DWI abnormalities and clinical characteristics in TIA patients

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.

Diagnosis, Workup, Risk Reduction of Transient Ischemic Attack in the Emergency Department Setting: A Scientific Statement From the American Heart Association

At least 240 000 individuals experience a transient ischemic attack each year in the United States. Transient ischemic attack is a strong predictor of subsequent stroke. The 90-day stroke risk after transient ischemic attack can be as high as 17.8%, with almost half occurring within 2 days of the index event. Diagnosing transient ischemic attack can also be challenging given the transitory nature of symptoms, often reassuring neurological examination at the time of evaluation, and lack of confirmatory testing. Limited resources, such as imaging availability and access to specialists, can further exacerbate this challenge. This scientific statement focuses on the correct clinical diagnosis, risk assessment, and management decisions of patients with suspected transient ischemic attack. Identification of high-risk patients can be achieved through use of comprehensive protocols incorporating acute phase imaging of both the brain and cerebral vasculature, thoughtful use of risk stratification scales, and ancillary testing with the ultimate goal of determining who can be safely discharged home from the emergency department versus admitted to the hospital. We discuss various methods for rapid yet comprehensive evaluations, keeping resource-limited sites in mind. In addition, we discuss strategies for secondary prevention of future cerebrovascular events using maximal medical therapy and patient education.

Diffusion kurtosis imaging in patients with tissue-negative transient ischemic attack

Approximately 50–60% of patients with a clinical transient ischemic attack (TIA) do not have diffusion-weighted imaging (DWI) evidence of cerebral ischemia. The purpose of this study was to assess the added diagnostic value of diffusion kurtosis imaging (DKI) in the evaluation of patients with TIA who have normal DWI findings. From September 2014 to May 2017, a total of 179 consecutive patients with suspected TIA were eligible for enrollment in our study. The inclusion criteria were a confirmed diagnosis of TIA confirmed by a stroke neurologist, MRI (including DWI and DKI) within 24 h after symptom onset, no stroke history, and no DWI lesion. A follow-up DWI was performed to establish stroke recurrence within a period of 90 days. A total of 98 patients who had no lesions on the baseline DWI were included for data analysis. Of these 98 patients, 31 (31.6%) had positive findings on the initial DKI. In 29 of the 31 (93.5%) patients, the location of the abnormality observed on DKI was consistent with the clinical symptoms. During the 90-day follow-up period, 14 (14.3%) patients developed recurrent stroke. The prevalence of recurrent stroke was higher in the DKI-positive group than in the DKI-negative group (29.0% vs. 7.5%, p = 0.01). A comparison between the patients with and without recurrent stroke showed that an abnormality on the baseline DKI was associated with stroke recurrence. Furthermore, 8 of the 9 stroke patients in the DKI-positive group developed a new ischemic lesion in the artery territory corresponding to the initial DKI abnormality. The new findings suggest the predictive value of DKI on the recurrence of stroke in the patients with TIA who have negative findings on conventional DWI.

Motor impairments in transient ischemic attack increase the odds of a positive diffusion-weighted imaging: A meta-analysis

BACKGROUND

Unilateral motor impairment is a key symptom used in the diagnosis of transient ischemic attack (TIA). Diffusion-weighted imaging (DWI) is a promising diagnostic tool for detecting ischemic lesions. While both motor impairments and DWI abnormalities are linked to the diagnosis of TIA, the association between these prognostic factors is not well understood.

OBJECTIVE

To examine the association between unilateral motor impairments and the odds of a positive DWI in TIA. Further, to determine whether the time between symptom onset and neuroimaging (delay to scan) influences the odds of a positive DWI.

METHODS

We used PRISMA guidelines to conduct a systematic search from 1989 to 2018. We included studies that reported number of individuals with/without unilateral motor symptoms and a positive/negative DWI.

RESULTS

Twenty-four studies from North America, Australia, Asia, and Europe were submitted to a meta-analysis. A pooled odds ratio of 1.80 (95% CI, 1.45-2.24, p = 0.00; I2 = 57.38) suggested that the odds of a positive DWI are greater in TIA individuals who experience motor symptoms as compared with those who experience no motor symptoms. Further, increasing the time delay to scan from the symptom onset (>2 days) did not influence the odds of a positive DWI as compared with an earlier scan (≤2 days).

CONCLUSIONS

The current meta-analysis provides cumulative evidence from 6710 individuals with TIA that the presence of motor symptoms increases the odds of a positive DWI by two-folds. These findings transform the clinical perception into evidence-based knowledge that motor impairments elevate the risk for brain tissue damage. Unilateral motor impairments in a cerebrovascular event should increase a physician's suspicion of detecting brain infarctions. These findings may influence the clinical management of TIA by generating faster response to motor impairments in TIA and accelerating referral to specialized stroke clinic.

[A case of recurrent transient global amnesia showing different symptom duration and MRI findings]

A 66-year-old man was admitted to our department with anterograde amnesia. He was diagnosed with transient global amnesia (TGA) because of the symptom lasting for several hours and no abnormal findings on MRI and EEG. About a year after the episode, he recurred amnesia lasting only for 20 minutes. MRI diffusion weighted image (DWI) revealed a small hyperintense signal in the right hippocampus, while there was no abnormality on EEG. We diagnosed him with recurrent TGA. This case may be interesting in that symptom duration and MRI-DWI finding are much different between two attacks of TGA.

