Correlation of perfusion- and diffusion-weighted MRI with NIHSS score in acute (<6.5 hour) ischemic stroke

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

The role of MRI as a prognostic tool in ischemic stroke

Magnetic resonance imaging (MRI) is an invaluable tool used in the diagnosis of ischemic stroke. Ongoing technological advances in MRI technology and advent of new imaging sequences has now made it possible to use MRI as a prognostic tool both in the acute and chronic stages of cerebral ischemia. This review summarizes the role of MRI in estimating final tissue outcome, specifically by providing information on severity and location of ischemic insult, cerebral blood flow dynamics, vascular status, and cerebral reserve. All of these predictions can then be used to make projections regarding clinical outcome, and can be refined by other prognostic models to estimate recovery and risk of further ischemic events. These algorithms, in the end, can ultimately help the clinician in tailoring therapies on an individual basis and optimize the risk-benefit ratio of therapeutic approaches used in the acute and chronic stages of ischemic stroke. The implementation of such prognostic algorithms to clinical imaging workstations and calculation of all the possible projections within minutes after completion of imaging are likely to become an integral part of clinical practice in the near future.

Identification of modifiable and nonmodifiable risk factors for neurologic deterioration after acute ischemic stroke

BACKGROUND

Neurologic deterioration (ND) after ischemic stroke has been shown to impact short-term functional outcome and is associated with in-hospital mortality.

METHODS

Patients with acute ischemic stroke who presented between July 2008 and December 2010 were identified and excluded for in-hospital stroke, presentation >48 hours since last seen normal, or unknown time of last seen normal. Clinical and laboratory data, National Institutes of Health Stroke Scale (NIHSS) scores, and episodes of ND (increase in NIHSS score ≥ 2 within a 24-hour period) were investigated.

RESULTS

Of the 596 patients screened, 366 were included (median age 65 years; 42.1% female; 65.3% black). Of these, 35.0% experienced ND. Patients with ND were older (69 v 62 years; P < .0001), had more severe strokes (median admission NIHSS score 12 v 5; P < .0001), carotid artery stenosis (27.0% v 16.8%; P = .0275), and coronary artery disease (26.0% v 16.4%; P = .0282) compared to patients without ND. Patients with ND had higher serum glucose on admission than patients without ND (125.5 v 114 mg/dL; P = .0036). After adjusting for crude variables associated with ND, age >65 years, and baseline NIHSS score >14 remained significant independent predictors of ND. In a logistic regression analysis adjusting for age and serum glucose, each 1-point increase in admission NIHSS score was associated with a 7% increase in the odds of ND (odds ratio 1.07; 95% confidence interval 1.04-1.10; P < .0001).

CONCLUSIONS

Older patients and patients with more severe strokes are more likely to experience ND. Initial stroke severity was the only significant, independent, and modifiable risk factor for ND, amenable to recanalization and reperfusion.

Survival and clinical outcome of dogs with ischaemic stroke

The objectives of the present study were to investigate survival time, possible predictors of survival and clinical outcome in dogs with ischaemic stroke. A retrospective study of dogs with a previous diagnosis of ischaemic stroke diagnosed by magnetic resonance imaging (MRI) was performed. The association between survival and the hypothesised risk factors was examined using univariable exact logistic regression. Survival was examined using Kaplan-Meier and Cox regression. Twenty-two dogs were identified. Five dogs (23%) died within the first 30days of the stroke event. Median survival in 30-day survivors was 505days. Four dogs (18%) were still alive by the end of the study. Right-sided lesions posed a significantly increased risk of mortality with a median survival time in dogs with right-sided lesions of 24days vs. 602days in dogs with left sided lesions (P=0.006). Clinical outcome was considered excellent in seven of 17 (41%) 30-day survivors. Another seven 30-day survivors experienced new acute neurological signs within 6-17months of the initial stroke event; in two of those cases a new ischaemic stroke was confirmed by MRI. In conclusion, dogs with ischaemic stroke have a fair to good prognosis in terms of survival and clinical outcome. However, owners should be informed of the risk of acute death within 30days and of the possibility of new neurological events in survivors. Mortality was increased in dogs with right-sided lesions in this study.

Advanced techniques using contrast media in neuroimaging

This article presents an overview of advanced magnetic resonance (MR) imaging techniques using contrast media in neuroimaging, focusing on T2*-weighted dynamic susceptibility contrast MR imaging and T1-weighted dynamic contrast-enhanced MR imaging. Image acquisition and data processing methods and their clinical application in brain tumors, stroke, dementia, and multiple sclerosis are discussed.

Medical image analysis methods in MR/CT-imaged acute-subacute ischemic stroke lesion: Segmentation, prediction and insights into dynamic evolution simulation models. A critical appraisal

Over the last 15 years, basic thresholding techniques in combination with standard statistical correlation-based data analysis tools have been widely used to investigate different aspects of evolution of acute or subacute to late stage ischemic stroke in both human and animal data. Yet, a wave of biology-dependent and imaging-dependent issues is still untackled pointing towards the key question: "how does an ischemic stroke evolve?" Paving the way for potential answers to this question, both magnetic resonance (MRI) and CT (computed tomography) images have been used to visualize the lesion extent, either with or without spatial distinction between dead and salvageable tissue. Combining diffusion and perfusion imaging modalities may provide the possibility of predicting further tissue recovery or eventual necrosis. Going beyond these basic thresholding techniques, in this critical appraisal, we explore different semi-automatic or fully automatic 2D/3D medical image analysis methods and mathematical models applied to human, animal (rats/rodents) and/or synthetic ischemic stroke to tackle one of the following three problems: (1) segmentation of infarcted and/or salvageable (also called penumbral) tissue, (2) prediction of final ischemic tissue fate (death or recovery) and (3) dynamic simulation of the lesion core and/or penumbra evolution. To highlight the key features in the reviewed segmentation and prediction methods, we propose a common categorization pattern. We also emphasize some key aspects of the methods such as the imaging modalities required to build and test the presented approach, the number of patients/animals or synthetic samples, the use of external user interaction and the methods of assessment (clinical or imaging-based). Furthermore, we investigate how any key difficulties, posed by the evolution of stroke such as swelling or reperfusion, were detected (or not) by each method. In the absence of any imaging-based macroscopic dynamic model applied to ischemic stroke, we have insights into relevant microscopic dynamic models simulating the evolution of brain ischemia in the hope to further promising and challenging 4D imaging-based dynamic models. By depicting the major pitfalls and the advanced aspects of the different reviewed methods, we present an overall critique of their performances and concluded our discussion by suggesting some recommendations for future research work focusing on one or more of the three addressed problems.

