Carotid CT angiography (CTA) can precede CTP in the stroke protocol. Temporal information of the bolus tracking series of CTA could allow for better timing and a decreased number of scans in CTP, resulting in less radiation exposure, if the shortening of CTP does not alter the calculated infarct core and penumbra or the resulting perfusion maps, which are essential for further treatment decisions. (2) Methods: 66 consecutive patients with ischemic stroke proven by follow-up imaging or endovascular intervention were included in this retrospective study approved by the local ethics committee. In each case, six simulated, stepwise shortened CTP examinations were compared with the original data regarding the perfusion maps, infarct core, penumbra and endovascular treatment decision. (3) Results: In simulated CTPs with 26, 28 and 30 scans, the infarct core, penumbra and PRR values were equivalent, and the resulting clinical decision was identical to the original CTP. (4) Conclusions: The temporal information of the bolus tracking series of the carotid CTA can allow for better timing and a lower radiation exposure by eliminating unnecessary scans in CTP.

Differential Influence of the COVID-19 Pandemic on Mechanical Thrombectomy and Bridging Therapy for Acute Ischemic Stroke

Background

The coronavirus disease 2019 (COVID-19) pandemic is having a dramatic impact on acute stroke care. Its effects may accompany stroke care for a long time. We compared the treatment, short-term and long-term functional outcomes of patients with AIS from 2019 to 2020. Our objective was to evaluate the effect of COVID-19 epidemic on mechanical thrombectomy (MT) in patients in our hospital.

Methods

We collected information on subjects treated with MT in 2019–2020, including age, sex, time from the onset to arterial sheath insertion, time from the onset to recanalization, the rate of lung infection and hemorrhagic transformation, modified Rankin scale (mRS), NHISS, and ASPECTS.

Results

The number of patients with MT decreased significantly by 26.6% in 2020 (p = 0.025). The pretreatment ASPECTS score for 2020 was significantly higher than 2019 (p = 0.004). Besides, the patients were more likely to develop lung infection (65 vs. 54.1%, p = 0.042) and had a higher risk of hemorrhagic transformation (47.4% vs. 30.4%, p = 0.005) in 2019. The discharged mRS reflected the worse short-term functional prognosis of patients with MT in 2019 (66 vs. 44.9%, p = 0.046). In the subgroup analysis of bridging thrombolysis (BT), more patients with BT are expected to have a poor short-term functional prognosis in 2020, according to the discharged mRS (62.5 vs. 37.5%, p = 0.024). However, there was no difference in mRS at 180 days between the two groups (p = 0.094).

Conclusion

For patients with MT, both short- and long-term functional outcomes were not significantly affected due to the mild condition of patients admitted to hospital in 2020. For patients with BT, the COVID-19 pandemic has prolonged the green channel time of stroke, leading to a poor short-term functional prognosis of patients with stroke in the pandemic period. There was no difference in the effectiveness of direct MT and BT during the COVID-19 pandemic.

Whole blood viscosity is associated with baseline cerebral perfusion in acute ischemic stroke

Whole blood viscosity (WBV) is the intrinsic resistance to flow developed due to the frictional force between adjacent layers of flowing blood. Elevated WBV is an independent risk factor for stroke. Poor microcirculation due to elevated WBV can prevent adequate perfusion of the brain and might act as an important secondary factor for hypoperfusion in acute ischaemic stroke. In the present study, we examined the association of WBV with basal cerebral perfusion assessed by CT perfusion in acute ischaemic stroke. Confirmed acute ischemic stroke patients (n = 82) presenting in hours were recruited from the single centre. Patients underwent baseline multimodal CT (non-contrast CT, CT angiography and CT perfusion). Where clinically warranted, patients also underwent follow-up DWI. WBV was measured in duplicate within 2 h after sampling from 5-mL EDTA blood sample. WBV was significantly correlated with CT perfusion parameters such as perfusion lesion volume, ischemic core volume and mismatch ratio; DWI volume and baseline NIHSS. In a multivariate linear regression model, WBV significantly predicted acute perfusion lesion volume, core volume and mismatch ratio after adjusting for the effect of occlusion site and collateral status. Association of WBV with hypoperfusion (increased perfusion lesion volume, ischaemic core volume and mismatch ratio) suggest the role of erythrocyte rheology in cerebral haemodynamic of acute ischemic stroke. The present findings open new possibilities for therapeutic strategies targeting erythrocyte rheology to improve cerebral microcirculation in stroke.

Assessment of computed tomography perfusion software in predicting spatial location and volume of infarct in acute ischemic stroke patients: a comparison of Sphere, Vitrea, and RAPID

BACKGROUND

CT perfusion (CTP) infarct and penumbra estimations determine the eligibility of patients with acute ischemic stroke (AIS) for endovascular intervention. This study aimed to determine volumetric and spatial agreement of predicted RAPID, Vitrea, and Sphere CTP infarct with follow-up fluid attenuation inversion recovery (FLAIR) MRI infarct.

METHODS

108 consecutive patients with AIS and large vessel occlusion were included in the study between April 2019 and January 2020 . Patients were divided into two groups: endovascular intervention (n=58) and conservative treatment (n=50). Intervention patients were treated with mechanical thrombectomy and achieved successful reperfusion (Thrombolysis in Cerebral Infarction 2b/2 c/3) while patients in the conservative treatment group did not receive mechanical thrombectomy or intravenous thrombolysis. Intervention and conservative treatment patients were included to assess infarct and penumbra estimations, respectively. It was assumed that in all patients treated conservatively, penumbra converted to infarct. CTP infarct and penumbra volumes were segmented from RAPID, Vitrea, and Sphere to assess volumetric and spatial agreement with follow-up FLAIR MRI.

RESULTS

Mean infarct differences (95% CIs) between each CTP software and FLAIR MRI for each cohort were: intervention cohort: RAPID=9.0±7.7 mL, Sphere=-0.2±8.7 mL, Vitrea=-7.9±8.9 mL; conservative treatment cohort: RAPID=-31.9±21.6 mL, Sphere=-26.8±17.4 mL, Vitrea=-15.3±13.7 mL. Overlap and Dice coefficients for predicted infarct were (overlap, Dice): intervention cohort: RAPID=(0.57, 0.44), Sphere=(0.68, 0.60), Vitrea=(0.70, 0.60); conservative treatment cohort: RAPID=(0.71, 0.56), Sphere=(0.73, 0.60), Vitrea=(0.72, 0.64).

CONCLUSIONS

Sphere proved the most accurate in patients who had intervention infarct assessment as Vitrea and RAPID overestimated and underestimated infarct, respectively. Vitrea proved the most accurate in penumbra assessment for patients treated conservatively although all software overestimated penumbra.