Severity of White Matter Lesions Correlates with Subcortical Diffusion-Weighted Imaging Abnormalities and Predicts Stroke Risk

BACKGROUND AND PURPOSE

The severity of white matter lesions (WMLs) has been strongly linked to small-vessel diseases or lacunar infarction. The present study aimed to investigate the correlation between severity of WMLs and distribution of diffusion-weighted imaging (DWI) hyperintensities, and to explore whether the severity of WMLs is an independent neuroimaging predictor of stroke risk after transient symptoms with infarction (TSI).

METHODS

We evaluated the presence and severity of WMLs on fluid-attenuated inversion recovery sequences using the age-related white matter changes scale and the location and size of hyperintensities on DWI sequences, respectively, in a prospective cohort study of TSI patients. The primary end point was recurrent stroke within 90 days.

RESULTS

A total of 191 consecutive TSI patients were eligible for inclusion in the present analysis. The average age of the patients was 57.3 ± 12.8 years. DWI abnormalities occurred more often in the deep white matter with increasing severity of WMLs (P < .001). During 90-day follow-up, Kaplan-Meier analysis showed that recurrent stroke was correlated to the severity of WMLs (P = .01). The Cox proportional hazards model revealed that WMLs were predictive of recurrent stroke (hazard ratio, 1.748; 95% confidence interval, 1.16-2.634; P = .008).

CONCLUSIONS

Severe WMLs were correlated with DWI hyperintensities in the deep white matter in TSI patients and contributed to an increased risk of recurrent stroke.

Radiological imaging in acute ischaemic stroke

Patients who suffer acute ischaemic stroke can be treated with thrombolysis if therapy is initiated early. Radiological evaluation of the intracranial tissue before such therapy can be given is mandatory. In this review current radiological diagnostic strategies are discussed for this patient group. Beyond non-enhanced computed tomography (CT), the standard imaging method for many years, more sophisticated CT stroke protocols including CT angiography and CT perfusion have been developed, and additionally an increasing number of patients are examined with magnetic resonance imaging as the first imaging method used. Advantages and challenges of the different methods are discussed.

Inter-rater agreement analysis of the Precise Diagnostic Score for suspected transient ischemic attack

Background

No definitive criteria are available to confirm the diagnosis of transient ischemic attack. Inter-rater agreement between physicians regarding the diagnosis of transient ischemic attack is low, even among vascular neurologists. We developed the Precise Diagnostic Score, a diagnostic score that consists of discrete and well-defined clinical and imaging parameters, and investigated inter-rater agreement in patients with suspected transient ischemic attack.

Methods

Fellowship-trained vascular neurologists, blinded to final diagnosis, independently reviewed retrospectively identical history, physical examination, routine diagnostic studies, and brain magnetic resonance imaging (diffusion and perfusion images) from consecutive patients with suspected transient ischemic attack. Each patient was rated using the 8-point Precise Diagnostic Score score, composed of a clinical score (0–4 points) and an imaging score (0–4 points). The composite Precise Diagnostic Score determines a Precise Diagnostic Score Likelihood of Brain Ischemia Scale: 0–1 = unlikely, 2 = possible, 3 = probable, 4–8 = very likely.

Results

Three raters reviewed data from 114 patients. Using Precise Diagnostic Score, all three raters scored a similar percentage of the clinical events as being “probable” or “very likely” caused by brain ischemia: 57, 55, and 58%. Agreement was high for both total Precise Diagnostic Score (intraclass correlation coefficient of 0.94) and for the Likelihood of Brain Ischemia Scale (agreement coefficient of 0.84).

Conclusions

Compared with prior studies, inter-rater agreement for the diagnosis of transient brain ischemia appears substantially improved with the Precise Diagnostic Score scoring system. This score is the first to include specific criteria to assess the clinical relevance of diffusion-weighted imaging and perfusion lesions and supports the added value of magnetic resonance imaging for assessing patients with suspected transient ischemic attack.

Itemized NIHSS subsets predict positive MRI strokes in patients with mild deficits

BACKGROUND

While imaging is useful in confirming the diagnosis of ischemic stroke, negative diffusion weighted imaging (DWI) is reported in up to 25% of patients. Our aim was to identify predictors of MRI-positive stroke from the itemized NIHSS.

METHODS

Data were derived from the Stroke Warning Information and Faster Treatment study from February 2006 to February 2010 among patients with mild deficits (NIHSS 0-5) and a final diagnosis of stroke by a vascular neurologist. All MRI sequences were reviewed for the presence or absence of an acute infarct on DWI. Multivariate logistic regression assessed factors predicting DWI-positive strokes; p<0.05 was considered significant.

RESULTS

894 patients had a discharge diagnosis of stroke; 709 underwent MRI and 28.0% were DWI negative. All patients with visual field deficits or neglect were DWI positive. On multivariate analysis including total NIHSS (0-2 vs. 3-5) and itemized NIHSS score subsets, predictors of a positive DWI were NIHSS score of 3-5 (OR=3.3, 95% CI: 1.8-6.1), motor deficits (OR=1.7, 95% CI: 1.1-2.8), ataxia (OR=1.9, 95% CI: 1.0-3.5), and absence of sensory deficits (OR=1.7, 95% CI: 1.0-2.7). We developed the NIHSS-m score that predicts DWI positivity in patients with mild deficits in the absence of neglect or visual field deficits.