MR perfusion imaging in acute ischemic stroke

Magnetic resonance (MR) perfusion imaging offers the potential for measuring brain perfusion in acute stroke patients, at a time when treatment decisions based on these measurements may affect outcomes dramatically. Rapid advancements in both acute stroke therapy and perfusion imaging techniques have resulted in continuing redefinition of the role that perfusion imaging should play in patient management. This review discusses the basic pathophysiology of acute stroke, the utility of different kinds of perfusion images, and research on the continually evolving role of MR perfusion imaging in acute stroke care.

Association of laterality and size of perfusion lesions on neurological deficit in acute supratentorial stroke

BACKGROUND

The influence of lesion size and laterality on each component of the National Institutes of Health Stroke Scale has not been delineated. The objective of this study was to use perfusion-weighted imaging to characterize the association of ischaemic volume and laterality on each component item and the total score of the <National Institutes of Health Stroke Scale.

METHODS

We analysed consecutive right-handed patients with first-ever supratentorial acute ischaemic strokes who underwent acute perfusion-weighted imaging at a single centre. Perfusion deficits were defined as mean transit time > 10 s. Ordinal regression was used to clarify the relationship between ischaemic volume, laterality, and <National Institutes of Health Stroke Scale scores.

RESULTS

Among 111 patients, 58 were left-hemisphere stroke, and 53 right-hemisphere stroke. Median ischaemic volume was 53 ml in left-hand stroke and 65 ml in right-hand stroke and median total National Institutes of Health Stroke Scale was 10 in left-hand stroke and eight in right-hand stroke. For individual National Institutes of Health Stroke Scale items, ischaemic volume correlated most closely with commands and visual field and most weakly with ataxia and neglect. Left-hand stroke predicted higher scores of total National Institutes of Health Stroke Scale and National Institutes of Health Stroke Scale items of questions, commands, right limb weakness, and language. Right-hand stroke predicted higher scores of left limb weakness and extinction.

CONCLUSIONS

Larger perfusion defects contribute to higher scores on the total and most individual items of the National Institutes of Health Stroke Scale. However, lesion laterality contributes substantially to half the item scores, with greater association of left than right-brain side. These findings indicate that imaging-deficit correlations will be improved by designating lesions into an atlas, taking into account side in addition to size.

Ischemic involvement of the primary motor cortex is a prognostic factor in acute stroke

BACKGROUND

The location of the primary motor cortex can be detected in healthy adults using the findings of 'T2 hypointensity' and the 'double layer sign' on 3 T diffusion-weighted imaging. The aim of this study was to assess whether ischemic involvement of the primary motor cortex can be identified on 3 T diffusion-weighted imaging within six-hours after stroke onset and to evaluate whether this finding could predict clinical outcome three-months after ischemic stroke.

METHODS

Sixty-five patients who had paralysis and ischemia of the anterior circulation underwent 3 T magnetic resonance imaging within six-hours of symptom onset. Follow-up MRI was obtained at 72 h. Anatomic localization and ischemic involvement of the primary motor cortex were evaluated on diffusion-weighted imaging by two investigators. Ischemic involvement on the primary motor cortex was classified into three grades. Ischemic lesion volumes were measured. We compared the favorable outcomes at three-months between subjects with and without ischemic involvement on the primary motor cortex using the NIHSS and modified Rankin Scale.

RESULTS

Ischemic involvement on the primary motor cortex was identified in 52% of patients. Interrater agreement coefficients were 0·93 for the identification of ischemic involvement of primary motor cortex. As defined by scores on the modified Rankin Scale, among the patients with ischemic involvement of the primary motor cortex were worse than the patients without ischemic involvement of the primary motor cortex (P = 0·01). The mean ischemic lesion volume at baseline diffusion-weighted imaging was 38·7 ± 41·7 cm(3) and was 89·8 ± 93·6 cm(3) at follow-up T2-WI. Ischemic involvement on the primary motor cortex (odds ratio: 14·7) was a determinant for worse outcome.

CONCLUSIONS

3T diffusion-weighted imaging can identify ischemic involvement on the primary motor cortex and may provide useful information for predicting outcome during the hyperacute stage. Ischemic involvement on the primary motor cortex has a significant negative impact on recovery.

Application of beta regression to analyze ischemic stroke volume in NINDS rt-PA clinical trials

BACKGROUND AND PURPOSE

Ischemic stroke lesion volumes have proven difficult to analyze due to the extremely skewed shape of their underlying distribution. We introduce an extension of generalized linear models, beta regression, as a possible method of modeling extremely skewed distributions as evidenced in ischemic stroke lesion volumes.

METHODS

The NINDS rt-PA clinical trials measured ischemic stroke lesion volume as a secondary trial outcome. Three-month lesion volumes from these trials were analyzed using beta regression. A multi-variable regression model associating explanatory variables with ischemic stroke lesion volumes was constructed using accepted model building strategies and compared with the previously published volumetric analysis.

