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

Patterns and predictors of blood-brain barrier permeability derangements in acute ischemic stroke

BACKGROUND AND PURPOSE

MRI permeability imaging is a promising approach to identify patients with acute ischemic stroke with an increased propensity for hemorrhagic transformation (HT). Permeability imaging provides direct visualization of blood-brain barrier derangements in ischemic fields.

METHODS

We retrospectively analyzed clinical and MRI data on patients with acute cerebral ischemia within the middle cerebral artery territory to identify the frequency, patterns, and predictors of permeability derangements and their association with HT types.

RESULTS

A total of 179 permeability scans was obtained in 127 patients (59 men; mean age, 66.8 years). Among 179 image sets (82 pre-/no treatment and 97 posttreatment), permeability derangements were present in 29 images, frequently at the basal ganglia (n=23) and rarely at the juxta-cortical area (n=6). After adjusting for covariates, diastolic pressure (OR, 1.12, per 1-mm Hg increase; 95% CI, 1.02 to 1.22) and s-glucose (OR, 1.04, per 1-mg/dL increase; 95% CI, 1.01 to 1.07) were independently associated with pretreatment permeability derangements, whereas low-density lipoprotein cholesterol (OR, 0.97, per 1-mg/dL increase; 95% CI, 0.94 to 0.99), malignant MRI profile (OR, 24.84; 95% CI, 1.50 to 412.93), and time from onset to recanalization therapy (OR, 1.47, per 1-hour increase; 95% CI, 1.10 to 1.96) were independently associated with permeability derangements after recanalization therapy. Types of HT varied among the patients with permeability derangements (no HT, 4; hemorrhagic infarct type, 12; and parenchymal hematoma, 13) and transient derangements (without subsequent HT) and normalization of derangements (in the presence of HT) on permeability images was observed in several cases.

CONCLUSIONS

Permeability derangements, a dynamic process associated with ischemic stroke pathophysiology and recanalization therapy, vary in pattern and evolution toward HT. Several prognostic and therapeutic predictors for HT are independently associated with pre- and posttreatment permeability derangements.

Perfusion CT: is it clinically useful?

Combining perfusion CT (CTP) with CT angiography (CTA) and noncontrast CT (NCCT) provides much more information about acute stroke pathophysiology than NCCT alone. This multimodal CT approach adds only a few minutes to the standard NCCT and is more accessible and rapidly available in most centres than MRI. CTP can distinguish between infarct core and penumbra, which is not possible with NCCT alone. A small infarct core and large penumbra, plus the presence of vessel occlusion on CTA may be an ideal imaging 'target' for thrombolysis. To date, multimodal CT has predominantly been assessed in hemispheric stroke due to its limited spatial coverage. This will become less of an issue as slice coverage continues to improve with new generation CT scanners. Apart from the concepts above, more specific CTP and CTA criteria that increase (or decrease) probability of response to thrombolytic treatment are yet to be determined. Nonetheless, CTP thus has the potential to improve patient selection for thrombolysis.

Impact of reperfusion after 3 hours of symptom onset on tissue fate in acute cerebral ischemia

BACKGROUND

Reperfusion of penumbral tissue is a promising strategy for treatment of acute cerebral ischemia more than 3 hours from symptom onset. However, there has been only sparse direct evidence that reperfusion after 3 hours prevents infarct growth.

METHODS

We analyzed clinical and serial magnetic resonance imaging (MRI) data on patients who received endovascular recanalization therapy 3-12 hours after last known well time. Multimodal MRIs were acquired pretreatment, early (1-20 hours), and late (2-7 days) after treatment. Degree of recanalization was assessed on end of procedure catheter angiogram, degree of reperfusion on early posttreatment perfusion MRI, and infarct growth by analysis of diffusion lesion volumes on pretreatment and late MRIs.

RESULTS

Twenty-seven (12 men, 15 women) underwent endovascular recanalization procedures at 6.0 +/- 2.1 hours (range, 3.0-11.5 hours) after last known well time. Immediate posttreatment perfusion lesion (Tmax > or =4 seconds) volume correlated strongly with infarct growth (r= .951, P < .001), exceeding the correlations of vessel recanalization score (r=-.198, P= .446) and pretreatment diffusion-perfusion mismatch volume (r= .518, P= .033). Without reperfusion, enlargement of DWI lesion volume was observed in all patients, and extent of enlargement depended on volume of immediate posttreatment perfusion defects.

CONCLUSION

Our data indicate that posttreatment reperfusion is the major determinant of threatened tissue outcome, and suggest reperfusion even after 3 hours of symptom onset can alter tissue fate over a wide range of mismatch volumes.

Potential use of oxygen as a metabolic biosensor in combination with T2*-weighted MRI to define the ischemic penumbra

We describe a novel magnetic resonance imaging technique for detecting metabolism indirectly through changes in oxyhemoglobin:deoxyhemoglobin ratios and T2(*) signal change during 'oxygen challenge' (OC, 5 mins 100% O(2)). During OC, T2(*) increase reflects O(2) binding to deoxyhemoglobin, which is formed when metabolizing tissues take up oxygen. Here OC has been applied to identify tissue metabolism within the ischemic brain. Permanent middle cerebral artery occlusion was induced in rats. In series 1 scanning (n=5), diffusion-weighted imaging (DWI) was performed, followed by echo-planar T2(*) acquired during OC and perfusion-weighted imaging (PWI, arterial spin labeling). Oxygen challenge induced a T2(*) signal increase of 1.8%, 3.7%, and 0.24% in the contralateral cortex, ipsilateral cortex within the PWI/DWI mismatch zone, and ischemic core, respectively. T2(*) and apparent diffusion coefficient (ADC) map coregistration revealed that the T2(*) signal increase extended into the ADC lesion (3.4%). In series 2 (n=5), FLASH T2(*) and ADC maps coregistered with histology revealed a T2(*) signal increase of 4.9% in the histologically defined border zone (55% normal neuronal morphology, located within the ADC lesion boundary) compared with a 0.7% increase in the cortical ischemic core (92% neuronal ischemic cell change, core ADC lesion). Oxygen challenge has potential clinical utility and, by distinguishing metabolically active and inactive tissues within hypoperfused regions, could provide a more precise assessment of penumbra.

