A trial of imaging selection and endovascular treatment for ischemic stroke

Collaterals: an important determinant of prolonged ischemic penumbra versus rapid cerebral infarction?

Intravenous tissue plasminogen activator is the mainstay for the treatment of acute ischemic stroke in patients presenting within 4.5 h of symptom onset. Studies have demonstrated that treating patients early leads to improved long-term outcomes. MR imaging currently allows quantification of the ischemic penumbra in order to better identify individuals most likely to benefit from intervention, irrespective of “time last seen normal.” Its increasing use in clinical practice has demonstrated individual differences in rate of infarction. One explanation for this variability is a difference in collateral blood flow. We report two cases that highlight the individual variability of infarction rate, and discuss potential underlying mechanisms that may influence treatment decisions and outcomes.

Republished: Society for Neuroscience in Anesthesiology and Critical Care expert consensus statement: Anesthetic management of endovascular treatment for acute ischemic stroke

Literature on the anesthetic management of endovascular treatment of acute ischemic stroke (AIS) is limited. Anesthetic management during these procedures is still mostly dependent on individual or institutional preferences. Thus, the Society of Neuroscience in Anesthesiology and Critical Care (SNACC) created a task force to provide expert consensus recommendations on anesthetic management of endovascular treatment of AIS. The task force conducted a systematic literature review (up to August 2012). Because of the limited number of research articles relating to this subject, the task force solicited opinions from experts in this area. The task force created a draft consensus statement based on the available data. Classes of recommendations and levels of evidence were assigned to articles specifically addressing anesthetic management during endovascular treatment of stroke using the standard American Heart Association evidence rating scheme. The draft consensus statement was reviewed by the Task Force, SNACC Executive Committee and representatives of Society of NeuroInterventional Surgery (SNIS) and Neurocritical Care Society (NCS) reaching consensus on the final document. For this consensus statement the anesthetic management of endovascular treatment of AIS was subdivided into 12 topics. Each topic includes a summary of available data followed by recommendations. This consensus statement is intended for use by individuals involved in the care of patients with acute ischemic stroke, such as anesthesiologists, interventional neuroradiologists, neurologists, neurointensivists and neurosurgeons.

Clinical trials in acute ischemic stroke

Acute ischemic stroke (AIS) is a major cause of mortality and disability and remains a serious and significant global health problem. The development of neurovascular protectants to treat AIS successfully has been beset by disappointments and setbacks. Many promising candidates have lacked significant pleiotropic protective activity for brain tissue and cerebral blood vessels in clinical trials, while those with protective activity have had poor bioavailability or high toxicity. Moreover, the majority of agents did not confer significant neurovascular protection or clinical efficacy, as measured by standard behavioral endpoints in clinical trials of heterogeneous populations of patients with AIS. The recombinant tissue plasminogen activator alteplase is approved in many countries for the treatment of AIS in the first 3 h after symptom onset. Many drug candidates have been subject to clinical trials, including those with anti-excitotoxic, anti-inflammatory, antioxidant, antiapoptotic/regenerative, calcium/adrenergic-modulating/antihypertensive, thrombolytic, nootropic/stimulant, fluid regulatory, or oxygen-delivering mechanisms of action. Some agents, such as tenecteplase, edaravone and minocycline, may be approved for global use in the future. This review evaluates almost all neurovascular protectants subject to clinical trial evaluation for the treatment of AIS, and includes 241 studies conducted between 1978 and 2014. The development of agents that reduce brain injury after AIS will require new and different approaches based on a deeper understanding of the pathophysiology of AIS. Moreover, the future treatment for AIS is likely to lie in combination therapy rather than monotherapy. Additional approaches to the testing and use of neurovascular protectants should be considered.

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.

To Tube or Not to Tube? The Role of Intubation during Stroke Thrombectomy

In the 10 years since the FDA first cleared the use of endovascular devices for the treatment of acute stroke, definitive evidence that such therapy improves outcomes remains lacking. The decision to intubate patients undergoing stroke thrombectomy impacts multiple variables that may influence outcomes after stroke. Three main areas where intubation may deleteriously affect acute stroke management include the introduction of delays in revascularization, fluctuations in peri-procedural blood pressure, and hypocapnia, resulting in cerebral vasoconstriction. In this mini-review, we discuss the evidence supporting these limitations of intubation during stroke thrombectomy and encourage neurohospitalists, neurocritical care specialists, and neurointerventionalists to carefully consider the decision to intubate during thrombectomy and provide strategies to avoid potential complications associated with its use in acute stroke.

Carotid Elongation Does Not Affect Angiographic Results of Mechanical Thrombectomy in Acute Stroke

BACKGROUND AND PURPOSE

New techniques have substantially raised recanalization rates of mechanical thrombectomy in acute ischemic stroke in the last few years with initial prospective trials reporting good neurological outcome in up to 58 % of the cases. However some recent reports questioning the benefit of endovascular therapy have initiated a discussion about the importance of patient-selection. The purpose of this study was to investigate whether an elongation of the carotid artery affects the angiographic outcome of the recanalization procedure in middle cerebral artery (MCA)-occlusions.

MATERIALS AND METHODS

The data of 54 patients with occlusions of the M1-segment who underwent mechanical thrombectomy were included. The lengths of the carotid arteries were measured using preinterventional computed tomography (CT)-angiograms. To take individual patient's height into account these lengths were divided by the length of the spine from the tip of the dens to the bottom of the th3 vertebral body (referred to as carotid-to-spine (CS)-Ratio). Angiographic results were scored according to the modified thrombolysis in cerebral infarction (mTICI)-score.

RESULTS

Recanalization with mTICI ≥ 2b was achieved in 83.3 %. The mean CS-Ratio was 1.32 ± 0.13. There was a significant correlation between the CS-Ratio and the age of the patients. There were no significant differences in the CS-Ratios of occlusions that were successfully recanalized and those that were not. Neither were there significant correlations of the CS-Ratio and the length of procedure or the number of deployments of the stentretrievers.