RESULTS

Beta regression produced a similar model when compared to the previous analysis published by the study group. All previously identified variables of importance were detected in the model building process. The age by treatment interaction described in previous studies was also found in this analysis, confirming the strong effect age has on stroke outcomes. Further, a treatment effect was elicited in terms of odds ratios, yielding a previously unknown quantification of the effect of rt-PA on lesion volumes.

CONCLUSIONS

Beta regression proved adept in modeling ischemic stroke lesions and offered the interpretation of covariates in terms of odds ratios. Beta regression is seen as a legitimate alternative to analyze ischemic stroke volumes.

Clopidogrel vs. aspirin treatment on admission improves 5-year survival after a first-ever acute ischemic stroke. data from the Athens Stroke Outcome Project

BACKGROUND AND AIMS

We undertook this study to compare the impact of aspirin vs. clopidogrel treatment on 5-year survival of patients experiencing a first-ever acute ischemic noncardioembolic stroke.

METHODS

This was a retrospective study involving patients with an acute ischemic stroke who had an indication for antiplatelet therapy (atherothrombotic, lacunar and cryptogenic stroke subtype). A total of 1228 (383 women) hospitalized due to an acute first-ever stroke and receiving aspirin (n = 880) or clopidogrel (n = 348) were finally involved. To determine the factors that independently predict 5-year survival statistical analysis including the Kaplan-Meier survival curve and multifactorial analysis (Cox regression) was performed.

RESULTS

Subjects treated with clopidogrel had improved 5-year survival compared with those receiving aspirin (log rank test: 16.4, p <0.0001). The difference in survival was evident as early as 6 months from index stroke: cumulative survival 93.8% for aspirin vs. 97% for clopidogrel (log rank test: 4.01, p = 0.045). The composite cardiovascular event (including stroke recurrence, myocardial infarction, unstable angina, coronary revascularization, aortic aneurysm rupture, peripheral atherosclerotic artery diseases, and sudden death) rates were lower in the clopidogrel group (n = 60, 17.2%) compared with the aspirin (n = 249, 28.3%) group (log rank test: 12.4, p <0.0001). This preferential effect of clopidogrel over aspirin was independent of age, gender, presence of cardiovascular disease other than stroke or cardiovascular risk factors as well as irrespective of the severity of stroke and days of hospitalization.

CONCLUSIONS

This study supports that clopidogrel is superior to aspirin in preventing death and cardiovascular events after an acute noncardioembolic ischemic stroke.

Severity of leukoaraiosis determines clinical phenotype after brain infarction

OBJECTIVE

To determine whether the extent of leukoaraiosis, a composite marker of baseline brain integrity, differed between patients with TIA with diffusion-weighted imaging (DWI) evidence of infarction (transient symptoms with infarction [TSI]) and patients with ischemic stroke.

METHODS

Leukoaraiosis volume on MRI was quantified in a consecutive series of 153 TSI and 354 ischemic stroke patients with comparable infarct volumes on DWI. We explored the relationship between leukoaraiosis volume and clinical phenotype (TIA or ischemic stroke) using a logistic regression model.

RESULTS

Patients with TSI tended to be younger (median age 66 vs 69 years, p = 0.062) and had smaller median normalized leukoaraiosis volume (1.2 mL, interquartile range [IQR] 0.2-4.7 mL vs 3.5 mL, IQR 1.2-8.6 mL, p < 0.001). In multivariable analysis controlling for age, stroke risk factors, etiologic stroke mechanism, infarct volume, and infarct location, increasing leukoaraiosis volume remained associated with ischemic stroke (odds ratio 1.05 per mL, 95%confidence interval 1.02-1.09, p = 0.004), along with infarct volume and infarct location.

CONCLUSION

The probability of ischemic stroke rather than TSI increases with increasing leukoaraiosis volume, independent of infarct size and location. Our findings support the concept that the integrity of white matter tracts connecting different parts of the brain could contribute to whether or not patients develop TSI or ischemic stroke in an event of brain infarction.

The NIHSS-plus: improving cognitive assessment with the NIHSS

BACKGROUND

The National Institutes of Health Stroke Scale (NIHSS) has been criticized for limited representation of cognitive dysfunction and bias towards dominant hemisphere functions. Patients may therefore receive a low NIHSS score despite a fairly large stroke. A broader scale including simple cognitive tests would improve the clinical and research utility of the NIHSS.

METHODS

We studied 200 patients with acute non-dominant hemispheric stroke who underwent cognitive testing and had MRI with diffusion-weighted imaging (DWI) within 5 days of presentation. We measured DWI volumes and retrospectively calculated NIHSS scores. We used linear regression to determine the role of selected cognitive tests, when added to the NIHSS, in predicting DWI volume.

RESULTS

The NIHSS predicted DWI volume in a univariate analysis, as did total line cancellation and a visual perception task. In a multivariate model, using log-transformed variables, the NIHSS (p=0.0002), line cancellation errors (p=0.02) and visual perception (p=0.004) each improved prediction of total infarct volume.

CONCLUSION

The addition of line cancellation and visual perception tasks significantly adds to the model of NIHSS alone in predicting DWI volume. We propose that these two cognitive tests, which together can be completed in 2-3 minutes, could be combined with the NIHSS to create an "NIHSS-plus" that more accurately represents a patient's ischemic tissue volume after a stroke. This scale requires further validation in a prospective study.

