CT angiography in the rapid triage of patients with hyperacute stroke to intraarterial thrombolysis: accuracy in the detection of large vessel thrombus

Imaging of acute ischemic stroke

In this article the individual components of multimodal computed tomography and multimodal magnetic resonance imaging are discussed, the current status of neuroimaging for the evaluation of the acute ischemic stroke is presented, and the potential role of a combined multimodal stroke protocol is addressed.

Ischemic stroke

The goal of stroke imaging is to appropriately select patients for different types of therapeutic management in order to optimize outcome and minimize potential complications. To accomplish this, the radiologist has to evaluate each case and tailor an imaging protocol to fit the patient's needs and best answer the clinical question. This review outlines the routinely used, current neuroimaging techniques and their role in the evaluation of the acute stroke patient. The ability of computed tomography and magnetic resonance imaging to adequately evaluate the infarcted brain parenchyma, the cerebral vasculature, and the ischemic, but potentially viable tissue, often referred to as the "ischemic penumbra," is compared The authors outline an imaging algorithm that has been employed at their institution, and briefly review endovascular therapies that can be used in specific patients for stroke treatment.

Neuroimaging of cerebral ischemia and infarction

The imaging workup for patients with suspected acute ischemic stroke has advanced significantly over the past few years. Evaluation is no longer limited to noncontrast computed tomography, but now frequently also includes vascular and perfusion imaging. Although acute stroke imaging has made significant progress in the last few decades with the development of multimodal approaches, there are still many unanswered questions regarding their appropriate use in the setting of daily patient care. It is important for all physicians taking care of stroke patients to be familiar with current multimodal computed tomography and magnetic resonance imaging techniques, including their strengths, limitations, and their role in guiding therapy.

Cost-effectiveness of multimodal CT for evaluating acute stroke

OBJECTIVE

Multimodal CT, including noncontrast CT (NCCT), CT with contrast, CT angiography (CTA), and perfusion CT (CTP), is increasingly used in acute stroke patients to identify candidates for endovascular therapy. Our goal is to explore the cost-effectiveness of multimodal CT as a diagnostic test.

METHODS

A Markov model compared multimodal CT to NCCT in a hypothetical cohort of nonhemorrhagic stroke patients presenting within 3 hours of symptom onset who were potential IV tPA candidates. Patients who failed to improve after IV tPA or in whom IV tPA was contraindicated were candidates for endovascular therapy. Direct costs (2008 USD), outcomes, and probabilities were obtained from the literature.

RESULTS

For the 3-month time horizon, multimodal CT had lower costs (-$1,716), had greater quality-adjusted life-years (QALYs, 0.004), and was the cost-effective choice 100% of the time for a willingness-to-pay of $100,000/QALY (probabilistic sensitivity analysis). The number needed to screen with multimodal CT to avoid 1 diagnostic angiogram was 2. Over a lifetime, multimodal CT had lower costs (-$2,058), had greater QALYs (0.008), and was cost-effective, with a 90.1% likelihood, for a willingness-to-pay of $100,000/QALY.

CONCLUSIONS

Multimodal CT appears to be a cost-saving screening tool over the short term. However, additional data regarding clinical outcomes following multimodal CT-guided intra-arterial treatment are needed before the long-term cost-effectiveness can be suitably addressed. This analysis can be incorporated into future discussions of multimodal CT as a diagnostic test for unselected patients, within and beyond the 3-hour IV tPA time window.

The role of CT and MRI in the emergency evaluation of persons with suspected stroke

As a growing number of therapeutic treatment options for acute stroke are being introduced, multimodal acute neuroimaging is assuming a growing role in the initial evaluation and management of patients. Multimodal neuroimaging, using either a CT or MRI approach, can identify the type, location, and severity of the lesion (ischemia or hemorrhage); the status of the cerebral vasculature; the status of cerebral perfusion; and the existence and extent of the ischemic penumbra. Both acute and long-term treatment decisions for stroke patients can then be optimally guided by this information.

Assessment of collateral flow with multi-phasic CT: correlation with diffusion weighted MRI in MCA occlusion

PURPOSE

To correlate collateral flow on multiphasic contrast enhancement computed tomography (CT) and graded ischemic changes on diffusion weighted MR in patients with acute middle cerebral artery (MCA) infarction.

MATERIALS AND METHODS

A retrospective evaluation of diffusion weighted images (DWIs) and three phasic contrast enhanced CT (CECT) was performed on 11 patients with MCA occlusions. The area of ischemic change on DWIs was graded according to the Alberta Stroke Program Early CT Score (ASPECTS) criteria. To evaluate collateral flow on three phasic CECT, we counted the number of contrast enhancing MCA branches distal to the occlusion site at the sylvian fissure from predetermined axial images. The collateral ratios of counted numbers to those at the normal side were calculated at each phase (CR1, CR2, CR3). We then compared collateral ratios from the three phasic CECT with ASPECTS data from DWIs.