CONCLUSION

NIHSS score subsets predict DWI positivity in mild strokes. The presence of neglect or visual field deficits on the NIHSS subsets is most likely to have an MRI correlate even in patients with low NIHSS.

Multimodal imaging in acute ischemic stroke

OPINION STATEMENT

Recent years have seen the development of novel neuroimaging techniques whose roles in the management of acute stroke are sometimes confusing and controversial. This may be attributable in part to a focus on establishing simplified algorithms and terminology that omit consideration of the basic pathophysiology of cerebral ischemia and, consequently, of the full potential for optimizing patients' care based upon their individual imaging findings. This review begins by discussing cerebral hemodynamic physiology and of the effects of hemodynamic disturbances upon the brain. Particular attention will be paid to the hemodynamic measurements and markers of tissue injury that are provided by common clinical imaging techniques, with the goal of enabling greater confidence and flexibility in understanding the potential uses of these techniques in various clinical roles, which will be discussed in the remainder of the review.

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.

Diffusion-weighted lesions in stroke patients with transient symptoms--where are they located?

BACKGROUND

MR diffusion-weighted imaging (DWI) has revolutionized neuroimaging and contributed to a tissue-based redefinition of transient ischemic attack (TIA). Stroke patients with DWI lesions may have neurological symptoms that resolve completely within 24 h, suggesting successful vessel recanalization. Prior studies of stroke patients with transient symptoms have not found any predilection for DWI lesions in any specific territory. Other studies have, however, reported an association between higher brain dysfunction and presence of DWI lesions in patients with transient ischemic symptoms, suggesting a high rate of cortical affection in these patients. We sought to see whether DWI location in stroke patients with transient symptoms <24 h differed from those with persistent symptoms ≥ 24 h. We hypothesized an association between transient symptoms <24 h and cortical DWI lesion localization due to a possible higher rate of vessel recanalization in patients with transient symptoms causing distal cortical infarctions.

METHODS

Ischemic stroke patients examined with DWI and admitted within 24 h after symptom onset between February 2006 and November 2013 were prospectively registered in a database (The Bergen NORSTROKE Registry). Based on neurological examination 24 h after admission, patients were classified as having either transient symptoms <24 h (DWI <24) or persistent symptoms ≥ 24 h (DWI ≥ 24). DWI lesions were classified into different groups depending on lesion location: cortical lesions, confined to the supratentorial cortex; large subcortical lesions, located in the hemispheric white matter, basal ganglia, internal capsule, thalamus or corona radiate with a diameter ≥ 15 mm; lacunar lesions, located in the same territory as large subcortical lesions with a diameter <15 mm; mixed cortical-subcortical lesions, located in both supratentorial cortex and subcortex; cerebellar lesions, confined to the cerebellum; brain stem lesions, confined to the brain stem; multiple locations, located in more than one of the above defined areas.

RESULTS

A total of 142 ischemic stroke patients had DWI <24 and 830 DWI ≥ 24. Cortical DWI location was more frequent in patients with DWI <24 (54.2% vs. 29.5%, p < 0.001), while proportions of mixed cortical-subcortical lesions (13.4% vs. 26.5%, p = 0.001) and lesions with multiple locations (5.6% vs. 11.1%, p = 0.048) were less frequent as compared to DWI ≥ 24. Cortical DWI location was independently associated with DWI <24 when adjusted for confounders in multiple regression analyses (OR 1.89, 95% CI 1.28-2.81, p = 0.001).

CONCLUSION

Cortical DWI location was independently associated with transient stroke symptoms <24 h. This may be explained by vessel recanalization, resulting in upstream transportation of remaining particles and distal cortical lesions.

Factors Associated with Cognitive Decline in Transient Ischemic Attack Patients

Chronic cerebrovascular disease and large ischemic stroke are both associated with cognitive impairment. Much less is known about the acute cognitive sequelae of transient ischemic attack (TIA). Although often overlooked, there is increasing evidence that cognitive impairment does occur following TIA. In some patients, cognitive changes persist after resolution of focal neurological deficits, but the temporal profile of these symptoms is unknown. In addition, clinical and imaging correlates of cognitive impairment after TIA have not been systematically studied. This under-studied and recognized problem has significant implications for TIA patient management. In this review, we summarize the evidence currently available and identify future research priorities.

Magnetic Resonance Imaging versus Computed Tomography in Transient Ischemic Attack and Minor Stroke: The More Υou See the More You Know

Background

Magnetic resonance imaging (MRI) is proposed as the preferred imaging modality to investigate patients with transient ischemic attack (TIA). This is mainly based on a higher yield of small acute ischemic lesions; however, direct prospective comparisons are lacking. In this study, we aimed to directly compare the yield of acute ischemic lesions on MRI and computed tomography (CT) in the emergency diagnosis of suspected TIA or minor stroke.