Intra-arterial versus intra-venous thrombolysis within and after the first 3 hours of stroke onset

The NINDS trial demonstrated for the first time the effectiveness of intravenous thrombolysis in improving outcome after acute ischemic stroke. The absolute benefit of this intervention was 11-13% greater chance of being normal or near normal (MRS ≤ 1) at 3 months. However, if patients with severe stroke were considered (NIHSS ≥ 20), the absolute benefit dropped to 5-6%, indicating that IV thrombolysis may not be as effective for large vessel occlusion. This observation was further supported by TCD studies that clearly demonstrated that large artery occlusions had a recanalization rate of 13-18% with IV rt-PA. Intra-arterial thrombolysis achieves recanalization rates of 60-70%. Since tissue viability is clearly important, it is time to stop defining rigid time windows and if there is a large penumbra (20-50%) and the occlusion is in a large artery, there exists a logic and a growing evidence to consider either bridge therapy or direct intra-arterial therapy.

Development of a new tool to correlate stroke outcome with infarct topography: a proof-of-concept study

Improving the ability to assess potential stroke deficit may aid the selection of patients most likely to benefit from acute stroke therapies. Methods based only on 'at risk' volumes or initial neurological condition do predict eventual outcome, but not perfectly. Given the close relationship between anatomy and function in the brain, we performed a proof-of-concept study to examine how well stroke outcome correlated with infarct location and extent. A prospective study of 60 patients with ischemic stroke (38 in the training set and 22 in the validation set), using an implementation of partial least squares with penalized logistic regression (PLS-PLR), was performed. The method yielded a model relating location of infarction (on a voxel-by-voxel basis) and neurological deficits. The area under the receiver operating characteristics curve (AUC) method was used to assess the accuracy of the method for predicting outcome. In the validation phase, this model indicated the presence of neglect (AUC 0.89), aphasia (AUC 0.79), right-arm motor deficit (0.94), and right-leg motor deficit (AUC 0.94) but less accurately indicated left-arm motor deficit (0.52) and left-leg motor deficit (0.69). The model indicated no to mild disability (Rankin</=2) versus moderate to severe disability (Rankin>2) with AUC 0.78. In this proof-of-concept study, we have demonstrated that stroke outcome correlates well with infarct location raising the possibility of accurate prediction of neurological deficit in the individual stroke patient using only information on infarct location and multivariate regression methods.

Perfusion imaging of the right perisylvian neural network in acute spatial neglect

Recent studies have suggested a tightly connected perisylvian neural network associated with spatial neglect. Here we investigated whether structural damage in one part of the network typically is accompanied with functional damage in other, structurally intact areas of this network. By combining normalized fluid-attenuated inversion-recovery (FLAIR) imaging, diffusion-weighted imaging (DWI), and perfusion-weighted imaging (PWI) we asked whether or not lesions centering on fronto-temporal regions co-occur with abnormal perfusion in structurally intact parietal cortex. With thresholds applied to delineate behaviourally relevant malperfusion of brain tissue, the analysis of normalized time-to-peak (TTP) and maximal signal reduction (MSR) perfusion maps did not reveal significant changes outside the area of structural damage. In particular, we found no abnormal perfusion in the structurally intact inferior parietal lobule (IPL) and/or the temporo-parietal junction (TPJ). The present results obtained in three consecutively admitted neglect patients with fronto-temporal lesions indicate that structural damage in one part of the right perisylvian network associated with spatial neglect does not necessarily require dysfunction by malperfusion in other, structurally intact parts of the network to provoke spatial neglect. The neural tissue in the fronto-temporal cortex appears to have an original role in processes of spatial orienting and exploration.

Inter- and intraobserver reliability of five MRI sequences in the evaluation of the final volume of cerebral infarct

PURPOSE

To evaluate the reproducibility of fluid attenuated inversion recovery (FLAIR) and four other magnetic resonance imaging (MRI) sequences in the quantitative assessment of final cerebral infarct volume.

MATERIALS AND METHODS

FLAIR, T1-3D, magnetization transfer ratio (MTR)-map, diffusion-weighted trace (DWI)-trace, and apparent diffusion coefficient (ADC)-map, were acquired and measured in 33 patients 30-45 days after onset of a first-ever ischemic stroke. The infarct area was visually detected and manually delineated two times by two readers separately after images and sequences randomization. The reliability was assessed by using an intraclass correlation coefficient (ICC) and its two-sided 95% confidence interval (95% CI).

RESULTS

DWI-trace had the best reliability, with an ICC of 0.96 (95% CI = 0.93-0.98). FLAIR had an ICC of 0.86 (95% CI = 0.73-0.93), and a much higher volume. T1-3D, MTR-map and ADC-map had lower reliability or excessive volume values equal to 0 in comparison to DWI-trace.

CONCLUSION

DWI-trace performed within 30th and 45th day following onset of acute ischemic stroke was the most reliable sequence for final infarct volume quantification. This sequence should be added to FLAIR evaluation to strengthen the statistical results of the pharmacological trials and reduce their variability.

Thrombolysis beyond the Three-Hour Time Window

Intravenous (i.v.) thrombolysis with tissue plasminogen activator (rt-PA, i.v. 0.9 mg/kg body weight) has been approved by European health authorities in 2002, with a 3-hr time window. The meta-analysis of i.v. rt-PA trials suggests efficacy of rt-PA up to 4.5 to 6 hr. However, treatment efficacy declines rapidly over time: the numbers of patients needed to treat to prevent 1 death or dependency are respectively 7, 12, and > 30 in the 0-3 hr, 0-6 hr, and 3-6 hr time windows. Magnetic resonance imaging may be the best way to select candidates for thrombolysis beyond 3 hr, on the basis of the presence of arterial occlusion and mismatch between diffusion and perfusion images. New trials are testing the possibility of extending the time window. Trials with new thrombolytic agents, ultrasound thrombolysis, and mechanical thrombolysis also are running or planned in the 3- to 6-hr time window. The 3-hr limit is just a matter of safety. Patients should be treated as soon as possible, and the earliest is the best.

