MRI versus CT-based thrombolysis treatment within and beyond the 3 h time window after stroke onset: a cohort study

MRI or CT for Suspected Acute Stroke: Association of Admission Image Modality with Acute Recanalization Therapies, Workflow Metrics and Outcomes

Objective

To examine rates of intravenous thrombolysis (IVT), mechanical thrombectomy (MT), door‐to‐needle (DTN) time, door‐to‐puncture (DTP) time, and functional outcome between patients with admission magnetic resonance imaging (MRI) versus computed tomography (CT).

Methods

An observational cohort study of consecutive patients using a target trial design within the nationwide Swiss‐Stroke‐Registry from January 2014 to August 2020 was carried out. Exclusion criteria included MRI contraindications, transferred patients, and unstable or frail patients. Multilevel mixed‐effects logistic regression with multiple imputation was used to calculate adjusted odds ratios with 95% confidence intervals for IVT, MT, DTN, DTP, and good functional outcome (mRS 0–2) at 90 days.

Results

Of the 11,049 patients included (mean [SD] age, 71 [15] years; 4,811 [44%] women; 69% ischemic stroke, 16% transient ischemic attack, 8% stroke mimics, 6% intracranial hemorrhage), 3,741 (34%) received MRI and 7,308 (66%) CT. Patients undergoing MRI had lower National Institutes of Health Stroke Scale (median [interquartile range] 2 [0–6] vs 4 [1–11]), and presented later after symptom onset (150 vs 123 min, p < 0.001). Admission MRI was associated with: lower adjusted odds of IVT (aOR 0.83, 0.73–0.96), but not with MT (aOR 1.11, 0.93–1.34); longer adjusted DTN (+22 min [13–30]), but not with longer DTP times; and higher adjusted odds of favorable outcome (aOR 1.54, 1.30–1.81).

Interpretation

We found an association of MRI with lower rates of IVT and a significant delay in DTN, but not in DTP and rates of MT. Given the delays in workflow metrics, prospective trials are required to show that tissue‐based benefits of baseline MRI compensate for the temporal benefits of CT. ANN NEUROL 2022;92:184–194

Comparative analysis of functional outcome for CT-based versus MRI-based evaluation in acute ischemic stroke prior to mechanical thrombectomy

Background

This study aims to compare functional outcome for Computed tomography (CT)-based versus Magnetic resonance imaging (MRI)-based evaluation in acute ischemic stroke patients prior to Mechanical thrombectomy (MT) in less than 6-h window period in anterior circulation stroke. Participants were patients admitted from September 2, 2018 to September 2, 2020 with an acute ischemic stroke who underwent mechanical thrombectomy treatment. Total duration of MRI stroke protocol and CT scan with Computed tomography angiography (CTA) was 12 min 57 s, and 9 min 23 s, respectively. Follow-up for periodic Modified Rankin Scale (MRS) was performed at 3 months.

Results

Number of patients included in the study were 152 with mean age of 54.6 (range 22–80) years with male predominance (n = 102). Mean GCS on admission was 12 (4–15) and 13(4–14) in CT and MRI group, respectively. National Institute of Health stroke scale (NIHSS) on admission was 17 (4–30) and 16(4–30) and at discharge was 7 (2–23) and 6(2–22) in CT-based group and MRI-based group, respectively. In the MRI group 65.5% had good outcome with mRS (0–2) at 3-month follow-up compared to 35.51% in CT group.

Conclusion

The current standard neuroimaging in acute ischemic stroke patients is CT and CTA brain. Using MRI over CT scan for acute ischemic stroke may improve clinical outcomes for the subgroup of patients who have an unclear diagnosis and who have higher risk of complications with MT. Even though MRI and MRA take longer period to acquire, patient’s clinical outcome was better in MRI group in comparison to CT group and was comparable to that of the five major endovascular trials.

Multimodal CT or MRI for IV thrombolysis in ischemic stroke with unknown time of onset

Objective

To investigate differences in procedure times, safety, and efficacy outcomes comparing 2 different protocols to enable thrombolysis in the extended or unknown time window after stroke onset with either multimodal CT or MRI.

Methods

Patients with ischemic stroke in the extended or unknown time window who received IV thrombolysis between January 2011 and May 2019 were identified from an institutional registry. Imaging-based selection was done by multimodal CT or MRI according to institutional treatment algorithms.

Results

IV thrombolysis was performed in 100 patients (54.3%) based on multimodal CT imaging and in 84 patients (45.7%) based on MRI. Baseline clinical data, including stroke severity and time from last seen normal to hospital admission, were similar in patients with CT and MRI. Door-to-needle times were shorter in patients with CT-based selection (median [interquartile range] 45 [37–62] minutes vs 75 [59–90] minutes; mean difference [95% confidence interval (CI)] −28 minutes [−35 to −21]). No differences were detected regarding the incidence of symptomatic intracranial hemorrhage (2 [2.0%] vs 4 [4.8%]; adjusted odds ratio [aOR] [95% CI] 0.47 [0.08–2.83]) and favorable outcome at day 90 (25 [33.8%] vs 33 [42.9%]; aOR 0.95 [0.45–2.02]).

Conclusion

IV thrombolysis in ischemic stroke in the unknown or extended time window appeared safe in CT- and MRI-selected patients, while the use of CT imaging led to faster door-to-needle times.

Classification of evidence

This study provides Class IV evidence that for patients with ischemic stroke in the extended or unknown time window, imaging-based selection for IV thrombolysis by multimodal CT compared to MRI led to shorter door-to-needle times.

Patients With Acute Ischemic Stroke Who Receive Brain Magnetic Resonance Imaging Demonstrate Favorable In-Hospital Outcomes

Background

Use of inpatient brain magnetic resonance imaging (MRI) in patients with acute ischemic stroke is highly institution dependent and has been associated with increased length and cost of hospital stay. We examined whether inpatient brain MRI in patients with acute ischemic stroke is associated with improved clinical outcomes to justify its resource requirements.