Methods

Consecutive patients aged 18 years or older presenting with minor stroke (NIHSS <4) or high-risk TIA and who were examined by a stroke neurologist within 24 h of symptom onset were prospectively enrolled in the CATCH study. Patients who had undergone both a baseline CT and an MRI within 24 h of symptom onset were included in this substudy. Baseline MRI and CT were interpreted independently to identify an acute ischemic lesion. The rates of acute ischemic lesions on CT and MRI were compared, and the volume of acute ischemic lesions was measured on MRI. In addition, the volume of acute ischemic lesions on MRI was compared between patients who had evidence of acute ischemia on CT and in those who did not.

Results

A total of 347 patients were included, 168 with TIAs, 147 with minor strokes and 32 with a final diagnosis of a mimic. Acute ischemic lesions were detected in 39% of TIAs by using MRI versus 8% by using CT (p < 0.0001) and in 86% of minor strokes by using MRI versus 18% by using CT (p < 0.0001). Compared to MRI, CT had a sensitivity of 20% and a specificity of 98% in identifying an acute ischemic lesion. The infarct volume on diffusion-weighted MRI was larger in cases where the CT also showed an acute ischemic lesion (median 5.07 ml, IQR 10) as compared to lesions seen only on MRI (median 0.68 ml, IQR 1.31, p < 0.0001).

Conclusion

MRI is superior to CT in detecting the small ischemic lesions occurring after TIA and minor stroke. Since these lesions are clinically relevant, MRI should be the preferred imaging modality in this setting.

Validity of negative high-resolution diffusion-weighted imaging in transient acute cerebrovascular events

BACKGROUND AND PURPOSE

A significant amount of strokes are reported to be diffusion-weighted imaging (DWI) negative in acute imaging. We attempted to quantify the rate of false-negative high-resolution (hr) DWI and to identify a valid screening tool to guide follow-up MRI to diagnose infarction initially not visible on hrDWI.

METHODS

An a priori-defined post hoc analysis of a prospective 3T MRI cohort of acute cerebrovascular events imaged within 24 hours of ictus. Basic demographics, risk factors, National Institute of Health Stroke Scale, and imaging parameters were recorded.

RESULTS

Of 151 patients with negative acute hrDWI, 63 received follow-up scans depicting infarction in 7 cases (11.1%). Persistence of clinical symptoms as established by National Institute of Health Stroke Scale on the following day was strongly associated with infarction on follow-up MRI (odds ratios, 17.5; 95% confidence interval, 2.83-108.12). Negative predictive value of follow-up National Institute of Health Stroke Scale was 0.96.

CONCLUSIONS

Infarcts are frequently invisible on initial hrDWI, but we may well trust in negative hrDWI in completely transient cerebrovascular events.

Clinical implications of increased use of MRI in TIA

BACKGROUND

Transient ischemic attack has been redefined as a tissue-based diagnosis and MRI recommended as the preferred imaging modality. We aimed to investigate whether an increased use of MRI leads to a decrease in the proportion of TIA as compared to cerebral infarction. We also sought to see whether DWI-positive patients with transient ischemic symptoms <24 h differ from DWI-negative TIA patients in terms of performed diagnostic investigations and clinical characteristics.

METHODS

Patients admitted with cerebral infarction or TIA in the period 2006-2011 were prospectively registered. The use of MRI in patients with transient ischemic symptoms <24 h and proportion of TIA were annually recorded. DWI-positive and DWI-negative patients with transient ischemic symptoms <24 h were compared in univariate analyses regarding baseline data, diagnostic investigations, and etiology. Multivariate analyses were performed to identify predictors of DWI lesions.

RESULTS

The use of MRI increased from 65.0% in 2006-2008 to 89.0% in 2009-2011 (P < 0.001). The proportion of TIA as compared to cerebral infarction decreased from 12.2% in 2006-2008 to 8.3% in 2009-2011 (P = 0.002). DWI-positive patients were more often examined with 24-h Holter monitoring (P < 0.001) and echocardiography (P < 0.001). Lower age (P < 0.001) and prior myocardial infarction (P < 0.029) were independently associated with DWI lesions in patients with transient ischemic symptoms <24 h.

CONCLUSIONS

An increased use of MRI and a tissue-based TIA definition resulted in a decrease in the proportion of TIA at discharge as compared to cerebral infarction. DWI-positive patients had a more extensive cardiac work-up and were associated with lower age and prior myocardial infarction.

Juxtacortical spots on fluid-attenuated inversion recovery images in cryptogenic transient ischemic attack

Background and Purpose

Juxtacortical spots are detected frequently on fluid-attenuated inversion recovery (FLAIR) images, but have not been extensively researched in patients with transient ischemic attack (TIA). We hypothesized that juxtacortical spots on FLAIR images are partly associated with right-to-left shunt (RLS) in TIA without clear etiology. The possibility of an association between the presence of RLS and juxtacortical spots on FLAIR images in patients with TIA without clear etiology was investigated, and the imaging findings of patients with and without RLS were compared.

Methods

This was a retrospective study of TIA patients who visited our tertiary stroke center consecutively within 72 hours of TIA onset. Cryptogenic TIA was defined as no clear etiology despite a routine diagnostic workup. The presence of RLS was examined by transcranial Doppler with an agitated saline test or transesophageal echocardiography. Juxtacortical spots were defined as small and round hyperintensities in the juxtacortex on FLAIR images, excluding white-matter hyperintensities.