Enhancing performance of a computed tomography perfusion software for improved prediction of final infarct volume in acute ischemic stroke patients

Computed tomography perfusion (CTP) is crucial for acute ischemic stroke (AIS) patient diagnosis. To improve infarct prediction, enhanced image processing and automated parameter selection have been implemented in Vital Images' new CTP+ software. We compared CTP+ with its previous version, commercially available software (RAPID and Sphere), and follow-up diffusion-weighted imaging (DWI). Data from 191 AIS patients between March 2019 and January 2020 was retrospectively collected and allocated into endovascular intervention (n = 81) and conservative treatment (n = 110) cohorts. Intervention patients were treated for large vessel occlusion, underwent mechanical thrombectomy, and achieved successful reperfusion of thrombolysis in cerebral infarction 2b/2c/3. Conservative treatment patients suffered large or small vessel occlusion and did not receive intravenous thrombolysis or mechanical thrombectomy. Infarct and penumbra were assessed using intervention and conservative treatment patients, respectively. Infarct and penumbra volumes were segmented from CTP+ and compared with 24-h DWI along with RAPID, Sphere, and Vitrea. Mean infarct differences (95% confidence intervals) and Spearman correlation coefficients (SCCs) between DWI and each CTP software product for intervention patients are: CTP+  = (5.8 ± 5.9 ml, 0.62), RAPID = (10.0  ± 5.2 ml, 0.73), Sphere = (3.0 ± 6.0 ml, 0.56), Vitrea = (7.2 ± 4.9 ml, 0.66). For conservative treatment patients, mean infarct differences and SCCs are: CTP+ = (-8.0 ± 5.4 ml, 0.64), RAPID = (-25.6 ± 11.5 ml, 0.60), Sphere = (-25.6 ± 8.0 ml, 0.66), Vitrea = (1.3 ± 4.0 ml, 0.72). CTP+ performed similarly to RAPID and Sphere in addition to its semi-automated predecessor, Vitrea, when assessing intervention patient infarct volumes. For conservative treatment patients, CTP+ outperformed RAPID and Sphere in assessing penumbra. Semi-automated Vitrea remains the most accurate in assessing penumbra, but CTP+ provides an improved workflow from its predecessor.

Imaging Ischemic and Hemorrhagic Disease of the Brain in Dogs

Strokes, both ischemic and hemorrhagic, are the most common underlying cause of acute, non-progressive encephalopathy in dogs. In effect, substantial information detailing the underlying causes and predisposing factors, affected vessels, imaging features, and outcomes based on location and extent of injury is available. The features of canine strokes on both computed tomography (CT) and magnetic resonance imaging (MRI) have been described in numerous studies. This summary article serves as a compilation of these various descriptions. Drawing from the established and emerging stroke evaluation sequences used in the investigation of strokes in humans, this summary describes all theoretically available sequences. Particular detail is given to logistics of image acquisition, description of imaging findings, and each sequence's advantages and disadvantages. As the imaging features of both forms of strokes are highly representative of the underlying pathophysiologic stages in the hours to months following stroke onset, the descriptions of strokes at various stages are also discussed. It is unlikely that canine strokes can be diagnosed within the same rapid time frame as human strokes, and therefore the opportunity for thrombolytic intervention in ischemic strokes is unattainable. However, a thorough understanding of the appearance of strokes at various stages can aid the clinician when presented with a patient that has developed a stroke in the days or weeks prior to evaluation. Additionally, investigation into new imaging techniques may increase the sensitivity and specificity of stroke diagnosis, as well as provide new ways to monitor strokes over time.

Assessment of a Bayesian Vitrea CT Perfusion Analysis to Predict Final Infarct and Penumbra Volumes in Patients with Acute Ischemic Stroke: A Comparison with RAPID

BACKGROUND AND PURPOSE

Brain CTP is used to estimate infarct and penumbra volumes to determine endovascular treatment eligibility for patients with acute ischemic stroke. We aimed to assess the accuracy of a Bayesian CTP algorithm in determining penumbra and final infarct volumes.

MATERIALS AND METHODS

Data were retrospectively collected for 105 patients with acute ischemic stroke (55 patients with successful recanalization [TICI 2b/2c/3] and large-vessel occlusions and 50 patients without interventions). Final infarct volumes were calculated using DWI and FLAIR 24 hours following CTP imaging. RAPID and the Vitrea Bayesian CTP algorithm (with 3 different settings) predicted infarct and penumbra volumes for comparison with final infarct volumes to assess software performance. Vitrea settings used different combinations of perfusion maps (MTT, TTP, CBV, CBF, delay time) for infarct and penumbra quantification. Patients with and without interventions were included for assessment of predicted infarct and penumbra volumes, respectively.

RESULTS

RAPID and Vitrea default setting had the most accurate final infarct volume prediction in patients with interventions ([Spearman correlation coefficient, mean infarct difference] default versus FLAIR: [0.77, 4.1 mL], default versus DWI: [0.72, 4.7 mL], RAPID versus FLAIR: [0.75, 7.5 mL], RAPID versus DWI: [0.75, 6.9 mL]). Default Vitrea and RAPID were the most and least accurate in determining final infarct volume for patients without an intervention, respectively (default versus FLAIR: [0.76, -0.4 mL], default versus DWI: [0.71, -2.6 mL], RAPID versus FLAIR: [0.68, -49.3 mL], RAPID versus DWI: [0.65, -51.5 mL]).

CONCLUSIONS

Compared with RAPID, the Vitrea default setting was noninferior for patients with interventions and superior in penumbra estimation for patients without interventions as indicated by mean infarct differences and correlations with final infarct volumes.

Performance of angiographic parametric imaging in locating infarct core in large vessel occlusion acute ischemic stroke patients

Purpose: Biomarkers related to hemodynamics can be quantified using angiographic parametric imaging (API), which is a quantitative imaging method that uses digital subtraction angiography (DSA). We aimed to assess the accuracy of API in locating infarct core within large vessel occlusion (LVO) acute ischemic stroke (AIS) patients. Approach: Data were retrospectively collected for 25 LVO AIS patients who achieved successful recanalization. DSA data from lateral and anteroposterior (AP) views were loaded into API software to generate hemodynamic parameter maps. Relative differences in hemispherical regions for each API parameter were calculated. Ground truth infarct core locations were obtained using 24-h follow-up fluid-attenuation inversion recovery (FLAIR) MRI imaging. FLAIR MRI infarct locations were registered with DSA images to determine infarct regions in API parameter maps. Relative differences across hemispheres for each API parameter were plotted against each other. A support vector machine was used to determine the optimal hyperplane for classifying regions as infarct or healthy tissue. Results: For the lateral and AP views, respectively, the most accurate classification of infarct regions came from plotting mean transit time (MTT) versus peak height (PH) [ accuracy = 0.8125 ± 0.0012 (95%)], the area under the receiver operator characteristic curve ( AUROC ) = 0.8946 ± 0.0000 (95%), and plotting MTT versus the area under the curve (AUC) [ accuracy = 0.7957 ± 0.0011 (95%), AUROC = 0.8759 ± 0.0000 (95%)]. Conclusions: API provides accurate assessment of locating ischemic core in AIS LVO patients and has the potential for clinical benefit by determining infarct core location and growth in real time for intraoperative decision making.

Time-dependent infarct volume affects the benefit of recanalization

Objectives

The benefit threshold of infarct volume from recanalization remains unclear. We assumed that the threshold decreased over time, and then investigated the benefit curve of infarct volume during different time periods.