Magnetic resonance imaging in clinical trials

PURPOSE OF REVIEW

The aim of this article is to review the latest clinical trials in neurological diseases where magnetic resonance imaging was used to assess treatment outcome.

RECENT FINDINGS

The unique sensitivity of magnetic resonance imaging for detecting disorders in the brain has made it an attractive noninvasive tool for assessing treatment efficacy in several diseases. Volumetric and functional magnetic resonance imaging have proved to represent robust biomarkers for the evaluation of anti-Alzheimer treatments, and have demonstrated a significant impact of cholinesterase inhibitors. The optimization of thrombolytic therapy in acute ischemic stroke has concentrated on the quantification of the ischemic penumbra, using perfusion-weighted and diffusion-weighted imaging. Standard assessment of T2 or fluid-attenuated inversion recovery lesion load remains the method of choice to evaluate new therapeutic strategy in multiple sclerosis. Other nonconventional quantitative magnetic resonance imaging techniques such as magnetic resonance volumetry, magnetization transfer imaging, diffusion-weighted imaging, or magnetic resonance spectroscopy are increasingly used in the field.

SUMMARY

Magnetic resonance imaging has become a major surrogate marker of treatment response in clinical trials of neurological disorders, offering the possibility to reduce the required sample size or to shorten the duration of the trial.

Focal fluid-attenuated inversion recovery hyperintensity within acute diffusion-weighted imaging lesions is associated with symptomatic intracerebral hemorrhage after thrombolysis

BACKGROUND AND PURPOSE

We investigated whether focal hyperintensity on fluid-attenuated inversion recovery image within acute infarcts is associated with symptomatic intracerebral hemorrhage (SICH) after thrombolysis.

METHODS

Patients with acute ischemic stroke who underwent MRI screening before thrombolysis were enrolled. The presence of focal fluid-attenuated inversion recovery hyperintensity within acute infarcts did not preclude thrombolysis. SICH was defined as hemorrhagic transformation with any neurological decline (SICH-1) or with an increase in National Institutes of Health Stroke Scale of >or=4 (SICH-2) within 48 hours.

RESULTS

Among 88 included patients, focal fluid-attenuated inversion recovery hyperintensity within acute infarct lesions was observed in 27 (30.7%) patients. Multivariate analysis showed that focal fluid-attenuated inversion recovery hyperintensity was independently associated with SICH-1 (OR, 13.64; 95% CI, 1.51 to 123.28) and SICH-2 (OR, 10.44; 95% CI, 1.11 to 98.35).

CONCLUSIONS

The presence of focal fluid-attenuated inversion recovery hyperintensity within acute infarcts may increase the risk of symptomatic intracerebral hemorrhage after thrombolysis.

Quantitative assessment of core/penumbra mismatch in acute stroke: CT and MR perfusion imaging are strongly correlated when sufficient brain volume is imaged

BACKGROUND AND PURPOSE

Our purpose was to determine (1) the correlation between quantitative CT and MR measurements of infarct core, penumbra, and mismatch; and (2) whether the difference between these measurements would alter patient selection for stroke clinical trials.

METHODS

We studied 45 patients with acute middle cerebral artery stroke imaged a mean of 3.8 hours after onset (range, 0.48 to 8.35 hours) who underwent CT perfusion and MR diffusion (DWI)/perfusion imaging within 3 hours of each other. The DWI and MR-mean transit time (MTT) abnormalities were visually segmented using a semiautomated commercial analysis program. The CT-cerebral blood volume) and CT-MTT lesions were automatically segmented using a relative cerebral blood volume threshold of 0.56 and a relative MTT threshold of 1.50 on commercially available software. Percent mismatch was defined as [(MTT-DWI)/DWI volume]x100. Pearson correlation coefficients were calculated.

RESULTS

There were significant correlations for DWI versus CT-cerebral blood volume lesion volumes (r2=0.88, P<0.001), for MR-MTT versus CT-MTT lesion volumes(r2=0.86, P<0.001), and for MR-MTT/DWI versus CT-MTT/CT-cerebral blood volume mismatch lesion volumes(r2=0.81, P<0.001). MR perfusion and CT perfusion agreed for determining: (1) infarct core < versus >or=100 mL in 41 of 45 (91.1%); (2) MTT lesion size < versus >2 cm diameter in 42 of 45 (93.3%); (3) mismatch < versus >20% in 41 of 45 (91.1%); and (4) inclusion versus exclusion from trial enrollment in 38 of 45 (84.4%) patients. Six of 7 disagreements were due to inadequate CT coverage.

CONCLUSIONS

Advanced MR and CT perfusion imaging measurements of core/penumbra mismatch for patient selection in stroke trials are highly correlated when CT perfusion coverage is sufficient to include most of the ischemic region. Although MR is currently the preferred imaging method for determining core and penumbra, CT perfusion is comparable and potentially more available.