RESULTS

Collateral ratios from the three phasic CECT were determined to be CR1 .48 ± .27, CR2 .73 ± .36 and CR3 .72 ± .30. We discovered a correlation between both the CR2 and ASPECTS (r= .675, P= .023) and the CR3 and ASPECTS (r= .664, P= .026).

CONCLUSION

The number of contrast enhancing branches distal to the MCA occlusion, as counted in the sylvian fissure on later phase images of multiphasic CECT, reflects the status of collateral flow, and correlates with ASPECTS on DWIs.

Functional contrast-enhanced CT for evaluation of acute ischemic stroke does not increase the risk of contrast-induced nephropathy

BACKGROUND AND PURPOSE

Concerns have recently grown regarding the safety of iodinated contrast agents used for CTA and CTP imaging. We tested whether the incidence of AN, defined by a >or=25% increase in the post-contrast scan creatinine level, was higher among patients with ischemic stroke who underwent a functional contrast-enhanced CT protocol compared with those who had no iodinated contrast administration.

MATERIALS AND METHODS

The contrast-exposed group consisted of 575 patients with acute ischemic stroke who underwent CTA (n = 313), CTA/CTP (n = 224), or CTA/CTP followed by conventional angiography (n = 38) within 24 hours of stroke onset and were consecutively enrolled in a prospective cohort study. The nonexposed group consisted of 343 patients with ischemic stroke, consecutively admitted to the same institution, who did not receive iodinated contrast material. Patients were stratified by baseline eGFR. In the primary analysis, the Fisher exact test was used to compare the incidence of AN between the contrast-exposed and the nonexposed patients at 24, 48, and 72 hours and on a cumulative basis. A secondary analysis compared the incidence of AN in patients who underwent conventional angiography following CTA/CTP versus patients who underwent CTA/CTP only.

RESULTS

The incidence of AN was 5% in the exposed and 10% in the nonexposed group (P = .003). Patients who underwent conventional angiography after contrast CT were at no greater risk of AN than patients who underwent CTA/CTP alone (26 patients, 5%; and 2 patients, 5%, respectively; P = .7).

CONCLUSIONS

Administration of a contrast-enhanced CT protocol involving CTA/CTP and conventional angiography in selected patients does not appear to increase the incidence of CIN.

Computed tomography and computed tomography angiography findings predict functional impairment in patients with minor stroke and transient ischaemic attack

INTRODUCTION

Abnormalities on acute magnetic resonance imaging predict outcome in minor stroke and transient ischaemic attack patients. We hypothesised that noncontrast computed tomography and computed tomography angiography findings in minor stroke and transient ischaemic attack patients would also predict functional outcome.

METHODS

We analysed consecutive patients with a transient ischaemic attack or a minor stroke with an National Institute of Health Stroke Scale <or=3 who were assessed with a noncontrast computed tomography and CT angiography of the circle of Willis and neck within 24 h of symptom onset. We assessed the association between clinical or imaging features and functional impairment on the modified Rankin Scale (mRS >or=2 ) at 90 days.

RESULTS

Among 457 patients, the median baseline National Institute of Health Stroke Scale score was 1. Median time from symptom onset to noncontrast computed tomography was 278 min (interquartile range 151-505) and median delay from noncontrast computed tomography to CT angiography was 3 min (interquartile range 0-13). At 90 days, 57 patients (12.5%) had a mRS >or=2. Clinical factors that were associated with functional impairment were age >or=60 years (RR 2.05 CI(95) 1.16-3.64) and baseline National Institute of Health Stroke Scale score >0 (RR 3.23 1.72-6.06). All the assessed computed tomography parameters (acute stroke on noncontrast computed tomography and intracranial or extracranial stenosis or occlusion) were individually predictive of functional impairment. A composite computed tomography imaging 'at risk' metric, defined by acute stroke on noncontrast computed tomography, Circle of Willis intracranial vessel occlusion or >or=50% stenosis, extracranial occlusion or >or=50% stenosis, was associated with poorer outcome (RR 2.92 CI(95) 1.81-4.71).

CONCLUSIONS

The presence of an acute stroke on noncontrast computed tomography or an intracranial or extracranial occlusion or stenosis was associated with an increased risk of functional impairment. Multi-modal computed tomography could be used to identify high-risk transient ischaemic attack or minor stroke patients.

Clinical predictors of significant findings on head computed tomographic angiography

BACKGROUND

Although head computed tomographic angiography (CTA) is a sensitive tool for the evaluation of neurological symptoms in the emergency department (ED), little is known about which clinical signs predict significant CTA findings.

OBJECTIVES

To identify clinical factors that predict significant findings on head CTA in patients presenting to the ED with neurological complaints.

METHODS

Retrospective chart review of consecutive adult patients undergoing head CTA over a 6-month period in an urban, tertiary care ED with an annual volume of 76,000. Significant head CTA findings were defined as clinically significant neurological abnormalities undetected by previous imaging studies. Demographics, chief complaint, results of the neurological examinations (NE), and head non-contrast computed tomography (CT) results were used as predictors of significant head CTA. All predictors with a univariate p < 0.2 using Pearson's chi-squared were entered stepwise into a multivariable logistic regression including odds ratios (OR), with inclusion restricted to p < 0.05.