Methods

We reviewed prospectively collected clinical and imaging data from acute ischemic stroke patients with internal carotid artery and M1 occlusion who underwent angiography before and 24 h after reperfusion therapy. Ordinal analyses of modified Rankin Scale scores were performed and curves were fitted.

Results

Of the included 445 patients, the median age was 71 years and 157 (35.3%) were women. The mean time from onset to treatment (OTT) was 248 ± 142 min. The median baseline infarct core volume was 49 (IQR 22–85) ml. Follow-up angiography revealed recanalization in 265 (59.6%) patients. The fitting curves showed that patients with an OTT ≤3 h would benefit from recanalization no matter how large the infarct volume was, whereas patients with an OTT between 3 and 4.5 h and with an infarct volume ≥ 125 ml, and those with an OTT ≥ 4.5 h and with an infarct volume ≥ 80 ml did not benefit from recanalization.

Conclusions

We established a time-dependent benefit threshold of infarct volume from recanalization, and thus suggested to estimate infarct core volume to select patients for reperfusion therapy in those with an OTT beyond 3 h.

•

The benefit of recanalization within 3 h is independent of infarct volume.

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The benefit threshold of infarct volume decreases over time if beyond 3 h.

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Infarct volume is recommended to aid in patient selection for reperfusion therapy.

Dose reduction in perfusion CT in stroke patients by lowering scan frequency does not affect automatically calculated infarct core volumes

BACKGROUND AND PURPOSE

CT Perfusion technique (CTP) is a quantitative, easily performed, accepted and reliable method for detection of ischemic brain changes. Based on calculated parameters, the size of ischemic penumbra and irreversibly damaged infarct core can be determined which helps guide treatment decisions. However, due to the dynamic nature of the CTP study, it is dose intensive. This study determines the consequences of retrospectively reducing the number of scans in the dynamic acquisition by half on the volume of the automatically calculated infarct core (non-viable tissue) and penumbra (tissue at risk) volumes. Our hypothesis was that equivalent volumetric information could be obtained at a substantial dose savings.

MATERIALS AND METHODS

Fifty one consecutive patients with occlusion of M1 and/or M2 segment of the middle cerebral artery and ischemic stroke proven by follow-up MRI were included. CTP scans were first analyzed in a standard fashion and automatically generated volumes measured in milliliters were recorded in a database. A second analysis was conducted after removing every second data acquisition from the sequential CTP scans. Automatic volume measurements were repeated, recorded and compared to the initial values obtained using the full dataset.

RESULTS

The two CTP protocols were statistically equivalent pertaining to automatic infarct core volume calculation but a case-by-case analysis revealed substantial overestimation in some cases.

CONCLUSION

Reduction of radiation exposure in CTP without objective loss of accuracy of automatically calculated infarct core volume is feasible but might lead to clinically relevant infarct core overestimation in individual cases.

The POST trial: initial post-market experience of the Penumbra system: revascularization of large vessel occlusion in acute ischemic stroke in the United States and Europe

Background and purpose

The purpose of this study was to assess the initial post-market experience of the device and how it is compared with the Penumbra Pivotal trial used to support the 510k application.

Methods

A retrospective case review of 157 consecutive patients treated with the Penumbra system at seven international centers was performed. Primary endpoints were revascularization of the target vessel (TIMI score of 2 or 3), good functional outcome as defined by a modified Rankin scale (mRS) score of ≤2 and incidence of procedural serious adverse events. Results were compared with those of the Penumbra pivotal trial.

Results

A total of 157 vessels were treated. Mean baseline values at enrollment were: age 65 years, NIHSS score 16. After use of the Penumbra system, 87% of the treated vessels were revascularized to TIMI 2 (54%) or 3 (33%) as compared with 82% reported in the Pivotal trial. Nine procedural serious adverse events were reported in 157 patients (5.7%). All-cause mortality was 20% (32/157), and 41% had a mRS of ≤2 at 90-day follow-up as compared with only 25% in the Pivotal trial. Patients who were successfully revascularized by the Penumbra system had significantly better outcomes than those who were not.

Conclusion

Initial post-market experience of the Penumbra system revealed that the revascularization rate and safety profile of the device are comparable to those reported in the Pivotal trial. However, the proportion of patients who had good functional outcome was higher than expected.

Leukoaraiosis as an outcome predictor in the acute and subacute phases of stroke

INTRODUCTION

Leukoaraiosis (LA) is one of the neuroimaging features of cerebral small vessel disease and is associated with poor long-term prognosis. Areas covered: This narrative review focuses on the predictive role of LA on the evolution of the ischemic brain damage and on the clinical outcome in the subacute phase of stroke and in the short-term period afterwards. Expert commentary: LA predicts poorer tissue outcome and clinical prognosis also in acute and subacute stroke. In acute stroke, LA is associated with a less favorable fate of brain infarct and is a marker of increased risk of thrombolysis-related hemorrhagic transformation. The impaired cerebral microcirculation in LA patients may sustain the progression of ischemic lesion and enhance the bleeding risk. The short-term worse clinical outcome in ischemic stroke and intracranial hemorrhage patients with LA might be attributable to a state of altered brain connectivity. Endothelial failure, reduced micro-vessels density, and deficient collateral flow together with reduced functional reserve are some of the involved mechanisms. Future studies should aim at bridging the gap between the knowledge about LA pathophysiology and the therapeutic improvement of brain tissue perfusion and at producing data on early rehabilitation of stroke patients with LA at high disability risk.

Precision Stroke Animal Models: the Permanent MCAO Model Should Be the Primary Model, Not Transient MCAO

An argument for preclinical stroke research to make more use of the permanent middle cerebral artery occlusion (MCAO) model, rather than transient MCAO, is presented. Despite STAIR recommending permanent MCAO as the primary model, preclinical stroke research has not been listened. In 2012, Hossmann reported that 64% of the treatment studies for MCAO used prompt transient MCAO models and only 36% of the studies used permanent MCAO or gradual transient MCAO (i.e., embolic stroke model). Then, in 2014 and 2015, 88% of published basic science studies on large vessel occlusion used the transient MCAO model. However, this model only represents 2.5-11.3% of large vessel stroke patients. Therefore, the transient MCAO model, which mimics stroke with reperfusion, does not accurately reflect the majority of clinical stroke cases. Thus, once again, the argument for studying permanent MCAO as a primary model is made and supported.

Identification of imaging selection patterns in acute ischemic stroke patients and the influence on treatment and clinical trial enrollment decision making

BACKGROUND AND PURPOSE

For the STroke Imaging Research (STIR) and VISTA-Imaging Investigators The purpose of this study was to collect precise information on the typical imaging decisions given specific clinical acute stroke scenarios. Stroke centers worldwide were surveyed regarding typical imaging used to work up representative acute stroke patients, make treatment decisions, and willingness to enroll in clinical trials.

METHODS

STroke Imaging Research and Virtual International Stroke Trials Archive-Imaging circulated an online survey of clinical case vignettes through its website, the websites of national professional societies from multiple countries as well as through email distribution lists from STroke Imaging Research and participating societies. Survey responders were asked to select the typical imaging work-up for each clinical vignette presented. Actual images were not presented to the survey responders. Instead, the survey then displayed several types of imaging findings offered by the imaging strategy, and the responders selected the appropriate therapy and whether to enroll into a clinical trial considering time from onset, clinical presentation, and imaging findings. A follow-up survey focusing on 6 h from onset was conducted after the release of the positive endovascular trials.