Methods and Results

The National Inpatient Sample database was queried retrospectively to find 94 003 patients who were admitted for acute ischemic stroke and then received inpatient brain MRI between 2012 and 2014. Multivariable regression analysis was performed with respect to a control group to assess for differences in the rates of inpatient mortality and complications, as well as the length and cost of hospital stay based on brain MRI use. Inpatient brain MRI was independently associated with lower rates of inpatient mortality (1.67% versus 3.09%; adjusted odds ratio [OR], 0.60; 95% CI, 0.53–0.68; P<0.001), gastrostomy (2.28% versus 2.89%; adjusted OR, 0.82; 95% CI, 0.73–0.93; P<0.001), and mechanical ventilation (1.97% versus 2.82%; adjusted OR, 0.68; 95% CI, 0.60–0.77; P<0.001). Brain MRI was independently associated with ≈0.32 days (8%) and $1131 (11%) increase in the total length (P<0.001) and cost (P<0.001) of hospital stay, respectively.

Conclusions

Inpatient brain MRI in patients with acute ischemic stroke is associated with substantial decrease in the rates of inpatient mortality and complications, at the expense of marginally increased length and cost of hospitalization.

Association of initial imaging modality and futile recanalization after thrombectomy

Objective

To test the hypothesis that selection by initial imaging modality (MRI vs CT) is associated with rate of futile recanalizations (FRs) after mechanical thrombectomy (MT), we assessed this association in a multicenter, retrospective observational registry (BEYOND-SWIFT [Registry for Evaluating Outcome of Acute Ischemic Stroke Patients Treated With Mechanical Thrombectomy], NCT03496064).

Methods

In 2,011 patients (49.7% female, median age 73 years [61–81]) included between 2009 and 2017, we performed univariate and multivariate analyses regarding the occurrence of FR. FRs were defined as 90-day modified Rankin Scale (mRS) score 4–6 despite successful recanalization in patients selected by MRI (n = 690) and CT (n = 1,321) with a sensitivity analysis considering only patients with mRS 5–6 as futile.

Results

MRI as compared to CT resulted in similar rates of subsequent MT (adjusted odds ratio [aOR] 1.048, 95% confidence interval [CI] 0.677–1.624). Rates of FR were as follows: 571/1,489 (38%) FR mRS 4–6 including 393/1,489 (26%) FR mRS 5–6. CT-based selection was associated with increased rates of FRs compared to MRI (44% [41%–47%] vs 29% [25%–32%], p < 0.001; aOR 1.77 [95% CI 1.25–2.51]). These findings were robust in sensitivity analysis. MRI-selected patients had a delay of approximately 30 minutes in workflow metrics in real-world university comprehensive stroke centers. However, functional outcome and mortality were more favorable in patients selected by MRI compared to patients selected with CT.

Conclusions

CT selection for MT was associated with an increased risk of FRs as compared to MRI selection. Efforts are needed to shorten workflow delays in MRI patients. Further research is needed to clarify the role of the initial imaging modality on FR occurrence and to develop a reliable FR prediction algorithm.

Wake-up stroke: imaging-based diagnosis and recanalization therapy

Wake-up stroke (WUS) is a subgroup of ischemic stroke in which patients show no abnormality before sleep while wake up with neurological deficits. In addition to the uncertain onset, WUS patients have difficulty to receive prompt and effective thrombolytic or reperfusion therapy, leading to relatively poor prognosis. A number of researches have indicated that CT or MRI based thrombolysis and endovascular therapy might have benefits for WUS patients. This review article narratively discusses the pathogenesis, risk factors, imaging-based diagnosis and recanalization treatments of WUS with the purpose of expanding current treatment options for this group of stroke patients and exploring better therapeutic methods. The result showed that multimodal MRI or CT scan might be the best methods for extending the time window of WUS and, therefore, a large proportion of WUS patients could have favorable prognosis.

Magnetic Resonance Imaging Versus Computed Tomography Angiography Based Selection for Endovascular Therapy in Patients With Acute Ischemic Stroke

Background and Purpose- Randomized trials comparing the use of multimodal magnetic resonance imaging (MRI) to multimodal computed tomography (CT)/ CT angiography (CTA) for selecting candidates for endovascular therapy (EVT) have not been reported. This study aimed to elucidate whether MRI-based selection for EVT is safe and effective within and after a 6-hour time window compared with conventional CTA-based selection. Methods- Data from a prospective, nationwide, multicenter stroke registry were analyzed. Workflow timelines were compared between patients selected for EVT based on MRI (the MRI group) and CTA (the CTA group). Multivariable ordinal and binary logistic regression analyses were performed to explore the relationships between decision imaging for EVT and clinical outcomes, including good and excellent outcomes (modified Rankin Scale scores of 0-2 and 0-1, respectively) at 3-month, modified Rankin Scale score distributions and safety outcomes (symptomatic intracranial hemorrhage [SICH] and mortality). Results- Ultimately, 1265 patients (age, 69±12 yrs; men, 55%) were enrolled in this study. The median National Institutes of Health Stroke Scale score was 15 (11-19). All workflow time metrics were significantly delayed in the MRI group compared with the CTA group. There was no difference in good 3-month outcomes in patients arriving within 6 hours of onset between the MRI and CTA groups (38.1% versus 38.5%), but SICH and mortality rates were lower in the MRI group than the CTA group (3.8% versus 7.7%, P=0.01 for SICH; 15.4% versus 20.9%, P=0.04 for mortality). In the multivariable analysis, decision imaging was not significantly associated with 3-month functional outcomes (all P>0.1) or mortality ( P=0.051); however, the MRI group was less likely to develop SICH than the CTA group ( P=0.01; odds ratio, 0.34 [95% CI, 0.17-0.77]). Conclusions- Our study found MRI-based selection for EVT was not associated with improving functional outcome compared with CT-based selection, but may be better at reducing the risk of SICH, despite the delays in all workflow time metrics.

[Acute treatment of ischemic stroke : Current standards]

Important milestones of acute ischemic stroke (AIS) treatment were achieved in recent years. The results of two randomized controlled trials revealed that intravenous thrombolysis is efficacious for treatment of AIS patients with a symptom onset <9 h or an unknown time of symptom onset in the presence of beneficial patterns in advanced stroke imaging. These patterns comprise the evidence of salvageable tissue at risk of infarction in perfusion of computed tomography (so-called penumbral imaging) or a mismatch between the diffusion-weighted imaging (DWI) und fluid-attenuated inversion recovery (FLAIR) sequences in magnetic resonance imaging (so-called DWI-FLAIR mismatch). Another two randomized controlled trials resulted in evidence of a high effectiveness of mechanical thrombectomy using advanced imaging of selected AIS patients with a symptom onset <24 h or an unknown time window. This article provides an overview of the current study results and recommendations for the selection of imaging for evidence-based effective acute treatment of stroke patients.