RESULTS

Chart review yielded 456 cases; 215 (47%) were male. Mean age was 62 (SD 20) years. There were 189 patients (41%) with abnormal CTAs. Multivariable logistic regression indicated five variables that predicted a clinically significant CTA: abnormal CT (OR 3.72), chief complaint of subarachnoid hemorrhage-type headache (OR 2.30), and motor deficit (OR 2.23), visual deficit (OR 2.23), and other focal deficit (OR 2.18) on NE. A chief complaint of trauma (OR 0.23) predicted a normal CTA.

CONCLUSIONS

Specific historical and focal neurological findings are useful for predicting clinically significant findings on head CTA.

Advanced imaging applications for endovascular procedures

Advanced imaging techniques, particularly in CT and MRI, have become state-of-the-art to support the performance of interventional neuroradiologic procedures. Multidetector CT scanners with submillimeter detectors and real-time workstations have allowed the use of a noninvasive study, CT angiography, as a first-line diagnostic study at many institutions to detect and evaluate the morphology of aneurysms. Follow-up for postsubarachnoid spasm now includes transcranial Doppler, CT angiography, and sometimes perfusion to guide therapy. While both intracranial and extracranial stenosis have long been well evaluated by MR and CT angiography, information about the intimal wall and plaque morphology is now possible. In the setting of acute ischemia, CT with perfusion or MR with diffusion and perfusion has increased the ability to separate territory at risk from infarcted tissue, and can help to guide more appropriate intervention. This article addresses current state-of the-art imaging applications as well as a few techniques on the horizon that show great promise in helping to characterize those lesions amenable to endovascular therapy.

Multimodal CT in stroke imaging: new concepts

A multimodal CT protocol provides a comprehensive noninvasive survey of acute stroke patients with accurate demonstration of the site of arterial occlusion and its hemodynamic tissue status. It combines widespread availability with the ability to provide functional characterization of cerebral ischemia, and could potentially allow more accurate selection of candidates for acute stroke reperfusion therapy. This article discusses the individual components of multimodal CT and addresses the potential role of a combined multimodal CT stroke protocol in acute stroke therapy.

IV vs. IA TPA in acute ischemic stroke with CT angiographic evidence of major vessel occlusion: a feasibility study

BACKGROUND AND AIMS

Studies suggest that stroke patients with thrombus in a major cerebral vessel respond less favorably to intravenous (IV) thrombolysis. The purpose of this study was to test the feasibility of a protocol comparing IV versus intra-arterial (IA) recombinant tissue plasminogen activator (TPA) in an acute ischemic stroke with major vessel occlusion.

METHODS

Consecutive ischemic stroke patients presenting <3 h from symptom onset with major vessel occlusion on CT angiogram (CTA) were randomly assigned to IV TPA (per NINDS protocol) or IA TPA (22 mg over 2 h). Demographics, times to presentation and thrombolysis, presenting NIH stroke scale (NIHSS) and 90-day NIHSS, Barthel Index, and modified Rankin Scale were recorded. CT-scans at 24-h were reviewed for presence of hemorrhage. Recanalization was determined by post-procedure MR angiograms, which are obtained the day after thrombolytic therapy.

RESULTS

Seven patients (median NIHSS = 16) were randomized to IV (N = 4) or IA (N = 3) TPA. There were no significant differences in the presentation NIHSS, time to presentation, or time to treatment between the two groups. Hemorrhage was noted in one patient in the IA group (asymptomatic) and one patient in the IV group (symptomatic). Recanalization was seen in all patients treated with IA TPA and none treated with IV TPA (P = 0.03, Fisher's Exact test).

CONCLUSIONS

We found that it is feasible to conduct a trial comparing IV vs. IA TPA in ischemic stroke patients with major vessel occlusion presenting <3 h from onset. Patients treated with IA TPA showed a trend toward higher rate of recanalization. A larger trial may be designed to test safety and effectiveness of IA TPA in this specific group of stroke patients.

Neuroimaging of ischemic stroke with CT and MRI: advancing towards physiology-based diagnosis and therapy

Acute ischemic stroke is the third leading cause of death and the major cause of significant disability in adults in the USA and Europe. The number of patients who are actually treated for acute ischemic stroke is disappointingly low, despite availability of effective treatments. A major obstacle is the short window of time following stroke in which therapies are effective. Modern imaging is able to identify the ischemic penumbra, a key concept in stroke physiology. Evidence is accumulating that identification of a penumbra enhances patient management, resulting in significantly improved outcomes. Moreover, unexpectedly large proportions of patients have a substantial ischemic penumbra beyond the traditional time window and are suitable for therapy. The widespread availability of modern MRI and computed tomography systems presents new opportunities to use physiology to guide ischemic stroke therapy in individual patients. This article suggests an evidence-based alternative to contemporary acute ischemic stroke therapy.

