Wake-up or unclear-onset strokes: are they waking up to the world of thrombolysis therapy?

Characteristics and outcomes of unknown onset stroke: The Japan Stroke Data Bank

BACKGROUND

Clinical outcomes of unknown onset stroke (UOS) are influenced by the enlargement of the therapeutic time window for reperfusion therapy. This study aimed to investigate and describe the characteristics and clinical outcomes of patients with UOS.

METHODS

Patients with acute ischemic stroke (AIS) who were admitted within 24 h of their last known well time, from January 2017 to December 2020, were included. Data were obtained from a long-lasting nationwide hospital-based multicenter prospective registry: the Japan Stroke Data Bank. The co-primary outcomes were the National Institutes of Stroke Scale (NIHSS) scores on admission and unfavorable outcomes at discharge, corresponding to modified Rankin Scale (mRS) scores of 3-6.

RESULTS

Overall, 26,976 patients with AIS were investigated. Patients with UOS (N = 5783, 78 ± 12 years of age) were older than patients with known onset stroke (KOS) (N = 21,193, 75 ± 13 years of age). Age, female sex, higher premorbid mRS scores, atrial fibrillation, and congestive heart failure were associated with UOS in multivariate analysis. UOS was associated with higher NIHSS scores (median = 8 [interquartile range [IQR]: 3-19] vs. 4 [1-10], adjusted incidence rate ratio = 1.37 [95% CI: 1.35-1.38]) and unfavorable outcomes (52.1 vs. 33.6%, adjusted odds ratio = 1.27 [1.14-1.40]). Intergroup differences in unfavorable outcomes were attenuated among females (1.12 [0.95-1.32] vs. males 1.38 [1.21-1.56], P = 0.040) and in the subgroup that received reperfusion therapy (1.10 [0.92-1.33] vs. those who did not receive therapy 1.23 [1.08-1.39], P = 0.012).

CONCLUSIONS

UOS was associated with unfavorable outcomes but to a lesser degree among females and patients receiving reperfusion therapy.

Magnetic Resonance Imaging in Acute Ischemic Stroke

Ischemic stroke is one of the leading causes of mortality and disability. The only effective non-surgical treatment for acute ischemic stroke within three to four and a half hours of the onset of symptoms is thrombolytic therapy. Time is of the essence when diagnosing and treating an acute ischemic stroke. After evaluating the advantages and disadvantages of thrombolysis, selecting the ideal patient for the indication is essential. Magnetic Resonance Imaging (MRI) is more sensitive and specific than Computed Tomography (CT) scans when identifying acute ischemic stroke. In approximately 80% of cases, infarcts are detectable within the first 24 hours. MRI can detect an ischemic stroke within a few hours of its onset. Multimodal imaging provides information for the diagnosis of ischemic stroke, patient selection for thrombolytic therapy, and prognosis estimation.

Use of DWI-FLAIR Mismatch to Estimate the Onset Time in Wake-Up Strokes

PURPOSE

To compare the MRI characteristics of patients with wake-up ischemic stroke (WUS) and with ischemic stroke with known onset time (clear-onset-time stroke, COS) to clarify the role of diffusion-weighted imaging-fluid-attenuated inversion recovery (DWI-FLAIR) mismatch in estimating the onset time of WUS patients.

PATIENTS AND METHODS

Two hundred patients with acute ischemic stroke were selected for complete brain MRI within six hours of symptom onset, including DWI and FLAIR sequences. The patients were divided into WUS (n = 78) and COS (n = 122) groups, based on whether the time of onset was known. The general conditions and imaging characteristics were collected to compare the DWI-FLAIR mismatch features between the two groups at different time intervals.

RESULTS

There was no significant difference in the DWI-FLAIR mismatch on MRI within 2 hour after the first found abnormality between the two groups (50.0% vs 71.8%, p = 0.180). With increasing time, the DWI-FLAIR mismatch decreased substantially in the WUS group, while a higher DWI-FLAIR mismatch presence persisted in the COS group within a four-hour interval from the onset of symptoms to the MRI. The DWI-FLAIR mismatch was significantly lower in the WUS group than in the COS group from symptom identification to MRI at 2-3 h, 3-4 h, and 4-5 h intervals (15% vs 60%, 10.5% vs 48%, 6.7% vs 45.4%; p < 0.01).

CONCLUSION

Our results suggest that the presence of DWI-FLAIR mismatch within 2 h of the first found abnormality was not significantly different between WUS and COS. Therefore, Patients with WUS within 2 hours after the first detected abnormality may be suitable for intravenous thrombolysis.

Evaluation of stroke related risk factors in wake up and non-wake up stroke patients

Wake-Up Stroke (WUS) is defined as a stroke with the unclear onset of symptoms and subsequent neurological deficits which perceived upon awakening. WUS patients are often excluded from acute fibrinolytic and reperfusion therapy due to the unknown exact time of symptoms onset. This study aimed to evaluate patients with and without WUS characteristics and associated risk factors at two tertiary hospitals. First, we prospectively evaluated consecutive patients with stroke symptoms and determined stroke sub groups by using Computed Tomography (CT) scan. Next, demographic and clinical characteristics including past medical and drug consumption history as well as cardiac function index (ejection fraction), LDL (mg/dl) level and hematologic parameters: hemoglobin (Hb); hematocrit (Hct); platelet (Plt) were assessed. Results: 510 patients (56.1% men and 43.9% women) with averaged age of 70 and 72 years were studied, respectively. Of 510 patients, 405 (79.4%) had non-WUS stroke (known-onset stroke) and 105 (20.6%) had WUS strokes (unknown-onset stroke). The WUS occurrence most likely was observed in ischemic stroke compared to hemorrhagic one. No significant differences were found between patients from both groups regarding stroke risk factors. However, hypertension and family history were more common in patients with WUS (p>0.05). Moreover, individuals with a previous cerebrovascular accident in WUS group were almost similar to non-WUS counterparts. No differences also detected in case of hematologic characteristics, heart function index and LDL levels between study groups (p>0.05). Together, wake-up stroke occurs in approximately 20% of stroke subjects. In this study, patients with WUS had more hypertension and family history.