CONCLUSION

In this retrospective analysis we report that carotid elongation does not affect angiographic results of mechanical thrombectomy in acute stroke.

Etiology and treatment of arterial ischemic stroke in children and young adults

OPINION STATEMENT

Stroke is the second leading cause of death worldwide (Go et al. Circulation 129:e28-292, 2014) and is a major cause of morbidity and mortality. Compared with older adults, arterial ischemic stroke (AIS) is relatively uncommon in children and young adults, comprising 5-10 % of all stroke (Biller Nat Rev Cardiol 6:395-97, 2009), but is associated with significant cost. In contrast to the declining overall incidence of stroke, some early studies suggest that the rate of stroke hospitalizations in children and young adults is rising (George et al. Ann Neurol 70:713-21, 2011; Kissela et al. Stroke 41:e224, 2010; Nguyen-Huynh et al. Stroke 43, 2012), emphasizing the importance of understanding the similarities and differences in etiology and treatment of AIS across the age spectrum. Among the most common causes of AIS in children are cardioembolism (often related to congenital heart disease), cervicocephalic arterial dissections, focal arteriopathy of childhood and several genetic and metabolic disorders, such as sickle cell disease (SCD). AIS in young adults is less well understood, but likely overlaps in etiology with both children and older adults. Young adults with AIS often have classic atherosclerotic risk factors similar to older adults, but are also more likely to have thrombophilias, cervicocephalic arterial dissections and cardioembolism, similar to children with AIS. Since little evidence exists regarding both acute treatment and secondary prevention after AIS in children and young adults, standard treatment practices are mainly extrapolated from research done in older adults. In most cases we recommend treating young adults per the guidelines published by the American Heart Association for adults with stroke (Jauch et al. Stroke 44:870-947, 2013; Kernan et al. Stroke 45:2160-2236, 2014) and children per the equivalent guidelines regarding pediatric stroke (Roach et al. Stroke 39:2644-91, 2008). It is also important in children and young adults to consider less common structural, metabolic and genetic risk factors for stroke, which may require more specific treatment. Other standard risk factors for stroke, including hypertension, hyperlipidemia and diabetes mellitus should also be addressed, but are less likely in children and young adults. Given the lack of data and possibility of rare underlying etiologies such as Antiphospholipid Antibody Syndrome or Ehlers-Danlos syndrome, we recommend including multiple specialists in the care of these patients, such as hematologists and vascular neurologists.

Cerebrovascular neurosurgery in evolution: the endovascular paradigm

Endovascular technique represents an important, minimally invasive approach to treating cerebrovascular disease. In this article, we discuss the origins of endovascular neurosurgery as a discipline in the context of important technical milestones, evidence-based medicine, and future cerebrovascular neurosurgical training. Cerebrovascular neurosurgery has seen a steady, convergent evolution toward the surgeon capable of seamless incorporation of open and endovascular approaches to any complex vascular disease affecting the central nervous system. Neurosurgery must assume the leadership role in the multidisciplinary neurovascular team.

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.

A comparison of two methods for MRI classification of at-risk tissue and core infarction

Objective: To compare how at-risk tissue and core infarction were defined in two major trials that tested the use of MRI in selecting acute stroke patients for endovascular recanalization therapy.

Methods: MRIs from 12 patients evaluated for possible endovascular therapy were processed using the methods published from two major trials, MR RESCUE and DEFUSE 2. Specifically, volumes of at-risk tissue and core infarction were generated from each patient’s MRI. MRIs were then classified as whether or not they met criteria for salvageable tissue: “penumbral pattern” for MR RESCUE and/or “target profile” for DEFUSE 2 as defined by each trial.

Results: Volumes of at-risk tissue measured by the two definitions were correlated (p = 0.017) while the volumes of core infarct were not (p = 0.059). The volume of at-risk tissue was consistently larger when defined by the penumbral pattern than the target profile while the volume of core infarct was consistently larger when defined by the target profile than the penumbral pattern. When these volumes were used to classify the MRI scans, 9 out of 12 patients (75%) were classified as having a penumbral pattern, while only 4 out of 12 patients (33%) were classified as having a target profile. Of the 9 patients classified as penumbral pattern, 5 (55%) were classified differently by the target profile.

Interpretation: Our analysis found that the MR RESCUE trial defined salvageable tissue in a way that made it more likely for patients be labeled as favorable for treatment. For the cohort of patients examined in this study, had they been enrolled in both trials, most of the patients identified as having salvageable tissue by the MR RESCUE trial would not have been considered to have salvageable tissue in the DEFUSE 2 trial. Caution should be taken in concluding that MRI selection for endovascular therapy is not effective as imaging selection criteria were substantially different between the two trials.

Sex differences in stroke: the contribution of coagulation

Stroke is now the leading cause of adult disability in the United States. Women are disproportionately affected by stroke. Women increasingly outnumber men in the elderly population, the period of highest risk for stroke. However, there is also a growing recognition that fundamental sex differences are present that contribute to differential ischemic sensitivity. In addition, gonadal hormone exposure can impact coagulation and fibrinolysis, key factors in the initiation of thrombosis. In this review we will discuss sex differences in stroke, with a focus on platelets, vascular reactivity and coagulation.

