Hyperacute Diffusion-Weighted Imaging Abnormalities in Transient Ischemic Attack Patients Signify Irreversible Ischemic Infarction

Presenting Symptoms and Diffusion-Weighted MRI Positivity by Time After Transient Neurologic Events: A Pooled Analysis of 3 Cohort Studies

BACKGROUND AND OBJECTIVE

The association between focal vs nonfocal presenting symptom and diffusion-weighted imaging (DWI) positivity in relation to onset-to-imaging time in patients with transient neurologic events remains unclear. We hypothesize that episodes consisting of focal symptoms would have proportionally higher DWI-positive imaging at later onset-to-imaging times.

METHODS

Patients with transient neurologic symptoms and a normal neurologic examination who had DWI in the combined data set of 3 cohort studies were included. We used logistic regression models to evaluate the association between each type of presenting symptom (motor weakness, speech impairment, sensory symptoms, vision loss, diplopia, gait instability, dizziness, headache, presyncope, and amnesia) and DWI positivity after adjusting for clinical variables (age, sex, history of stroke, dyslipidemia, coronary artery disease, atrial fibrillation, symptoms duration [<10, 10-59, ≥60 minutes, or unclear], and study source). We stratified the results by onset-to-imaging time categories (<6 hours, 6-23 hours, and ≥24 hours).

RESULTS

Of the total 2,411 patients (1,345 male, median age 68 years), DWI-positive lesions were detected in 598 patients (24.8%). The prevalence of DWI positivity was highest in those with motor weakness (34.7%), followed by speech impairment (33.5%). In a multivariable analysis, the presence of motor weakness, speech impairment, and sensory symptoms was associated with DWI positivity, while vision loss and headache were associated with lower odds of DWI positivity, but nevertheless had 13.6% and 15.3% frequency of DWI positive. The odds of being DWI positive varied by onset-to-imaging time categories for motor weakness, with greater odds of being DWI positive at later imaging time (<6 hours: odds ratio [OR] 1.25, 95% confidence interval [CI] 0.84-1.87; 6-23 hours: OR 2.24, 95% CI 1.47-3.42; and ≥24 hours: OR 2.42, 95% CI 1.74-3.36; interaction p = 0.033). Associations of other symptoms with DWI positivity did not vary significantly by time categories.

DISCUSSION

We found that onset-to-imaging time influences the relationship between motor weakness and DWI positivity in patients with transient neurologic events. Compared with motor, speech, and sensory symptoms, visual or nonfocal symptoms carry a lower but still a substantive association with DWI positivity.

An assessment of the cost-effectiveness of magnetic resonance, including diffusion-weighted imaging, in patients with transient ischaemic attack and minor stroke: a systematic review, meta-analysis and economic evaluation

BACKGROUND

Patients with transient ischaemic attack (TIA) or minor stroke need rapid treatment of risk factors to prevent recurrent stroke. ABCD2 score or magnetic resonance diffusion-weighted brain imaging (MR DWI) may help assessment and treatment.

OBJECTIVES

Is MR with DWI cost-effective in stroke prevention compared with computed tomography (CT) brain scanning in all patients, in specific subgroups or as 'one-stop' brain-carotid imaging? What is the current UK availability of services for stroke prevention?

DATA SOURCES

Published literature; stroke registries, audit and randomised clinical trials; national databases; survey of UK clinical and imaging services for stroke; expert opinion.

REVIEW METHODS

Systematic reviews and meta-analyses of published/unpublished data. Decision-analytic model of stroke prevention including on a 20-year time horizon including nine representative imaging scenarios.