Wake-up stroke: imaging-based diagnosis and recanalization therapy

Wake-up stroke (WUS) is a subgroup of ischemic stroke in which patients show no abnormality before sleep while wake up with neurological deficits. In addition to the uncertain onset, WUS patients have difficulty to receive prompt and effective thrombolytic or reperfusion therapy, leading to relatively poor prognosis. A number of researches have indicated that CT or MRI based thrombolysis and endovascular therapy might have benefits for WUS patients. This review article narratively discusses the pathogenesis, risk factors, imaging-based diagnosis and recanalization treatments of WUS with the purpose of expanding current treatment options for this group of stroke patients and exploring better therapeutic methods. The result showed that multimodal MRI or CT scan might be the best methods for extending the time window of WUS and, therefore, a large proportion of WUS patients could have favorable prognosis.

Machine learning-based segmentation of ischemic penumbra by using diffusion tensor metrics in a rat model

Background

Recent trials have shown promise in intra-arterial thrombectomy after the first 6–24 h of stroke onset. Quick and precise identification of the salvageable tissue is essential for successful stroke management. In this study, we examined the feasibility of machine learning (ML) approaches for differentiating the ischemic penumbra (IP) from the infarct core (IC) by using diffusion tensor imaging (DTI)-derived metrics.

Methods

Fourteen male rats subjected to permanent middle cerebral artery occlusion (pMCAO) were included in this study. Using a 7 T magnetic resonance imaging, DTI metrics such as fractional anisotropy, pure anisotropy, diffusion magnitude, mean diffusivity (MD), axial diffusivity, and radial diffusivity were derived. The MD and relative cerebral blood flow maps were coregistered to define the IP and IC at 0.5 h after pMCAO. A 2-level classifier was proposed based on DTI-derived metrics to classify stroke hemispheres into the IP, IC, and normal tissue (NT). The classification performance was evaluated using leave-one-out cross validation.

Results

The IC and non-IC can be accurately segmented by the proposed 2-level classifier with an area under the receiver operating characteristic curve (AUC) between 0.99 and 1.00, and with accuracies between 96.3 and 96.7%. For the training dataset, the non-IC can be further classified into the IP and NT with an AUC between 0.96 and 0.98, and with accuracies between 95.0 and 95.9%. For the testing dataset, the classification accuracy for IC and non-IC was 96.0 ± 2.3% whereas for IP and NT, it was 80.1 ± 8.0%. Overall, we achieved the accuracy of 88.1 ± 6.7% for classifying three tissue subtypes (IP, IC, and NT) in the stroke hemisphere and the estimated lesion volumes were not significantly different from those of the ground truth (p = .56, .94, and .78, respectively).

Conclusions

Our method achieved comparable results to the conventional approach using perfusion–diffusion mismatch. We suggest that a single DTI sequence along with ML algorithms is capable of dichotomizing ischemic tissue into the IC and IP.

Machine Learning Approach to Identify Stroke Within 4.5 Hours

Background and Purpose- We aimed to investigate the ability of machine learning (ML) techniques analyzing diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging to identify patients within the recommended time window for thrombolysis. Methods- We analyzed DWI and FLAIR images of consecutive patients with acute ischemic stroke within 24 hours of clear symptom onset by applying automatic image processing approaches. These processes included infarct segmentation, DWI, and FLAIR imaging registration and image feature extraction. A total of 89 vector features from each image sequence were captured and used in the ML. Three ML models were developed to estimate stroke onset time for binary classification (≤4.5 hours): logistic regression, support vector machine, and random forest. To evaluate the performance of ML models, the sensitivity and specificity for identifying patients within 4.5 hours were compared with the sensitivity and specificity of human readings of DWI-FLAIR mismatch. Results- Data from a total of 355 patients were analyzed. DWI-FLAIR mismatch from human readings identified patients within 4.5 hours of symptom onset with 48.5% sensitivity and 91.3% specificity. ML algorithms had significantly greater sensitivities than human readers (75.8% for logistic regression, P=0.020; 72.7% for support vector machine, P=0.033; 75.8% for random forest, P=0.013) in detecting patients within 4.5 hours, but their specificities were comparable (82.6% for logistic regression, P=0.157; 82.6% for support vector machine, P=0.157; 82.6% for random forest, P=0.157). Conclusions- ML algorithms using multiple magnetic resonance imaging features were feasible even more sensitive than human readings in identifying patients with stroke within the time window for acute thrombolysis.

Wake-up stroke: From pathophysiology to management

Wake-up strokes (WUS) are strokes with unknown exact time of onset as they are noted on awakening by the patients. They represent 20% of all ischemic strokes. The chronobiological pattern of ischemic stroke onset, with higher frequency in the first morning hours, is likely to be associated with circadian fluctuations in blood pressure, heart rate, hemostatic processes, and the occurrence of atrial fibrillation episodes. The modulation of stroke onset time also involves the sleep-wake cycle as there is an increased risk associated with rapid-eye-movement sleep. Furthermore, sleep may have an impact on the expression and perception of stroke symptoms by patients, but also on brain tissue ischemia processes via a neuroprotective effect. Obstructive sleep apnea syndrome is particularly prevalent in WUS patients. Until recently, WUS was considered as a contra-indication to reperfusion therapy because of the unknown onset time and the potential cerebral bleeding risk associated with thrombolytic treatment. A renewed interest in WUS has been observed over the past few years related to an improved radiological evaluation of WUS patients and the recent demonstration of the clinical efficacy of reperfusion in selected patients when the presence of salvageable brain tissue on advanced cerebral imaging is demonstrated.