Results

Of the 132 patients with cryptogenic TIA examined for this study, 70 (53.0%) had RLS. Juxtacortical spots on FLAIR images were detected more frequently in patients with RLS than in those without. The independent factors for the presence of juxtacortical spots were RLS [odds ratio (OR)=3.802, 95% confidence interval (95% CI)=1.74-8.2; p=0.001] and age (OR=1.058, 95% CI=1.01-1.10; p=0.004) by multivariate analysis. The number of juxtacortical spots was significantly higher among patients with a moderate-to-large RLS than in those with a small or no RLS.

Conclusions

The findings of the present study demonstrate a significant association between the presence of RLS and the occurrence of juxtacortical spots on FLAIR images in patients with cryptogenic TIA.

Synchronized Babinski and Chaddock signs preceded the MRI findings in a case of repetitive transient ischemic attack

We herein report a 53-year-old female with repeated transient ischemic attack (TIA) symptoms including 13 instances of right hemiparesis that decreased in duration over 4 days. Two separate examinations using diffusion weighted image (DWI) in magnetic resonance imaging (MRI) revealed normal findings, but we observed that both Babinski and Chaddock signs were completely synchronized with her right hemiparesis. We were only able to diagnose this case of early stage TIA using clinical signs. This diagnosis was confirmed 4 days after the onset by the presence of abnormalities on the MRI. DWI-MRI is generally useful when diagnosing TIA, but a neurological examination may be more sensitive, especially in the early stages.

Use of cranial CT to identify a new infarct in patients with a transient ischemic attack

Research on infarct detection by noncontrast cranial computed tomography (CCT) in patients with transient ischemic attack (TIA) is sparse. However, the aims of this study are to determine the frequency of new infarcts in patients with TIA, to evaluate the independent predictors of infarct detection, and to investigate the association between a new infarct and early short-term risk of stroke during hospitalization. We prospectively evaluated 1533 consecutive patients (mean age, 75.3 ± 11 years; 54% female; mean National Institutes of Health Stroke Scale [NIHSS] score, 1.7 ± 2.9) with TIA who were admitted to hospital within 48 h of symptom onset. A new infarct was detected by CCT in 47 (3.1%) of the 1533 patients. During hospitalization, 17 patients suffered a stroke. Multivariate logistic regression analysis revealed the following independent predictors for infarct detection: NIHSS score ≥10 (odds ratio [OR], 4.8), time to CCT assessment >6 h (OR 2.2), and diabetes (OR 2.3). The evidence of a new infarct was not associated with the risk of stroke after TIA. The frequency of a new infarct in patients with TIA using CCT is low. The use of the CCT tool to predict the stroke risk during hospitalization in patients with TIA is found to be inappropriate. The estimated clinical predictors are easy to use and may help clinicians in the TIA work up.

ABCD(2) as a screening tool for cerebral infarction on stroke MRI?

BACKGROUND

The newly proposed transient ischemic attack (TIA) definition demands for MRI exclusion of infarction. Due to limited resources other tools than MRI predicting tissue infarction would be valuable. We hypothesized that ABCD(2) risk score is a valid screening tool for diffusion-weighted imaging (DWI) lesions.

METHODS

TIA patients were prospectively enrolled in an observational MRI study to receive acute and follow-up stroke MRI. ABCD(2) scores were calculated, and sociodemographics and risk factors were recorded.

RESULTS

One hundred and thirty-two TIA patients were enrolled over nine months. Five patients were excluded due to different diagnosis. Forty-five of the 127 remaining patients showed acute ischemic lesions on DWI. Median ABCD(2) scores for DWI-negative and -positive patients were 4 and 5, respectively. Ordinal, trichotomized and dichotomized ABCD(2) were significantly associated to DWI. Univariate analysis of single score items and other risk factors demonstrated unilateral weakness, duration of symptoms and smoking as predictive for DWI restrictions. In multivariate analysis unilateral weakness remained significant.

CONCLUSIONS

High-risk ABCD(2) score due to the impact of hemiparesis is associated with the occurrence of DWI lesions but is still not accurate enough for a reliable differentiation of cerebrovascular events with and without MRI lesions.

Acute perfusion and diffusion abnormalities predict early new MRI lesions 1 week after minor stroke and transient ischemic attack

BACKGROUND AND PURPOSE

Transient ischemic attack and minor stroke are associated with high ischemic recurrence in the first week. We prospectively studied the correlation between baseline diffusion/perfusion deficits and development of new ischemic lesions.

METHODS

Patients with transient ischemic attack and those with minor stroke (n=50) underwent MRI at admission. Acute perfusion-weighted imaging deficit (Tmax+2-second delay) and diffusion-weighted imaging (DWI) lesion volumes were measured planimetrically. Follow-up scans were examined for new DWI/fluid-attenuated inversion recovery lesions at Days 7 and 30.