[Computed tomography in acute ischemic stroke. Current developments compared with stroke MRI]

Modern multimodal acute stroke computed tomography (CT) includes noncontrast cranial CT (NCT), CT angiography (CTA), and CT perfusion imaging (CTP). Compared to stroke MRI, NCT is faster and easier. Multimodal CT can determine acute stroke etiology: Is arterial occlusion or intracerebal hemorrhage present? How extensive are the perfusion disturbance and infarct core, respectively? The information from NCT is sufficient for making acute stroke thrombolysis decisions within 4.5 h from symptom onset. The therapeutic effect of CTA and CTP--as well as acute stroke MRI--on improved functional outcome has still not been established.

Intracranial thrombus extent predicts clinical outcome, final infarct size and hemorrhagic transformation in ischemic stroke: the clot burden score

BACKGROUND

In ischemic stroke, functional outcomes vary depending on site of intracranial occlusion. We tested the prognostic value of a semiquantitative computed tomography angiography-based clot burden score.

METHODS

Clot burden score allots major anterior circulation arteries 10 points for presence of contrast opacification on computed tomography angiography. Two points each are subtracted for thrombus preventing contrast opacification in the proximal M1, distal M1 or supraclinoid internal carotid artery and one point each for M2 branches, A1 and infraclinoid internal carotid artery. We retrospectively studied patients with disabling neurological deficits (National Institute of Health Stroke Scale score >or=5) and computed tomography angiography within 24-hours from symptom onset. We analyzed percentages independent functional outcome (modified Rankin Scale score <or=2), final infarct Alberta Stroke Program Early Computed Tomography Score and parenchymal hematoma rates across categorized clot burden score groups and performed multivariable analysis.

RESULTS

We identified 263 patients (median age 73-years, National Institute of Health Stroke Scale score 10, onset-to-computed tomography angiography time 165 min). Clot burden score<10 was associated with reduced odds of independent functional outcome (odds ratio 0.09 for clot burden score<or=5; odds ratio 0.22 for clot burden score 6-7; odds ratio 0.48 for clot burden score 8-9; all versus clot burden score 10; P<0.02 for all). Lower clot burden scores were associated with lower follow-up Alberta Stroke Program Early Computed Tomography Scores (P<0.02 for all). Lower clot burden scores were associated with lower follow-up Alberta Stroke Program Early CT Scores (P<0.001) and higher parenchymal hematoma rates (P=0.008). Inter-rater reliability for clot burden score was 0.87 (lower 95% confidence interval 0.71) and intra-rater reliability 0.96 (lower 95% confidence interval 0.92).

CONCLUSION

The quantification of intracranial thrombus extent with the clot burden score predicts functional outcome, final infarct size and parenchymal hematoma risk acutely. The score needs external validation and could be useful for patient stratification in stroke trials.

Frequency and clinical course of stroke and transient ischemic attack patients with intracranial nonocclusive thrombus on computed tomographic angiography

BACKGROUND AND PURPOSE

We sought to determine the frequency and clinical course of patients with acute ischemic stroke or transient ischemic attack (TIA) who had intracranial nonocclusive thrombus (iNOT) on CT angiography (CTA).

METHODS

We retrospectively (June 2002-March 2007) reviewed consecutive patients with acute ischemic stroke or TIA who had CTA performed acutely for diagnostic work-up. A neuroradiologist reviewed all cases with potential iNOT. Criteria to diagnose iNOT rather than occlusive thrombus or atherosclerotic stenosis were: (1) residual lumen present and eccentric; (2) nontapering thrombus; (3) smooth and well-defined thrombus margins; and (4) absence of vessel wall calcification. We defined functional independence at discharge as modified Rankin scale score </=2.

RESULTS

Of 865 patients, 23 (2.7%) exhibited iNOT on CTA (43% women, mean age 69+/-14 years, median National Institute of Health Stroke Scale score 3 [range, 0-23]; median onset-to-CTA time 3.5 hours [range, 0.9-75]). Four patients (17%) deteriorated clinically during the hospital course and had persistent new focal neurological deficits. All of them were functionally dependent at discharge. All 19 patients (83%) without persistent clinical deterioration (2 patients had recurrent TIAs) were functionally independent at discharge.

CONCLUSIONS

Intracranial nonocclusive thrombus on CTA is relatively uncommon. The majority of patients have a good clinical outcome. However, some patients deteriorate clinically and are functionally dependent at discharge.

Rate of arterial occlusion in patients with acute ischemic stroke

OBJECTIVE

Computed tomographic angiography (CTA) was invented more than 20 years ago, but only gained acceptance recently, thanks to advancements in the computer technology. It can demonstrate areas of arterial stenosis or occlusion with accuracy nearly that of digital subtraction angiography (DSA). It is also able to clearly illustrate calcification, which is more difficult to define on magnetic resonance angiography and is not clearly depicted on DSA.

METHODS

Our retrospective study attempted to clarify the rate of occlusion or stenosis in the patients with acute ischemic stroke.