Outcome of multimodal MRI-guided intravenous thrombolysis in patients with stroke with unknown time of onset

Objective

Intravenous tissue plasminogen activator (tPA) is the standard therapy for patients with acute ischaemic stroke (AIS) within 4.5 hours of onset. Recent trials have expanded the endovascular treatment window to 24 hours. We investigated the efficacy and safety of using multimodal MRI to guide intravenous tPA treatment for patients with AIS of unknown time of onset (UTO).

Methods

Data on patients with AIS with UTO and within 4.5 hours of onset were reviewed. Data elements collected and analysed included: demographics, National Institutes of Health Stroke Scale (NIHSS) score at baseline and 2 hours, 24 hours, 7 days after thrombolysis and before discharge, the modified Rankin Scale (mRS) score at 3 months after discharge, imaging findings and any adverse event.

Results

Forty-two patients with UTO and 62 in control group treated within 4.5 hours of onset were treated with intravenous tPA. The NIHSS scores after thrombolysis and/or before discharge in UTO group were significantly improved compared with the baseline (p<0.05). Between the two groups, no significant differences in NIHSS score were observed (p>0.05). Utilising the non-inferiority test, to compare mRS scores (0–2) at 3 months between the two groups, the difference was 5.2% (92% CI, OR 0.196). Patients in the UTO group had mRS scores of 0-2, which were non-inferior to the control group. Their incidence of adverse events was similar.

Conclusions

Utilising multimodal MRI to guide intravenous only thrombolysis for patients with AIS with UTO was safe and effective. In those patients with AIS between 6 and 24 hours of time of onset but without large arterial occlusion, intravenous thrombolysis could be considered an option.

Safety and cost-effectiveness thrombolysis by diffusion-weighted imaging and fluid attenuated inversion recovery mismatch for wake-up stroke

Wake-up stroke, defined as patients who wake up with stroke symptoms which were not present prior to falling asleep, accounted for 14%-25% of acute ischemic stroke. Due to the unknown time of symptom onset, wake-up stoke was not in including criteria of intravenous thrombolysis. Several large randomized stroke trials using diffusion-weighted imaging(DWI)and fluid attenuated inversion recovery(FLAIR)mismatch patient selection may identify a subset of patients with wake-up stroke that can safely and effectively benefit from intravenous thrombolysis. In addition, economic factor was another important limitation to generalize thrombolysis treatment. Fortunately, MRI-based thrombolysis was a cost-effective treatment for wake-up stroke compared to these patients with no thrombolysis.

Thrombolytic Therapy in Wake-Up Stroke Patients

OBJECTIVE

The aim of the study is to review existing and ongoing trial data on wake-up stroke (WUS) patients for thrombolytic therapy.

METHODS

A literature search was conducted in PubMed (conception-October 2016) using the terms wake-up stroke, acute ischemic stroke, wake-up thrombolysis, computed tomography imaging in wake-up stroke, and magnetic resonance imaging in wake-up stroke. Ongoing trials were found using the ClinicalTrials.gov website.

RESULTS

The search yielded 61 articles in PubMed and 7 ongoing trials. After removing duplicate/irrelevant articles, 33 articles and relevant references were reviewed; of these, 6 articles and 3 ongoing trials were included. Two retrospective studies evaluating the characteristics between WUS and known-onset stroke were identified; the only significant difference between groups was the ability to receive treatment with tissue plasminogen activator (tPA). One study suggested that perfusion brain imaging may be useful to identify patients that may benefit from tPA. In addition, 3 studies have evaluated WUS treatment; all used different methods to identify potential patients. Two of 3 studies showed that treatment with tPA is associated with better outcomes when controlling for baseline National Institutes of Health Stroke Scale. No difference in safety outcomes was seen between groups for all 3 studies.

CONCLUSIONS

Available data suggest promising strategies to identify WUS patients who may benefit from thrombolysis. Once on-going trials are complete, there may be sufficient information to redefine tPA eligibility for previously excluded patients.

Collateral response modulates the time–penumbra relationship in proximal arterial occlusions

Objective

While clinical benefit from thrombolysis decreases with increase in time from stroke onset, the relationship of acute physiologic tissue compartments and collateral response to stroke onset time remains unclear.

Methods

We studied consecutive patients with proximal arterial occlusions (n = 355) with whole-brain perfusion CT with CT angiography within 6 hours of stroke onset. Penumbra and core were defined using voxel-based thresholds. Tissue mismatch was defined as the ratio of penumbra to core. Collateral scores were assessed using a previously validated visual score.

Results

Mean (SD) age was 72.1 (12.4) years, median (interquartile range) NIH Stroke Scale score 16 (4), mean (SD) time to imaging 152.5 (69.7) minutes. Penumbra volume (Spearman ρ = 0.119,p= 0.026) and mismatch increased (Spearman ρ = 0.115,p= 0.030) with time from onset. Core volume decreased (Spearman ρ = −0.112,p= 0.035) while collateral scores increased with time (Spearman ρ = 0.117,p= 0.028). On multivariable regression, good collateral scores predicted longer time since onset (β = 0.101,p= 0.039) while mismatch was not a predictor (β = 0.001,p= 0.351). Good collateral score was the strongest independent predictor of final infarct volume and improvement in clinical deficit.

Conclusions

In our large patient cohort study of proximal arterial occlusions, we found an incremental collateral response and preserved penumbral volume with time. Thus, tissue viability can be maintained in this time window (0–6 hours) after stroke if leptomeningeal collaterals are able to sustain the penumbra. Our findings suggest that a longer therapeutic window may exist for intra-arterial intervention and that multimodal imaging may have a role in strokes of unknown onset time.