[Quality assurance indicators for risk management in the follow-up of medical care received by acute ischemic stroke patients]

Although recommendations for diagnosis and treatment of stroke are available, the aim of this study was to identify indicators of quality and risk management for acute ischemic stroke hospital patients. We conducted a descriptive study of stroke patients who were diagnosed less than 12 hours before admission to the Pitié-Salpêtrière hospital's neurology and stroke unit. Data were collected using a literature review and from existing recommendation. During the study period (August 2003 through April 2005) 310 eligible patients were identified. In 87.5% of the cases, patients suffered from a cerebral infarction and in 10.3% from an intracranial haemorrhage. The initial deficit was mild to severe. The average time between the first symptoms and admission in the stroke unit was 212 +/- 130 minutes. Forty percent of patients who underwent a thrombolysis did so within the first 3 hours. The average length of stay in the stroke unit was 17.5 days. Thirty-one percent of the patients were discharged to go home, 47% to a rehabilitation unit and 8% died. Ten indicators of quality and risk management are proposed, taking in account the events before admission, hospital care, side effects, duration of stay, discharge location and the handicap.

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.

Impact of collateral flow on tissue fate in acute ischaemic stroke

BACKGROUND

Collaterals may sustain penumbra prior to recanalisation yet the influence of baseline collateral flow on infarct growth following endovascular therapy remains unknown.

METHODS

Consecutive patients underwent serial diffusion and perfusion MRI before and after endovascular therapy for acute cerebral ischaemia. We assessed the relationship between MRI diffusion and perfusion lesion indices, angiographic collateral grade and infarct growth. Tmax perfusion lesion maps were generated and diffusion-perfusion mismatch regions were divided into Tmax >or=4 s (severe delay) and Tmax >or=2 but <4 s (mild delay).

RESULTS

Among 44 patients, collateral grade was poor in 7 (15.9%), intermediate in 20 (45.5%) and good in 17 (38.6%) patients. Although diffusion-perfusion mismatch volume was not different depending on the collateral grade, patients with good collaterals had larger areas of milder perfusion delay than those with poor collaterals (p = 0.005). Among 32 patients who underwent day 3-5 post-treatment MRIs, the degree of pretreatment collateral circulation (r = -0.476, p = 0.006) and volume of diffusion-perfusion mismatch (r = 0.371, p = 0.037) were correlated with infarct growth. Greatest infarct growth occurred in patients with both non-recanalisation and poor collaterals. Multiple regression analysis revealed that pretreatment collateral grade was independently associated with infarct growth.

CONCLUSION

Our data suggest that angiographic collateral grade and penumbral volume interactively shape tissue fate in patients undergoing endovascular recanalisation therapy. These angiographic and MRI parameters provide complementary information about residual blood flow that may help guide treatment decision making in acute cerebral ischaemia.

Clinical review: Imaging in ischaemic stroke--implications for acute management

Imaging has become a cornerstone of stroke management, translating pathophysiological knowledge to everyday decision-making. Plain computed tomography is widely available and remains the standard for initial assessment: the technique rules out haemorrhage, visualizes the occluding thrombus and identifies early tissue hypodensity and swelling, which have different implications for thrombolysis. Based on evidence from positron emission tomography (PET), however, multimodal imaging is increasingly advocated. Computed tomography perfusion and angiography provide information on the occlusion site, on recanalization and on the extent of salvageable tissue. Magnetic resonance-based diffusion-weighted imaging (DWI) has exquisite sensitivity for acute ischaemia, however, and there is increasingly robust evidence that DWI combined with perfusion-weighted magnetic resonance imaging (PWI) and angiography improves functional outcome by selecting appropriate patients for thrombolysis (small DWI lesion but large PWI defect) and by ruling out those who would receive no benefit or might be harmed (very large DWI lesion, no PWI defect), especially beyond the 3-hour time window. Combined DWI–PWI also helps predict malignant oedema formation and therefore helps guide selection for early brain decompression. Finally, DWI–PWI is increasingly used for patient selection in therapeutic trials. Although further methodological developments are awaited, implementing the individual pathophysiologic diagnosis based on multimodal imaging is already refining indications for thrombolysis and offers new opportunities for management of acute stroke patients.

Systemic thrombolysis based on CT or MRI stroke imaging

BACKGROUND

Computed tomography (CT) and magnetic resonance imaging (MRI) are tools of investigation in acute stroke. We wondered if the additional information offered by MRI outweighs the disadvantage of its longer scanning duration for systemic thrombolysis.

METHODS

Two hundred ninety-four consecutive patients (66 +/- 13 years) were subjected to thrombolysis between 1999 and 2004. Inclusion criteria were ischemic infarction, scoring at entry and discharge with the NIH stroke scale and modified Rankin scale, systemic thrombolysis within 3 hours after symptom onset, multimodal MRI or standard CT. Subgroup analysis of 42 patients compared standard CT with CT and CT angiography.

RESULTS

Patients were similarly affected on admission (P > .1). At discharge, 6 days after stroke onset, the patients investigated with MRI were less impaired than those investigated with standard CT (P < .05). Symptomatic hemorrhage was rare in both groups. Also, patients investigated with CT and CT angiography were less impaired at discharge than those with standard CT (P < .02). A multifactorial regression showed that systolic blood pressure, glucose level and initial neurological impairment determined the neurological outcome at discharge.

CONCLUSIONS

Systolic blood pressure, glucose level and neurological impairment but not the imaging modality determined the neurological outcome following systemic thrombolysis in the 3-hour window.