RESULTS

The pooled recurrent stroke rate after TIA (53 studies, 30,558 patients) is 5.2% [95% confidence interval (CI) 3.9% to 5.9%] by 7 days, and 6.7% (5.2% to 8.7%) at 90 days. ABCD2 score does not identify patients with key stroke causes or identify mimics: 66% of specialist-diagnosed true TIAs and 35-41% of mimics had an ABCD2 score of ≥ 4; 20% of true TIAs with ABCD2 score of < 4 had key risk factors. MR DWI (45 studies, 9078 patients) showed an acute ischaemic lesion in 34.3% (95% CI 30.5% to 38.4%) of TIA, 69% of minor stroke patients, i.e. two-thirds of TIA patients are DWI negative. TIA mimics (16 studies, 14,542 patients) make up 40-45% of patients attending clinics. UK survey (45% response) showed most secondary prevention started prior to clinic, 85% of primary brain imaging was same-day CT; 51-54% of patients had MR, mostly additional to CT, on average 1 week later; 55% omitted blood-sensitive MR sequences. Compared with 'CT scan all patients' MR was more expensive and no more cost-effective, except for patients presenting at > 1 week after symptoms to diagnose haemorrhage; strategies that triaged patients with low ABCD2 scores for slow investigation or treated DWI-negative patients as non-TIA/minor stroke prevented fewer strokes and increased costs. 'One-stop' CT/MR angiographic-plus-brain imaging was not cost-effective.

LIMITATIONS

Data on sensitivity/specificity of MR in TIA/minor stroke, stroke costs, prognosis of TIA mimics and accuracy of ABCD2 score by non-specialists are sparse or absent; all analysis had substantial heterogeneity.

CONCLUSIONS

Magnetic resonance with DWI is not cost-effective for secondary stroke prevention. MR was most helpful in patients presenting at > 1 week after symptoms if blood-sensitive sequences were used. ABCD2 score is unlikely to facilitate patient triage by non-stroke specialists. Rapid specialist assessment, CT brain scanning and identification of serious underlying stroke causes is the most cost-effective stroke prevention strategy.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Distal hyperintense vessels on FLAIR images predict large-artery stenosis in patients with transient ischemic attack

INTRODUCTION

Distal hyperintense vessels (DHV) are frequently detected by fluid-attenuated inversion recovery (FLAIR) imaging in patients with acute ischemic stroke. Despite its relevance to patient care outcomes, the presence of DHV has not been evaluated in patients with transient ischemic attack (TIA).

METHODS

We performed a retrospective analysis of all TIA patients admitted to the study hospital from 2006 to 2010 who had undergone magnetic resonance imaging (MRI) within 24 h of symptom onset followed by further intracranial and extracranial vascular imaging. We then analyzed the relationship between DHV, large artery severe stenosis or occlusion (LASO), and clinical presentation.

RESULTS

Forty-three TIA patients were enrolled in this study. DHV signals on FLAIR images were positive in 14 (33 %) patients. Patients with DHV were significantly more likely to have severe stenosis or occlusion in intracranial (P = 0.01) and extracranial vessels (P = 0.04) than patients without DHV. DHV was associated independently with LASO (odds ratio = 6.1; 95 % CI, 1.2-31.5).

CONCLUSION

Evaluation of DHV signals on FLAIR images may facilitate prediction of LASO in TIA patients and therefore enable prompt vascular assessment.

Early Diffusion Weighted MRI as a Negative Predictor for Disabling Stroke After ABCD 2 Score Risk Categorization in Transient Ischemic Attack Patients

Background and Purpose— The prognostic value early diffusion-weighted magnetic resonance imaging (DWMRI) adds in the setting of transient ischemic attack (TIA), after risk stratification by a clinical score, is unclear. The purpose of this study is to evaluate, after ABCD 2 score risk categorization in admitted TIA patients, whether negative DWMRI performed within 24 hours of symptom onset improves on the identification of patients at low risk for experiencing a disabling stroke within 90 days.

Methods— At 15 North Carolina hospitals, we enrolled a prospective nonconsecutive sample of admitted TIA patients. We excluded patients not undergoing a DWMRI within 24 hours of admission and patients for whom a dichotomized (≤ or >3) ABCD 2 score could not be calculated. We conducted a medical record review to determine disabling ischemic stroke outcomes within 90 days.