RESULTS

We received 548 responses from 35 countries including 282 individual centers; 78% of the centers originating from Australia, Brazil, France, Germany, Spain, United Kingdom, and United States. The specific onset windows presented influenced the type of imaging work-up selected more than the clinical scenario. Magnetic Resonance Imaging usage (27-28%) was substantial, in particular for wake-up stroke. Following the release of the positive trials, selection of perfusion imaging significantly increased for imaging strategy.

CONCLUSIONS

Usage of vascular or perfusion imaging by Computed Tomography or Magnetic Resonance Imaging beyond just parenchymal imaging was the primary work-up (62-87%) across all clinical vignettes and time windows. Perfusion imaging with Computed Tomography or Magnetic Resonance Imaging was associated with increased probability of enrollment into clinical trials for 0-3 h. Following the release of the positive endovascular trials, selection of endovascular only treatment for 6 h increased across all clinical vignettes.

Predictive Value of RAPID Assessed Perfusion Thresholds on Final Infarct Volume in SWIFT PRIME (Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment)

BACKGROUND AND PURPOSE

Computed tomography perfusion imaging can estimate the size of the ischemic core, which can be used for the selection of patients for endovascular therapy. The relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) thresholds chosen to identify ischemic core influence the accuracy of prediction. We aimed to analyze the accuracy of various rCBV and rCBF thresholds for predicting the 27-hour infarct volume using RAPID automated analysis software from the SWIFT PRIME trial (Solitaire With the Intention for Thrombectomy as Primary Endovascular Treatment) data.

METHODS

Patients from the SWIFT PRIME study who achieved complete reperfusion based on time until the residue function reached its peak >6 s perfusion maps obtained at 27 hours were included. Patients from both the intravenous tissue-type plasminogen activator only and endovascular groups were included in analysis. Final infarct volume was determined on magnetic resonance imaging (fluid-attenuated inversion recovery images) or computed tomography scans obtained 27 hours after symptom onset. The predicted ischemic core volumes on rCBV and rCBF maps using thresholds ranging between 0.2 and 0.8 were compared with the actual infarct volume to determine the most accurate thresholds.

RESULTS

Among the 47 subjects, the following baseline computed tomography perfusion thresholds most accurately predicted the actual 27-hour infarct volume: rCBV=0.32, median absolute error (MAE)=9 mL; rCBV=0.34, MAE=9 mL; rCBF=0.30, MAE=8.8 mL; rCBF=0.32, MAE=7 mL; and rCBF=0.34, MAE=7.3.

CONCLUSIONS

Brain regions with rCBF 0.30 to 0.34 or rCBV 0.32 to 0.34 thresholds provided the most accurate prediction of infarct volume in patients who achieved complete reperfusion with MAEs of ≤9 mL.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01657461.

Intravenous Thrombolysis for Acute Ischemic Stroke due to Cervical Internal Carotid Artery Occlusion

BACKGROUND

Internal carotid artery (ICA) occlusions are poorly responsive to intravenous thrombolysis with tissue plasminogen activator (IV-tPA) in acute ischemic stroke (AIS). Most study populations have combined intracranial and extracranial ICA occlusions for analysis; few have studied purely cervical ICA occlusions. We evaluated AIS patients with acute cervical ICA occlusion treated with IV-tPA to identify predictors of outcomes.

METHODS

We studied 550 consecutive patients with AIS who received IV-tPA and identified 100 with pure acute cervical ICA occlusion. We evaluated the associations of vascular risk factors, National Institutes of Health Stroke Scale (NIHSS) score, and leptomeningeal collateral vessel status via 3 different grading systems, with functional recovery at 90 days, mortality, recanalization of the primary occlusion, and symptomatic intracranial hemorrhage (SICH). Modified Rankin Scale score 0-1 was defined as an excellent outcome.

RESULTS

The 100 patients had mean age of 67.8 (range 32-96) and median NIHSS score of 19 (range 4-33). Excellent outcomes were observed in 27% of the patients, SICH in 8%, and mortality in 21%. Up to 54% of the patients achieved recanalization at 24 hours. On ordinal regression, good collaterals showed a significant shift in favorable outcomes by Maas, Tan, or ASPECTS collateral grading systems. On multivariate analysis, good collaterals also showed reduced mortality (OR .721, 95% CI .588-.888, P = .002) and a trend to less SICH (OR .81, 95% CI .65-1.007, P = .058). Interestingly, faster treatment was also associated with favorable functional recovery (OR 1.028 per minute, 95% CI 1.010-1.047, P = .001).

CONCLUSIONS

Improved outcomes are seen in patients with early acute cervical ICA occlusion and better collateral circulation. This could be a valuable biomarker for decision making.

Interaction of Recanalization, Intracerebral Hemorrhage, and Cerebral Edema After Intravenous Thrombolysis

BACKGROUND AND PURPOSE

Both intracerebral hemorrhage (ICH) and brain edema have been attributed to reperfusion after intravenous thrombolysis. We explored the interaction of recanalization and core size for imaging outcomes (ICH and vasogenic brain edema).

METHODS

In patients with anterior circulation occlusion given intravenous thrombolysis <4.5 hours and imaged with computed tomographic (CT) perfusion and CT angiography, we defined volumes of core (relative delay time >2 s and relative cerebral blood flow <40%) and penumbra (relative delay time >2 s). CT and CT angiography at 24 hours were reviewed for ICH (European Cooperative Acute Stroke Study [ECASS]-2 definition), early vasogenic edema (third International Stroke Trial [IST-3] criteria), and recanalization (thrombolysis in myocardial infarction 2-3). Independent effects of recanalization, core volume and potential interactions on edema, ICH and day 90 outcomes were estimated by logistic regression.

RESULTS

In 123 patients, there was a trend for recanalization to be associated with H1/2 ICH (odds ratio [OR], 2.3 [0.97-5.5]; P=0.06) but not with PH1/2 ICH (OR, 1.7 [0.33-8.8]; P=0.5), any edema, or significant brain edema (OR, 1.45 [0.4-4.9]; P=0.55). Ischemic core (>50 mL) was associated with any ICH (OR, 4.0 [1.6-9.5]; P=0.003), edema (OR, 5.4 [2-14]; P<0.01), and significant brain edema (OR, 17.4 [5.3-57]; P<0.01) but not with PH1/2 ICH (OR, 1.2 [0.23-6.5]; P=0.8), after controlling for recanalization. There was no significant interaction of recanalization and large core for any adverse outcomes.

CONCLUSIONS

Large ischemic core was associated with poorer outcomes and both early vasogenic brain edema and ICH, but recanalization on 24-hour CT angiography was associated with clinically favorable outcome. There was no significant interaction of recanalization and large core volume for any outcomes. The association of hemorrhage or brain edema with post-thrombolysis reperfusion is unclear.