[Development of new stroke therapies: outlook for neuroprotective drugs]

Stroke remains one of the most urgent medical problems of our times. The failure of most neuroprotective drugs in clinical trials led to the initiation of the Stroke Therapy Academic Industry Roundtable guidelines. Due to this improvement, the positive clinical trial results with the free radical scavenger NXY-059 (SAINT I) was encouraging. However, the subsequent SAINT II trial did not confirm these results. In this article we critically review the history of preclinical and clinical trials based on experience of NXY-059 development and present recommendations for potential future preclinical and clinical development of neuroprotective stroke therapy.

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.

Guidelines for management of ischaemic stroke and transient ischaemic attack 2008

This article represents the update of the European Stroke Initiative Recommendations for Stroke Management. These guidelines cover both ischaemic stroke and transient ischaemic attacks, which are now considered to be a single entity. The article covers referral and emergency management, Stroke Unit service, diagnostics, primary and secondary prevention, general stroke treatment, specific treatment including acute management, management of complications, and rehabilitation.

Local intraarterial fibrinolysis administered in aliquots for the treatment of central retinal artery occlusion: the Johns Hopkins Hospital experience

BACKGROUND AND PURPOSE

Central retinal artery occlusion results in acute visual loss with poor spontaneous recovery. Current standard therapies do not alter the natural history of disease. Several open-label clinical studies using continuous infusion of thrombolytic agents have suggested that local intraarterial fibrinolysis (LIF) is efficacious in the treatment of central retinal artery occlusion. The aim is to compare the visual outcome in patients with acute central retinal artery occlusion of presumed thromboembolic etiology treated with LIF administered in aliquots with that of patients treated with standard therapy.

METHODS

We conducted a single-center, nonrandomized interventional study of consecutive patients with acute central retinal artery occlusion from July 1999 to July 2006.

RESULTS

Twenty-one patients received LIF and 21 received standard therapy. Seventy-six percent of subjects in the LIF group had a visual acuity improvement of one line or more compared with 33% in the standard therapy group (P=0.012, Fisher exact). Multivariate logistic regression controlling for gender, history of prior stroke/transient ischemic attack, and history of hypercholesterolemia showed that patients who received tissue plasminogen activator were 36 times more likely to have improvement in visual acuity (P=0.0001) after adjusting for these covariates. Post hoc analysis showed that patients who received tissue plasminogen activator were 13 times more likely to have improvement in visual acuity of 3 lines or more (P=0.03) and 4.9 times more likely to have a final visual acuity of 20/200 or better (P=0.04). Two groin hematomas were documented in the LIF group. No ischemic strokes, retinal or intracerebral hemorrhages were documented.

CONCLUSIONS

LIF administered in aliquots is associated with an improvement in visual acuity compared with standard therapy and has few side effects.

National use of thrombolysis with alteplase for acute ischaemic stroke via telemedicine in Denmark: a model of budgetary impact and cost effectiveness

AIM

The purpose of this analysis was to assess the budgetary impact and cost effectiveness of the national use of thrombolysis with alteplase (recombinant tissue plasminogen activator; rt-PA) for acute ischaemic stroke via telemedicine in Denmark.

METHODS

Computations were based on a Danish health economic model of thrombolysis treatment of acute ischaemic stroke via telemedicine. Cost data for stroke units and satellite clinics were taken from the first practical experiences in Denmark with implementing thrombolysis via telemedical linkage to the Stroke Department at Aarhus University Hospital. Effectiveness data were taken from a published pooled analysis of results from randomized controlled trials of alteplase.

RESULTS

The calculations showed that the additional total costs to the hospitals of implementing thrombolysis with alteplase for acute ischaemic stroke via telemedicine were approximately $US3.0 (range 2.0-5.8) million per year in the case of five centres and five satellite clinics, or $US3.6 (range 2.4-7.0) million per year based on seven centres and seven satellite clinics. The incremental cost-effectiveness ratio was calculated to be approximately $US50,000 when taking a short time perspective (1 year), but thrombolysis was dominant (both cheaper and more effective) after as little as 2 years and cost effectiveness improved over longer time scales.

CONCLUSION

The budgetary impact of using thrombolysis with alteplase for acute ischaemic stroke via telemedicine depends on the existing capacity and organizational conditions at the local hospitals. The health economic model computations suggest that the macroeconomic costs may balance with savings in care and rehabilitation after as little as 2 years, and that potentially large long-term savings are associated with thrombolysis with alteplase delivered by telemedicine, although the long-term calculations are uncertain.

MRI assessment followed by successful mechanical recanalization of a complete tandem (internal carotid/middle cerebral artery) occlusion and reversal of a 10-hour fixed deficit

BACKGROUND

Mechanical clot extraction up to 8 hours after stroke onset is an alternative strategy for opening large vessels, especially for patients ineligible for intravenous thrombolysis. Safety beyond this therapeutic window is untested.

METHODS

An 81-year-old woman presented 8 hours after she developed left-sided weakness and dysarthria with a National Institutes of Health Stroke Scale (NIHSS) score fluctuating between 6 and 13. Neuroimaging revealed a large perfusion deficit with no diffusion abnormalities. An emergent cerebral angiogram revealed a complete internal carotid artery terminus occlusion.

RESULTS

Successful mechanical thrombectomy was performed without complication and resulted in almost complete reversal of the patient's deficit to an NIHSS score of 1, 10 hours after stroke onset.

CONCLUSION

Patients with large hypoperfused areas and minimal diffusion abnormalities on the MRI may benefit from mechanical thrombectomy beyond an 8-hour window.