Ischemic stroke subtype is associated with outcome in thrombolyzed patients

OBJECTIVES

The impact of ischemic stroke subtype on clinical outcome in patients treated with intravenous tissue-type plasminogen activator (IV-tPA) is sparsely examined. We studied the association between stroke subtype and clinical outcome in magnetic resonance imaging (MRI)-evaluated patients treated with IV-tPA.

MATERIAL AND METHODS

We conducted a single-center retrospective analysis of MRI-selected stroke patients treated with IV-tPA between 2004 and 2010. The Trial of ORG 10172 in Acute Stroke Treatment criteria were used to establish the stroke subtype by 3 months. The outcomes of interest were a 3-month modified Rankin Scale score of 0-1 (favorable outcome), and early neurological improvement defined as complete remission of neurological deficit or improvement of ≥4 on the National Institute of Health Stroke Scale at 24 h. The outcomes among stroke subtypes were compared with multivariable logistic regression.

RESULTS

Among 557 patients, 202 (36%) had large vessel disease (LVD), 153 (27%) cardioembolic stroke (CE), 109 (20%) small vessel disease, and 93 (17%) were of other or undetermined etiology. Early neurological improvement was present in 313 (56.4%) patients, and 361 (64.8%) patients achieved a favorable outcome. Early neurological improvement and favorable outcome were more likely in CE patients compared with LVD patients (odds ratio (OR), 2.1 (95% confidence interval, 1.4-3.3), and 2.0 (95% confidence interval, 1.2-3.3), respectively).

CONCLUSIONS

Cardioembolic stroke patients were more likely to achieve early neurological improvement and favorable outcome compared with LVD stroke following MRI-based IV-tPA treatment. This finding may reflect a difference in the effect of IV-tPA among stroke subtypes.

MRI based thrombolysis for FLAIR-negative stroke patients within 4.5-6h after symptom onset

To investigate the feasibility of DWI-FLAIR mismatch in identifying patients who might benefit from thrombolytic therapy within 4.5-6h, we analyzed the data of 105 ischemic stroke patients with known time of symptom onset who underwent MRI within 6h of stroke and thrombolysis between December 2006 and December 2013. They were divided into three groups: symptom onset within 4.5h (n=66); 4.5-6h and FLAIR images negative (n=9); and 4.5-6h and FLAIR images positive (n=30). Outcome of thrombolysis was assessed for each group by recanalization rate, National Institutes of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS) scores. The results showed that mismatch between positive DWI and negative FLAIR images identified patients within 4.5h of symptom onset with sensitivity, specificity, positive predictive value and negative predictive value of 40.9%, 76.9%, and 75% and 43.5%. Recanalization rate, NIHSS score and mRS score were all better in both the 0-4.5h and 4.5-6h FLAIR-negative groups than in the 4.5-6h FLAIR-positive group (p<0.05). These data demonstrate that within 4.5-6h of symptom onset, patients with negative FLAIR images may benefit from thrombolysis therapy.

Desmoteplase for Acute Ischemic Stroke within 3 to 9 Hours after Symptom Onset: Evidence from Randomized Controlled Trials

Recent studies have shown inconsistent results regarding the value of desmoteplase for treating acute ischemic stroke (AIS) when administered within an extended time window. We performed a meta-analysis to explore the value of desmoteplase in AIS treatment. The MEDLINE, EMBASE, and Cochrane Library databases were searched for randomized controlled trials (RCTs) that had evaluated desmoteplase versus placebo for AIS. The primary outcomes were intracranial hemorrhage (ICH) within 72 hours and favorable outcome at Day 90. We pooled 819 patients from 5 RCTs. Desmoteplase treatment showed a neutral effect on favorable outcome (P = 0.42) but a favorable safety profile in terms of ICH (P = 0.64) compared with the placebo group. In the subgroup analysis, 90 μg/kg desmoteplase, a late time to treatment (6–9 hours), and serious stroke symptoms at baseline (NIHSS > 12) subgroups showed high risks of ICH (P ≤ 0.02). A high dose of desmoteplase (125 μg/kg) showed a tendency to improve recanalization (P = 0.05), but was also associated with an increased risk of death (P = 0.04). In conclusion, desmoteplase administered over an extended time window had no significant effect on functional recovery but exhibited a favorable safety profile in patients with AIS.

A Retrospective Study of thrombolysis with 0.6 mg/kg Recombinant Tissue Plasminogen Activator (rt-PA) in Mild Stroke

We sought to assess the safety, effectiveness and cost of 0.6 mg/kg rt-PA treatment for patients with acute mild stroke and to compare that with 0.9 mg/kg. We retrospectively analyzed consecutive acute ischemic stroke patients who had a NIHSS score ≤5 at admission and who were treated with rt-PA within 4.5 hours of symptom onset. The demographic data, clinical outcomes and hospitalization cost were analyzed. A total of 108 patients were included. Forty six patients (42.6%) received a 0.6 mg/kg dosage of rt-PA. The baseline characteristics of the two groups were well matched (p > 0.05). Regarding the safety and effectiveness, the 0.6 mg/kg dosage group had a comparable proportion of symptomatic intracranial hemorrhage (sICH) (0.6 mg/kg, 4.3% vs 0.9 mg/kg, 4.8%; p > 0.05), early neurological deterioration (END) (19.6% vs 17.7%; p > 0.05), in-hospital mortality (4.3% vs 1.6%; p > 0.05), and a similar rate of favorable functional outcome (mRS score 0–1) at 3 months (73.9% vs 71.0%; p > 0.05) to those who received the standard dosage. However, the hospital cost was markedly lower in the 0.6 mg/kg group (0.6  mg/kg, 3,401.7 USD vs 0.9  mg/kg, 4,157.4 USD; p < 0.01). Our study suggest that 0.6 mg/kg rt-PA shared similar effectiveness and safety profile compared with that of 0.9 mg/kg in treating mild stroke, but cost less.

[Invasive stroke treatment - Study results and clinical routine : Lost in translation?]