RESULTS

Over the period of 7 months, 93 consecutive patients were admitted with acute ischemic stroke. Fifty-six patients underwent CTA and were included in this study. Most of the patients were admitted after 6 hours following onset of symptoms. There were 28 men and 28 women, and 80.4% of the cohort was of African-American origin. The majority of strokes were attributed to small-vessel disease (25/56). The rest of the cases were deemed secondary to atheroembolism (15/56), cardioembolism (9/56) or of unclear etiology (7/56). In 24 (42.9%) patients, CTA failed to reveal any abnormalities of the cerebrovascular tree. CTA demonstrated arterial occlusion in ten (17.9%) patients and stenosis of extracranial or intracranial arteries on the symptomatic side in 22 (39.2%) patients. There was very good correlation between CTA and ultrasound techniques (carotid duplex and transcranial Doppler). CTA was superior in demonstrating distal intracranial stenosis.

CONCLUSION

Overall, CTA is an extremely valuable and fast way to emergently evaluate the cerebrovascular anatomy, making it very useful for pre-thrombolysis evaluation of patients with ischemic stroke.

CT angiography-source image hypoattenuation predicts clinical outcome in posterior circulation strokes treated with intra-arterial therapy

BACKGROUND AND PURPOSE

The aim of this study was to correlate CT angiography-source image (CTA-SI) parenchymal hypoattenuation with clinical outcome in patients with vertebrobasilar occlusion treated with intra-arterial thrombolysis.

METHODS

In 16 patients with vertebrobasilar occlusion treated with intra-arterial thrombolysis, we graded CTA-SI parenchymal hypoattenuation in the medulla, pons, midbrain, thalamus, cerebellum, occipital lobe, inferior parietal lobe, and medial temporal lobe. The grading scale was: 0, no hypoattenuation; 1, <50% hypoattenuation; and 2, >50% hypoattenuation. On CTA, we assessed clot location and length and collaterals. Outcome was measured with modified Rankin score.

RESULTS

Mean patient age was 68.3 years (range, 47 to 86 years), National Institutes of Health Stroke Scale was 28 (range, 11 to 40), time to CTA was 5.2 hours (range, 0.69 to 15.32), and time from CTA to intra-arterial thrombolysis was 5 hours (range, 2.25 to 10.38 hours). There were 4 basilar, 2 vertebral, and 10 combined occlusions. Eleven patients had near complete, 4 had partial, and one had no recanalization. Independent outcome predictors measured as modified Rankin score at 3 months were CTA-SI pons and midbrain scores(cumulative r=0.81, P<0.001). For outcome dichotomized into death versus survival, the CTA-SI pons score (P=0.0037) was the only independent predictor.

CONCLUSIONS

Hypoattenuation in the pons and midbrain on pretreatment CTA-SI correlates highly with clinical outcome in patients with vertebrobasilar occlusion treated with intra-arterial thrombolysis.

Extent of hypoattenuation on CT angiography source images predicts functional outcome in patients with basilar artery occlusion

BACKGROUND AND PURPOSE

Quantification of early ischemic changes (EIC) may predict functional outcome in patients with basilar artery occlusion (BAO). We tested the validity of a novel CT score, the posterior circulation Acute Stroke Prognosis Early CT score (pc-ASPECTS).

METHODS

Pc-ASPECTS allots the posterior circulation 10 points. Two points each are subtracted for EIC in midbrain or pons and 1 point each for EIC in left or right thalamus, cerebellum or PCA-territory, respectively. We studied 2 different populations: (1) patients with suspected vertebrobasilar ischemia and (2) patients with BAO. We applied pc-ASPECTS to noncontrast CT (NCCT), CT angiography source images (CTASI), and follow-up image by 3-reader consensus. We calculated sensitivity for ischemic changes and analyzed the predictivity of pc-ASPECTS for independent (modified Rankin Scale [mRS] score </=2) and favorable (mRS score </=3) outcome.

RESULTS

Of 130 patients with suspected vertebrobasilar ischemia, 72% (94) had posterior circulation stroke, 8% (10) transient ischemic attack, and 20% (26) nonischemic etiology. Sensitivity for ischemic changes was improved with CTASI compared to NCCT (65% [95% CI, 57% to 73%] versus 46% [95% CI, 37% to 55%], respectively). Pc-ASPECTS score on CTASI but not NCCT predicted functional independence (OR 1.58; P=0.005 versus 1.22; P=0.42, respectively). Of 46 patients with BAO, 52% (12/23) with CTASI pc-ASPECTS score >/=8 but only 4% (1/23) with a score <8 had favorable functional outcome (RR 12.1; 95% CI, 1.7 to 84.9). This difference was consistent in 21 patients with angiographic recanalization (RR 7.7; 95% CI, 1.1 to 52.1).

CONCLUSIONS

The CTASI pc-ASPECTS score may identify BAO patients unlikely to have a favorable outcome despite recanalization.

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.