Does diffusion-weighted imaging represent the ischemic core? An evidence-based systematic review

BACKGROUND AND PURPOSE

Diffusion-weighted(DWI) hyperintensity is hypothesized to represent irreversibly infarcted tissue (ischemic core) in the setting of acute stroke [corrected]. Measurement of the ischemic core has implications for both prognosis and therapy. We wished to assess the level of evidence in the literature supporting this hypothesis.

MATERIALS AND METHODS

We performed a systematic review of the literature relating to tissue outcomes of DWI hyperintense stroke lesions in humans. The methodologic rigor of studies was evaluated by using criteria set out by the Oxford Centre for Evidence-Based Medicine. Data from individual studies were also analyzed to determine the prevalence of patients demonstrating lesion progression, no change, or lesion regression compared with follow-up imaging.

RESULTS

Limited numbers of highly methodologically rigorous studies (Oxford levels 1 and 2) were available. There was great variability in observed rates of DWI lesion reversal (0%-83%), with a surprisingly high mean rate of DWI lesion reversal (24% of pooled patients). Many studies did not include sufficient data to determine the precise prevalence of DWI lesion growth or reversal.

CONCLUSIONS

The available tissue-outcome evidence supporting the hypothesis that DWI is a surrogate marker for ischemic core in humans is troublingly inconsistent and merits an overall grade D based on the criteria set out by the Oxford Centre for Evidence-Based Medicine.

Expediting MRI-based proof-of-concept stroke trials using an earlier imaging end point

BACKGROUND AND PURPOSE

Before Phase III trials of acute stroke therapies, proof-of-concept MRI trials are increasingly used to gauge the likelihood of success. Given that animal models use infarct volume as the end point, Phase II trials have aimed to translate the findings using infarct growth. These trials could be expedited if subacute diffusion-weighted imaging lesion volume replaced late T2-weighted lesion volume as the primary end point.

METHODS

In the Echoplanar Imaging Thrombolytic Evaluation Trial, patients with acute ischemic stroke presenting within 3 to 6 hours were randomized to tissue plasminogen activator or placebo. We assessed correlations between acute (Day 1), subacute (Day 3 to 5) as well as late (Day 90) lesion volumes and clinical outcome (National Institutes of Health Stroke Scale). We compared lesion growth between placebo- and tissue plasminogen activator-treated patients.

RESULTS

All 3 scans were performed in 72 of 101 patients (32 tissue plasminogen activator, 40 placebo). Median time to subacute imaging was 3 days (interquartile range, 2 to 4) and 90 days (interquartile range, 90 to 95) for the late scan. Increase in lesion volume from acute to subacute scans was smaller in the tissue plasminogen activator group compared with the placebo group (6.77 mL; interquartile range, 2.30 to 49.10; versus 30.00 mL; interquartile range, 7.19 to 85.93; P=0.03). Subsequent shrinkage did not reveal significant treatment effects. Correlation coefficient between acute and late lesion volumes was 0.81 (P<0.01). Subacute and late lesion volumes were strongly correlated (rho=0.94, P<0.01). Correlation coefficient for acute, subacute, and late lesion volume and late National Institutes of Health Stroke Scale score was 0.64 (P<0.01), 0.81 (P<0.01), and 0.77 (P<0.01), respectively.

CONCLUSIONS

These findings suggest that subacute imaging at Day 3 after thrombolysis is an appropriate imaging end point for proof-of-concept MRI-based stroke treatment trials and can replace later MRI measurements.

Management of acute ischemic stroke

Stroke is the third leading cause of death and the leading cause of disability in the United States. This article summarizes the management of acute ischemic stroke, including conventional and novel therapies. The article provides an overview of the initial management, diagnostic work-up, treatment options, and supportive measures that need to be considered in the acute phase of ischemic stroke.

Developments in neuroimaging for acute ischemic stroke: diagnostic and clinical trial applications

Over the past several years, active investigation into neuroimaging in the setting of acute ischemic stroke has improved our understanding of and ability to visualize the dynamic pathophysiology of acute cerebrovascular disease. Efforts surrounding the application of multimodal CT and MRI have resulted in a growing body of data from systematic evaluations of different parameters, experience in the use of these techniques in guiding clinical decision making, and clinical trials employing neuroimaging for patient selection, for proof of principle, and as a surrogate outcome measure.

An acute ischemic stroke classification instrument that includes CT or MR angiography: the Boston Acute Stroke Imaging Scale

BACKGROUND AND PURPOSE

A simple classification instrument based on imaging that predicts outcomes in patients with acute ischemic stroke is lacking. We tested the hypotheses that the Boston Acute Stroke Imaging Scale (BASIS) classification instrument effectively predicts patient outcomes and is superior to the Alberta Stroke Program Early CT Score (ASPECTS) in predicting outcomes in acute ischemic stroke.

MATERIALS AND METHODS

Of 230 prospectively screened, consecutive patients with acute ischemic stroke, 87 had noncontrast CT (NCCT)/CT angiography (CTA), and 118 had MR imaging/MR angiography (MRA) at admission and were classified as having major stroke by BASIS criteria if they had a proximal cerebral artery occlusion or, if no occlusion, imaging evidence of significant parenchymal ischemia; all of the others were classified as minor strokes. Outcomes included death, length of hospitalization, and discharge disposition. BASIS was compared with ASPECTS (dichotomized > or <or=7) in 87 patients who had NCCT/CTA.