OBJECTIVE

How can the overwhelmingly positive results of the five randomized thrombectomy trials published in 2015 be transferred to the clinical routine?

MATERIAL AND METHODS

Analysis of trial-specific characteristics with regard to implementation of mechanical thrombectomy into clinical routine.

RESULTS

Stroke patients with symptomatic proximal artery occlusion are principally eligible for mechanical thrombectomy; however, the stroke patients included in the thrombectomy trials are not representative of all stroke patients. They were carefully selected according to clinical and imaging criteria as well as to the time window from symptom onset. Furthermore, they were treated in highly selected specialized stroke centers. Analysis of the five trials and the Catalan population-based SONIIA registry revealed that the observed number needed to treat (NNT) of 5 to reach a modified Rankin scale (mRS) score of 0-2 only applies to approximately 1 % of all stroke patients. The NNT for the remaining patients who are principally eligible for thrombectomy requires further study. Currently, centralization seems to be useful to facilitate mechanical thrombectomy in routine care leading to several problems that have to be dealt with in particular regions. Secondary transport to thrombectomy centers plays a major role in this context and has to be provided with highest priority.

CONCLUSION

Only careful analysis of study results and the background circumstances will enable adequate organization and successful practical implementation of this highly effective therapy in the clinical routine. Regional conditions have to be considered and will be crucial in this context.

Stroke- on- Awakening: Safety of CT-CTA Based Selection for Reperfusion Therapy

BACKGROUND

We studied the safety of use of acute reperfusion therapies in patients with stroke- on- awakening using a computed tomographic angiography (Cta) based large vessel occlusion-good scan paradigm in clinical routine.

METHODS

the Cta database of the Calgary stroke program was reviewed for the period January 2003-March 2010. patients with stroke-on-awakening with large artery occlusions on Cta, who received conservative, iV thrombolytic and/or endovascular treatment at discretion of the attending stroke neurologist were analyzed. time of onset was defined by the time last seen or known to be normal. Baseline non-contrast Ct scan (nCCt) alberta Stroke program early Ct Score (aSpeCtS) > 7 was considered a good scan. hemorrhage was defined on follow-up brain imaging using eCaSS 3 criteria. independence (mrS≤2) at three months was considered a good clinical outcome. Standard descriptive statistics and multivariable analysis were done.

RESULTS

among 532 patients with large artery occlusions, 70 patients with stroke-on-awakening (13.1%) were identified. the median age was 69.5 (iQr 24) and 41 (58.6%) were female; 41 (58.6%) received anti-platelets only and 29 (41.4%) received thrombolytic treatment [iV-12 (17.1%), iV/ia-12 (17.1%) and ia-5(7.1%)]. unadjusted analysis showed that baseline nCCt aSpeCtS ≤ 7 (p=0.002) and higher nihSS scores (p=0.018) were associated with worse outcomes. there were no ph2 hemorrhages in the iV thrombolytic or endovascular treated group. functional outcome was not different by treatment.

CONCLUSION

When carefully selected using Ct –Cta, by a good scan (aSpeCtS > 7) occlusion paradigm, acute reperfusion therapies in patients with stroke-on-awakening can be performed safely in clinical routine.

Diffusion tensor imaging and functional MRI

The advances in diffusion-weighted imaging (DWI), diffusion tensor imaging (DTI), and functional magnetic resonance imaging (fMRI) over the last 20 years have vastly contributed to improving the understanding of the brain structure and function in patients with many diseases of the central nervous system (CNS). DWI is commonly used, for instance, in the diagnostic workup of stroke, CNS neoplasia, and rapidly progressive dementia cases. The new DTI methods provide more specific information about the most destructive aspects of tumors, neurodegenerative dementia, and multiple sclerosis pathology and give a more complete picture of the complex pathologic mechanisms of these conditions. More recently, fMRI has provided insight to the mechanisms of brain adaptation and plasticity to damage related to many neurologic conditions and has further extended our ability to understand the functional significance of pathologic changes in these diseases. Although at present fMRI does not have a role in the diagnosis, routine assessment, and monitoring of neurologic diseases, significant efforts are under way in order to achieve harmonization of both acquisition and postprocessing procedures, which are likely to contribute to a significant change of the clinical scenario.

Physiologic imaging in acute stroke: Patient selection

Treatment of acute stroke is changing, as endovascular intervention becomes an important adjunct to tissue plasminogen activator. An increasing number of sophisticated physiologic imaging techniques have unique advantages and applications in the evaluation, diagnosis, and treatment-decision making of acute ischemic stroke. In this review, we first highlight the strengths, weaknesses, and possible indications for various stroke imaging techniques. How acute imaging findings in each modality have been used to predict functional outcome is discussed. Furthermore, there is an increasing emphasis on using these state-of-the-art imaging modalities to offer maximal patient benefit through IV therapy, endovascular thrombolytics, and clot retrieval. We review the burgeoning literature in the determination of stroke treatment based on acute, physiologic imaging findings.

MRI-guided selection of patients for treatment of acute ischemic stroke

PURPOSE OF REVIEW

To summarize what is known about the use of MRI in acute stroke treatment (predominantly thrombolysis), to examine the assumptions and theories behind the interpretation of magnetic resonance images of acute ischemic stroke and how they are used to select patients for therapies, and to suggest directions for future research.

RECENT FINDINGS

Recent studies have been contradictory about the usefulness of MRI in selecting patients for treatment. New MRI models for selecting patients have emerged that focus not only on the ischemic penumbra but also on the infarct core. Fixed time-window selection parameters are being replaced by timing-based individualized MRI stroke features. New ways to interpret traditional MRI stroke sequences are emerging.

SUMMARY

Although the efficacy of acute stroke treatment is time dependent, the use of fixed time windows cannot account for individual differences in infarct evolution, which could potentially be detected with MRI. Although MRI shows promise for identifying patients who should be treated, as well as excluding patients who should not be treated, definitive evidence is still lacking. Future research should focus on validating the use of MRI to select patients for intravenous therapies in extended time windows.

Sensitivity of diffusion- and perfusion-weighted imaging for diagnosing acute ischemic stroke is 97.5%

BACKGROUND AND PURPOSE

MRI using diffusion-weighted imaging (DWI) is the most sensitive diagnostic imaging modality for early detection of ischemia, but how accurate is it and how much does perfusion-weighted imaging (PWI) add to the sensitivity have to be known.