Rapid Assessment of Perfusion–Diffusion Mismatch

Background and Purpose— For MR perfusion–diffusion (PWI-DWI) mismatch to become routine in thrombolysis patient selection, rapid and reliable assessment tools are required. We examined interrater variability in PWI/DWI volume measurements and developed a rapid assessment tool based on the Alberta Stroke Program Early CT Scores (ASPECTS) system.

Methods— DWI and PWI were performed in 35 patients with stroke <6 hours after symptom onset. DWI lesion and PWI (time to peak) volumes were measured with planimetric techniques by 4 raters and the 95% limits of agreement calculated. ASPECT scores were assessed separately by 4 investigators (2 experienced and 2 inexperienced) for DWI (MR DWI scores) and PWI (MR time to peak scores). MR mismatch scores were calculated as MR DWI-MR time to peak scores.

Results— Interobserver variability was much greater for PWI (95% limit of agreement=±72.3 mL) than for DWI (95% limit of agreement=±12.6 mL). A semiautomated PWI volume (time to peak+2 s) was therefore used to calculate mismatch volume. MR mismatch scores ≥2 predicted 20% PWI-DWI mismatch by volume with mean 78% sensitivity (range, 72% to 84%) and 88% specificity (range, 83% to 90%). There was excellent agreement on mismatch classification using MR mismatch scores between experienced raters (weighted kappa scores of 0.94) with agreement in 34 of 35 cases. Agreement was less consistent between inexperienced raters (weighted kappa=0.49, 28 of 35 cases).

Conclusions— Variability in planimetric mismatch measurements arises primarily from differences in PWI volume assessment. High specificity and interrater reliability may make MR mismatch scores an ideal rapid screening tool for potential thrombolysis patients.

Time is brain: is MRI the clock?

PURPOSE OF REVIEW

MRI is increasingly used as the primary imaging modality in acute stroke, since it allows treatment based on individual pathophysiology rather than strict time windows.

RECENT FINDINGS

PET studies have confirmed that regions with disturbed diffusion frequently indicate irreversible tissue damage, although they may in part be viable. The mismatch between a larger perfusion deficit and a smaller diffusion abnormality contains both critically hypoperfused regions as well as oligemic regions. Although mismatch is thus not perfect, recent prospective trials have convincingly shown that mismatch patients treated with revascularization therapies benefit from reperfusion, while patients without mismatch do not. This is particularly important for patients presenting beyond the first three hours. In addition, several studies have investigated MRI as a tool to assess the risk of thrombolytic treatment. Parameters reflecting severe ischemia, blood-brain barrier damage and preexisting small-vessel disease emerge as risk factors for intracerebral hemorrhage, while microbleeds are not clearly associated with an increased risk.

SUMMARY

Based on data from prospective trials, the mismatch concept is an acceptable method to identify patients who benefit from recanalization therapies. The concept, however, still needs to be further improved and standard definitions are required before widespread use can be recommended.

Pathophysiology of ischaemic stroke: insights from imaging, and implications for therapy and drug discovery

Preventing death and limiting handicap from ischaemic stroke are major goals that can be achieved only if the pathophysiology of infarct expansion is properly understood. Primate studies showed that following occlusion of the middle cerebral artery (MCA)--the most frequent and prototypical stroke, local tissue fate depends on the severity of hypoperfusion and duration of occlusion, with a fraction of the MCA territory being initially in a 'penumbral' state. Physiological quantitative PET imaging has translated this knowledge in man and revealed the presence of considerable pathophysiological heterogeneity from patient to patient, largely unpredictable from elapsed time since onset or clinical deficit. While these observations underpinned key trials of thrombolysis, they also indicate that only patients who are likely to benefit should be exposed to its risks. Accordingly, imaging-based diagnosis is rapidly becoming an essential component of stroke assessment, replacing the clock by individually customized management. Diffusion- and perfusion-weighted MR (DWI-PWI) and CT-based perfusion imaging are increasingly being used to implement this, and are undergoing formal validation against PET. Beyond thrombolysis per se, knowledge of the individual pathophysiology also guides management of variables like blood pressure, blood glucose and oxygen saturation, which can otherwise precipitate the penumbra into the core, and the oligaemic tissue into the penumbra. We propose that future therapeutic trials use physiological imaging to select the patient category that best matches the drug's presumed mode of action, rather than lumping together patients with entirely different pathophysiological patterns in so-called 'large trials', which have all failed so far.

Magnetic resonance imaging (MRI) of inflammation in stroke

Magnetic resonance imaging (MRI) of inflammation is based on the in vivo magnetic labelling of macrophages, the most abundant cells involved in the post-ischemic inflammatory response, by nanoparticles of iron oxides. Such approach has been successfully applied to study experimental rodent models of focal cerebral ischemia and has proved feasible in pioneer clinical studies. Despite current limitations, MRI of inflammation may become an important tool for the investigation of novel ischemic stroke therapeutics targeted at inflammation.

Prediction of hemorrhagic transformation after recanalization therapy using T2*-permeability magnetic resonance imaging

OBJECTIVE

Predicting hemorrhagic transformation (HT) is critical in the setting of recanalization therapy for acute stroke. Dedicated magnetic resonance imaging (MRI) sequences for detection of increased blood-brain barrier (BBB) permeability recently have been developed. We evaluated the ability of a novel MRI permeability technique to detect baseline derangements predictive of various forms of HT after recanalization therapy.