Discovery and Longitudinal Evaluation of Candidate Biomarkers for Ischaemic Stroke by Mass Spectrometry-Based Proteomics

Application of acute therapies such as thrombolysis for ischaemic stroke (IS) is constrained because of diagnostic uncertainty and the dynamic nature of stroke biology. To investigate changes in blood proteins after stroke and as a result of thrombolysis treatment we performed label-free quantitative proteomics on serum samples using high-resolution mass spectrometry and long high-performance liquid chromatography gradient (5 hours) combined with a 50-cm column to optimise the peptide separation. We identified (false discovery rate [FDR]: 1%) and quantified a total of 574 protein groups from a total of 92 samples from 30 patients. Ten patients were treated by thrombolysis as part of a randomised placebo-controlled trial and up to 5 samples were collected from each individual at different time points after stroke. We identified 26 proteins differently expressed by treatment group (FDR: 5%) and significant changes of expression over time for 23 proteins (FDR: 10%). Molecules such as fibrinogen and C-reactive protein showed expression profiles with a high-potential clinical utility in the acute stroke setting. Protein expression profiles vary acutely in the blood after stroke and have the potential to allow the construction of a stroke clock and to have an impact on IS treatment decision making.

Unknown onset ischemic strokes in patients last-seen-well >4.5 h: differences between wake-up and daytime-unwitnessed strokes

Patients with unknown time of stroke onset (UOS) represent around one-third of ischemic stroke patients. These are patients with wake-up stroke (WUS) or daytime-unwitnessed stroke (DUS), often presenting outside the time-window for reperfusion therapy. UOS patients presenting between 4.5 and 12 h after time of last-seen-well were included. Clinical and imaging characteristics were compared between WUS and DUS patients. Good functional outcome was defined as a modified Rankin scale of ≤2 at follow-up. Sixty-one UOS patients were included: 42 WUS and 19 DUS patients. Stroke severity at presentation was mild to moderate with a median National Institutes of Health Stroke Scale of 5 in WUS and 6 in DUS patients. Time between last-seen-well and presentation at the hospital was shorter in patients with DUS compared to WUS (506 vs 362 min, p < 0.01). CT imaging results were similar, with a median Alberta Stroke Program Early CT Score of 10 for both WUS and DUS patients. After correction for age and NIHSS at presentation, no difference in good functional outcome was found between WUS (52%) and DUS (22%). In patients with unknown onset ischemic strokes presenting between 4.5 and 12 h after time of last-seen-well, clinical and radiological features were in large part similar between WUS and DUS. The outcome in the overall cohort was rather poor despite a favorable neuroimaging profile at presentation. These findings underscore the need for clinical trials in patients in whom stroke onset time is unknown.

Unclear-onset stroke: Daytime-unwitnessed stroke vs. wake-up stroke

BACKGROUND AND PURPOSE

The onset of wake-up stroke and daytime-unwitnessed stroke is unclear. Though the clinical importance is similar by both being excluded from reperfusion therapy, the characteristics of daytime-unwitnessed stroke are less known than that of wake-up stroke. Here, we compared the characteristics between daytime-unwitnessed stroke and wake-up stroke.

METHODS

Unclear-onset (i.e., last-known normal time ≠ first-found abnormal time) stroke patients admitted within 24 h of recognition of stroke between February 2011 and October 2013 were reviewed. Demographics and clinical and imaging variables were compared between patients with daytime-unwitnessed stroke and those with wake-up stroke.

RESULTS

Among the 762 ischemic stroke patients, 276 (36.2%) had unclear-onset stroke (104 daytime-unwitnessed stroke and 172 wake-up stroke). Compared to wake-up stroke, daytime-unwitnessed stroke patients had a higher prevalence of cardioembolic stroke and more frequently presented altered mental status (p < 0.001) and/or aphasia (p < 0.001) with more severe neurological deficit (p < 0.001). However, the time from symptom recognition to hospital arrival was shorter (p < 0.001), and diffusion-weighted image-fluid-attenuated inversion recovery image mismatch (p = 0.02) and perfusion-diffusion mismatch (p = 0.001) were also more frequently observed in daytime-unwitnessed stroke. Finally, the proportion of patients eligible for thrombolysis (p < 0.001) was higher in daytime-unwitnessed stroke patients.

CONCLUSIONS

Clinical and imaging characteristics of daytime-unwitnessed stroke significantly differ from those of wake-up stroke. Daytime-unwitnessed stroke patients are more likely to receive reperfusion therapy, as they arrive at the hospital earlier after symptom recognition, compared to wake-up stroke patients.

Unclear-onset intracerebral hemorrhage: Clinical characteristics, hematoma features, and outcomes

Background and purpose Although unclear-onset ischemic stroke, including wake-up ischemic stroke, is drawing attention as a potential target for reperfusion therapy, acute unclear-onset intracerebral hemorrhage has been understudied. Clinical characteristics, hematoma features, and outcomes of patients who developed intracerebral hemorrhage during sleep or those with intracerebral hemorrhage who were unconscious when witnessed were determined. Methods Consecutive intracerebral hemorrhage patients admitted within 24 hours after onset or last-known normal time were classified into clear-onset intracerebral hemorrhage and unclear-onset intracerebral hemorrhage groups. Outcomes included initial hematoma volume, initial National Institutes of Health Stroke Scale score, hematoma growth on 24-hour follow-up computed tomography, and vital and functional prognoses at 30 days. Results Of 377 studied patients (122 women, 69 ± 11 years old), 147 (39.0%) had unclear-onset intracerebral hemorrhage. Patients with unclear-onset intracerebral hemorrhage had larger hematoma volumes (p = 0.044) and higher National Institutes of Health Stroke Scale scores (p < 0.001) than those with clear-onset intracerebral hemorrhage after multivariable adjustment for risk factors and comorbidities. Hematoma growth was similarly common between the two groups (p = 0.176). There were fewer patients with modified Rankin Scale (mRS) scores of 0-2 (p = 0.033) and more patients with mRS scores of 5-6 (p = 0.009) and with fatal outcomes (p = 0.049) in unclear-onset intracerebral hemorrhage group compared with clear-onset intracerebral hemorrhage as crude values, but not after adjustment. Conclusions Patients with unclear-onset intracerebral hemorrhage presented with larger hematomas and higher National Institutes of Health Stroke Scale scores at emergent visits than those with clear-onset intracerebral hemorrhage, independent of underlying characteristics. Unclear-onset intracerebral hemorrhage patients showed poorer 30-day vital and functional outcomes than clear-onset intracerebral hemorrhage patients; these differences seem to be mainly due to initial hematoma volumes and National Institutes of Health Stroke Scale scores.