Results— Over 35 months, 944 TIA patients met inclusion criteria, of whom 4% (n=41) had a disabling ischemic stroke within 90 days. In analyses stratified by low versus moderate/high ABCD 2 score, the combination of a low risk ABCD 2 score and a negative early DWMRI had excellent sensitivity (100%, 95% CI 34 to 100) for identifying low-risk patients. In patients classified as moderate to high risk, a negative early DWMRI predicted a low risk of disabling ischemic stroke within 90 days (sensitivity 92%, 95% CI 80 to 97; NLR 0.11, 95% CI 0.04 to 0.32).

Conclusions— After risk stratification by the ABCD 2 score, early DWMRI enhances the prediction of a low risk for disabling ischemic stroke within 90 days. Further study is warranted in a large, consecutive TIA population of early DWMRI as a sensitive negative predictor for disabling stroke within 90 days.

Proposal for a universal definition of cerebral infarction

BACKGROUND AND PURPOSE

Cerebral infarction is a leading cause of disability and death worldwide but has no uniform international definition.

SUMMARY OF REVIEW

Recent diagnostic advances have revised fundamental concepts in cerebral and cardiac ischemia. Cardiologists, already possessed of a nosologic framework distinguishing myocardial infarction from unstable angina on the basis of tissue state, promulgated a new "universal" tissue definition of myocardial infarction incorporating insights afforded by assays of cardiac troponin, a serum biomarker exquisitely sensitive to myocardial injury. Concurrently, vascular neurologists proposed a new tissue, rather than time, criterion to distinguish transient ischemia attack from cerebral infarction, responding to perspectives provided by diffusion MRI and cerebral blood volume CT, imaging biomarkers highly sensitive to neuronal injury. To complete this conceptual realignment, vascular neurology must now advance a clear, uniform, and operationalizable tissue definition of cerebral infarction. This review proposes cerebral infarction be defined as brain or retinal cell death due to prolonged ischemia. This definition categorizes both pannecrosis and neuronal dropout ("complete" and "incomplete" infarcts in classic neuropathologic terminology) as cerebral infarcts. Making the presence of any neuronal or glial cell death essential yields a definition of cerebral infarction that has high relevance to patients, physicians, and policymakers; is more easily applied in clinical practice; fosters action in acute care; harmonizes with myocardial ischemia classification; and focuses diagnostic evaluation on the cause of brain ischemia and the occurrence of end organ injury.

CONCLUSIONS

The term cerebral infarction should be used when there is evidence of brain or retinal cell death due to cerebral ischemia.

Diffusion-negative MRI in acute ischemic stroke: a case report

Background

Diffusion-weighted magnetic resonance imaging is a very sensitive tool for the early diagnosis of acute ischemic stroke. This is employed in some stroke centers as the primary screening tool to select patients eligible for thrombolysis.

Methods

We present the case of a 49-years old Chinese man whose diffusion-weighted magnetic resonance imaging performed 12 hours of symptom onset was negative.

Results

Although the initial diffusion-weighted magnetic resonance imaging was negative, the imaging repeated after 4 days despite static neurological symptoms and signs, could demonstrate an acute medullary infarction.

Conclusion

Diffusion-weighted imaging may not be100% sensitive in very early stages, especially in posterior circulation strokes. Our case serves as a reminder that clinical assessment still retains priority until a diagnostic modality offering 100% sensitivity and specificity is discovered.

Clinical impact of MRI perfusion disturbances and normal diffusion in acute stroke patients

PURPOSE

In acute ischemic stroke MR-imaging typically shows diffusion abnormalities surrounded by reduced perfusion signifying the so-called ischemic penumbra. Mismatch between diffusion and perfusion abnormalities gives indication for thrombolysis. But is there an indication for thrombolytic treatment, if there is no diffusion abnormality but pathologic perfusion combined with acute stroke symptoms?.

MATERIAL AND METHODS

MR-imaging of 1465 patients treated on our Stroke Unit between June 2004 and May 2007 retrospectively are analyzed. 6 patients met the inclusion criteria of severe neurological symptoms, large territorial perfusion disturbances, lack of diffusion abnormalities and complete neurological recovery after treatment.