METHODS

In this single-center study, we collected epidemiological, imaging, and outcome data on all patients with stroke undergoing MRI-based treatment with intravenous tissue-type plasminogen activator at our center from 2004 to 2010. The DWI negative patients were identified, and we calculated the sensitivity and specificity of DWI and additional PWI for diagnosing acute ischemic stroke. We compared DWI positive and negative patients to identify characteristics associated with DWI negativity.

RESULTS

Five hundred sixty-nine consecutive patients were treated with intravenous tissue-type plasminogen activator on the basis of an acute MRI. A DWI lesion was evident in 518 patients. Forty-seven patients were DWI negative; however, a relevant PWI lesion was found in 33 of these patients. Four stroke mimics were treated with intravenous tissue-type plasminogen activator and 1 of these patients had a DWI lesion. Thus, 8% of all patients with stroke were DWI negative. The combination of DWI and PWI resulted in a sensitivity of 97.5% for the ischemic stroke diagnosis. DWI negativity was associated with less severe strokes, location in the posterior circulation, a longer time from onset to scan, and an improved 90-day outcome. The cause of small-vessel disease was more likely to be DWI negative.

CONCLUSIONS

The combination of DWI and PWI before intravenous tissue-type plasminogen activator confirms the diagnosis in 97.5% of all ischemic strokes.

Perfusion CT for selecting patients with acute ischemic stroke for intravenous thrombolytic therapy

PURPOSE

To determine rates of death, disability, and symptomatic intracranial hemorrhage ( SICH symptomatic ICH ) among patients with acute ischemic stroke selected for thrombolytic therapy by using perfusion computed tomography (CT) by conducting a systematic review and meta-analysis.

MATERIALS AND METHODS

A search of the literature up to July 2012 was performed by using MEDLINE, EMBASE, the Cochrane Library, PubMed, and Google Scholar on terms including "brain ischemia" and "perfusion imaging." The search was unrestricted by language of publication. Two reviewers extracted study data and independently assessed the risk of study bias. Outcomes of patients selected by using perfusion CT, including case-fatality rate, favorable outcome (modified Rankin Scale [ mRS modified Rankin Scale ] score, ≤2), and rates of SICH symptomatic ICH , were estimated.

RESULTS

Thirteen experimental or observational studies that included patients who received intravenous thrombolytic treatment after perfusion CT were identified. The methodologic quality of the small studies was generally good. Overall, 90-day mortality was 10.0% (95% confidence interval [ CI confidence interval ]: 5.4%, 15.9%). Among patients treated within 3 hours of symptom onset, mortality was 12.5% (95% CI confidence interval : 6.7%, 19.7%), a favorable outcome ( mRS modified Rankin Scale score, ≤2) was seen in 42.5% of patients (95% CI confidence interval : 16.6%, 70.9%), and the SICH symptomatic ICH rate was 3.3% (95% CI confidence interval : 0.7%, 7.7%). Among patients treated more than 3 hours after symptom onset, mortality was 2.9% (95% CI confidence interval : 0.0%, 12.7%), 69.9% of patients (95% CI confidence interval : 0%, 83.5%) had a favorable outcome, and the SICH symptomatic ICH rate was 3.9% (95% CI confidence interval : 0.8%, 9.2%).

CONCLUSION

The outcomes (mortality, morbidity, and SICH symptomatic ICH rates) for patients selected with perfusion CT to receive intravenous thrombolytic treatment more than 3 hours after symptom onset appear favorable.

MRI before intraarterial therapy in ischemic stroke: feasibility, impact, and safety

Intraarterial therapy (IAT) in acute ischemic stroke is effective for opening occlusions of major extracranial or intracranial vessels. Clinical efficacy data are lacking pointing to a need for proper patient selection. We examined feasibility, clinical impact, and safety profile of magnetic resonance imaging (MRI) for patient selection before IAT. In this single-center study, we collected epidemiologic, imaging, and outcome data on all intraarterial-treated patients presenting with anterior circulation occlusions at our center from 2004 to 2011. Magnetic resonance imaging was the first imaging choice. Computer tomography (CT) was performed in the presence of a contraindication. We treated 138 patients. Mean age was 64 years and median National Institutes of Health Stroke Scale (NIHSS) was 17. Major reperfusion (thrombolysis in cerebral infarction (TICI) 2b+3) was achieved in 52% and good outcome defined as modified Rankin Scale (mRS) score 0 to 2 at 90 days was achieved in 41%. Mortality at 90 days was 10%. There was only one symptomatic hemorrhage. Recanalization, age, and stroke severity were associated with outcome. Preprocedure MRI was obtained in 83%. Good outcome was significantly associated with smaller diffusion-weighted imaging (DWI) lesion size at presentation and not with the size of the perfusion lesion. It is feasible to triage patients for IAT using MRI with acceptable rates of poor outcome and symptomatic hemorrhage.

Efficacy of systemic thrombolysis within 4.5 h from stroke symptom onset: a single-centre clinical and diffusion-perfusion 3T MRI study

PURPOSE

The efficacy of thrombolytic treatment with recombinant tissue plasminogen activator (rt-PA) within 3 h from stroke onset has been extensively supported by randomised placebo-controlled multicentre trials. In our single-centre study, we investigated the efficacy of intravenous (IV) administration of rt-PA within 4.5 h of stroke onset, in terms of clinical and radiological outcome, using a 3T magnetic resonance (MR) scanner in a cohort of patients similar to that of multicentre clinical trials.

MATERIALS AND METHODS

Consecutive patients treated with IV rt-PA were compared with an historical cohort of untreated patients (controls). Inclusion criteria were: (1) infarction of the middle cerebral artery territory, (2) eligibility for IV rt-PA treatment, and (3) 3T perfusion- and diffusion-weighted MR imaging and MR angiography performed within 4.5 h and repeated after 5-7 days. Stroke severity was assessed with the National Institutes of Health Stroke Scale (NIHSS). Growth of the DWI lesion, saved hypoperfused tissue, and clinical outcome was assessed and compared in treated patients and controls.