Comparing different analysis methods for quantifying the MRI amide proton transfer (APT) effect in hyperacute stroke patients

Amide proton transfer (APT) imaging is a pH mapping method based on the chemical exchange saturation transfer phenomenon that has potential for penumbra identification following stroke. The majority of the literature thus far has focused on generating pH-weighted contrast using magnetization transfer ratio asymmetry analysis instead of quantitative pH mapping. In this study, the widely used asymmetry analysis and a model-based analysis were both assessed on APT data collected from healthy subjects (n = 2) and hyperacute stroke patients (n = 6, median imaging time after onset = 2 hours 59 minutes). It was found that the model-based approach was able to quantify the APT effect with the lowest variation in grey and white matter (≤ 13.8 %) and the smallest average contrast between these two tissue types (3.48 %) in the healthy volunteers. The model-based approach also performed quantitatively better than the other measures in the hyperacute stroke patient APT data, where the quantified APT effect in the infarct core was consistently lower than in the contralateral normal appearing tissue for all the patients recruited, with the group average of the quantified APT effect being 1.5 ± 0.3 % (infarct core) and 1.9 ± 0.4 % (contralateral). Based on the fitted parameters from the model-based analysis and a previously published pH and amide proton exchange rate relationship, quantitative pH maps for hyperacute stroke patients were generated, for the first time, using APT imaging.

MR CLEAN, a multicenter randomized clinical trial of endovascular treatment for acute ischemic stroke in the Netherlands: study protocol for a randomized controlled trial

BACKGROUND

Endovascular or intra-arterial treatment (IAT) increases the likelihood of recanalization in patients with acute ischemic stroke caused by a proximal intracranial arterial occlusion. However, a beneficial effect of IAT on functional recovery in patients with acute ischemic stroke remains unproven. The aim of this study is to assess the effect of IAT on functional outcome in patients with acute ischemic stroke. Additionally, we aim to assess the safety of IAT, and the effect on recanalization of different mechanical treatment modalities.

METHODS/DESIGN

A multicenter randomized clinical trial with blinded outcome assessment. The active comparison is IAT versus no IAT. IAT may consist of intra-arterial thrombolysis with alteplase or urokinase, mechanical treatment or both. Mechanical treatment refers to retraction, aspiration, sonolysis, or use of a retrievable stent (stent-retriever). Patients with a relevant intracranial proximal arterial occlusion of the anterior circulation, who can be treated within 6 hours after stroke onset, are eligible. Treatment effect will be estimated with ordinal logistic regression (shift analysis); 500 patients will be included in the trial for a power of 80% to detect a shift leading to a decrease in dependency in 10% of treated patients. The primary outcome is the score on the modified Rankin scale at 90 days. Secondary outcomes are the National Institutes of Health stroke scale score at 24 hours, vessel patency at 24 hours, infarct size on day 5, and the occurrence of major bleeding during the first 5 days.

DISCUSSION

If IAT leads to a 10% absolute reduction in poor outcome after stroke, careful implementation of the intervention could save approximately 1% of all new stroke cases from death or disability annually.

TRIAL REGISTRATION

NTR1804 (7 May 2009)/ISRCTN10888758 (24 July 2012).

Endovascular stroke therapy

BACKGROUND

Following the development of intravenous thrombolysis as a successful treatment for ischaemic stroke, advances in neurointerventional radiology have facilitated endovascular approaches to treatment. This article reviews the available endovascular therapeutic options and their evidence-base.

SUMMARY

Initial studies demonstrated that endovascular treatment of ischaemic stroke with intra-arterial thrombolysis and/or the use of clot-retrieval, thrombus aspiration and stent-retriever devices produced early recanalisation and reperfusion and improved neurological outcome. More recent randomised trials, however, have failed to show translation of recanalisation into successful clinical outcome with 'time to treatment' proving crucial. In this rapidly evolving field, combined therapy incorporating intravenous and intra-arterial thrombolysis in combination with endovascular clot-retrieval has been developed and further studies are expected to yield better evidence to guide the optimal treatment of acute cerebral ischaemia.

Geographic access to acute stroke care in the United States

BACKGROUND AND PURPOSE

Only 3% to 5% of patients with acute ischemic stroke receive intravenous recombinant tissue-type plasminogen activator (r-tPA) and <1% receive endovascular therapy. We describe access of the US population to all facilities that actually provide intravenous r-tPA or endovascular therapy for acute ischemic stroke.

METHODS

We used US demographic data and intravenous r-tPA and endovascular therapy rates in the 2011 US Medicare Provider and Analysis Review data set. International Classification of Diseases-Ninth Revision codes 433.xx, 434.xx and 436 identified acute ischemic stroke cases. International Classification of Diseases-Ninth Revision code 99.10 defined intravenous r-tPA treatment and International Classification of Diseases-Ninth Revision code 39.74 defined endovascular therapy. We estimated ambulance response times using arc-Geographic Information System's network analyst and helicopter transport times using validated models. Population access to care was determined by summing the population contained within travel sheds that could reach capable hospitals within 60 and 120 minutes.

RESULTS

Of 370,351 acute ischemic stroke primary diagnosis discharges, 14,926 (4%) received intravenous r-tPA and 1889 (0.5%) had endovascular therapy. By ground, 81% of the US population had access to intravenous-capable hospitals within 60 minutes and 56% had access to endovascular-capable hospitals. By air, 97% had access to intravenous-capable hospitals within 60 minutes and 85% had access to endovascular hospitals. Within 120 minutes, 99% of the population had access to both intravenous and endovascular hospitals.

CONCLUSIONS

More than half of the US population has geographic access to hospitals that actually deliver acute stroke care but treatment rates remain low. These data provide a national perspective on acute stroke care and should inform the planning and optimization of stroke systems in the United States.

Multimodal Computed Tomography Based Definition of Cerebral Imaging Profiles for Acute Stroke Reperfusion Therapy (CT-DEFINE): Results of a Prospective Observational Study

PURPOSE

To prospectively evaluate the prognostic impact of multimodal computed tomography-based imaging in ischemic stroke patients potentially eligible for reperfusion therapy.