RESULTS

Twenty-eight patients (56%) had acute DWI lesions. New DWI lesions developed in 9 of 50 patients (18%) at 1 week and 11 of 50 (cumulative 22%) at 4 weeks. Patients with new infarcts were more likely to have baseline DWI lesions (χ²=8.264, P=0.003). Baseline DWI lesion volume was significantly larger in those who developed new lesions at Day 7 (median, 13.2 mL; interquartile range, 12 versus median 0.1 mL; interquartile range, 2 mL; P<0.001) and Day 30 (11.1 mL; interquartile range, 13 mL versus 0.1 mL; interquartile range, 13 mL; P<0.001). Thirty-eight patients had baseline perfusion-weighted imaging. Patients with recurrent lesions were more likely to have baseline perfusion deficits (χ²=19.5, P<0.0001). All new lesions developed within the baseline hypoperfused regions. Baseline DWI lesion volume predicted new lesion development at day 7 (OR, 1.17 per mL; CI, 1.05 to 1.30; P=0.005) and Day 30 (OR, 1.39 per mL; CI, 1.03 to 1.26; P=0.009) by regression analysis.

CONCLUSIONS

Early recurrence of stroke is much more likely in patients with larger baseline DWI and perfusion-weighted imaging lesions. MRI lesion "recurrence" appears to be related to completion of the natural history of the original cerebrovascular syndrome rather than de novo events in most patients.

How much would performing diffusion-weighted imaging for all transient ischemic attacks increase MRI utilization?

OBJECTIVES

The American Heart Association recently redefined TIA to exclude patients with infarction on neuroimaging. Given its advantages, MRI/diffusion-weighted imaging (DWI) was recommended as the preferred imaging modality. We determined how frequently MRI/DWI was performed for TIA and ascertained the proportion of clinically defined TIA patients who had ischemic lesions on DWI in our community in 2005.

METHODS

All clinically defined TIA cases among residents of a 5-county region around Cincinnati who presented to emergency departments were identified during 2005. Demographics and medical history, whether MRI/DWI was performed, and DWI findings were recorded. Generalized estimating equations were used to compare groups to account for the design of the study and multiple events per patient.

RESULTS

Of 834 TIA events in 799 patients, 323 events (40%) had MRI/DWI performed. Patients who had MRI/DWI were younger (mean, 66 vs 70 years; P=0.03), had less severe prestroke disability (baseline modified Rankin Scale score, 0; 44% vs 34%; P=0.02), were less likely to have previous stroke or TIA (42% vs 56%; P=0.002), and were less likely to have atrial fibrillation (10% vs 16%; P=0.01). Of the 323 events with DWI, 51 (15%) had evidence of acute infarction. Patients with positive DWI were older (75 vs 64 years; P=0.0001) and more likely to have atrial fibrillation (21% vs 7%; P=0.002).

CONCLUSIONS

Performing MRI/DWI on all clinically defined TIA patients in our community would reveal more cases of actual infarction but would more than double current use. Future studies should assess whether MRI/DWI is warranted for all TIA patients.

Transient ischemic attack: are there different types or classes? Risk of stroke and treatment options

Recent advances in neuroimaging have revolutionized the evaluation of the clinical syndrome of transient ischemic attack (TIA). Diffusion-weighted imaging demonstrates microinfarctions (< 1 cm(3)) in approximately 50% of patients with TIA, establishing that not all clinically transient spells are transient at the tissue level. The clinical syndrome of TIA that is associated with ischemic brain injury is called "transient symptoms with infarction" (TSI). TSI appears to be a different subset because it harbors higher risk of imminent stroke than "TIA with no infarction." Armed with the evidence of ischemia as the cause of transient spell, clinicians can pursue the most appropriate therapy for stroke prevention by targeting the underlying etiology of brain ischemia.

An optimized mouse model for transient ischemic attack

Transient ischemic attacks (TIAs) are brief neurological deficits ofcerebrovascular origin that are followed by complete clinical recovery. Although a plethora of animal models exist for ischemic stroke, a verified TIA model is lacking. We aimed to optimize such a model in mice, investigating the impact of varying durations (from 2.5 to 20 minutes) of intraluminal middle cerebral artery occlusion (MCAo). Three conditions were required to mimic clinical TIA reliably: 1) an objective demonstration of occlusion and reperfusion (assessed by laser Doppler flowmetry); 2) no permanent neurological deficit (assessed by sensorimotor neurological evaluation); and 3) no lesion at 24 hours after reperfusion (assessed by magnetic resonance imaging [MRI]). We observed high incidences of MRI lesions with MCAo durations of 15 minutes or longer. In contrast, no permanent neurological deficits or MRI lesions were observed in animals with MCAo below or equal to 10 minutes. Middle cerebral artery occlusion of 12.5 minutes rarely induced MRI lesions, but histopathologic evaluation using routine and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining revealed minute ischemic changes even after 2.5-minute MCAo. Abundance of necrotic and apoptotic changes gradually increased with the duration of ischemia. These results indicate that 10 minutes or shorter focal cerebral ischemia proves a suitable mouse TIA model; in addition, they indicate that MRI-negative microscopic ischemic damage may occur with even a few minutes of arterial occlusion.