RESULTS

Forty-three patients treated with rt-PA and 69 controls were eligible for the analysis. Treated patients showed higher percentages of saved hypoperfused tissue (75 vs. 40 %; p = 0.009), vessel recanalisation (65 vs. 27.5%; p = 0.003), and haemorrhagic transformation (21 vs. 7%; p = 0.004), without any clinically significant haemorrhages. Furthermore, treated patients had a significant improvement of NIHSS at 24 h (p < 0.001), at discharge (p ≤ 0.001), and at the 3-month clinical evaluation (p < 0.001), while similar rates of both treated patients and controls achieved a 3-month modified Rankin scale ≤ 2 (62 and 65%; p = 0.7).

CONCLUSION

Treatment with IV rt-PA within 4.5 h of stroke onset preserves a significant amount of brain tissue from final infarction, and increases the possibility of early and late clinical improvement.

Endovascular treatment of acute ischemic stroke

Endovascular stroke therapy has revolutionized the management of patients with acute ischemic stroke in the last decade and has facilitated the development of sophisticated stroke imaging techniques and a multitude of thrombectomy devices. This article reviews the scientific basis and current evidence available to support endovascular revascularization and provides brief technical details of the various methods of endovascular thrombectomy with case examples.

Advanced neuroimaging to guide acute stroke therapy

Traditionally non-contrast CT has been considered the first choice imaging modality for acute stroke. Acute ischemic stroke patients presenting to the hospital within 3-hours from symptom onset and without any visible hemorrhages or large lesions on CT images are considered optimum reperfusion therapy candidates. However, non-contrast CT alone has been unable to identify best reperfusion therapy candidates outside this window. New advanced imaging techniques are now being used successfully for this purpose. Non-invasive CT or MR angiography images can be obtained during initial imaging evaluation for identification and characterization of vascular lesions, including occlusions, aneurysms, and malformations. Either CT-based perfusion imaging or MRI-based diffusion and perfusion imaging performed immediately upon arrival of a patient to the hospital helps estimate the extent of fixed core and penumbra in ischemic lesions. Patients having occlusive lesions with small fixed cores and large penumbra are preferred reperfusion therapy candidates.

CT perfusion-guided patient selection for endovascular recanalization in acute ischemic stroke: a multicenter study

BACKGROUND

The treatment of acute ischemic stroke is traditionally centered on time criteria, although recent evidence suggests that physiologic neuroimaging may be useful. In a multicenter study we evaluated the use of CT perfusion, regardless of time from symptom onset, in patients selected for intra-arterial treatment of ischemic stroke.

METHODS

Three medical centers retrospectively assessed stroke patients with a National Institute of Health Stroke Scale of ≥ 8, regardless of time from symptom onset. CT perfusion maps were qualitatively assessed. Patients with defined salvageable penumbra underwent intra-arterial revascularization of their occlusion. Functional outcome using the modified Rankin Score (mRS) was recorded.

RESULTS

Two hundred and forty-seven patients were selected to undergo intra-arterial treatment based on CT perfusion imaging. The median time from symptom onset to procedure was 6 h. Patients were divided into two groups for analysis: ≤ 8 h and >8 h from symptom onset to endovascular procedure. We found no difference in functional outcome between the two groups (42.8% and 41.9% achieved 90-day mRS ≤ 2, respectively (p=1.0), and 54.9% vs 55.4% (p=1.0) achieved 90-day mRS ≤ 3, respectively). Overall, 48 patients (19.4%) had hemorrhages, of which 20 (8.0%) were symptomatic, with no difference between the groups (p=1.0).

CONCLUSIONS

In a multicenter study, we demonstrated similar rates of good functional outcome and intracranial hemorrhage in patients with ischemic stroke when endovascular treatment was performed based on CT perfusion selection rather than time-guided selection. Our findings suggest that physiologic imaging-guided patient selection rather than time for endovascular reperfusion in ischemic stroke may be effective and safe.

Selection of possible responders to thrombolytic therapy in acute ischemic stroke

Ischemic stroke is one of the leading causes of death and morbidity worldwide, and systemic thrombolytic treatment is still the first-line therapy within 4.5 h from symptom onset. Selecting patients for treatment response is mandatory in any time window but challenging as well. The authors aim to support stroke physicians in their individual decision making. Besides evidence from clinical trials, some suggestions included here exclusively reflect the authors' opinions. This article presents clinical and imaging criteria of selecting patients reasonably, offering causal therapy to a growing number of patients.

Automated vs manual delineations of regions of interest- a comparison in commercially available perfusion MRI software

Background

In perfusion magnetic resonance imaging a manual approach to delineation of regions of interest is, due to rater bias and time intensive operator input, clinically less favorable than an automated approach would be. The goal of our study was to compare the performances of these approaches.

Methods

Using Stroketool, PMA and Perfscape/Neuroscape perfusion maps of cerebral blood flow, mean transit time and Tmax were created for 145 patients with acute ischemic stroke. Volumes of hypoperfused tissue were calculated using both a manual and an automated protocol, and the results compared between methods.

Results

The median difference between the automatically and manually derived volumes was up to 210 ml in Perfscape/Neuroscape, 123 ml in PMA and 135 ml in Stroketool. Correlation coefficients between perfusion volumes and radiological and clinical outcome were much lower for the automatic volumes than for the manually derived ones.

Conclusions

The agreement of the two methods was very poor, with the automated use producing falsely exaggerated volumes of hypoperfused tissue. Software improvements are necessary to enable highly automated protocols to credibly assess perfusion deficits.

Current acute stroke trials and their potential impact on the therapeutic time window

Several trials in acute stroke are underway or have been completed recently. Among the latter, ECASS 3 was a milestone regarding the extension of the rigid 3-h time window out to 4.5 h for intravenous thrombolysis with recombinant tissue plasminogen activator. Several other approaches are being tested for thrombolytic therapy, among them modern imaging-based patient selection of patients and interventional approaches. Other pharmaceutical strategies include neuroprotection, and restoration, biophysical approaches, such as near infrared laser therapy, hemodynamic augmentation, and sphenopalatine ganglion stimulation. This perspective will cover the recently completed and currently recruiting acute stroke trials with respect to their potential role in expanding the therapeutic time window for acute ischemic stroke.