METHODS

Anterior circulation stroke patients underwent non-contrast CT (NCCT), CT-angiography, and CT-perfusion within 12 h from symptom-onset. Patients could be treated with intravenous-tissue plasminogen activator (IV-tPA), endovascular or combined reperfusion therapies. Cerebral imaging profiles (IP) were NCCT-Alberta Stroke Program Early CT Score (ASPECTS) > 7 (IP1); NCCT-ASPECTS > 5 and proximal occlusion on CT-angiography (IP2); CT-perfusion mismatch between cerebral blood volume (CBV)-ASPECTS, and cerebral blood flow (CBF)-ASPECTS ≥ 2 (IP3). Favorable outcome was defined as modified Rankin Scale ≤ 2 at 3 months.

RESULTS

Of 102 included patients, 62 (61%) received any reperfusion therapy. In IP2 and IP3, favorable outcome was more frequent in patients with reperfusion therapy than in those without; however, this did not reach statistical significance (IP2: 39% vs 15%, p = 0.26; IP3: 50% vs 17 %; p = 0.31). No difference was seen in IP1 (58% vs 58%, p = 1.0). In IP2, patients with IV-tPA alone achieved better functional outcome (50% vs 11%, p = 0.03) and lower mortality (0% vs 28%, p = 0.045) than those without.

CONCLUSIONS

Our results suggest a benefit with imaging profile selection based upon the combination of a small-to-moderate-sized infarction and a visible intracranial occlusion in patients receiving IV-tPA. Reperfusion therapy may be futile in patients without proven vessel occlusion.

Acute stroke reperfusion therapy trends in the expanded treatment window era

BACKGROUND

The American Heart Association/American Stroke Association (AHA/ASA) recommended an expansion of the time window for acute ischemic stroke (AIS) reperfusion with intravenous (IV) recombinant tissue plasminogen activator (rt-PA) from 3 to 4.5 hours after symptom onset. We examine rates of IV and intra-arterial (IA) reperfusion before and after the recommendations to track guideline adoption in community practice.

METHODS

Patients with AIS in the Paul Coverdell National Acute Stroke Registry spanning years 2007-2012 were identified. Trends in rates of IV rt-PA versus IA therapy were examined. Outcomes included symptomatic intracerebral hemorrhage (sICH), in-hospital mortality, ability to ambulate at discharge, and discharge destination.

RESULTS

From 2007 to 2012, there were 182,235 AIS patients (median age, 72 years; 51.5% women) in the database at the time of analysis. AIS patients receiving IV rt-PA increased significantly from 3.7% in 2007 to 5.1% in 2012 in the ≤3 hours time window and from .2% in 2007 to 1.3% in 2012 in the 3-4.5 hours time window (P < .001 for both). There was also a significant increase in the rate of IA therapy between 2007 and 2012 (P < .001). There was a significant decrease in the rate of sICH among patients who received any reperfusion between 2007 and 2012.

CONCLUSIONS

There was a trend for increased utilization of IV rt-PA in the 0-3 hours and the 3-4.5 hours time windows, which began around the same time as the publication of AHA/ASA recommendations in 2009. This increase was associated with an increase in IA treatment rates along with a decrease in overall sICH rates for patients receiving any reperfusion.

Penumbra pattern assessment in acute stroke patients: comparison of quantitative and non-quantitative methods in whole brain CT perfusion

Background And Purpose

While penumbra assessment has become an important part of the clinical decision making for acute stroke patients, there is a lack of studies measuring the reliability and reproducibility of defined assessment techniques in the clinical setting. Our aim was to determine reliability and reproducibility of different types of three-dimensional penumbra assessment methods in stroke patients who underwent whole brain CT perfusion imaging (WB-CTP).

Materials And Methods

We included 29 patients with a confirmed MCA infarction who underwent initial WB-CTP with a scan coverage of 100 mm in the z-axis. Two blinded and experienced readers assessed the flow-volume-mismatch twice and in two quantitative ways: Performing a volumetric mismatch analysis using OsiriX imaging software (MM_VOL) and visual estimation of mismatch (MM_EST). Complementarily, the semiquantitative Alberta Stroke Programme Early CT Score for CT perfusion was used to define mismatch (MM_ASPECTS). A favorable penumbral pattern was defined by a mismatch of ≥30% in combination with a cerebral blood flow deficit of ≤90 ml and an MM_ASPECTS score of ≥1, respectively. Inter- and intrareader agreement was determined by Kappa-values and ICCs.

Results

Overall, MM_VOL showed considerably higher inter-/intrareader agreement (ICCs: 0.751/0.843) compared to MM_EST (0.292/0.749). In the subgroup of large (≥50 mL) perfusion deficits, inter- and intrareader agreement of MM_VOL was excellent (ICCs: 0.961/0.942), while MM_EST interreader agreement was poor (0.415) and intrareader agreement was good (0.919). With respect to penumbra classification, MM_VOL showed the highest agreement (interreader agreement: 25 agreements/4 non-agreements/κ: 0.595; intrareader agreement 27/2/0.833), followed by MM_EST (22/7/0.471; 23/6/0.577), and MM_ASPECTS (18/11/0.133; 21/8/0.340).

Conclusion

The evaluated approach of volumetric mismatch assessment is superior to pure visual and ASPECTS penumbra pattern assessment in WB-CTP and helps to precisely judge the extent of 3-dimensional mismatch in acute stroke patients.

The role of imaging in acute ischemic stroke

Neuroimaging has expanded beyond its traditional diagnostic role and become a critical tool in the evaluation and management of stroke. The objectives of imaging include prompt accurate diagnosis, treatment triage, prognosis prediction, and secondary preventative precautions. While capitalizing on the latest treatment options and expanding upon the "time is brain" doctrine, the ultimate goal of imaging is to maximize the number of treated patients and improve the outcome of one the most costly and morbid disease. A broad overview of comprehensive multimodal stroke imaging is presented here to affirm its utilization.

Endovascular treatment of acute ischemic stroke: the end or just the beginning?