RESULTS

BASIS classification by NCCT/CTA was equivalent to MR imaging/MRA. Fifty-six of 205 patients were classified as having major strokes including all 6 of the deaths. A total of 71.4% and 15.4% of major and minor stroke survivors, respectively, were discharged to a rehabilitation facility, whereas 14.3% and 79.2% of patients with major and minor strokes were discharged to home. The mean length of hospitalization was 12.3 and 3.3 days for the major and minor stroke groups, respectively (all outcomes, P < .0001). In 87 NCCT/CTA patients, BASIS and ASPECTS agreed in 22 major and 44 minor strokes. BASIS classified 21 patients as having major strokes who were classified as having minor strokes by ASPECTS. The BASIS major/ASPECTS minor stroke group had outcomes similar to those classified as major strokes by both instruments.

CONCLUSIONS

The BASIS classification instrument is effective and appears superior to ASPECTS in predicting outcomes in acute ischemic stroke.

Neurologic assessment of somatosensory dysfunction following an experimental rodent model of cerebral ischemia

The modified adhesive removal (sticky-tape) test is an assessment of somatosensory dysfunction following cerebral ischemia in rats. This test is less time consuming than the original protocol by virtue of requiring minimal pre-training. We present a detailed protocol describing how to conduct the modified adhesive removal (sticky-tape) test. Following right middle cerebral artery occlusion (rMCAo) using an intraluminal filament, animals undergo the modified sticky-tape test (MST) on post-operative days 1, 3, 7 and 10. For the test, a non-removable tape sleeve is placed around the animal's paw and the time to remove the stimulus is measured. The time spent attending to this stimulus is also recorded. Animals undergoing MST for the first time demonstrate nearly-uniform excellent performance. However, following rMCAo, the ratio of left to right performance on the MST is significantly different at all time points. In short, the MST accurately assesses neurological dysfunction in rodents, not only with minimal pre-training, but also with accurate localization to the side of injury.

Pattern of time-dependent reduction of histologically determined infarct volume after focal ischaemia in mice

The mouse model of transcranial permanent occlusion of the middle cerebral artery (tpMCAO) is widely used in stroke research. Here we quantified infarct size using a conventional histological method at several post-ischaemic times, going beyond the commonly analysed period of up to 2 days, following artery occlusion. Two different mouse strains, which are widely used for pharmacological studies of neuroprotection and for genetic engineering, were used. A drill whole was made into the skull of anaesthetised mice and ischaemia was induced by electrocoagulation of the middle cerebral artery. In both mouse strains tested (C57Black/6 and NMRI), the measured infarct volumes decreased significantly during the first days after tpMCAO. Notably, 13 days after surgery, ischaemic and sham-operated animals had indistinguishably small lesions, which where in the range of only 5% of the infarct size on day 2 post-ischaemia. The standard method of calculating oedema and shrinkage correction provided no sufficient explanation for this significant decrease in infarct volume. There was, however, evidence that structural changes in the residual ipsilateral hemisphere may compromise the significance of results arising from the method of calculating oedema and shrinkage correction. In conclusion, our study indicates that the pronounced and fast, time-dependent decrease in histologically defined infarct volume can compromise results when studying the lasting neuroprotective effects of potential drugs.

Early evolution of deficits in acute ischemic stroke: mean transit time, relative blood volume, and relative blood flow

The objective of this prospective pilot study was to determine the evolution of imaging characteristics of perfusion-weighted imaging (PWI), including mean transit time (MTT), relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), diffusion-weighted imaging (DWI), and magnetic resonance (MR) angiography in the first 48 hours after an acute cerebral infarction. In 5 patients with suspected middle cerebral artery (MCA) territory infarction, images were obtained on 4 occasions during the first 48 hours (6-10 hours, 15-18 hours, 22-24 hours, and 48 hours) by an imaging protocol that included echoplanar DWI, PWI, and MR angiography. No patients received thrombolytic or neuroprotective agents. Four of the 5 patients had MCA occlusions on the initial MR angiogram. Presumably, the MCA had recanalized in 1 patient before the first MR angiogram. Recanalization of the MCA was observed by the second scan in 1 patient and by the fourth scan in the remaining 3 patients. The mean MTT volume deficit was greater than the DWI volume (mismatch) until the final MR examination at 48 hours. The mean rCBV and rCBF volumes were larger than the DWI volume (mismatch) on the first MR examination but were smaller on the second and subsequent examinations. Decrease in the size of the MTT volume before recanalization of the MCA was most likely due to opening of collateral channels, but the greatest decrease in the size of the MTT volume occurred with recanalization of the MCA. All patients had progressive enlargement of the abnormal DWI volume. The MR changes following acute cerebral infarction are dynamic, with the volume of the diffusion abnormality nearly doubling between 6 to 10 hours and 48 hours. The volume of the acute MTT abnormality (6-10 hours) is approximately twice the size of the diffusion abnormality at 48 hours. The volume of the rCBV and rCBF between 6 and 10 hours after ictus is a good reflection of the diffusion abnormality at 48 hours.

QEEG prognostic value in acute stroke

The objective of our study is to determine the predictive value of QEEG in patients suffering from an acute ischemic cerebral stroke. Twenty-eight patients were studied within the first 72 hours of clinical evolution of middle cerebral artery territory ischemic stroke. Thirty-seven QEEG recordings were obtained: 13 in the first 24 hours after cerebral stroke onset, 9 between 24-48 hours and 15 between 48-72 hours. Absolute Energies (AE) were the QEEG selected variables for statistical analysis: first, AE Z values were calculated using the Cuban QEEG norms, then the maximum and minimum AE Z values were selected within each frequency band and total power. The medians of the five neighboring Z values were also chosen. Regression models were estimated using the RANKIN scores as dependent variables and the selected QEEG variables as independent, then outcome predictions at hospital discharge and 3 months later were calculated. Percentages of concordance and errors between the estimated and real outcome scores were obtained. Alpha and theta AE were the best predictor for short-term outcome and delta AE for long-term outcome. We conclude that QEEG performed within the first 72 hours of ischemic stroke might be a powerful tool predicting short- and long-term outcome.