Preclinical stroke research--advantages and disadvantages of the most common rodent models of focal ischaemia

This review describes the most commonly used rodent models and outcome measures in preclinical stroke research and discusses their strengths and limitations. Most models involve permanent or transient middle cerebral artery occlusion with therapeutic agents tested for their ability to reduce stroke-induced infarcts and improve neurological deficits. Many drugs have demonstrated preclinical efficacy but, other than thrombolytics, which restore blood flow, none have demonstrated efficacy in clinical trials. This failure to translate efficacy from bench to bedside is discussed alongside achievable steps to improve the ability of preclinical research to predict clinical efficacy: (i) Improvements in study quality and reporting. Study design must include randomization, blinding and predefined inclusion/exclusion criteria, and journal editors have the power to ensure statements on these and mortality data are included in preclinical publications. (ii) Negative and neutral studies must be published to enable preclinical meta-analyses and systematic reviews to more accurately predict drug efficacy in man. (iii) Preclinical groups should work within networks and agree on standardized procedures for assessing final infarct and functional outcome. This will improve research quality, timeliness and translational capacity. (iv) Greater uptake and improvements in non-invasive diagnostic imaging to detect and study potentially salvageable penumbral tissue, the target for acute neuroprotection. Drug effects on penumbra lifespan studied serially, followed by assessment of behavioural outcome and infarct within in the same animal group, will increase the power to detect drug efficacy preclinically. Similar progress in detecting drug efficacy clinically will follow from patient recruitment into acute stroke trials based on evidence of remaining penumbra.

[Indications for thrombolysis in ischemic stroke]

Cerebral MRI with angio-MR are more effective than CT scan for selecting patients with ischemic stroke for thrombolysis. The use of cerebral MRI has to be available 24h a day and everyday as a standardized emergency procedure. Off-label criteria for thrombolysis after acute ischemic stroke are too restritive and have to be revised. In acute ischemic stroke, imaging that shows the collateral circulation within the hypoperfusion area has to be used to estimate the potential of therapeutic revascularization. When there are contraindications for intravenous thrombolysis, the endovascular approach must be argued individually by neurologists and neurointerventionalists together.

Acute ischemic stroke: infarct core estimation on CT angiography source images depends on CT angiography protocol

PURPOSE

To test whether the relationship between acute ischemic infarct size on concurrent computed tomographic (CT) angiography source images and diffusion-weighted (DW) magnetic resonance images is dependent on the parameters of CT angiography acquisition protocols.

MATERIALS AND METHODS

This retrospective study had institutional review board approval, and all records were HIPAA compliant. Data in 100 patients with anterior-circulation acute ischemic stroke and large vessel occlusion who underwent concurrent CT angiography and DW imaging within 9 hours of symptom onset were analyzed. Measured areas of hyperintensity at acute DW imaging were used as the standard of reference for infarct size. Information regarding lesion volumes and CT angiography protocol parameters was collected for each patient. For analysis, patients were divided into two groups on the basis of CT angiography protocol differences (patients in group 1 were imaged with the older, slower protocol). Intermethod agreement for infarct size was evaluated by using the Wilcoxon signed rank test, as well as by using Spearman correlation and Bland-Altman analysis. Multivariate analysis was performed to identify predictors of marked (≥20%) overestimation of infarct size on CT angiography source images.

RESULTS

In group 1 (n=35), median hypoattenuation volumes on CT angiography source images were slightly underestimated compared with DW imaging hyperintensity volumes (33.0 vs 41.6 mL, P=.01; ratio=0.83), with high correlation (ρ=0.91). In group 2 (n=65), median volume on CT angiography source images was much larger than that on DW images (94.8 vs 17.8 mL, P<.0001; ratio=3.5), with poor correlation (ρ=0.49). This overestimation on CT angiography source images would have inappropriately excluded from reperfusion therapy 44.4% or 90.3% of patients eligible according to DW imaging criteria on the basis of a 100-mL absolute threshold or a 20% or greater mismatch threshold, respectively. Atrial fibrillation and shorter time from contrast material injection to image acquisition were independent predictors of marked (≥20%) infarct size overestimation on CT angiography source images.

CONCLUSION

CT angiography protocol changes designed to speed imaging and optimize arterial opacification are associated with significant overestimation of infarct size on CT angiography source images.

Imaging-based treatment selection for intravenous and intra-arterial stroke therapies: a comprehensive review

Reperfusion therapy is the only approved treatment for acute ischemic stroke. The current approach to patient selection is primarily based on the time from stroke symptom onset. However, this algorithm sharply restricts the eligible patient population, and neglects large variations in collateral circulation that ultimately determine the therapeutic time window in individual patients. Time alone is unlikely to remain the dominant parameter. Alternative approaches to patient selection involve advanced neuroimaging methods including MRI diffusion-weighted imaging, magnetic resonance and computed tomography perfusion imaging and noninvasive angiography that provide potentially valuable information regarding the state of the brain parenchyma and the neurovasculature. These techniques have now been used extensively, and there is emerging evidence on how specific imaging data may result in improved clinical outcomes. This article will review the major studies that have investigated the role of imaging in patient selection for both intravenous and intra-arterial therapies.

Safety and clinical outcome of thrombolysis in ischaemic stroke using a perfusion CT mismatch between 3 and 6 hours

OBJECTIVE

It may be possible to thrombolyse ischaemic stroke (IS) patients up to 6 h by using penumbral imaging. We investigated whether a perfusion CT (CTP) mismatch can help to select patients for thrombolysis up to 6 h.

METHODS

A cohort of 254 thrombolysed IS patients was studied. 174 (69%) were thrombolysed at 0-3 h by using non-contrast CT (NCCT), and 80 (31%) at 3-6 h (35 at 3-4.5 h and 45 at 4.5-6 h) by using CTP mismatch criteria. Symptomatic intracerebral haemorrhage (SICH), the mortality and the modified Rankin Score (mRS) were assessed at 3 months. Independent determinants of outcome in patients thrombolysed between 3 and 6 h were identified.

RESULTS

The baseline characteristics were comparable in the two groups. There were no differences in SICH (3% v 4%, p = 0.71), any ICH (7% v 9%, p = 0.61), or mortality (16% v 9%, p = 0.15) or mRS 0-2 at 3 months (55% v 54%, p = 0.96) between patients thrombolysed at 0-3 h (NCCT only) or at 3-6 h (CTP mismatch). There were no significant differences in outcome between patients thrombolysed at 3-4.5 h or 4.5-6 h. The NIHSS score was the only independent determinant of a mRS of 0-2 at 3 months (OR 0.89, 95% CI 0.82-0.97, p = 0.007) in patients treated using CTP mismatch criteria beyond 3 h.