METHODS

We retrospectively analyzed the clinical and pretreatment MRI data on patients undergoing recanalization therapy for acute cerebral ischemia at a university medical center from January 2004 to November 2006. Pretreatment MRI permeability images derived from perfusion source data were compared with posttreatment imaging to evaluate whether baseline BBB permeability derangements may predict HT after recanalization therapy. The use of a novel permeability technique to illustrate BBB derangements was based on the detection of decreased signal intensity at later time points in perfusion MRI acquisition, signifying continued local accumulation of contrast caused by leakage.

RESULTS

Among 32 patients, some degree of HT occurred in 12. Permeability image abnormalities at baseline were present in 7 of 12 patients with HT and none of the 20 patients without HT on follow-up images. The sensitivity of permeability abnormality for parenchymal hematoma was 83%. False-negative findings were noted in five cases, most commonly asymptomatic or minor HT after mechanical clot retrieval.

INTERPRETATION

Permeability images derived from pretreatment perfusion MRI source data may identify patients at risk for HT with high specificity. Our preliminary demonstration of permeability imaging based on standard perfusion data for prediction of hemorrhage merits further study with dedicated MRI BBB permeability acquisitions and multicenter validation.

Can the Ischemic Penumbra Be Identified on Noncontrast CT of Acute Stroke?

Background and Purpose— Early ischemic changes on noncontrast CT in acute stroke include both hypoattenuation and brain swelling, which may have different pathophysiological significance.

Methods— Noncontrast CT and CT perfusion brain scans from patients with suspected acute stroke <6 hours after onset were reviewed. Five raters independently scored noncontrast CTs blind to clinical data using the Alberta Stroke Program Early CT Score (ASPECTS). Each ASPECTS region was scored as hypodense or swollen. A separate reviewer measured time to peak and cerebral blood volume in each ASPECTS region on CT perfusion. Time to peak and cerebral blood volume were compared for each region categorized as normal, hypodense, or isodense and swollen.

Results— Scans of 32 subjects a median 155 minutes after onset yielded 228 regions with both CT perfusion and noncontrast CT data. Isodense swelling was associated with significantly higher cerebral blood volume ( P =0.016) and with penumbral perfusion (posttest:pretest likelihood ratio 1.44 [95% CI: 0.68 to 2.90]), whereas hypodensity was associated with more severe time to peak delay and with core perfusion (likelihood ratio 3.47 [95% CI: 1.87 to 6.34]). Neither isodense swelling nor hypodensity was sensitive for prediction of perfusion pattern, but appearances were highly specific (87.2% and 91.0% for penumbra and core, respectively). Intrarater agreement was good or excellent, but interrater agreement for both hypodensity and swelling was poor.

Conclusions— Regions exhibiting hypoattenuation are likely to represent the infarct core, whereas regions that are isodense and swollen have increased cerebral blood volume and are more likely to signify penumbral perfusion. Although noncontrast CT is not sensitive for detection of core and penumbra, appearances are specific. Some information on tissue viability can therefore be obtained from noncontrast CT.

Bleeding risk analysis in stroke imaging before thromboLysis (BRASIL): pooled analysis of T2*-weighted magnetic resonance imaging data from 570 patients

BACKGROUND AND PURPOSE

There has been speculation that the risk of secondary symptomatic intracranial hemorrhage (SICH) may be increased after thrombolytic therapy in ischemic stroke patients who have cerebral microbleeds (CMBs) on T2*-weighted magnetic resonance imaging. Because of this concern, some centers withhold potentially beneficial thrombolytic therapy from these patients.

METHODS

We analyzed magnetic resonance imaging data acquired within 6 hours after symptom onset from 570 ischemic stroke patients treated with intravenous tissue plasminogen activator in 13 centers in Europe, North America, and Asia. Baseline T2*-weighted magnetic resonance images were evaluated for the presence of CMBs. The primary end point was SICH, defined as clinical deterioration with an increase in the National Institutes of Health Stroke Scale score by >or=4 points, temporally related to a parenchymal hematoma on follow-up-imaging.

RESULTS

A total of 242 CMBs were detected in 86 of 570 patients (15.1%). The number of CMBs ranged from 1 to 77 in the individual patient, with >or=5 CMBs in 6 of 570 patients (1.1%). Proportions of patients with SICH were 5.8% (95% CI, 1.9 to 13.0) in the presence of CMBs and 2.7% (95% CI, 1.4 to 4.5) in patients without CMBs (P=0.170, Fisher's exact test), resulting in no significant absolute increase in the risk of SICH of 3.1% (95% CI, -2.0 to 8.3).

CONCLUSIONS

The data suggest that if there is any increased risk of SICH attributable to CMBs, it is likely to be small and unlikely to exceed the benefits of thrombolytic therapy. No reliable conclusion regarding risk in the rare patient with multiple CMBs can be reached.

Ischaemic stroke: acute management, intensive care, and future perspectives

Recently, a number of developments in the acute management of stroke have necessitated active involvement of neurocritical care. This review focuses on the immediate care, including intensive care, that may make a difference to the patient outcome. Recent research, that highlights the importance of acute management of stroke in terms of thrombolysis, thrombolytic agents, decompressive surgery, and hypothermia, has been reviewed.

MRI-based and CT-based thrombolytic therapy in acute stroke within and beyond established time windows: an analysis of 1210 patients

BACKGROUND AND PURPOSE

The use of intravenous thrombolysis is restricted to a minority of patients by the rigid 3-hour time window. This window may be extended by using modern imaging-based selection algorithms. We assessed safety and efficacy of MRI-based thrombolysis within and beyond 3 hours compared with standard CT-based thrombolysis.