Effect of Collaterals on Clinical Presentation, Baseline Imaging, Complications, and Outcome in Acute Stroke

BACKGROUND AND PURPOSE

Good CTA collaterals independently predict good outcome in acute ischemic stroke. Our aim was to evaluate the role of collateral circulation and its added benefit over CTP-derived total ischemic volume as a predictor of baseline NIHSS score, total ischemic volume, hemorrhagic transformation, final infarct size, and a modified Rankin Scale score >2.

MATERIALS AND METHODS

This was a retrospective study of 395 patients with stroke dichotomized by recanalization (recanalization positive/recanalization negative) and collateral status. Clot burden score was quantified on baseline CTA. Total ischemic volumes were derived from thresholded CTP maps. Final infarct size was assessed on follow-up CT/MRI. We performed uni-/multivariate analyses for each outcome, adjusting for rtPA status, using general linear (continuous variables) and logistic (binary variables) regression. Model comparison with collateral score and total ischemic volume was performed using the F or likelihood ratio test.

RESULTS

Collateral presence independently and inversely predicted all outcomes except hemorrhagic transformation in patients who were recanalization negative and mRS >2 in patients who were recanalization positive. The greatest collateral benefit occurred in patients who were recanalization negative, contributing 16.5% and 19.2% of the variability for final infarct size and mRS >2. The collateral score model is superior to the total ischemic volume for mRS >2 prediction, but a combination of total ischemic volume and collateral score is superior for mRS >2 and final infarct prediction (24% and 28% variability, respectively). In patients who were recanalization positive, a model including collateral score and total ischemic volume was superior to that of total ischemic volume for hemorrhagic transformation and final infarct prediction but was muted compared with patients who were recanalization negative (11.3% and 16.9% variability).

CONCLUSIONS

Collateral circulation is an independent predictor of all outcomes, but the magnitude of significance varies, greater in patients who were recanalization negative versus recanalization positive. Total ischemic volume assessment is complementary to collateral score in many cases.

Noninvasive Qureshi Grading Scheme Predicts 90-Day mRS in Patients with Acute Ischemic Stroke

BACKGROUND

The Qureshi grading scheme is an effective classification system for evaluating the severity of acute arterial occlusion. However, this scheme is of limited utility because it is based on invasive angiography. In this study, we assessed whether a relationship between a noninvasive Qureshi score, based on magnetic resonance angiography (MRA) or computed tomography angiography (CTA), and 90-day functional outcome could be observed in patients with acute ischemic stroke.

METHODS

A stroke neurologist evaluated all patients with acute ischemic stroke who presented to the emergency room within 12 hour of symptom onset. Two neurologists independently assessed the noninvasive Qureshi score from initial MRA or CTA. We assessed the relationship between the noninvasive Qureshi grading scheme and clinical outcome on day 90.

RESULTS

Of a total 125 patients, 75 underwent MRA and 50 underwent CTA. Interobserver reliability showed good agreement (κ = .62). The noninvasive Qureshi score for MRA or CTA and that for CTA alone were directly associated with a good 90-day functional outcome (odds ratio, .672; P = .016 and odds ratio, .511; P = .042).

CONCLUSIONS

The noninvasive Qureshi scheme using MRA or CTA provides meaningful information about long-term functional outcomes in patients with acute ischemic stroke.

Acute Stroke Imaging Part II: The Ischemic Penumbra

In acute ischemic stroke, the volume of threatened but potentially salvageable tissue, i.e. the ischemic penumbra, is critical to the success of all acute therapeutic interventions, most notably thrombolysis. Despite the availability of both CT and MRI based techniques to detect and assess the penumbra, advanced imaging of this type remains under-utilized. Although the optimal selection criteria are still being refined and technical improvements are ongoing, rapid imaging of the penumbra appears to be the most promising approach to expanding the acute thrombolysis population, as well as tailoring treatment based on specific pathophysiological findings. This second article in a two-part series reviews current evidence for penumbral-based treatment selection and discusses the barriers to implementation of these advanced imaging techniques in acute stroke management protocols.

Novel Approaches in Evaluating and Predicting the Potential Benefit of Middle Cerebral Artery Angioplasty & Stenting

OBJECTIVE

Our aim was to investigate a novel approach to perform preoperative evaluation patients who underwent middle cerebral artery (MCA) percutaneous transluminal angioplasty and stenting (PTAS).

METHOD

Sixty-five patients with symptomatic MCA stenosis of at least >70% who underwent MCA PTAS were enrolled. The multimodal stroke assessment using CT (MOSAIC) score was used to evaluate the preoperative condition. The Alberta Stroke Program Early Computed Tomography Scoring (ASPECTS) was used to assess the time-to-peak (TTP) parameter of Computer tomography perfusion (CTP). The factors potentially improving TTP following stenting were investigated. The prognostic value of the MOSAIC scores to predict TTP improvement was analyzed and compared.

RESULTS

The MOSAIC score was a reliable prognostic tool for the degree of improvement of TTP (odds ratio 1.89 [1.08-2.07], P < .01) in patients with PTAS. The MOSAIC score had a higher prognostic accuracy than the degree of CBF deficit, the degree of stenosis, and the amount of tissue infarction. During 1-year follow-up, the stroke and death rate of was 8.1%, the in-stent restenosis rate was 6.5%, and good final outcome (modified Rankin Scale ≤ 2) was observed in 76.9%.

CONCLUSIONS

The MOSAIC score can be reliably used in selecting patients with MCA stenosis for PTAS.

Low dose CT perfusion in acute ischemic stroke

INTRODUCTION

The purpose of this investigation is to determine if CT perfusion (CTP) measurements at low doses (LD = 20 or 50 mAs) are similar to those obtained at regular doses (RD = 100 mAs), with and without the addition of adaptive statistical iterative reconstruction (ASIR).

METHODS

A single-center, prospective study was performed in patients with acute ischemic stroke (n = 37; 54% male; age = 74 ± 15 years). Two CTP scans were performed on each subject: one at 100 mAs (RD) and one at either 50 or 20 mAs (LD). CTP parameters were compared between the RD and LD scans in regions of ischemia, infarction, and normal tissue. Differences were determined using a within-subjects ANOVA (p < 0.05) followed by a paired t test post hoc analysis (p < 0.01).

RESULTS

At 50 mAs, there was no significant difference between cerebral blood flow (CBF), cerebral blood volume (CBV), or time to maximum enhancement (Tmax) values for the RD and LD scans in the ischemic, infarcted, or normal contralateral regions (p < 0.05). At 20 mAs, there were significant differences between the RD and LD scans for all parameters in the ischemic and normal tissue regions (p > 0.05).

CONCLUSION

CTP-derived CBF and CBV are not different at 50 mAs compared to 100 mAs, even without the addition of ASIR. Current CTP protocols can be modified to reduce the effective dose by 50 % without altering CTP measurements.