Acute Stroke Imaging for Thrombolytic Therapy – An Update

More than ten years after its approval intravenous thrombolysis with rtPA still is the only approved therapy for acute ischemic stroke. In this review we aim to give an up-to-date overview of acute stroke imaging within and outside of approved indications for thrombolysis. We discuss the potential applications of modern CT techniques such as CT angiography and perfusion CT as well as stroke MRI for the selection-based treatment of acute ischemic stroke. Recent publications regarding diagnostic strength as well as new randomized trials and larger prospective but open studies are reviewed and discussed. Finally we present a suggestion for the selection of patients for thrombolysis within and beyond the 3-hour time window in the form of an institutional algorithm prioritizing according to present evidence and pathophysiological reasoning.

Symptomatic intracerebral hemorrhage following thrombolytic therapy for acute ischemic stroke: a review of the risk factors

BACKGROUND

Symptomatic intracerebral hemorrhage (SICH) following thrombolytic therapy for acute ischemic stroke is associated with a high rate of morbidity and mortality. Knowledge of the risk factors associated with SICH following thrombolyitc therapy may provide insight into the pathophysiological mechanisms underlying the development of SICH, lead to the development of treatments that reduce the risk of SICH and have implications for the design of future stroke trials.

METHODS

Relevant studies were identified through a search in Pubmed. Included studies used multivariate analyses to identify independent risk factors for SICH following thrombolytic therapy. For each variable that was found to have a significant association with SICH, a secondary literature search was conducted to identify additional reports on the specific relationship between that variable and SICH.

SUMMARY OF REVIEW

Twelve studies met inclusion criteria for the systematic review. Extent of hypoattenuated brain parenchyma on pretreatment CT and elevated serum glucose or history of diabetes were independent risk factors for thrombolysis-associated SICH in six of the twelve studies. Symptom severity was an independent risk factor in three of the studies and advanced age, increased time to treatment, high systolic blood pressure, low platelets, history of congestive heart failure and low plasminogen activator inhibitor levels were found to be independent risk factors for SICH in a single study. Although these data should not alter the current guidelines for the use of rt-PA in acute stroke, they may help develop future strategies aimed at reducing the rate of thrombolysis-associated SICH.

Guidelines for the Early Management of Adults With Ischemic Stroke

Purpose— Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

Methods— Members of the panel were appointed by the American Heart Association Stroke Council’s Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council’s Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

Results— Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Evaluation of the clinical-diffusion and perfusion-diffusion mismatch models in DEFUSE

BACKGROUND AND PURPOSE

The perfusion-diffusion mismatch (PDM) model has been proposed as a tool to select acute stroke patients who are most likely to benefit from reperfusion therapy. The clinical-diffusion mismatch (CDM) model is an alternative method that is technically less challenging because it does not require perfusion-weighted imaging. This study is an evaluation of these 2 models in the DEFUSE dataset.

METHODS

DEFUSE is an open-label multicenter study in which acute stroke patients were treated with intravenous tPA between 3 and 6 hours after symptoms onset and an MRI was obtained before and 3 to 6 hours after treatment. Presence of PDM and CDM was determined for each patient.

RESULTS

Based on conventional predefined mismatch criteria, PDM was present in 54% of the DEFUSE population and CDM in 62%. There was no agreement beyond chance between the 2 mismatch models (kappa 0.07). The presence of PDM was associated with an increased chance of favorable clinical response after reperfusion (OR, 5.4; P=0.039). Reperfusion was not associated with a significant increase in the rate of favorable clinical response in patients with CDM (OR, 2.2; P=0.34). Using optimized mismatch criteria, determined retrospectively based on DEFUSE data, the OR for favorable clinical response was 70 (P=0.001) for PDM and 5.1 (P=0.066) for CDM.

CONCLUSIONS

The PDM model appears to be more accurate than the CDM model for selecting patients who are likely to benefit from reperfusion therapy in the 3- to 6-hour time window.

Validation of an acute ischemic stroke model: does diffusion-weighted imaging lesion volume offer a clinically significant improvement in prediction of outcome?

BACKGROUND AND PURPOSE

Prediction models for ischemic stroke outcome have the potential to contribute prognostic information in the clinical and/or research setting. The importance of diffusion-weighted magnetic resonance imaging (DWI) in the prediction of clinical outcome, however, is unclear. The purpose of this study was to combine acute clinical data and DWI lesion volume for ischemic stroke patients to determine whether DWI improves the prediction of clinical outcome.

METHODS

Patients (N=382) with baseline DWI data from the Glycine Antagonist In Neuroprotection and citicoline (010 and 018) trials were used to develop the prediction models by multivariable logistic regression. Data from prospectively collected patients (N=266) from the Acute Stroke Accurate Prediction Study were used to externally validate the model equations. The models predicted either full recovery or nursing home-level disability/death, as defined by the National Institutes of Health Stroke Scale, Barthel Index, or modified Rankin Scale.

RESULTS

The full-recovery models with DWI lesion volume had areas under the receiver operating characteristic curves (AUCs) of 0.799 to 0.821, and those without DWI lesion volume had AUCs of 0.758 to 0.798. The nursing home-level disability/death models with DWI had AUCs of 0.832 to 0.882, and those without DWI had AUCs of 0.827 to 0.867. All models had mean absolute errors < or =0.4 for calibration.

CONCLUSIONS

All 12 models had excellent discrimination and calibration, with 8 of 12 meeting prespecified performance criteria (AUC > or =0.8, mean absolute error < or =0.4). Although DWI lesion volume significantly increased model explanatory power, the magnitude of increase was not large enough to be clinically important.

Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups: the American Academy of Neurology affirms the value of this guideline as an educational tool for neurologists

PURPOSE

Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

METHODS

Members of the panel were appointed by the American Heart Association Stroke Council's Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council's Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

RESULTS

Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Critical care of acute ischemic stroke

Stroke is the third leading cause of death and the leading cause of disability in the United States. This article summarizes the critical care of acute ischemic stroke, including conventional and novel therapies. The article provided an overview of the initial management, diagnostic workup, treatment options, and supportive measures that need to be considered in the acute phase of ischemic stroke.

Outcome prediction in acute monohemispheric stroke via magnetoencephalography

BACKGROUND

Following an ischemic stroke a highly variable clinical outcome is commonly evident despite similar onset symptoms as well as lesion characteristics. The aim of this study was to identify indexes providing early prediction of functional recovery, in addition to clinical severity and lesion dimension at onset of stroke.

METHODS

In 32 patients, magnetoencephalographic (MEG) parameters collected in the acute phase (<10 days from symptoms onset, T0) from affected (AH) and unaffected (UH) hemispheres at rest and evoked by sensory stimuli were evaluated in association with the clinical outcome in a stabilized phase (T1, median 7.8 months) classified with three levels: worsening, partial and full recovery.

RESULTS

Multiple multinomial logistic regression indicated AH gamma and UH delta band powers able to prognosticate clinical outcome at T1. After inclusion in this analysis, lesion volume had the strongest predictive ability, and UH delta band power remained as a predictive factor with a measurable cut-off, maximizing both sensitivity and specificity of the prediction: a patient with UH delta below cut-off would recover to some extent; a patient with UH delta above cut-off would have a probability of about 70% to worsen.

CONCLUSIONS

MEG UH delta and AH gamma band powers were found to provide useful information about long-term outcome prognosis. Only the increase of delta band activity in the unaffected hemisphere contains information about the outcome in addition to the lesion volume.

Clinical-diffusion mismatch defined by NIHSS and ASPECTS in non-lacunar anterior circulation infarction

OBJECTIVES

Instead of the mismatch in MRI between the perfusion-weighted imaging (PWI) lesion and the smaller diffusion-weighted imaging (DWI) lesion (PWI-DWI mismatch), clinical-DWI mismatch (CDM) has been proposed as a new diagnostic marker of brain tissue at risk of infarction in acute ischemic stroke. The Alberta Stroke Program Early CT Score (ASPECTS) has recently been applied to detect early ischemic change of acute ischemic stroke. The present study applies the CDM concept to DWI data and investigated the utility of the CDM defined by the NIH Stroke Scale (NIHSS) and ASPECTS in patients with non-lacunar anterior circulation infarction.

METHODS

Eighty-seven patients with first ever ischemic stroke within 24 hours of onset with symptoms of non-lacunar anterior circulation infarction with the NIHSS score>or=8 were enrolled. Initial lesion extent was measured by the ASPECTS on DWI within 24 hours, and initial neurological score was measured by the NIHSS. As NIHSS>or=8 has been suggested as a clinical indicator of a large volume of ischemic brain tissue, and the majority of patients with non-lacunar anterior infarction with score of NIHSS<8 had lesions with ASPECTS>or=8 on DWI, so CDM was defined as NIHSS>or=8 and DWI-ASPECTS 8>or=. We divided patients into matched and mismatched patient groups, and compared them with respect to background characteristics, neurological findings, laboratory data, radiological findings and outcome.

RESULTS

There were 35 CDM-positive patients (P group, 40.2%) and 52 CDM-negative patients (N group , 59.8%). P group patients had a higher risk of early neurological deterioration (END) than N group patients (37.1% vs 13.5%, p<0.05), which were always accompanied by lesion growth defined by 2 or more points decrease on ASPECTS (36 to 72 hours after onset on CT). The NIHSS at entry were significantly lower in the P group, but there was no difference in the outcome at three months measured by the modified Rankin Scale. However, CDM was not an independent predictor of END by multiple logistic regression analysis.

CONCLUSIONS

Patients with CDM had high rate of early neurological deterioration and lesion growth. CDM defined as NIHSS>or=8 and DWI-ASPECTS>or=8 can be another marker for detecting patients with tissue at risk of infarction, but more work is needed to clarify whether this CDM method is useful in acute stroke management.

Measurement Properties of the National Institutes of Health Stroke Scale for People With Right- and Left-Hemisphere Lesions: Further Analysis of the Clomethiazole for Acute Stroke Study–Ischemic (Class-I) Trial

OBJECTIVE

To assess the psychometric properties of the National Institutes of Health Stroke Scale (NIHSS) in people with either left or right acute hemisphere stroke for the purpose of improving the scale's sensitivity in detecting neurologic impairment.

DESIGN

Secondary analysis of data from the Clomethiazole for Acute Stroke Study-Ischemic using the Rasch partial credit model. We evaluated the data's measurement properties using item-total correlations, Rasch item fit statistics, principle component analysis of standardized person and item residuals, differential item functioning, separation reliability, and the separation ratio.

SETTING

Original data were collected in academic and community hospitals as part of a clinical trial.

PARTICIPANTS

People with acute ischemic stroke who were seen within 12 hours of onset: 380 people with left-hemisphere stroke and 347 with right-hemisphere stroke.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE

The NIHSS.

RESULTS

Items of the NIHSS function differently in the right- and left-hemisphere lesion groups. We constructed for each group separate linear scales consisting of a subset of items of the NIHSS to improve its measurement properties.

CONCLUSIONS

Our findings provide initial support for the use of individual, targeted scales for measurement of impairment after ischemic stroke. Low person separation reliability may be a consequence of the sample, which included only people with large ischemic cortical strokes.