METHODS

Five European stroke centers pooled the core data of their CT- and MRI-based prospective thrombolysis databases. Safety outcomes were predefined as symptomatic intracranial hemorrhage and mortality. Primary efficacy outcome was a favorable outcome (modified Rankin Scale 0 to 1). We performed univariate and multivariate analyses for all end points, including age, National Institutes of Health Stroke Scale, treatment group (CT <3 hours, MRI <3 hours and >3 hours), and onset to treatment time as variables.

RESULTS

A total of 1210 patients were included (CT <3 hours: N=714; MRI <3 hours: N=316; MRI >3 hours: N=180). Median age, National Institutes of Health Stroke Scale, and onset to treatment time were 69, 67, and 68.5 years (P=0.66); 12, 13, and 14 points (P=0.019); and 130, 135, and 240 minutes (P<0.001). Symptomatic intracranial hemorrhage rates were 5.3%, 2.8%, and 4.4% (P=0.213); mortality was 13.7%, 11.7%, and 13.3% (P=0.68). Favorable outcome occurred in 35.4%, 37.0%, and 40% (P=0.51). Age and National Institutes of Health Stroke Scale were independent predictors for all safety and efficacy outcomes. The overall use of MRI significantly reduced symptomatic intracranial hemorrhage (OR: 0.520, 95% CI: 0.270 to 0.999, P=0.05). Beyond 3 hours, the use of MRI significantly predicted a favorable outcome (OR: 1.467; 95% CI: 1.017 to 2.117, P=0.040). Within 3 hours and for all secondary end points, there was a trend in favor of MRI-based selection over standard <3-hour CT-based treatment.

CONCLUSIONS

Despite significantly longer time windows and significantly higher baseline National Institutes of Health Stroke Scale scores, MRI-based thrombolysis is safer and potentially more efficacious than standard CT-based thrombolysis.

[Thrombolysis for ischemic stroke: an update]

Even 10 years after the approval of thrombolysis this life-saving and disability reducing therapy is still underused. Important reasons for that are very strict inclusion criteria such as the early and narrow time-window, fear of bleeding complications and doubts regarding the effectiveness. An intensive and constant effort is required to educate the public that stroke is a treatable emergency. In addition to the medical reasons, economic considerations in a context of decreasing resources emphasize the importance of effective stroke treatment. The results of numerous recent studies such as the European register SITS-MOST help to strengthen the confidence in thrombolysis. In addition the development and advancement of new imaging tools such as multiparametric MRI and advanced CT-techniques will improve patient selection and may enable us to extend the time-window for treatment. Intraarterial thrombolysis, "bridging" methods and new devices for intravascular intervention are the subjects of intensive ongoing research. Even though no randomized trials are available intraarterial thrombolysis is the treatment of choice for acute basilar occlusion, but if this intervention is not available an intravenous approach may be an equal alternative.

Thrombolytic therapy for acute ischaemic stroke in octogenarians: selection by magnetic resonance imaging improves safety but does not improve outcome

BACKGROUND

Owing to the fear of an increased bleeding risk, thrombolytic therapy is withheld from many patients with acute stroke > 80 years of age.

OBJECTIVE

To analyse the risk for symptomatic intracranial haemorrhage (sICH), morbidity and mortality after thrombolytic therapy in octogenarians focusing, in particular, on whether patients selected using magnetic resonance imaging (MRI) had a better risk:benefit ratio.

METHODS

The prospectively collected single-centre data of all patients treated with systemic thrombolytic therapy for acute ischaemic stroke since 1998 (n = 468) were reviewed, and patients > or = 80 years (n = 90) were compared with those aged < 80 years (n = 378). In addition, the group of octogenarians was analysed with respect to initial imaging modality.

RESULTS

The overall rate of sICH in the octogenarians was 6.9%, compared with 5.3% in younger patients (p = 0.61). In older patients selected by computed tomography, the rate of sICH was 9.4%; no patient selected by MRI had sICH (p = 0.10). Mortality in the octogenarians selected by computed tomography was 29.7% after 3 months as compared with 26.9% in the patients selected by MRI (p = 1.0). 20.3% of the octogenarians selected by computed tomography and 15.4% of those selected by MRI had a favourable outcome (modified Rankin scale < or = 1) after 3 months (p = 0.77).

CONCLUSION

Compared with younger patients, octogenarians do not have an increased risk of sICH. The use of MRI to select octogenarians for thrombolytic therapy seemed to decrease the risk of sICH, but did not influence the overall outcome after 3 months.

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.

Pattern of cortex and white matter involvement in severe middle cerebral artery ischemia

BACKGROUND AND PURPOSE

In middle cerebral artery (MCA) stroke, ischemia usually is unevenly distributed within the MCA territory. We sought to investigate which brain structures are critical for the acute neurological deficit in severe MCA stroke.

METHODS

We used magnetic resonance (MR) imaging and statistical parametric mapping in 64 consecutive stroke patients (64 +/-13 years) to study the pattern of the initial perfusion abnormality.

RESULTS

Patients with lesion progression had more severe time-to-peak (TTP) abnormalities (P < .0001) in the inferior frontal gyrus, superior temporal gyrus, insula, and underlying hemispheric white matter than those with lesion regression. Also, patients with lesion progression had more severe T2 abnormalities on day 8 than those with lesion regression. In contrast, the changes of water diffusion were similar among the two groups resulting in a perfusion-diffusion mismatch in lesion progression. TTP-lesions were related to the neurological deficit score (r(s)=-0.563, P < .0001), T2-lesions (r= 0.686, P < .0001), and cerebral artery abnormalities assessed on MR-angiography (r(s)= 0.399, P < .01).