Reperfusion therapies for acute ischemic stroke: an update

Acute ischemic stroke is a major cause of morbidity and mortality in developed countries. Intravenous thrombolysis with tissue plasminogen activator (tPA) within 4.5 hours of symptoms onset significantly improves clinical outcomes in patients with acute ischemic stroke. This narrow window for treatment leads to a small proportion of eligible patients to be treated. Intravenous or intra-arterial trials, combined intravenous/intra-arterial trials, and newer devices to mechanically remove the clot from intracranial arteries have been investigated or are currently being explored to increase patient eligibility and to improve arterial recanalization and clinical outcome. New retrievable stent-based devices offer higher revascularization rates with shorter time to recanalization and are now generally preferred to first generation thrombectomy devices such as Merci Retriever or Penumbra System. These devices have been shown to be effective for opening up occluded vessels in the brain but its efficacy for improving outcomes in patients with acute stroke has not yet been demonstrated in a randomized clinical trial. We summarize the results of the major systemic thrombolytic trials and the latest trials employing different endovascular approaches to ischemic stroke.

Future directions for intra-arterial therapy for acute ischaemic stroke: is there life after three negative randomized controlled studies?

Background: The three randomised controlled trials, Interventional Management of Stroke III (IMS3), Mechanical Retrieval and Revascularization of Stroke Clots Using Embolectomy (MR RESCUE) and Synthesis Expanasion: A Randomized Controlled Trial on Intra-Arterial Versus Intravenous Thrombolysis in Acute Ischaemic Stroke (SYNTHESIS EXP) showed no significant difference in clinical outcomes comparing intra-arterial (IA) therapy with intravenous thrombolysis. This article will explore the reasons for failure to show superiority of IA therapy. Summary: There are many reasons for the disappointing results of the three randomised controlled trials. Opposing views on IA therapy exist. Critics argue that only a small percentage of patients will be eligible for IA therapy and that it will never be cost-effective. Additionally, current trials have failed to address superior recanalization rates of new generation devices and lack of patient selection by advanced imaging. Time-to-treatment is longer in these randomised controlled trials and stroke outcomes were worse than anticipated. The current randomised controlled trials also took long periods to complete. There is emerging evidence that general anesthetic negatively influences outcome. Next generation trials will attempt to address these issues. Key Messages: There are disparate explanations for the disappointing results from the three IA therapy randomized controlled studies. Poor recanalisation rates with first generation endovascular devices, lack of advanced neuroimaging to aid in patient selection, lack of data surrounding the use of general anaesthesia, and prolonged time-to-treatment are potential contributors to negative results. The new generation of trials has the potential of addressing these pressing issues.

Computed tomographic angiography and cerebral blood volume can predict final infarct volume and outcome after recanalization

BACKGROUND AND PURPOSE

Recanalization rates are higher in acute anterior stroke treated with stent-retrievers when compared with older techniques. However, some still have sizeable infarcts and poor outcome. This may be related to underestimation of core infarct on nonenhanced computed tomography (NECT). CT angiography (CTA) source images (CTASI) and CT perfusion may be more informative. We hypothesize that core infarct estimation with NECT, CTA, and CT perfusion predicts infarct at 24 hours and outcome after fast recanalization.

METHODS

Consecutive good recanalization patients with proximal anterior circulation stroke were evaluated. We assessed Alberta Stroke Program Early CT Score (ASPECTs) on NECT for subtle early infarct, hypodensity, loss of gray-white (CTASI), and low cerebral blood volume (CBV; CT perfusion). Sensitivity and specificity for predicting infarct by region were calculated.

RESULTS

Of 46 patients, 36 (78%) had successful thrombectomy. Median ASPECTS was 10 for NECT early infarct and frank hypodensity; for CBV, CTASI-ASPECTS was 8. CTASI had the highest sensitivity of 71% and specificity of 82% for 24 hours NECT infarct. There was moderate correlation and concordance between CBV/24-hour NECT (Rp=0.51; Rc=0.50) and CTASI/24-hour NECT (Rp=0.54 and Rc=0.53). Thirty-four patients (74%) had good outcomes. Median ASPECTS was higher on CTASI (8 versus 5; P=0.04) and CBV (9 versus 5; P=0.03) for patients with good versus bad outcome. There were better outcomes with increasing CTASI-ASPECTS (P=0.004) and CBV-ASPECTS (P=0.02).

CONCLUSIONS

CTASI and CBV were better at predicting 24-hour infarct and outcome than NECT. Appropriate advanced imaged guided selection may improve outcomes in large-vessel stroke treated with the newest techniques.

Diagnostic and Prognostic Impact of pc-ASPECTS Applied to Perfusion CT in the Basilar Artery International Cooperation Study

BACKGROUND AND PURPOSE

The posterior circulation Acute Stroke Prognosis Early CT Score (pc-APECTS) applied to CT angiography source images (CTA-SI) predicts the functional outcome of patients in the Basilar Artery International Cooperation Study (BASICS). We assessed the diagnostic and prognostic impact of pc-ASPECTS applied to perfusion CT (CTP) in the BASICS registry population.

METHODS

We applied pc-ASPECTS to CTA-SI and cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) parameter maps of BASICS patients with CTA and CTP studies performed. Hypoattenuation on CTA-SI, relative reduction in CBV or CBF, or relative increase in MTT were rated as abnormal.

RESULTS

CTA and CTP were available in 27/592 BASICS patients (4.6%). The proportion of patients with any perfusion abnormality was highest for MTT (93%; 95% confidence interval [CI], 76%-99%), compared with 78% (58%-91%) for CTA-SI and CBF, and 46% (27%-67%) for CBV (P < .001). All 3 patients with a CBV pc-ASPECTS < 8 compared to 6/23 patients with a CBV pc-ASPECTS ≥ 8 had died at 1 month (RR 3.8; 95% CI, 1.9-7.6).

CONCLUSION

CTP was performed in a minority of the BASICS registry population. Perfusion disturbances in the posterior circulation were most pronounced on MTT parameter maps. CBV pc-ASPECTS < 8 may indicate patients with high case fatality.

Relative Cerebral Blood Volume as a Marker of Durable Tissue-at-Risk Viability in Hyperacute Ischemic Stroke

Background and Purpose—

Selection of best responders to reperfusion therapies could be aided by predicting the duration of tissue-at-risk viability, which may be dependant on collateral circulation status. We aimed to identify the best predictor of good collateral circulation among perfusion computed tomography (PCT) parameters in middle cerebral artery (MCA) ischemic stroke and to analyze how early MCA response to intravenous thrombolysis and PCT-derived markers of good collaterals interact to determine stroke outcome.

Methods—

We prospectively studied patients with acute MCA ischemic stroke treated with intravenous thrombolysis who underwent PCT before treatment showing a target mismatch profile. Collateral status was assessed using a PCT source image–based score. PCT maps were quantitatively analyzed. Cerebral blood volume (CBV), cerebral blood flow, and Tmax were calculated within the hypoperfused volume and in the equivalent region of unaffected hemisphere. Occluded MCAs were monitored by transcranial Duplex to assess early recanalization. Main outcome variables were brain hypodensity volume and modified Rankin scale score at day 90.

Results—

One hundred patients with MCA ischemic stroke imaged by PCT received intravenous thrombolysis, and 68 met all inclusion criteria. A relative CBV (rCBV) >0.93 emerged as the only predictor of good collaterals (odds ratio, 12.6; 95% confidence interval, 2.9–55.9; P =0.001). Early MCA recanalization was associated with better long-term outcome and lower infarct volume in patients with rCBV<0.93, but not in patients with high rCBV. None of the patients with rCBV<0.93 achieved good outcome in absence of early recanalization.