[Acute ischemic stroke. Diagnostic imaging and interventional options]

Stroke is the third most common cause of death after myocardial infarction and neoplasms in industrialized countries and the most common cause for permanent disability with impairment of an independent life style. In addition to the socioeconomic problems caused by a disabling stroke, it is to be expected that with an increasing average age of the population, the number of stroke patients will increase as well [4]. The need for effective and widely available therapies against this severe disease is highly evident. Diagnostic imaging is indispensable in order to apply these therapies efficiently and precisely. In addition to the established intravenous thrombolytic therapy with rt-PA within the first 3 h, a therapeutic benefit can also be achieved with thrombolysis inside the time-window 3-6 h, whereas the rate of symptomatic intracerebral hemorrhages increases. Local intraarterial fibrinolysis (LIF) within 6 h is effective and safe and may lead to considerable improvement despite an initially severe medical condition [13]. Besides LIF, interventional techniques for mechanical recanalization of intracranial vessel occlusions are becoming increasingly more established. According to international guidelines for the treatment of acute stroke, computed tomography (CT) is considered to be the most important technical diagnostic tool if available round-the-clock. Alternatively, magnetic resonance tomography (MRT) may primarily be performed if carried out without delay and if the imaging protocol contains a sequence suitable for exclusion of hemorrhages.

Comparison of two imaging protocols for acute stroke: unenhanced cranial CT versus a multimodality cranial CT protocol with perfusion imaging

The aim of the study was to validate a multimodality cranial computed tomography (CCT) protocol for patients with acute stroke in the United Arab Emirates as a basic imaging procedure for a stroke unit. Therefore, a comparative study was conducted between two groups: retrospective, historical group 1 with early unenhanced CCT and prospective group 2 undergoing a multimodality CCT protocol. Follow-up unenhanced CCT>48 h served as gold standard in both groups. Group 1: Early unenhanced CCT of 50 patients were evaluated retrospectively, using Alberta Stroke Program Early CT Score, and compared with the definite infarction on follow-up CCT. Group 2: 50 patients underwent multimodality CCT (unenhanced CCT, perfusion studies: cerebral blood flow, cerebral blood volume, mean transit time and CT angiography)<8 h after clinical onset and follow-up studies. Modified National Institute of Health Stroke Scale was used clinically in both groups. Group 1 showed 38 men, 12 women, clinical onset 2-8 h before CCT and modified National Institute of Health Stroke Scale 0-28. Group 2 included 38 men, 12 women, onset 3-8 h before CCT, modified National Institute of Health Stroke Scale 0-28. Sensitivity was 58.3% in group 1 and 84.2% in group 2. Computed tomography angiography detected nine intracranial occlusions/stenoses. The higher sensitivity of the multimodality CCT protocol justifies its use as a basic diagnostic tool for the set-up of a first-stroke unit in the United Arab Emirates.

High-concentration contrast media in neurological multidetector-row CT applications: implications for improved patient management in neurology and neurosurgery

Dynamic CT scanning after intravenous injection of iodine contrast medium (CM) was proposed in the very early days of CT. The goal was to characterize tissue by extracting information from the temporal course of enhancement. In the early 1980s, modeling algorithms were already described in the literature for the quantitative calculation of cerebral blood flow (CBF). However, cerebral applications suffered from the insufficient temporal resolution available at that time and the central nervous system was already seen primarily as an MRI domain. The renaissance of dynamic CT in neurological applications came in the middle of the 1990s with the introduction of thrombolytic therapy in acute stroke. With CT being the primary imaging modality, getting additional hemodynamic information from the same device without having to move the patient appeared attractive. Multimodal CT protocols allow a comprehensive diagnosis of the emergency stroke patient in less than 15 minutes by combining nonenhanced CT (NECT), perfusion CT (PCT) and CT angiography (CTA). Dynamic PCT can also render important information in patients with intraaxial brain tumors, allowing differentiation not only between lymphoma and glioma but also between low-grade and high-grade glioma by quantifying local cerebral blood volume (CBV) and permeability of the blood-brain barrier (BBB). However, even if a shorter imaging time permits a reduction in volume of CM, adequate total iodine levels must be preserved for dynamic CT applications. Increased concentrations of iodine are therefore helpful to obtain adequate total iodine levels for imaging.

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.

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.

Systematic comparison of perfusion-CT and CT-angiography in acute stroke patients

OBJECTIVE

To systematically evaluate the accuracy of noncontrast computed tomography (NCT), perfusion computed tomography (PCT), and computed tomographic angiography (CTA) in determining site of occlusion, infarct core, salvageable brain tissue, and collateral flow in a large series of patients suspected of acute stroke.

METHODS

We retrospectively identified all consecutive patients with signs and symptoms suggesting hemispheric stroke of < 48 hours in duration who were evaluated on admission by NCT, PCT, and CTA, and underwent a follow-up CT/CTA or magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) within 6 months of initial imaging. Two neuroradiologists evaluated NCT for hypodensity, PCT for infarct core and salvageable brain tissue, and CTA source images and maximal intensity projections for site of occlusion, infarct core, and collateral flow. Follow-up CTA and MRA were assessed for persistent arterial occlusion or recanalization. Follow-up CT and MRI were reviewed for final infarct location and volume, and used as a gold standard to calculate sensitivity (SE) and specificity (SP) of initial imaging.