Various endovascular intraarterial approaches are available for treating patients with acute ischemic stroke who present with severe neurological deficits. Three recent randomized trials-Interventional Management of Stroke (IMS) III, Mechanical Retrieval and Recanalization of Stroke Clots Using Embolectomy (MR RESCUE), and Synthesis Expansion: A Randomized Controlled Trial on Intra-Arterial Versus Intravenous Thrombolysis in Acute Ischemic Stroke (SYNTHESIS Expansion)-evaluated the efficacy of endovascular treatment of acute ischemic stroke and, after failing to demonstrate any significant clinical benefit of endovascular therapies, raised concerns and questions in the medical community regarding the future of endovascular treatment for acute ischemic stroke. In this paper, the authors review the evolution of endovascular treatment strategies for the treatment of acute stroke and provide their interpretation of findings and potential limitations of the three recently published randomized trials. The authors discuss the advantage of stent-retriever technology over earlier endovascular approaches and review the current status and future directions of endovascular acute stroke studies based on lessons learned from previous trials.

Endovascular stroke intervention in young patients with large vessel occlusions

OBJECT

Endovascular therapy has become a widely used method for achieving arterial recanalization in patients who are ineligible for intravenous thrombolysis or those in whom it is unsuccessful. Young stroke patients with large vessel occlusions may particularly benefit from endovascular intervention. This study aims to assess the authors' experience with the use of modern endovascular techniques to treat young patients (≤ 55 years old) with acute ischemic stroke and large vessel occlusions.

METHODS

Young patients (≤ 55 years old) undergoing endovascular intervention for acute ischemic stroke at the authors' institution were identified from a prospectively maintained database. Only those patients with a confirmed large vessel occlusion were included. Modified Rankin Scale (mRS) scores were determined at 90 days during a follow-up visit. A multivariate analysis was performed to determine predictors of outcome (mRS score 0-2).

RESULTS

A total of 45 patients met the inclusion criteria. The mean age of the patients in this series was 45 ± 9.6 years. The mean admission NIH Stroke Scale score was 14.1 ± 5 (median 13.5). Mechanical thrombectomy was performed using the Solitaire FR device in 13 (29%) patients and the Merci/Penumbra systems in 32 (71%) patients. The rate of successful recanalization (Thrombolysis In Myocardial Infarction [TIMI] scale Grade II-III) was 93% (42/45). Only 1 patient (2.2%) had a symptomatic intracranial hemorrhage following intervention. One patient (2.2%) sustained a vessel perforation intraoperatively. The rate of 90-day favorable outcome (mRS score 0-2) was 77.5% and the rate of 90-day satisfactory outcome (mRS score 0-3) was 90%. The 90-day mortality rate was 7.5%. In multivariate analysis, postprocedure TIMI grade was the only statistically significant independent predictor of 90-day outcome (OR 3.3, 95% CI 1.01-1.19; p = 0.05).

CONCLUSIONS

The results of this study demonstrate that endovascular therapy provides remarkably high rates of arterial recanalization and favorable outcomes in young patients with acute ischemic stroke and large vessel occlusions. These findings support aggressive interventional strategies in these patients. Randomized, controlled trials reflecting modern acute ischemic stroke treatment will be needed to confirm the findings of this study.

The ischemic penumbra: the location rather than the volume of recovery determines outcome

PURPOSE OF REVIEW

The clinical efficiency of thrombolysis is explained by the rescue of ischemic penumbra areas resulting from early arterial recanalization. The perfusion-diffusion weighted imaging mismatch is a commonly used MRI surrogate of the ischemic penumbra. However, the randomized trials testing the mismatch hypothesis have been negative. We will review the 'mismatch concept' and the recent studies that aim to localize the clinically eloquent areas of penumbra in middle cerebral artery (MCA) infarcts.

RECENT FINDINGS

New methods of image analysis have shown that poor outcomes after MCA stroke are related to infarction of an extremely well localized area of the periventricular white matter and adjacent internal capsule, where projections and association tracts are crossing and converging. This area almost colocalizes with the area salvaged by early arterial recanalization and is located extremely close to the initial ischemic core.

SUMMARY

The location of the area that correlates with disability in MCA stroke patients and that is salvaged by early arterial recanalization is in the same specific region of the deep white matter, close to the initial ischemic core. These findings may have important implications for designing new recanalization trials and support the importance of basic research on white-matter neuroprotection.

Intravenous fibrinolysis eligibility: a survey of stroke clinicians' practice patterns and review of the literature

BACKGROUND

The indications and contraindications for intravenous (IV) recombinant tissue plasminogen activator (rtPA) use in ischemic stroke can be confusing to the practicing neurologist. Here we seek to describe practice patterns regarding decision-making among US stroke clinicians.

METHODS

Stroke clinicians (attending and fellow) from the 8 National Institutes of Health SPOTRIAS (Specialized Programs of Translational Research in Acute Stroke) centers were asked to complete a survey ahead of the 2012 SPOTRIAS Investigators' meeting.

RESULTS

A total of 51 surveys were collected (71% response rate). Most of the responders were attending physicians (68%). Only 18% of clinicians reported strictly adhering to current American Heart Association guidelines for treatment within 3 hours from symptom onset; this increased to 51% for the European Cooperative Acute Stroke Study (ECASS) III criteria in the 3 to 4.5 hours time frame. All clinicians treat eligible patients in the 3 to 4.5 hours time frame. The great majority will recommend rtPA in the following scenarios: (1) elderly individuals irrespective of age (97%); (2) severe stroke irrespective of National Institutes of Health Stroke Scale (NIHSS) (95%); or (3) suspected stroke with seizures at symptom onset (91%). None recommended rtPA in the setting of an international normalized ratio >1.7. Most clinicians defined mild strokes as an exclusion based on the perceived disability of the deficit (80%) rather than on a specific NIHSS threshold.