Differentiation of the Infarct Core from Ischemic Penumbra within the First 4.5 Hours, Using Diffusion Tensor Imaging-Derived Metrics: A Rat Model

Objective

To investigate whether the diffusion tensor imaging-derived metrics are capable of differentiating the ischemic penumbra (IP) from the infarct core (IC), and determining stroke onset within the first 4.5 hours.

Materials and Methods

All procedures were approved by the local animal care committee. Eight of the eleven rats having permanent middle cerebral artery occlusion were included for analyses. Using a 7 tesla magnetic resonance system, the relative cerebral blood flow and apparent diffusion coefficient maps were generated to define IP and IC, half hour after surgery and then every hour, up to 6.5 hours. Relative fractional anisotropy, pure anisotropy (rq) and diffusion magnitude (rL) maps were obtained. One-way analysis of variance, receiver operating characteristic curve and nonlinear regression analyses were performed.

Results

The evolutions of tensor metrics were different in ischemic regions (IC and IP) and topographic subtypes (cortical, subcortical gray matter, and white matter). The rL had a significant drop of 40% at 0.5 hour, and remained stagnant up to 6.5 hours. Significant differences (p < 0.05) in rL values were found between IP, IC, and normal tissue for all topographic subtypes. Optimal rL threshold in discriminating IP from IC was about -29%. The evolution of rq showed an exponential decrease in cortical IC, from -26.9% to -47.6%; an rq reduction smaller than 44.6% can be used to predict an acute stroke onset in less than 4.5 hours.

Conclusion

Diffusion tensor metrics may potentially help discriminate IP from IC and determine the acute stroke age within the therapeutic time window.

Stroke- on- Awakening: Safety of CT-CTA Based Selection for Reperfusion Therapy

BACKGROUND

We studied the safety of use of acute reperfusion therapies in patients with stroke- on- awakening using a computed tomographic angiography (Cta) based large vessel occlusion-good scan paradigm in clinical routine.

METHODS

the Cta database of the Calgary stroke program was reviewed for the period January 2003-March 2010. patients with stroke-on-awakening with large artery occlusions on Cta, who received conservative, iV thrombolytic and/or endovascular treatment at discretion of the attending stroke neurologist were analyzed. time of onset was defined by the time last seen or known to be normal. Baseline non-contrast Ct scan (nCCt) alberta Stroke program early Ct Score (aSpeCtS) > 7 was considered a good scan. hemorrhage was defined on follow-up brain imaging using eCaSS 3 criteria. independence (mrS≤2) at three months was considered a good clinical outcome. Standard descriptive statistics and multivariable analysis were done.

RESULTS

among 532 patients with large artery occlusions, 70 patients with stroke-on-awakening (13.1%) were identified. the median age was 69.5 (iQr 24) and 41 (58.6%) were female; 41 (58.6%) received anti-platelets only and 29 (41.4%) received thrombolytic treatment [iV-12 (17.1%), iV/ia-12 (17.1%) and ia-5(7.1%)]. unadjusted analysis showed that baseline nCCt aSpeCtS ≤ 7 (p=0.002) and higher nihSS scores (p=0.018) were associated with worse outcomes. there were no ph2 hemorrhages in the iV thrombolytic or endovascular treated group. functional outcome was not different by treatment.

CONCLUSION

When carefully selected using Ct –Cta, by a good scan (aSpeCtS > 7) occlusion paradigm, acute reperfusion therapies in patients with stroke-on-awakening can be performed safely in clinical routine.

Wake-up stroke: Dawn of a new era

Wake-up stroke or stroke with unclear onset of symptoms is known to occur in one-fourth of ischemic stroke patients. These patients are not considered for thrombolytic therapy based on time designation of their symptom onset as per the current guidelines. Observational studies have investigated the pathophysiology and suggested actual onset of symptoms to be approximate to the awakening time for these patients. Use of advanced imaging modalities in these patients tends to identify favorable patient profiles for thrombolysis. Results of the ongoing trials will likely beckon a seminal juncture in stroke therapy and deliver critical modifications in the current treatment guidelines for thrombolysis in this substantial, yet neglected, group of stroke patients. In this article, we have reviewed the predisposing factors, preferred imaging modalities and various ongoing thrombolytic and endovascular trials to date for patients with unclear time of symptom onset or who wake up with stroke symptoms.

Modeling the Cost Effectiveness of Neuroimaging-Based Treatment of Acute Wake-Up Stroke

BACKGROUND

Thrombolytic treatment (tissue-type plasminogen activator [tPA]) is only recommended for acute ischemic stroke patients with stroke onset time <4.5 hours. tPA is not recommended when stroke onset time is unknown. Diffusion-weighted MRI (DWI) and fluid attenuated inversion recovery (FLAIR) MRI mismatch information has been found to approximate stroke onset time with some accuracy. Therefore, we developed a micro-simulation model to project health outcomes and costs of MRI-based treatment decisions versus no treatment for acute wake-up stroke patients.