RESULTS

A total of 113 patients were considered for analysis, including 55 patients with a final diagnosis of stroke. CTA source images were the most accurate technique in the detection of the site of occlusion (SE = 95%; SP = 100%). Decreased cerebral blood volume on PCT was the most accurate predictor of final infarct volume (SE = 80%; SP = 97%), Increased mean transit time on PCT was predictive of the tissue at risk for infarction in patients with persistent arterial occlusion. CTA maximal intensity projections was the best technique to quantify the degree of collateral circulation.

INTERPRETATION

The most accurate assessment of the site of occlusion, infarct core, salvageable brain tissue, and collateral circulation in patients suspected of acute stroke is afforded by a combination of PCT and CTA.

Acute ischemic stroke: overview of recent therapeutic developments

Stroke, a disorder encompassing all cerebrovascular accidents, is a public health problem of immense proportions across the globe. Therapeutic efforts are directed at three aspects: prevention, acute treatment, and rehabilitation. Preventative measures, which in many instances mirror those for cardiovascular disease, can achieve the greatest public health impact. Measures that enhance the recovery of neurologic function and reduce neurologic disability after stroke can also affect a large population of handicapped stroke survivors. In the past 10 years, the greatest changes have occurred in the field of acute stroke treatment. Ultra-early-stage therapies with the potential to dramatically reverse severe neurologic deficits, or halt their progression, have caused a restructuring of the emergency care of neurologic patients. The parallels with the evolution of emergency treatment of acute coronary syndromes after 1970 are striking. This review focuses on aspects of stroke therapy that are either just entering, or soon to enter, current practice.

Technology Insight: recanalization with drugs and devices during acute ischemic stroke

Revascularization therapy is pivotal to saving ischemic brain from infarction. Two major randomized trials of intravenous thrombolytic therapy have established clear clinical benefit, especially for strokes caused by small-vessel occlusion. Ischemic stroke caused by large-vessel intracranial occlusion carries higher morbidity, however, and intravenous thrombolytics are less capable of opening these large vessels. This observation makes a case for delivering thrombolytics directly into the clot, or simply removing the clot mechanically. Intra-arterial thrombolytic drugs have been shown to be effective for treating middle cerebral artery occlusions in a major randomized trial. In the past 2 years, a family of mechanical thrombectomy catheters designed to remove rather than dissolve the offending clot has received FDA clearance. Such devices offer alternative therapy to patients who cannot receive thrombolytics, and can also be used in combination with thrombolytics to safely restore cerebral perfusion. Mechanical techniques have not been directly compared with intra-arterial thrombolytic strategies, but these devices might be superior to thrombolytics within vessels with particularly high clot burden, such as the carotid terminus and the basilar artery. Comprehensive stroke centers are currently available in major metropolitan areas to treat stroke via intra-arterial means, and are likely to become 'hubs' to 'spoke' hospitals that are credentialed as primary stroke centers. This design will allow any patient timely access to state-of-the-art stroke treatment tailored to their needs.

Acute endovascular stroke therapy

A decade after the US Food and Drug Administration (FDA) approved intravenous tissue plasminogen activator for treatment of acute ischemic stroke, the public health impact of this treatment on stroke outcome remains limited. The extremely small time window for treatment and very low recanalization rates in large artery strokes are its major shortcomings. Endovascular therapies for the treatment of acute stroke have rapidly evolved during this time period and may overcome these limitations. FDA approval of the Mechanical Embolus Removal in Cerebral Ischemia (MERCI) concentric retriever in August 2004 for the treatment of occluded brain arteries has spurred trials of newer devices for mechanical thrombolysis in acute stroke. At present, there are two major National Institutes of Health-sponsored randomized controlled trials testing endovascular treatments in acute stroke. In this article, we provide an experience-guided review of the current approach to the endovascular treatment of acute ischemic stroke and current evidence for various strategies. We first emphasize the key aspects of patient selection, including the increasingly central role of perfusion/diffusion imaging. The technical aspects of chemical, mechanical, ultrasound-based, and multimodal approaches are provided along with the authors' own experiences. Most of the endovascular modalities tested in clinical trials show recanalization rates in the range of 50% to 65%. However, no one modality is clearly superior. In practice, multimodal treatment strategy is often employed to achieve rapid recanalization of occluded cerebral vessels and minimize chances of hemorrhage. This may become the standard of care in the future.

Choice of Neuroimaging in Perioperative Acute Stroke Management

At the time of this publication, the fast examination time, wide availability, lack of contraindications, and high accuracy for detecting hemorrhage make NCCT the diagnostic study of choice for initial evaluation of patients who have preoperative stroke. NCCT also has a role in excluding patients who will not benefit from IV thrombolysis, including those who have ICH and patients who have ASPECTS less than 7 or ischemic signs exceeding one third of the MCA territory. Because optimal selection of inpatients who have acute stroke mandates not just brain tissue data but also information about the aortic arch, cervical and intracranial vasculature, and cerebral hemodynamics, additional imaging with multimodal CT technology can, in one scanning session, depicts early ischemic changes, demonstrates hypoperfusion/ischemic penumbra, and locates the vascular lesion. When combined with the clinical scenario, the information provided by CT often is sufficient to help clinicians decide on the appropriate treatment, especially determining eligibility for thrombolysis. The rapidly evolving field of neuroradiology will provide a newer armamentarium in the near future. Although MRI can provide more precise information, it is more time consuming and currently should be considered the method of choice for follow-up imaging, rather than initial imaging, in patients who have perioperative stroke.