CONCLUSIONS

Most surveyed stroke clinicians seem to find that the current IV rtPA eligibility criteria for the 3-hour time frame too restrictive. All would recommend rtPA to eligible patients in the 3 to 4.5 hours time frame despite the absence of an U.S. Food and Drug Administration (FDA)-approved indication.

Update in the management of acute ischemic stroke

Acute ischemic stroke is the fourth leading cause of death and the leading cause of disability in the United States. Stroke is a medical emergency. The development of stroke systems of care has changed the way practitioners view and treat this devastating disease. Ample evidence has shown that patients presenting early and receiving intravenous thrombolytic therapy have the best chance for significant improvement in functional outcome, particularly if they are transported to specialized stroke centers. Early detection and management of medical and neurologic complications is key at preventing further brain damage in patients with acute ischemic stroke.

Trends of hospitalized acute stroke care in Germany from clinical trials to bedside. Comparison of nation-wide administrative data 2008-2012

Promising advances in stroke medicine have been reported recently regarding specialized stroke unit (SU) care, expansion of the time window of iv thrombolysis (IVT), mechanical thrombectomy (MT), and decompressive hemicraniectomy (DHC) for malignant brain infarction. It remains unclear to what extent new evidence of therapeutic procedures is transferred to the "real-world" of everyday hospital care. We analyzed epidemiologic and procedural therapeutic trends of hospitalized acute stroke patients in Germany by the comparison of administrative hospital data of the years 2008 (n=219,359) and 2012 (n=239,394). Proportion of specialized SU care rose from 43.4% to 56.9%. Even in age-matched analysis women were less likely to obtain this procedure. Rate of IVT increased from 5.6% to 10.2%. 32% of IVT therapies in 2012 were performed in patients over 80 years. Number of MT increased exponentially from 298 to 3906 procedures. Number of DHC did not increase significantly (2008=636; 2011=796). A strong momentum in transferring scientific insights to the "real-world" stroke care in Germany was documented. Increase of IVT therapy is largely due to the increase of off-label treatment. Almost every 46 th patient <80 years was treated by MT in 2012. Despite proven benefits in selected patients, utilization of DHC remained almost stable.

Dynamic perfusion and diffusion MRI of cortical spreading depolarization in photothrombotic ischemia

Cortical spreading depolarization (CSD) is known to exacerbate ischemic damage, as the number of CSDs correlates with the final infarct volumes and suppressing CSDs improves functional outcomes. To investigate the role of CSD in ischemic damage, we developed a novel rat model of photothrombotic ischemia using a miniature implantable optic fiber that allows lesion induction inside the magnetic resonance imaging (MRI) scanner. We were able to precisely control the location and the size of the ischemic lesion, and continuously monitor dynamic perfusion and diffusion MRI signal changes at high temporal resolution before, during and after the onset of focal ischemia. Our model showed that apparent diffusion coefficient (ADC) and cerebral blood flow (CBF) in the ischemic core dropped immediately after lesion onset by 20±6 and 41±23%, respectively, and continually declined over the next 5h. Meanwhile, CSDs were observed in all animals (n=36) and displayed either a transient decrease of ADC by 17±3% or an increase of CBF by 104±15%. All CSDs were initiated from the rim of the ischemic core, propagated outward, and confined to the ipsilesional cortex. Additionally, we demonstrated that by controlling the size of perfusion-diffusion mismatch (which approximates the penumbra) in our model, the number of CSDs correlated with the mismatch area rather than the final infarct volume. This study introduces a novel platform to study CSDs in real-time with high reproducibility using MRI.

A novel magnetic resonance imaging approach to collateral flow imaging in ischemic stroke

OBJECTIVE

Dedicated magnetic resonance (MR) imaging (MRI) sequences for evaluation of collaterals can be generated using MR perfusion (MRP) source data. We compared a novel collateral flow imaging technique with digital subtraction angiography (DSA) for determining collateral circulation in acute stroke and evaluated the ability of MR-based collateral flow maps to predict outcomes after recanalization therapy.

METHODS

Consecutive patients who were candidates for endovascular treatment were enrolled. A collateral flow map derived from MRP source data was generated by manual or automatic postprocessing. Collateral grading based on the collateral flow map was performed and compared with grading based on DSA. Clinical and radiological outcomes were evaluated according to MR-based collateral grading and early reperfusion (ER) status.

RESULTS

There was good correlation between MRI-based and DSA-based collateral grades (weighted κ-coefficient = 0.70). Collateral status and achievement of ER were the 2 main determinants of a favorable functional outcome and neurological improvement, in addition to infarct growth. Regardless of achievement of ER, better collaterals were significantly associated with a lower modified Rankin score at day 90 (p < 0.001 for trend in both ER(-) and ER(+) ). Most symptomatic intracranial hemorrhages occurred in patients with a poor collateral grade and ER(+) , whereas no patient with excellent collaterals suffered symptomatic intracranial hemorrhage or died.

INTERPRETATION

MRI techniques to assess collaterals are rapidly being developed, and may provide insight into collateral perfusion. The combination of collateral images derived from pretreatment MRP source data and reperfusion status is a robust predictor of outcomes in acute ischemic stroke.

Detection of ischemic penumbra using combined perfusion and T2* oxygen challenge imaging

Background

Acute ischemic stroke is common and disabling, but there remains a paucity of acute treatment options and available treatment (thrombolysis) is underutilized. Advanced brain imaging, designed to identify viable hypoperfused tissue (penumbra), could target treatment to a wider population. Existing magnetic resonance imaging and computed tomography-based technologies are not widely used pending validation in ongoing clinical trials. T2* oxygen challenge magnetic resonance imaging, by providing a more direct readout of tissue viability, has the potential to identify more patients likely to benefit from thrombolysis – irrespective of time from stroke onset – and patients within and beyond the 4·5 h thrombolysis treatment window who are unlikely to benefit and are at an increased risk of hemorrhage.