CONCLUSIONS

In major MCA, stroke ischemia was most severe in the central portion of the MCA territory. It is suggested that involvement of hemispheric white matter accentuated the neurological deficit probably by affecting cortico-cortical and cortico-subcortical fibers.

Debunking 7 myths that hamper the realization of randomized controlled trials on intra-arterial thrombolysis for acute ischemic stroke

BACKGROUND AND PURPOSE

Although intravenous (IV) thrombolysis is the standard treatment for patients with ischemic stroke occurring within 3 hours from symptom onset, a few interventional neuroradiologists have been treating this category of patients by an intra-arterial (IA) route for >25 years. However, evidence is still required to support the clinical feeling that IA treatment, which needs longer time and greater complexity, leads to a better outcome. Therefore, the objective of the present review was to analyze beliefs and myths underlying the selection of patients for IA thrombolysis.

METHODS

We identified and debunked the following myths on IA thrombolysis: (1) IA thrombolysis works better than IV because it achieves higher recanalization rates; (2) IA thrombolysis works better than IV after the 3-hour window; (3) IA thrombolysis works better than IV in vertebrobasilar stroke; (4) carotid duplex, transcranial doppler, CT angiography, or MRA should be used to screen for major vessel occlusion treatable with IA thrombolysis; (5) to be treated with IA thrombolysis, patients should be selected with diffusion/perfusion MRI; (6) IA thrombolysis should be used as a "rescue" therapy for IV thrombolysis; and (7) the efficacy of IA thrombolysis depends on the thrombolytic agent or the device used.

CONCLUSIONS

Evidence on acute stroke management with IA thrombolysis is scant. Therefore, neither clinicians nor patients have enough information to make truly informed decisions about the most appropriate treatment. Only randomized controlled trials can clear uncertainties about the possible superiority of IA over IV thrombolysis. Regretfully, case series on IA treatment have limited the organization of such trials and have only favored the spread of myths.

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.

Coagulation, coma, and outcome in bacterial meningitis--an observational study of 38 adult cases

OBJECTIVES

The purpose of this study was to evaluate the epidemiology of intravascular coagulation in bacterial meningitis and to recognise the associations with disease severity and outcome.

METHODS

Thirty-eight consecutively admitted adult patients with microbiologically proven bacterial meningitis were observed prospectively for platelets count (PLT), platelets-decline (dPLT), prothrombin ratio (PTr), INR, and D-dimer levels during the first three days in relation to disease severity (Glasgow Coma Scale--GCS, APACHE-III) and outcome (Glasgow Outcome Scale--GOS).

RESULTS

The prevalence of activated coagulation measured by abnormal laboratory results varied respectively: PTr--30%, INR--36%, PLT--38%, dPLT--50%, and D-dimer--88%. Patients with GCS <9 at admission presented with laboratory results suggesting triggered coagulation: dPLT 48 vs. 15%/day (p=0.0246), INR 1.6 vs. 1.12 (p=0.0014), PTr 76 vs. 93% (p=0.0020). An unfavourable outcome (GOS 1-4) was observed in 42% of patients and was associated with: PLT <170 or >265 G/L (OR--24.4; p=0.0006), PTr <82% (OR--5.00; p=0.0388), INR >1.1 (OR--5.04; 0.0336), and D-dimer >850 ng/ml (OR--24.0; p=0.0033).

CONCLUSIONS

Coagulation was activated in a majority of patients with bacterial meningitis and related to coma and unfavourable outcome.

Established treatments for acute ischaemic stroke

This article reviews the recommended management of patients presenting to accident and emergency departments with acute ischaemic stroke, and focuses on thrombolysis. The review includes initial management, recommended clinical, laboratory, and radiographic examinations. Appropriate general medical care, consisting of monitoring of oxygenation, fever, blood pressure, and blood glucose concentrations are examined. Criteria for thrombolysis with intravenous recombinant tissue plasminogen activator (rt-PA) are discussed. Complications of rt-PA therapy, such as haemorrhagic transformation and angio-oedema, are reviewed. An approach to management of rt-PA complications is outlined. Only a small percentage of acute ischaemic stroke patients meet criteria for rt-PA; therefore, alternative acute treatment strategies are also discussed. Acute medical and neurological complications in stroke patients are analysed, along with recommendations for treatment.

Cost-effectiveness of intravenous thrombolysis with alteplase within a 3-hour window after acute ischemic stroke

BACKGROUND AND PURPOSE

The aim of this study was to assess the costs and cost-effectiveness of intravenous thrombolysis treatment with alteplase (Actilyse) of acute ischemic stroke with 24-hour in-house neurology coverage and use of magnetic resonance imaging.

METHODS

A health economic model was designed to calculate the marginal cost-effectiveness ratios for time spans of 1, 2, 3 and 30 years. Effect data were extracted from a meta-analysis of six large-scale randomized and placebo-controlled studies of thrombolytic therapy with alteplase. Cost data were extracted from thrombolysis treatment at Aarhus Hospital, Denmark, and from previously published literature.

RESULTS

The calculated cost-effectiveness ratio after the first year was $55,591 US per quality-adjusted life-year (base case). After the second year, computation of the cost-effectiveness ratio showed that thrombolysis was cost-effective. The long-term computations (30 years) showed that thrombolysis was a dominant strategy compared with conservative treatment given the model premises.

CONCLUSIONS

A high-quality thrombolysis treatment with 24-hour in-house neurology coverage and magnetic resonance imaging might not be cost-effective in the short term compared with conservative treatment. In the long term, there are potentially large-scale health economic cost savings.