Computed tomography angiography and computed tomography perfusion in ischemic stroke: A step-by-step approach to image acquisition and three-dimensional postprocessing

Recent technical advances in both image acquisition and postprocessing have enabled computed tomography angiography (CTA) with computed tomography perfusion to become front-line tools for acute stroke evaluation in many institutions. This article provides a step-by-step approach to utilizing these technologies, particularly in the rapid triage of appropriate stroke patients to reperfusion therapies. The specific contrast injection, image acquisition, and 3D postprocessing protocols for high-quality CTA, currently in use at our institution, are delineated. An important point of emphasis is how preliminary angiographic and cerebral perfusion observations can be made immediately at the scanner to expedite emergent therapy. Also explored is the manner in which a dedicated 3D lab can support a high clinical volume, including a large percentage of emergent studies. An accurate yet time-efficient approach for the neuroradiologist to integrate 3D interpretation with CTA source data review is offered. Several important imaging and interpretive pitfalls in stroke CTA are illustrated.

Computed Tomographic Angiography in Stroke Imaging: Fundamental Principles, Pathologic Findings, and Common Pitfalls

The development of multidetector row computed tomography (MDCT) now permits visualization of the entire vascular tree that is relevant for the management of stroke within 15 seconds. Advances in MDCT have brought computed tomography angiography (CTA) to the frontline in evaluation of stroke. CTA is a rapid and noninvasive modality for evaluating the neurovasculature. This article describes the role of CTA in the management of stroke. Fundamentals of contrast delivery, common pathologic findings, artifacts, and pitfalls in CTA interpretation are discussed.

CT perfusion in acute stroke

As new treatments are developed for stroke, the potential clinical applications of CT perfusion (CTP) imaging in the diagnosis, triage, and therapeutic monitoring of these diseases are certain to increase. Technical advances in scanner hardware and software should no doubt continue to increase the speed, coverage, and resolution of CTP imaging. CTP offers the promise of efficient use of imaging resources and, potentially, of decreased morbidity. Most importantly, current CT technology already permits the incorporation of CTP as part of an all-in-one acute stroke examination to answer the four fundamental questions of stroke triage quickly and accurately, further increasing the contribution of imaging to the diagnosis and treatment of acute stroke.

Modern Emergent Stroke Imaging: Pearls, Protocols, and Pitfalls

Stroke remains one of the most important clinical diagnoses for which patients are referred to the radiologist for emergent imaging. Timely and accurate imaging guides admission from the emergency department or transfer to a hospital with a dedicated stroke service, triage to the intensive care unit, anticoagulation, thrombolysis, and many other forms of treatment and management. It is important to approach each patient's imaging needs logically and tailor each work-up, and constantly to review the entire process for potential improvements. Time saved in getting an accurate diagnosis of stroke may indeed decrease morbidity and mortality. This article discusses the current management of stroke imaging and reviews the relevant literature.

Recent Advances in the Interventional Treatment of Acute Ischemic Stroke

BACKGROUND

Acute ischemic stroke is a major cause of morbidity and mortality in Europe, North America, and Asia. Recent advances over the past decade have been made in the interventional approach to patients with a stroke. These include intravenous (i.v.) trials, intra-arterial (i.a.) trials, combined i.v./i.a. trials, and newer devices undergoing current clinical evaluation to mechanically remove clot within the cerebral circulation.

METHODS

A summary of the latest interventional approaches to stroke, from the interventional neuroradiology perspective, is presented. Results of the major thrombolytic trials over the past decade are summarized. Newer devices and approaches for ischemic stroke patients, including the recently completed Phase 1/2 MERCI (Mechanical Embolus Removal in Cerebral Ischemia) Trial are presented.

RESULTS

The Proact 1 and 2 trials involving i.a. thrombolytic therapy in patients who present with an acute middle cerebral artery stroke within 6 h from symptom onset have demonstrated significant benefit over the control group, for improved outcomes at 90 days. The MERCI trial has demonstrated, in 114 patients with moderate to severe strokes, that patients who are able to be recanalized have significant neurological improvement versus those who were not able to be recanalized.

CONCLUSIONS

Continued advances in the interventional approach to acute stroke treatment, with further clinical trials, are warranted. Early reports are encouraging regarding both combination thrombolytic drug trials and mechanical device trials for these patients.

CT Angiography Source Image Evaluation for Stroke

Computed tomography angiogram of the head and neck has lately become a pivotal imaging modality in the patient with acute stroke symptoms due to its high resolution, accuracy, speed, and sensitivity in the assessment of brain parenchyma and vascular patency.