Aims

This study employs serial multimodal imaging and voxel-based analysis to develop optimal data processing for T2* oxygen challenge penumbra assessment. Tissue in the ischemic hemisphere is compartmentalized into penumbra, ischemic core, or normal using T2* oxygen challenge (single threshold) or T2* oxygen challenge plus cerebral blood flow (dual threshold) data. Penumbra defined by perfusion imaging/apparent diffusion coefficient mismatch (dual threshold) is included for comparison.

Methods

Permanent middle cerebral artery occlusion was induced in male Sprague-Dawley rats (n = 6) prior to serial multimodal imaging: T2* oxygen challenge, diffusion-weighted and perfusion imaging (cerebral blood flow using arterial spin labeling).

Results

Across the different methods evaluated, T2* oxygen challenge combined with perfusion imaging most closely predicted 24 h infarct volume. Penumbra volume declined from one to four-hours post-stroke: mean ± SD, 77 ± 44 to 49 ± 37 mm³ (single T2* oxygen challenge-based threshold); 55 ± 41 to 37 ± 12 mm³ (dual T2* oxygen challenge/cerebral blood flow); 84 ± 64 to 42 ± 18 mm³ (dual cerebral blood flow/apparent diffusion coefficient), as ischemic core grew: 155 ± 37 to 211 ± 36 mm³ (single apparent diffusion coefficient threshold); 178 ± 56 to 205 ± 33 mm³ (dual T2* oxygen challenge/cerebral blood flow); 139 ± 30 to 168 ± 38 mm³ (dual cerebral blood flow/apparent diffusion coefficient). There was evidence of further lesion growth beyond four-hours (T2-defined edema-corrected infarct, 231 ± 19 mm³).

Conclusions

In conclusion, T2* oxygen challenge combined with perfusion imaging has advantages over alternative magnetic resonance imaging techniques for penumbra detection by providing serial assessment of available penumbra based on tissue viability.

Establishment of government-initiated comprehensive stroke centers for acute ischemic stroke management in South Korea

BACKGROUND AND PURPOSE

In 2008, the Ministry of Health and Welfare of South Korea initiated the Regional Comprehensive Stroke Center (CSC) program to decrease the incidence and mortality of stroke nationwide. We evaluated the performance of acute ischemic stroke management after the Regional CSC program was introduced.

METHODS

The Ministry of Health and Welfare established 9 Regional CSCs in different provinces from 2008 to 2010. All Regional CSCs have been able to execute the critical processes independently for stroke management since 2011. The Ministry of Health and Welfare was responsible for program development and financial support, the Regional CSC for program execution, and the Korea Centers for Disease Control and Prevention for auditing the execution. We analyzed prospectively collected data on the required indices from 2011 and repeated the analysis the following year for comparison.

RESULTS

After the Regional CSCs were established, the first brain image was taken within 1 hour from arrival at the emergency room for all patients with stroke; the length of hospital stay decreased from 14 to 12 days; for the rapid execution of thrombolysis, the first brain image was taken within 12 minutes; intravenous and intra-arterial thrombolysis were started within 40 and 110 minutes, respectively, after emergency room arrival; and the hospital stay of thrombolytic patients decreased from 19 to 15 days.

CONCLUSIONS

The Regional CSC program has improved the performance of acute stroke management in South Korea and can be used as a model for rapidly improving stroke management.

Intravenous thrombolysis in acute ischemic stroke: standard and potential future applications

Acute ischemic stroke is a medical emergency requiring urgent treatment. Randomized clinical trial and Phase IV data have provided unequivocal evidence that intravenous thrombolysis with recombinant tissue plasminogen activator (rt-PA) improves early functional outcomes by restoring brain perfusion. Moreover, these studies have shed substantial light on the factors which are associated with more favorable outcome with tPA and are related to the highest benefit-to-risk ratio. Stroke physicians should consider vascular imaging techniques to aid decision making with thrombolytic therapy. The presence of intracranial occlusion is the target of treatment with early recanalization being the goal. Successful use of intravenous thrombolysis depends on a sound understanding of the decision-making process and organization of the treating team who strives for early treatment initiation and strict adherence to the protocol. Intravenous rt-PA within 4.5 h of onset should now be a standard treatment of acute disabling ischemic stroke throughout the world. This review also summarizes intravenous thrombolysis contraindications as well as the safety of novel reperfusion therapies including tenecteplase, sonothrombolysis and the combination of alteplase with direct thrombin inhibitors or glycoprotein IIb/IIIa receptor antagonists.

Impact of age and baseline NIHSS scores on clinical outcomes in the mechanical thrombectomy using solitaire FR in acute ischemic stroke study

BACKGROUND AND PURPOSE

Age and stroke severity are inversely correlated with the odds of favorable outcome after ischemic stroke. A previously proposed score for Stroke Prognostication Using Age and NIHSS Stroke Scale (SPAN) indicated that SPAN-100-positive patients (ie, age + NIHSS score = 100 or more) do not benefit from IV-tPA. If this finding holds true for endovascular therapy, this score can impact patient selection for such interventions. This study investigated whether a score combining age and NIHSS score can improve patients' selection for endovascular stroke therapy.

MATERIALS AND METHODS

The SPAN index was calculated for patients in the prospective Solitaire FR Thrombectomy for Acute Revascularization study: an international single-arm multicenter cohort for anterior circulation stroke treatment by using the Solitaire FR. The proportion with favorable outcome (90-day mRS score ≤2) was compared between SPAN-100-positive versus-negative patients.