Transient ischemic attack may present a target for normobaric hyperoxia treatment

According to the new revised tissue-based definition, transient ischemic attack is a transient episode of neurological dysfunction caused by a focal brain, spinal cord, or retinal ischemia without acute infarction. This review addresses the pathophysiology of transient ischemic attack and the impact of normobaric hyperoxia on the penumbral tissue. Neuroimaging in transient ischemic attack patients and advances in penumbra imaging allow the transient ischemic attack, from pathophysiological viewpoint, to be defined as an ischemic penumbra of varied duration, which could proceed to a cerebral infarction or reduce to a benign oligemia. Persisting perfusion abnormalities are observed, despite resolution of the neurological symptoms. Preclinical and clinical studies have shown that the normobaric hyperoxia treatment is associated with improvement of hemodynamic and metabolic disturbances, particularly in the penumbral tissue. Transient ischemic attack, considered an ischemic penumbra, may present an ideal target for early normobaric hyperoxia therapy, administered as soon as possible after the onset of the neurological deficit. Follow-up perfusion imaging could guide and individualize the treatment.

Predicting recurrent stroke after minor stroke and transient ischemic attack

The risk of a subsequent stroke following an acute transient ischemic attack or minor stroke is high, with 90-day risk at approximately 10%. Identification of those patients at the highest risk for recurrent stroke following a transient ischemic attack or minor stroke may allow risk-specific management strategies to be implemented, such as hospital admission with expedited work-up for those at high risk and emergency room discharge for those at low risk. Predictors of recurrent stroke, including the ABCD2 score, brain imaging and the stroke mechanism, are reviewed in this article, with a focus on recent literature. An emphasis is placed on the importance of early imaging of the brain parenchyma (diffusion-weighted imaging) and vascular imaging to identify patients at high risk for recurrence. The need for identification of the cause of the initial event, allowing therapies to be tailored to the individual patient, is discussed.

Diffusion and perfusion MR imaging of acute ischemic stroke

Diffusion and perfusion MR imaging have proven to be highly useful in the clinical description and understanding of acute and hyperacute ischemic stroke. In this article, the authors give a brief overview of the basic concepts of diffusion and perfusion imaging and describe some of the current developments, applications, challenges, and limitations of these techniques as applied to cerebral ischemia.

Yield of combined perfusion and diffusion MR imaging in hemispheric TIA

OBJECTIVE

Transient ischemic attacks (TIA) predict future stroke. However, there are no sensitive and specific diagnostic criteria for TIA and interobserver agreement regarding the diagnosis is poor. Diffusion-weighted MRI (DWI) demonstrates acute ischemic lesions in approximately 30% of TIA patients; the yield of perfusion-weighted MRI (PWI) is unclear.

METHODS

We prospectively performed both DWI and PWI within 48 hours of symptom onset in consecutive patients admitted with suspected hemispheric TIAs of <24 hours symptom duration. Two independent raters, blinded to clinical features, assessed the presence and location of acute DWI and PWI lesions. Lesions were correlated with suspected clinical localization and baseline characteristics. Clinical features predictive of a PWI lesion were assessed.

RESULTS

Forty-three patients met the inclusion criteria. Thirty-three percent had a PWI lesion and 35% had a DWI lesion. Seven patients (16%) had both PWI and DWI lesions and 7 (16%) had only PWI lesions. The combined yield for identification of either a PWI or a DWI was 51%. DWI lesions occurred in the clinically suspected hemisphere in 93% of patients; PWI lesions in 86%. PWI lesions occurred more frequently when the MRI was performed within 12 hours of symptom resolution, in patients with symptoms of speech impairment, and among individuals younger than 60 years.

CONCLUSIONS

The combination of early diffusion-weighted MRI and perfusion-weighted MRI can document the presence of a cerebral ischemic lesion in approximately half of all patients who present with a suspected hemispheric transient ischemic attack (TIA). MRI has the potential to improve the accuracy of TIA diagnosis. ACA = anterior cerebral artery; CI = confidence interval; DWI = diffusion-weighted MRI; ICA = internal carotid artery; MCA = middle cerebral artery; MRA = magnetic resonance angiography; MTT = mean transit time; OR = odds ratios; PCA = posterior cerebral artery; PWI = perfusion-weighted MRI; RR = risk ratios; TIA = transient ischemic attacks; TOAST = Trial of Org 10172 in Acute Stroke Treatment.

Diffusion-Weighted Imaging-Negative Patients With Transient Ischemic Attack Are at Risk of Recurrent Transient Events

BACKGROUND AND PURPOSE

Among patients presenting with a transient ischemic attack (TIA), some clinical features predispose to recurrent TIA, whereas others predispose to subsequent strokes. We assessed the implication of negative diffusion-weighted imaging on a baseline MRI in predicting subsequent TIA.

METHODS

We prospectively studied patients presenting in the emergency department within 12 hours of a TIA (motor or speech). All patients had a MRI within 24 hours of the index event. The primary outcome was TIA within 1 year of study entry. The 1-year risk of stroke was also evaluated.

RESULTS

A total of 85 patients had a MRI, among which 35 patients (41.2%) had a diffusion-weighted imaging lesion. The mean time from symptom onset to MRI was 12.1 hours. Patients without a diffusion-weighted imaging lesion on baseline MRI were 4.6 times (27.4% versus 5.9%; P<0.05) more likely to have a subsequent TIA at 1 year than patients with a diffusion-weighted imaging lesion, but 4.3 times (2.1% versus 9.1%; P=0.19) less likely to have a subsequent stroke.