RESULTS

In all six patients MTT measurements showed a significantly depressed perfusion in the symptomatic hemisphere (p<0.02). Time-to-peak delay correlated with the mean transit time delay (0.949, p<0.01). Indication for thrombolysis was based on perfusion abnormalities and clinical symptoms. Stroke symptoms could be reversed in all patients without any complication.

CONCLUSION

Whereas diffusion imaging could not reveal any abnormality, perfusion analysis legitimated therapy with systemic thrombolysis in heavily affected patients. This work underlines the importance of multimodal MR imaging for guiding treatment decisions in acute stroke patients.

Large-artery stenosis predicts subsequent vascular events in patients with transient ischemic attack

Background and purpose

We investigated subsequent vascular events in patients with transient ischemic attack (TIA) and determined the predictors of such events among vascular risk factors including large-artery disease, TIA-symptom duration, and acute ischemic lesions on diffusion-weighted imaging (DWI).

Methods

We identified 98 consecutive patients with TIA who visited a tertiary university hospital and underwent DWI and brain magnetic resonance angiography within 48 hours of symptom onset. We reviewed the medical records to assess the clinical characteristics of TIA, demographics, and the subsequent vascular events including acute ischemic stroke, TIA, and myocardial infarction.

Results

Large-artery disease was detected in 55 patients (56%). Ten patients (10%) experienced TIA symptoms for longer than 1 hour, and acute infarctions on DWI were identified in 30 patients (31%). During the mean follow-up period of 19 months, seven patients (7%) had an acute ischemic stroke and 20 patients (20%) had TIA. Retinal artery occlusion in two patients, spinal cord infarction in one patient, and peripheral vascular claudication in one patient were also recorded. Cox proportional-hazards multivariate analysis revealed that large-artery disease was an independent predictor of subsequent cerebral ischemia (hazard ratio [HR], 2.8; 95% confidence interval [CI], 1.1-7.1; p=0.02) and subsequent vascular events (HR, 2.9; 95% CI, 1.2-6.7; p=0.01).

Conclusions

In patients with TIA, large-artery disease is an independent predictor of subsequent vascular events. Acute infarction on DWI and a symptom duration of more than 1 hour are not significantly correlated with a higher risk of subsequent vascular events. These findings suggest that the underlying vascular status is more important than symptom duration or acute ischemic lesion on DWI.

National study on emergency department visits for transient ischemic attack, 1992-2001

OBJECTIVES

To describe the epidemiology of U.S. emergency department (ED) visits for transient ischemic attack (TIA) and to measure rates of antiplatelet medication use, neuroimaging, and hospitalization during a ten-year time period.

METHODS

The authors obtained data from the 1992-2001 National Hospital Ambulatory Medical Care Survey. TIA cases were identified by having ICD-9 code 435.

RESULTS

From 1992 to 2001, there were 769 cases, representing 2,969,000 ED visits for TIA. The population rate of 1.1 ED visits per 1,000 U.S. population (95% CI = 0.92 to 1.30) was stable over time. TIA was diagnosed in 0.3% of all ED visits. Physicians administered aspirin and other antiplatelet agents to a small percentage of patients, and 42% of TIA patients (95% CI = 29% to 55%) received no medications at all in the ED. Too few data points existed to measure a statistically valid trend over time. Physicians performed computed tomography scanning in 56% (95% CI = 45% to 66%) of cases and performed magnetic resonance imaging (MRI) in < 5% of cases, and there was a trend toward increased imaging over time. Admission rates did not increase during the ten-year period, with 54% (95% CI = 42% to 67%) admitted. Regional differences were noted, however, with the highest admission rate found in the Northeast (68%).

CONCLUSIONS

Between 1992 and 2001, the population rate of ED visits for TIA was stable, as were admission rates (54%). Antiplatelet medications appear to be underutilized and to be discordant with published guidelines. Neuroimaging increased significantly. These findings may reflect the limited evidence base for the guidelines, educational deficits, or other barriers to guideline implementation.