RESULTS

Of the 202 patients enrolled, 196 had baseline NIHSS scores. Fifteen (7.7%) patients were SPAN-100-positive. There was no difference in the rate of successful reperfusion (Thrombolysis In Cerebral Infarction 2b or 3) between SPAN-100-positive versus -negative groups (93.3% versus 82.8%, respectively; P = .3). Stroke SPAN-100-positive patients had a significantly lower proportion of favorable clinical outcomes (26.7% versus 60.8% in SPAN-100-negative, P = .01). In a multivariable analysis, SPAN-100-positive status was associated with lower odds of favorable outcome (OR, 0.3; 95% CI, 0.1-0.9; P = .04). A higher baseline Alberta Stroke Program Early CT Score and a short onset to revascularization time also predicted favorable outcome in the multivariable analysis.

CONCLUSIONS

A significantly lower proportion of patients with a positive SPAN-100 achieved favorable outcome in this cohort. SPAN-100 was an independent predictor of favorable outcome after adjusting for time to treatment and the extent of preintervention tissue damage according to the Alberta Stroke Program Early CT Score.

Early experience with stent retrievers and comparison with previous-generation mechanical thrombectomy devices for acute ischemic stroke

Object

There is limited information regarding patient outcomes following interventions for stroke during the window for endovascular therapy. Studies have suggested that recently approved stent retrievers are safer and more effective than earlier-generation thrombectomy devices. The authors compared cases in which the Solitaire-FR device was used to those in which a MERCI or Penumbra device was used.

Methods

This study is a single-center retrospective review of 102 consecutive cases of acute stroke in which patients were treated with mechanical thrombectomy devices between 2007 and 2013. Multivariate models, adjusted for confounding factors, were used to investigate functional independence (modified Rankin Scale [mRS] score ≤ 2, and successful reperfusion (thrombolysis in cerebral infarction [TICI] score ≥ 2b).

Results

Thrombectomy device had a significant impact on functional independence (mRS score ≤ 2) at discharge from the hospital (p = 0.040). Solitaire-FR treatment resulted in significantly more patients being discharged as functionally independent in comparison with MERCI treatment (p = 0.016). A multivariate model found the use of Solitaire-FR to improve the odds of good clinical outcome in comparison with prior-generation devices (OR 6.283, 95% CI 1.785–22.119, p = 0.004). Additionally, the use of Solitaire-FR significantly increased the odds of successful reperfusion (OR 3.247, 95% CI 1.160–9.090, p = 0.025).

Conclusions

The stent retriever Solitaire-FR significantly improved the odds of functional independence and successful revascularization of the arterial tree. New interventional technology for stroke continues to mature, but randomized trials are needed to establish the actual benefit to specific patient populations.

Snapshot MR technique to measure OEF using rapid frequency mapping

Magnetic resonance (MR)-based oxygen extraction fraction (OEF) measurement techniques that use blood oxygen level-dependent (BOLD)-based approaches require the measurement of the R2' decay rate and deoxygenated blood volume to derive the local oxygen saturation in vivo. We describe here a novel approach to measure OEF using rapid local frequency mapping. By modeling the MR decay process in the static dephasing regime as two separate dissipative and oscillatory effects, we calculate the OEF from local frequencies measured across the brain by assuming that the biophysical mechanisms causing OEF-related frequency changes can be determined from the oscillatory effects. The Parameter Assessment by Retrieval from Signal Encoding (PARSE) technique was used to acquire the local frequency change maps. The PARSE images were taken on 11 normal volunteers, and 1 patient exhibiting hemodynamic stress. The mean MR-OEF in 11 normal subjects was 36.66±7.82%, in agreement with positron emission tomography (PET) literature. In regions of hemodynamic stress induced by vascular steal, OEF exhibits the predicted focal increases. These preliminary results show that it is possible to measure OEF using a rapid frequency mapping technique. Such a technique has numerous advantages including speed of acquisition, is noninvasive, and has sufficient spatial and temporal resolution.

Six-Minute Magnetic Resonance Imaging Protocol for Evaluation of Acute Ischemic Stroke

Background and Purpose—

If magnetic resonance imaging (MRI) is to compete with computed tomography for evaluation of patients with acute ischemic stroke, there is a need for further improvements in acquisition speed.

Methods—

Inclusion criteria for this prospective, single institutional study were symptoms of acute ischemic stroke within 24 hours onset, National Institutes of Health Stroke Scale ≥3, and absence of MRI contraindications. A combination of echo-planar imaging (EPI) and a parallel acquisition technique were used on a 3T magnetic resonance (MR) scanner to accelerate the acquisition time. Image analysis was performed independently by 2 neuroradiologists.

Results—

A total of 62 patients met inclusion criteria. A repeat MRI scan was performed in 22 patients resulting in a total of 84 MRIs available for analysis. Diagnostic image quality was achieved in 100% of diffusion-weighted imaging, 100% EPI-fluid attenuation inversion recovery imaging, 98% EPI-gradient recalled echo, 90% neck MR angiography and 96% of brain MR angiography, and 94% of dynamic susceptibility contrast perfusion scans with interobserver agreements ( k ) ranging from 0.64 to 0.84. Fifty-nine patients (95%) had acute infarction. There was good interobserver agreement for EPI-fluid attenuation inversion recovery imaging findings ( k =0.78; 95% confidence interval, 0.66–0.87) and for detection of mismatch classification using dynamic susceptibility contrast-Tmax ( k =0.92; 95% confidence interval, 0.87–0.94). Thirteen acute intracranial hemorrhages were detected on EPI-gradient recalled echo by both observers. A total of 68 and 72 segmental arterial stenoses were detected on contrast-enhanced MR angiography of the neck and brain with k =0.93, 95% confidence interval, 0.84 to 0.96 and 0.87, 95% confidence interval, 0.80 to 0.90, respectively.

Conclusions—

A 6-minute multimodal MR protocol with good diagnostic quality is feasible for the evaluation of patients with acute ischemic stroke and can result in significant reduction in scan time rivaling that of the multimodal computed tomographic protocol.