METHODS AND FINDINGS

The model assigned simulated patients a true stroke onset time from a specified probability distribution. DWI-FLAIR mismatch estimated stroke onset <4.5 hours with sensitivity and specificity of 0.62 and 0.78, respectively. Modified Rankin Scale (mRS) scores reflected tPA treatment effectiveness accounting for patients' true stroke onset time. Discounted lifetime costs and benefits (quality-adjusted life years [QALYs]) were projected for each strategy. Incremental cost-effectiveness ratios (ICERs) were calculated for the MRI-based strategy in base-case and sensitivity analyses. With no treatment, 45.1% of simulated patients experienced a good stroke outcome (mRS score 0-1). Under the MRI-based strategy, in which 17.0% of all patients received tPA despite stroke onset times >4.5 hours, 46.3% experienced a good stroke outcome. Lifetime discounted QALYs and costs were 5.312 and $88,247 for the no treatment strategy and 5.342 and $90,869 for the MRI-based strategy, resulting in an ICER of $88,000/QALY. Results were sensitive to variations in patient- and provider-specific factors such as sleep duration, hospital travel and door-to-needle times, as well as onset probability distribution, MRI specificity, and mRS utility values.

CONCLUSIONS

Our model-based findings suggest that an MRI-based treatment strategy for this population could be cost-effective and quantifies the impact that patient- and provider-specific factors, such as sleep duration, hospital travel and door-to-needle times, could have on the optimal decision for wake-up stroke patients.

Computed tomography perfusion-based thrombolysis in wake-up stroke

Wake-up stroke (WUS) patients are typically excluded from reperfusion treatment, as the time of symptoms onset is unknown. The purpose of this study is to evaluate the clinical outcome and safety of intravenous thrombolysis with rt-PA in patients with WUS eligible for therapy using computed tomography perfusion criteria (CTP), compared to patients treated with rt-PA within 4.5 h of symptoms onset (non-WUS). This is an experimental, open-label trial, controlled against the best therapy currently in use. Primary endpoints were functional independence after 3 months [modified Rankin scale (mRS) ≤ 1] for clinical outcome and symptomatic intracerebral hemorrhage (SICH) for safety. Secondary endpoints were no or only mild disability after 3 months (mRS ≤ 2) for clinical outcome, total intracerebral hemorrhage (TICH) and contrast-induced nephropathy (CIN) for safety. 170 patients were treated, 143 non-WUS patients and 27 patients with WUS. Strokes of cardioembolic origin were most common in WUS patients (p < 0.001). Primary endpoints: mRS ≤ 1 was found in 35.8 % (non-WUS: 36.4% vs. WUS 33.3%; p = 0.62) and SICH was observed in 3.4 % of non-WUS patients and in WUS patients (p = 0.32). Secondary endpoints: mRS ≤ 2 was observed in 66.4 % of patients (non-WUS: 67.1% vs. WUS 62.9%; p = 0.67), TICH in 13.5 % of patients (13.9 % non-WUS vs. 11.1 % WUS; p = 0.69). CIN was documented in 3.7 % of WUS patients. rt-PA treatment carried out in WUS patients selected on the basis of CTP data demonstrate comparable clinical outcome and safety with respect to non-WUS patients. The study supports the hypothesis that a selected group of WUS patients may be suitable for thrombolysis.

Wake-up Stroke and Stroke within the Therapeutic Window for Thrombolysis Have Similar Clinical Severity, Imaging Characteristics, and Outcome

BACKGROUND

Wake-up stroke (WUS) represents 25% of all ischemic strokes. There is conflicting evidence concerning clinical severity, imaging characteristics, and outcome when WUS is compared with stroke of known time of onset. Our aim was to compare WUS patients with patients with ischemic stroke within the therapeutic window (STW) for thrombolysis.

METHODS

This is a retrospective hospital-based study of all consecutive patients hospitalized for acute ischemic stroke during 2013. Patients with STW, WUS, and WUS with computed tomography (CT)  at 3 hours or less after awakening (WUS≤3h) were selected for the study. The methods used include a review of clinical records, an independent quantification of early signs of ischemia on admission CT scan, and determination of functional outcome on follow-up.

RESULTS

Of 554 patients evaluated, 190 had STW, 113 had WUS (20.4%), and 25 had WUS≤3h. Among all WUS patients, 33.6% did not have any other formal contraindication for thrombolysis besides undetermined time of onset. WUS patients had demographic characteristics, vascular risk factors, and clinical severity similar to STW patients. Mild or absent early signs of ischemia on admission CT in WUS≤3h patients were similar to those in STW patients when adjusted for clinical severity (odds ratio [OR] = .50, 95% confidence interval [CI]=.17-1.47). Favorable prognosis in WUS≤3h was similar to STW when adjusted for age, clinical severity, and thrombolysis (OR = .53, 95% CI=.09-3.14).

CONCLUSIONS

This study strengthens the evidence that clinical and early imaging characteristics of WUS patients are similar to those of patients with stroke who are eligible for thrombolysis based on the time window criteria, and patients with WUS do not have a worse short outcome.

Favorable Bridging Therapy Based on DWI-FLAIR Mismatch in Patients with Unclear-Onset Stroke

BACKGROUND AND PURPOSE

Standard selection criteria for revascularization therapy usually exclude patients with unclear-onset stroke. Our aim was to evaluate the efficacy and safety of revascularization therapy in patients with unclear-onset stroke in the anterior circulation and to identify the predictive factors for favorable clinical outcome.

MATERIALS AND METHODS

We retrospectively analyzed 41 consecutive patients presenting with acute stroke with unknown time of onset treated by intravenous thrombolysis and/or mechanical thrombectomy. Only patients without well-developed fluid-attenuated inversion recovery changes of acute diffusion lesions on MR imaging were enrolled. Twenty-one patients were treated by intravenous thrombolysis; 19 received, simultaneously, intravenous thrombolysis and mechanical thrombectomy (as a bridging therapy); and 1 patient, endovascular therapy alone. Clinical outcome was evaluated at 90 days by using the mRS. Mortality and symptomatic intracranial hemorrhage were also reported.