CONCLUSIONS

The absence of a diffusion-weighted imaging lesion on the baseline scan predicts recurrent transient events rather than stroke.

Current management of transient ischemic attack

Transient ischemic attack (TIA) is a precursor to ischemic stroke. At least half of patients with TIA have a new, small ischemic lesion demonstrable on magnetic resonance imaging using a diffusion weighted sequence. The risk of subsequent major stroke is 10-20% in the next 3 months with much of that risk front-loaded in the first week. Strategies to identify and treat high-risk patients need to be defined. The optimal treatment approach and the timing of interventions, both medical and surgical, remains unknown. In general, aspirin is the first line of treatment to prevent further stroke. Other antiplatelet agents such as clopidogrel alone or in combination with aspirin and the combination aspirin/extended-release dipyridamole may be administered. Endarterectomy or carotid stenting is of great benefit to patients with TIA secondary to stenosis in the extracranial carotid artery.

Sudden bilateral blindness in Wernicke's encephalopathy: case report and review of the literature

We report on a patient suffering from bilateral sudden blindness as initial symptom of Wernicke's encephalopathy (WE). A 37-year-old male alcoholic was admitted to a psychiatric clinic because of excessive alcohol consumption (3.4 per thousand). 24 h later he developed acute bilateral blindness with no light perception, downbeat nystagmus, bilateral ocular abduction deficits, cerebellar ataxia as well as a slight psychomotor slowing and mild disorientation. MRI including diffusion-weighted imaging and MR-angiography 3 h after symptom onset did not reveal findings suggestive for ischemic stroke. Immediate iv-application of thiamine led to a nearly complete remission of the neuroophthalmologic symptoms within 12 h. Although we critically discuss other potential etiologies, we conclude that the complex clinical picture with initial sudden blindness is an unusual presentation of WE.

Systematic Review of Associations Between the Presence of Acute Ischemic Lesions on Diffusion-Weighted Imaging and Clinical Predictors of Early Stroke Risk After Transient Ischemic Attack

BACKGROUND AND PURPOSE

Early risk of stroke after a transient ischemic attack can be reliably predicted with risk scores based on clinical features of the patient and of the ischemic event, but it is unclear how these features correlate with findings on brain imaging.

METHODS

We performed a systematic review of the literature and identified all previous studies which reported patient characteristics and the nature of transient ischemic attack symptoms in relation to appearances on diffusion-weighted imaging (DWI). We then performed a meta-analysis of the associations between the components of the risk scores and positive DWI. Authors were contacted for additional unpublished data.

RESULTS

Nineteen studies were identified by the systematic review, and additional unpublished data were obtained from 11 of these studies. On meta-analysis, several components of the risk scores were associated with positive DWI, including symptom duration > or =60 minutes (13 studies, odds ratio [OR], 1.50; 95% CI, 1.16 to 1.96; P=0.004), dysphasia (9 studies, OR, 2.25; 95% CI, 1.57 to 3.22; P<0.001), dysarthria (8 studies, OR, 1.73; 95% CI, 1.11 to 2.68; P=0.03) and motor weakness (9 studies, OR, 2.20; 95% CI, 1.56 to 3.10; P<0.001). However patient age, sex, hypertension and diabetes were not associated with the presence of DWI lesions. From an etiologic perspective, atrial fibrillation (9 studies, OR, 2.75; 95% CI, 1.78 to 4.25; P<0.001) and ipsilateral > or =50% carotid stenosis (10 studies, OR, 1.93; 95% CI, 1.34 to 2.76; P=0.001) were associated with positive DWI.

CONCLUSIONS

Presence of acute ischemic lesions on DWI correlates with several clinical features known to predict stroke risk after transient ischemic attack. Large studies (sample size >1000) will therefore be required to determine the independent prognostic value of DWI and its interactions with these clinical characteristics.

Reversible brain ischemia: lessons from transient ischemic attack

PURPOSE OF REVIEW

In recent years, there has been considerable scientific inquiry regarding transient ischemic attack. In an effort to synthesize at times conflicting data, this paper will review the recent evidence and provide a critical overview of reversible brain ischemia.

RECENT FINDINGS

Transient ischemic attack is now understood to indicate a higher risk of recurrence than completed ischemic stroke. Efforts to unravel the mechanisms of this instability following transient ischemic attack using imaging studies have led to new concepts and definitions, and sparked further debate. While imaging has increased diagnostic certainty, it has yet to provide reliable prognostic markers. The evidence suggests that risk of clinical recurrence is most closely linked to the degree to which the initial deficit reverses. From a tissue level, however, there are also data to support the notion of a 'stroke-prone state' following both transient ischemic attack and completed stroke, suggesting that mechanistically they may be less distinct than previously thought. Transient ischemic attack may simply highlight the dynamic nature of all acute ischemic cerebrovascular syndromes.

SUMMARY

Reversible brain ischemia is a harbinger for subsequent ischemic stroke. Although recent advances have focused on imaging markers, the most important predictor of risk following brain ischemia is degree of early clinical reversibility.