CONCLUSIONS

The use of a CTP mismatch model may help to guide thrombolysis decisions up to 6 h after IS onset.

Blood-brain barrier permeability derangements in posterior circulation ischemic stroke: frequency and relation to hemorrhagic transformation

BACKGROUND

Early disruption of the blood-brain barrier (BBB) due to severe ischemia can be detected by MRI T2* permeability imaging. In middle cerebral artery (MCA) infarction, pretreatment T2* permeability derangements have been found in 22% of patients and are powerful predictors of hemorrhagic transformation after revascularization therapy. The frequency, clinical correlates, and relation to hemorrhagic transformation of permeability derangements in posterior circulation have not been previously explored, and may differ as ischemia volume and collateral status are different between vertebrobasilar and MCA infarcts.

METHODS

We analyzed clinical and pretreatment MRI data on consecutive patients undergoing recanalization therapy for acute vertebrobasilar ischemia at a medical center November 2001 through September 2009. Pretreatment MRI permeability images were derived from perfusion source imaging acquisitions. Permeability abnormality was detected as persisting increased signal intensity at later time points in perfusion MRI acquisition, indicating local accumulation of contrast caused by BBB leakage.

RESULTS

Among the 14 patients meeting study entry criteria, mean age was 71.1 years and median pretreatment NIHSS was 20.5. Permeability imaging abnormality was present in 1 of the 14 patients (7%). Among 14 patients, post-treatment parenchymal hematoma occurred in one and more minor degrees of hemorrhagic transformation in four. The one patient with pretreatment permeability abnormality was the patient to develop post-treatment parenchymal hematoma (Fisher's exact test, P=0.07).

CONCLUSION

Pretreatment permeability abnormality, an indicator of BBB derangements, is an infrequent finding in acute posterior circulation ischemic stroke and may be associated with an increased risk of parenchymal hematoma development undergoing recanalization therapy.

Clinical applications of diffusion MR imaging for acute ischemic stroke

Diffusion magnetic resonance imaging is the best imaging tool for detecting acute ischemic brain injury. Studies have shown its high accuracy for delineating irreversible tissue damage within the first few hours after stroke onset; however, the true value of any diagnostic tool is whether it can be used to guide clinical management. This review discusses the role of diffusion imaging in the evaluation of the patient with acute ischemic stroke, and how this role is influenced by other important stroke-related variables, including the level of vessel occlusion and the clinical deficit. The review focuses on decision-making for intravenous and intra-arterial reperfusion therapies.

Search for a map and threshold in perfusion MRI to accurately predict tissue fate: a protocol for assessing lesion growth in patients with persistent vessel occlusion

BACKGROUND

The MRI-based mismatch concept has been used to estimate the risk of infarction in ischemic stroke. Based on multiple studies on magnetic resonance perfusion imaging, it seems unlikely that any perfusion parameter threshold will provide a reliable prediction of radiological or clinical outcome for all patients. The goal of our study was to find a minimally biased yet maximally useful perfusion postprocessing protocol which would offer the treating physician a useful estimate of tissue fate.

METHODS

One hundred and forty-five acute ischemic stroke patients, admitted within 24 h after stroke to the Charité-University Medicine Hospital in Berlin between March 2008 and November 2009, were included in this study. Using three different software packages (Perfscape/Neuroscape, PMA and Stroketool), maps of mean transit time, cerebral blood flow (CBF) and T(max) were created. Three different thresholds were applied on each parameter map and subsequent volumes of hypoperfused tissue were calculated.

RESULTS

Overall, the maps and thresholds giving the least amount of overestimation of the final infarct volume were T(max) 8 s in Perfscape/Neuroscape, CBF 20 ml/100 g/min in PMA and CBF 15% (of the highest value on the scale for a given patient) in Stroketool. In patients with persistent vessel occlusion, a CBF map with a restrictive threshold showed volumes of tissue at definite risk of infarction in up to 100% of patients. The additional use of a CBF map with a high threshold enabled identification of patients without penumbras.

CONCLUSIONS

No combination of software, map and threshold was able to give a reliable estimate of tissue fate for either all patients or any subgroup of patients. However, in patients with vessel occlusion, combination of a CBF map with a low and a high threshold can enable calculation of the minimum volume of brain tissue that will inevitably be lost if the occlusion persists.

Stroke penumbra defined by an MRI-based oxygen challenge technique: 2. Validation based on the consequences of reperfusion

Magnetic resonance imaging (MRI) with oxygen challenge (T(2)(*) OC) uses oxygen as a metabolic biotracer to define penumbral tissue based on CMRO(2) and oxygen extraction fraction. Penumbra displays a greater T(2)(*) signal change during OC than surrounding tissue. Since timely restoration of cerebral blood flow (CBF) should salvage penumbra, T(2)(*) OC was tested by examining the consequences of reperfusion on T(2)(*) OC-defined penumbra. Transient ischemia (109 ± 20 minutes) was induced in male Sprague-Dawley rats (n=8). Penumbra was identified on T(2)(*)-weighted MRI during OC. Ischemia and ischemic injury were identified on CBF and apparent diffusion coefficient maps, respectively. Reperfusion was induced and scans repeated. T(2) for final infarct and T(2)(*) OC were run on day 7. T(2)(*) signal increase to OC was 3.4% in contralateral cortex and caudate nucleus and was unaffected by reperfusion. In OC-defined penumbra, T(2)(*) signal increased by 8.4% ± 4.1% during ischemia and returned to 3.25% ± 0.8% following reperfusion. Ischemic core T(2)(*) signal increase was 0.39% ± 0.47% during ischemia and 0.84% ± 1.8% on reperfusion. Penumbral CBF increased from 41.94 ± 13 to 116.5 ± 25 mL per 100 g per minute on reperfusion. On day 7, OC-defined penumbra gave a normal OC response and was located outside the infarct. T(2)(*) OC-defined penumbra recovered when CBF was restored, providing further validation of the utility of T(2)(*) OC for acute stroke management.