RESULTS

Median patient age was 72 years (range, 17-89 years). Mean initial NIHSS score was 14.5 ± 5.7. Successful recanalization (TICI 2b-3) was assessed in 61% of patients presenting with an arterial occlusion, symptomatic intracranial hemorrhage occurred in 2 patients (4.9%), and 3 (7.3%) patients died. After 90 days, favorable outcome (mRS 0-2) was observed in 25 (61%) patients. Following multivariate analysis, initial NIHSS score (OR, 1.43; 95% CI, 1.13-1.82; P = .003) and bridging therapy (OR, 37.92; 95% CI, 2.43-591.35; P = .009) were independently associated with a favorable outcome at 3 months.

CONCLUSIONS

The study demonstrates the safety and good clinical outcome of acute recanalization therapy in patients with acute stroke in the anterior circulation and an unknown time of onset and a DWI/FLAIR mismatch on imaging. Moreover, bridging therapy versus intravenous thrombolysis alone was independently associated with favorable outcome at 3 months.

Evaluation of Cerebral Perfusion in Patients Undergoing Intravenous Recombinant Tissue Plasminogen Activator Thrombolysis

Currently, the indication for thrombolytic therapy using intravenous recombinant tissue plasminogen activator (rt-PA) is restricted strictly to patients with acute ischemic stroke within 4.5 h of onset. The effect of rt-PA declines over time; therefore, we need to minimize the time delay while generating imaging information. The use of cerebral blood flow imaging is not recommended within this time window. Conversely, the balance of efficacy and the risk of bleeding complications differ among patients > 4.5 h after onset. Several ongoing studies are using mismatch concepts to extend the therapeutic time window for rt-PA. Long-awaited reliable software, such as RAPID and PMA, are now available to analyze computed tomography/magnetic resonance perfusion data. Patients with wake-up stroke (WUS) are another group that can be used to expand rt-PA candidates. Diffusion fluid- attenuated inversion recovery mismatch is a promising imaging surrogate to select good candidates with WUS. These trials will cause a therapeutic paradigm shift from time-based to tissue-based strategies in the near future.

IV thrombolysis for treatment of patients with stroke upon awakening: Yes? No?

Current guidelines recommend IV administration of recombinant tissue plasminogen activator (rtPA) to carefully selected patients who can be treated within 4.5 hours of ischemic stroke onset. Patients whose neurologic symptoms are discovered upon awakening (wake-up stroke) generally are not given rtPA because of the uncertainty about the time of stroke onset. This group of patients may be relatively large. Preliminary reports suggest that patients with wake-up stroke who can be treated within 4.5 hours of discovery may respond similarly to patients with an established time of stroke onset. Clinical trials, which are selecting patients to treat primarily based on imaging surrogates, are under way. Pending the results of these trials, data about the utility of clinical or imaging findings that would identify those patients who could be treated and information about the safety and efficacy of IV rtPA in this situation are not available.

Wake-up Strokes Are Similar to Known-Onset Morning Strokes in Severity and Outcome

BACKGROUND

Stroke symptoms noticed upon waking, wake-up stroke, account for up to a quarter of all acute ischemic strokes. Patients with wake-up stroke, however, are often excluded from thrombolytic therapy.

METHODS

Using our prospectively collected stroke registry, wake-up stroke and known-onset morning strokes were identified. Wakeup stroke was defined as a patient who was asleep >3 hours and first noted stroke symptoms upon awakening between 0100 and 1100. Known-onset morning stroke was defined as a patient who had symptom onset while awake during the same time interval. We compared wake-up stoke to known-onset morning stroke with respect to patient demographics, stroke severity, etiology and outcomes.

RESULTS

One-quarter of patients with acute ischemic strokes (391/1415) had documented time between 0100 and 1100 of symptom onset: 141 (36%) wake-up strokes and 250 (64%) known-onset morning strokes. No difference in baseline characteristics, stroke severity, stroke etiology, neurologic deterioration, discharge disposition or functional outcome was detected. Known-onset morning stroke patients were significantly more likely to get thrombolytic therapy and have higher risk of in-hospital mortality. Wake-up stroke patients tended to be older, have higher diastolic blood pressure and have longer length of hospital stay.

DISCUSSION

While patients with wake-up stroke were similar to patients with known-onset morning stroke in many respects, patients with known onset morning stroke were significantly more likely to get treated with thrombolytic therapy and have higher in-hospital mortality.

Magnetic resonance imaging in acute ischemic stroke treatment

Although intravenous administration of tissue plasminogen activator is the only proven treatment after acute ischemic stroke, there is always a concern of hemorrhagic risk after thrombolysis. Therefore, selection of patients with potential benefits in overcoming potential harms of thrombolysis is of great importance. Despite the practical issues in using magnetic resonance imaging (MRI) for acute stroke treatment, multimodal MRI can provide useful information for accurate diagnosis of stroke, evaluation of the risks and benefits of thrombolysis, and prediction of outcomes. For example, the high sensitivity and specificity of diffusion-weighted image (DWI) can help distinguish acute ischemic stroke from stroke-mimics. Additionally, the lesion mismatch between perfusion-weighted image (PWI) and DWI is thought to represent potential salvageable tissue by reperfusion therapy. However, the optimal threshold to discriminate between benign oligemic areas and the penumbra is still debatable. Signal changes of fluid-attenuated inversion recovery image within DWI lesions may be a surrogate marker for ischemic lesion age and might indicate risks of hemorrhage after thrombolysis. Clot sign on gradient echo image may reflect the nature of clot, and their location, length and morphology may provide predictive information on recanalization by reperfusion therapy. However, previous clinical trials which solely or mainly relied on perfusion-diffusion mismatch for patient selection, failed to show benefits of MRI-based thrombolysis. Therefore, understanding the clinical implication of various useful MRI findings and comprehensively incorporating those variables into therapeutic decision-making may be a more reasonable approach for expanding the indication of acute stroke thrombolysis.