Conclusions—

High rCBV was the strongest marker of good collaterals and may characterize durable tissue-at-risk viability in hyperacute MCA ischemic stroke.

[Multimodal imaging protocols and their predictive role in acute stroke functional outcome]

Brain imaging plays a central role in the assessment of patients with acute ischemic stroke. Within a few minutes, modern multimodal imaging protocols can provide one with comprehensive information about prognosis, management, and outcome of the disease, and may detect changes in the intracranial structures reflecting severity of the ischemic injury depicted by four Ps: parenchyma (of the brain), pipes (i.e., the cerebral blood vessels), penumbra, and permeability (of the blood brain barrier). In this article, we have reviewed neuroradiological predictors of stroke functional outcome in the light of the aforementioned four Ps.

Endovascular treatment of acute carotid occlusion

OBJECTIVES

Acute cervical carotid occlusion is one of the most challenging scenarios encountered in endovascular stroke treatment.

PATIENTS AND METHODS

A retrospective analysis of 11 consecutive non-dissection stroke patients with concomitant cervical carotid and intracranial occlusion treated with intraarterial (IA) mechanical thrombectomy and/or pharmacologic thrombolysis over five years at two academic hospitals was performed. Data was analyzed using Fisher's exact test.

RESULTS

Patients included 3 females and 8 males. Average age was 64.7 years (range 30-94 years). All patients had both cervical carotid and intracranial occlusions. Intracranial occlusion involved the internal carotid artery in 7 patients and the middle cerebral artery in 4 patients. All of the patients received intracranial IA Tissue Plasminogen Activator (tPA). Six patients received carotid stents for cervical occlusion as part of their treatment. Five patients received only IA tPA via collateral circulation. Of the patients receiving stents, 5 of 6 (83.3%) had successful recanalization (Thrombolysis in Cerebral Ischemia 2b or 3 flow). Only 1 of 5 (20%) patients who did not receive stents prior to intracranial treatment had successful recanalization. The difference in recanalization rates approached statistical significance (p=.08). There were 4 total in-hospital mortalities: 2 in the group that received stents prior to thrombolysis and 2 in the non-stent group. There were 2 clinically significant hemorrhages in the study, both in the stent group.

CONCLUSIONS

Revascularization of the cervical carotid occlusion prior to treatment of the intracranial occlusion led to increased rates of recanalization in patients with tandem extracranial and intracranial occlusions. Whether a clinical benefit can be consistently derived likely relies on other factors, including the evaluation of cerebral perfusion.

Prediction of Recanalization Trumps Prediction of Tissue Fate

Background and Purpose—

To determine whether infarct core or penumbra is the more significant predictor of outcome in acute ischemic stroke, and whether the results are affected by the statistical method used.

Methods—

Clinical and imaging data were collected in 165 patients with acute ischemic stroke. We reviewed the noncontrast head computed tomography (CT) to determine the Alberta Score Program Early CT score and assess for hyperdense middle cerebral artery. We reviewed CT-angiogram for site of occlusion and collateral flow score. From perfusion-CT, we calculated the volumes of infarct core and ischemic penumbra. Recanalization status was assessed on early follow-up imaging. Clinical data included age, several time points, National Institutes of Health Stroke Scale at admission, treatment type, and modified Rankin score at 90 days. Two multivariate regression analyses were conducted to determine which variables predicted outcome best. In the first analysis, we did not include recanalization status among the potential predicting variables. In the second, we included recanalization status and its interaction between perfusion-CT variables.

Results—

Among the 165 study patients, 76 had a good outcome (modified Rankin score ≤2) and 89 had a poor outcome (modified Rankin score >2). In our first analysis, the most important predictors were age ( P <0.001) and National Institutes of Health Stroke Scale at admission ( P =0.001). The imaging variables were not important predictors of outcome ( P >0.05). In the second analysis, when the recanalization status and its interaction with perfusion-CT variables were included, recanalization status and perfusion-CT penumbra volume became the significant predictors ( P <0.001).

Conclusions—

Imaging prediction of tissue fate, more specifically imaging of the ischemic penumbra, matters only if recanalization can also be predicted.

Location of the clot and outcome of perfusion defects in acute anterior circulation stroke treated with intravenous thrombolysis

BACKGROUND AND PURPOSE

The location of the clot is a major determinant of ischemic stroke outcome. We studied the impact of the location (ICA, proximal M1 segment of the MCA, distal M1 segment, and M2 segment and more distally) of the clot on the CT perfusion parametric maps, the mismatch ratio, the amount of salvaged brain tissue, and the imaging and clinical outcomes in a retrospective acute (<3 hours) stroke cohort treated with intravenous thrombolysis.

MATERIALS AND METHODS

We reviewed 105 patients who underwent admission multimodal CT that revealed an occluded vessel on CTA. CT perfusion was successfully performed in 58 patients (55%). Differences among the parameters in different vessel positions were studied with the ANCOVA by using onset-to-imaging time as a covariate followed by pair-wise testing.

RESULTS

There were no significant differences in potential confounding variables among the groups. A clot proximal to the M2 segment produced a significantly larger defect on the MTT map. A clot in the ICA resulted in a significantly larger CBV lesion compared with the distal M1 segment, the M2 segment, and the M3 segment. In general, a more proximal thrombus created a larger CBV defect. The fraction of penumbra that was salvaged at 24 hours was higher in the more distal vessel positions.

CONCLUSIONS

Admission CBV defects are larger in proximal vessel occlusions. More of the penumbra can be salvaged if the occlusion is located distally. This effect seems to reach a plateau in the distal M1 segment of the MCA.

Intracerebral hemorrhage secondary to intravenous and endovascular intraarterial revascularization therapies in acute ischemic stroke: an update on risk factors, predictors, and management

Intracerebral hemorrhage (ICH) secondary to intravenous and intraarterial revascularization strategies for emergent treatment of acute ischemic stroke is associated with high mortality. ICH from systemic thrombolysis typically occurs within the first 24-36 hours of treatment initiation and is characterized by rapid hematoma development and growth. Pathophysiological mechanisms of revascularization therapy-induced ICH are complex and involve a combination of several distinct processes, including the direct effect of thrombolytic agents, disruption of the blood-brain barrier secondary to ischemia, and direct vessel damage from wire and microcatheter manipulations during endovascular procedures. Several definitions of ICH secondary to thrombolysis currently exist, depending on clinical or radiological characteristics used. Multiple studies have investigated clinical and laboratory risk factors associated with higher rates of ICH in this setting. Early ischemic changes seen on noncontrast CT scanning are strongly associated with higher rates of hemorrhage. Modern imaging techniques, particularly CT perfusion, provide rapid assessment of hemodynamic parameters of the brain. Specific patterns of CT perfusion maps can help identify patients who are likely to benefit from revascularization or to develop hemorrhagic complications. There are no established guidelines that describe management of revascularization therapy-induced ICH, and great variability in treatment protocols currently exist. General principles that apply to the management of spontaneous ICH might not be as effective for revascularization therapy-induced ICH. In this article, the authors review current knowledge of risk factors and radiological predictors of ICH secondary to stroke revascularization techniques and analyze medical and surgical management strategies for ICH in this setting.

Leukoaraiosis and sex predict the hyperacute ischemic core volume

BACKGROUND AND PURPOSE

Leukoaraiosis (LA) and male sex have been associated with decreased cerebrovascular reactivity, which potentially adversely affects tissue viability in acute stroke. Therefore, we aimed to elucidate the contribution of LA-severity and sex to the extent of the hyperacute ischemic core volume after intracranial large artery occlusion.

METHODS

We analyzed data from 87 patients with acute intracranial large artery occlusion who had acute multimodal computed tomography-imaging. LA-severity was assessed using the van Swieten scale on noncontrast computed tomography. Computed tomography perfusion data were analyzed using automatic calculation of the mean transit time and hyperacute cerebral blood volume defects. Multivariate linear and logistic regression analyses were used to identify independent predictors of the hyperacute infarct-volume.

RESULTS

Severe LA (van Swieten Scale, 3-4; odds ratio, 43.22; 95% CI, 6.26-298.42; P<0.001) and male sex (odds ratio, 7.52; 95% CI, 1.38-40.86; P=0.020) were independently associated with a hyperacute cerebral blood volume-lesion >25 mL on multivariate logistic regression analysis. Multivariate linear regression analysis confirmed the association between severe LA (P<0.001) and male sex (P=0.01) with larger cerebral blood volume-lesions. There was no significant difference in the absolute or relative mean transit time-lesion volumes when stratified by LA-severity or sex. Women had significantly smaller cerebral blood volume-lesion volumes compared with men (P=0.036).

CONCLUSIONS

Severe LA and male sex are associated with larger infarct cores, which adds to the notion that sex and LA alter the brain's intrinsic susceptibility to acute cerebral ischemia. Future, larger studies are needed to confirm our observation that women have smaller core volumes and its significance.

Multiparametric MRI and CT models of infarct core and favorable penumbral imaging patterns in acute ischemic stroke

BACKGROUND AND PURPOSE

Objective imaging methods to identify optimal candidates for late recanalization therapies are needed. The study goals were (1) to develop magnetic resonance imaging (MRI) and computed tomography (CT) multiparametric, voxel-based predictive models of infarct core and penumbra in acute ischemic stroke patients, and (2) to develop patient-level imaging criteria for favorable penumbral pattern based on good clinical outcome in response to successful recanalization.

METHODS

An analysis of imaging and clinical data was performed on 2 cohorts of patients (one screened with CT, the other with MRI) who underwent successful treatment for large vessel, anterior circulation stroke. Subjects were divided 2:1 into derivation and validation cohorts. Pretreatment imaging parameters independently predicting final tissue infarct and final clinical outcome were identified.

RESULTS

The MRI and CT models were developed and validated from 34 and 32 patients, using 943 320 and 1 236 917 voxels, respectively. The derivation MRI and 2-branch CT models had an overall accuracy of 74% and 80%, respectively, and were independently validated with an accuracy of 71% and 79%, respectively. The imaging criteria of (1) predicted infarct core ≤90 mL and (2) ratio of predicted infarct tissue within the at-risk region ≤70% identified patients as having a favorable penumbral pattern with 78% to 100% accuracy.

CONCLUSIONS

Multiparametric voxel-based MRI and CT models were developed to predict the extent of infarct core and overall penumbral pattern status in patients with acute ischemic stroke who may be candidates for late recanalization therapies. These models provide an alternative approach to mismatch in predicting ultimate tissue fate.

Factors affecting pre- and post-stenting computed tomography perfusion in patients with middle cerebral artery stenosis

The aim of this study was to investigate the factors affecting pre- and post-stenting head computed tomography perfusion (CTP) in patients with middle cerebral artery stenosis. A total of 25 patients with severe middle cerebral artery stenosis were enrolled. CTP was performed prior to and following stenting. Scores were allocated to the time-to-peak (TTP) parameter of CTP using the Alberta stroke program early computed tomography scoring (ASPECTS) scale. The factors possibly affecting pre- and post-stenting CTP were analyzed. All the patients exhibited markedly prolonged TTP on the affected side prior to stenting, compared with the healthy side. Following surgery, the TTP was improved in all patients. The preoperative ASPECTS score was negatively correlated with the degree of middle cerebral artery stenosis with a correlation coefficient of −5.78. The preoperative vascular stenosis rate was positively correlated with the improvement degree of the ASPECTS score with a correlation coefficient of 1.137 (P=0.001). TTP is a sensitive parameter for evaluating the effect of stenting on middle cerebral artery stenosis. TTP prior to and following stenting may be quantitatively assessed using the ASPECTS scale. Patients with serious stenosis and/or good collateral circulation are able to benefit more from stenting.

Endovascular treatment of acute ischemic stroke: current indications

Endovascular stroke therapy is an effective means of achieving reperfusion in stroke patients with proximal cerebral artery occlusions. However, current guideline recommendations express uncertainty regarding the clinical efficacy of catheter-based treatments, given the lack of supportive trial data. A critical problem is that it remains unclear which patients will benefit from endovascular therapy. As such, patient selection is likely highly variable in clinical practice. This article will review the existing data to discuss the clinical and imaging factors that are relevant to patient outcomes, and which may be used to guide endovascular treatment decisions. Anterior circulation strokes represent the primary focus of this review.

Implementation of a patient selection protocol for intra-arterial therapy increases treatment rates in patients with acute ischemic stroke

BACKGROUND

Strategies for patient selection for intra-arterial therapy (IAT) in acute ischemic stroke (AIS) are highly variable. The degree of protocol adoption and treatment rates associated with implementation of a service-wide patient selection IAT protocol were assessed.

METHODS

All patients with AIS prospectively recorded in our stroke database from January 2007 to June 2009 were reviewed. The IAT patient selection protocol was implemented in March 2008. Patients were defined as likely to benefit (LTB) from IAT if they had brain imaging completed within 6 h from last known well time, NIH Stroke Scale score ≥ 8, infarct volume ≤ 100 ml and evidence of proximal artery occlusion.

RESULTS

Of 1348 subjects identified, 118 (8.7%) met the criteria for LTB and 62 (52%) underwent IAT. There was a significant increase in rates of IAT among LTB patients after protocol implementation (61% vs 40%, p<0.02). In LTB patients, factors associated with IAT were stroke duration (OR 0.78, 95% CI 0.6 to 0.9 per hour), arrival within later calendar months during study period (OR 1.1, 95% CI 1.02 to 1.2 per month), intravenous tissue plasminogen activator (OR 0.6, 95% CI 0.4 to 0.9) and age (OR 0.98, 95% CI 0.95 to 1.02 per year). After multivariable adjustment, only stroke duration (OR 0.65, 95% CI 0.5 to 0.8 per hour) remained an independent predictor of IAT.

CONCLUSIONS

Most patients with AIS did not meet our criteria for LTB and only 52% of those defined as LTB received IAT. Protocol adoption increased the use of IAT over time; however, further exploration of factors associated with the reasons for non-treatment and the impact of IAT on outcomes is necessary.