The role of imaging in acute ischemic stroke

Neuroimaging has expanded beyond its traditional diagnostic role and become a critical tool in the evaluation and management of stroke. The objectives of imaging include prompt accurate diagnosis, treatment triage, prognosis prediction, and secondary preventative precautions. While capitalizing on the latest treatment options and expanding upon the "time is brain" doctrine, the ultimate goal of imaging is to maximize the number of treated patients and improve the outcome of one the most costly and morbid disease. A broad overview of comprehensive multimodal stroke imaging is presented here to affirm its utilization.

THrombolysis for Acute Wake-up and unclear-onset Strokes with alteplase at 0·6 mg/kg (THAWS) Trial

Rationale

Because of lack of information regarding timing of stroke, patients who suffer stroke during sleep are generally ineligible for intravenous thrombolysis, although many of these patients could potentially recover with this treatment. Magnetic resonance image findings with positive diffusion-weighted imaging and no marked parenchymal hyperintensity on fluid-attenuated inversion recovery (negative pattern) can identify acute ischemic stroke patients within 4·5 h from symptom onset.

Aims

The THrombolysis for Acute Wake-up and unclear-onset Strokes with alteplase at 0·6 mg/kg trial aims to determine the efficacy and safety of intravenous thrombolysis with alteplase at 0·6 mg/kg body weight, the approved dose for Japanese stroke patients, using magnetic resonance image-based selection in ischemic stroke patients with unclear time of symptom onset, and compare findings with standard treatment.

Design

This is an investigator-initiated, multicenter, prospective, randomized, open-treatment, blinded-end-point clinical trial. The design is similar to the Efficacy and Safety of MRI-based Thrombolysis in Wake-up Stroke trial. Patients with unclear-onset time of stroke symptoms beyond 4·5 h and within 12 h after the time of the last-known-well period and within 4·5 h after symptom recognition, who showed a negative fluid-attenuated inversion recovery pattern, are randomized to either intravenous thrombolysis or standard treatment.

Study outcomes

The primary efficacy end-point is modified Rankin Scale 0–1 at 90 days. The safety outcome measures are symptomatic intracranial hemorrhage at 22–36 h, and major bleeding and mortality at 90 days.

Discussion

This trial may help determine if low-dose alteplase at 0·6 mg/kg should be recommended as a routine clinical strategy for ischemic stroke patients with unclear-onset time.

Diffusion-weighted image and fluid-attenuated inversion recovery image mismatch: unclear-onset versus clear-onset stroke

BACKGROUND AND PURPOSE

Mismatch in lesion visibility between diffusion-weighted image and fluid-attenuated inversion recovery image (DWI-FLAIR mismatch) has been proposed as a biomarker for the estimation of ischemic lesion age. The actual onset in some patients with unclear-onset stroke (UnCOS) may be close to the first-found abnormal time. We hypothesized that patients with UnCOS within a particular time window might have a similar DWI-FLAIR mismatch profile with patients with clear-onset stroke (COS).

METHODS

Patients who underwent MRI within 6 hours from first-found abnormal time were recruited retrospectively. Clinical characteristics and the proportion of DWI-FLAIR and perfusion-weighted image-DWI mismatch in each time window were compared between UnCOS and COS.

RESULTS

The final analysis included 259 patients (114 with UnCOS and 145 with COS). Patients with UnCOS were older and had more severe stroke at baseline. Risk factors, stroke subtypes, and perfusion-weighted image-DWI mismatch did not differ between the 2 groups. The proportion of patients with DWI-FLAIR mismatch in UnCOS did not differ from COS within 2 hours of first-found abnormal time (50.0% versus 51.5%; P=0.92), but it was significantly lower in UnCOS than in COS at 2 to 3 hours (16.1% versus 44.4%; P=0.02), 3 to 4 hours (13.8% versus 36.4%; P=0.04), and 4 to 5 hours (5.6% versus 29.6%; P=0.05).

CONCLUSIONS

The proportion of DWI-FLAIR mismatch in UnCOS within the first 2 hours from first-found abnormal time was similar with COS, but it sharply decreased beyond 2 hours. These data suggest that patients with UnCOS within 2 hours of symptom detection may be good candidates for multimodal imaging-based thrombolysis.

Wake-up (or wake-up for) stroke: a treatable stroke

A 74-year-old man was admitted to the Emergency Room of our institution with worsening dysarthria, left-side weakness and hypoesthesia (NIHSS score: 5) since his awakening at 7:30 a.m. The evening before, he had gone to sleep at 10:30 p.m. Brain computed tomography (CT) and cervicocranial CT angiography showed low density attenuation of the right caudate nucleus head and lenticular nucleus and sub-total occlusion of ipsilateral middle cerebral artery (MCA) pre-bi/trifurcation M1 segment. Brain CT perfusion showed an ischemic core in the right striatal region, surrounded by a wide region of ischemic penumbra. Although the onset of symptoms, defined as "time last-seen well", was 14 hours before presentation, the following worsening of neurological conditions (NIHSS score: 12) and the evidence of cerebral blood flow / cerebral blood volume mismatch at CT perfusion led us to propose neuroendovascular treatment on the basis of an off-label use. Neuroendovascular treatment by Penumbra system was achieved and the right MCA was only partially recanalized. The patient was discharged with NIHSS score of 12. At six months, modified Rankin scale score was 3. To the best of our knowledge, this is the first Italian case report describing a patient who underwent successful neuroendovascular treatment for a "wake-up stroke" without clinical worsening nor major complications and an acceptable clinical outcome. This was possible thanks to an extension of the therapeutic window guided by CT perfusion.

Imaging recommendations for acute stroke and transient ischemic attack patients: A joint statement by the American Society of Neuroradiology, the American College of Radiology, and the Society of NeuroInterventional Surgery

SUMMARY

Stroke is a leading cause of death and disability worldwide. Imaging plays a critical role in evaluating patients suspected of acute stroke and transient ischemic attack, especially before initiating treatment. Over the past few decades, major advances have occurred in stroke imaging and treatment, including Food and Drug Administration approval of recanalization therapies for the treatment of acute ischemic stroke. A wide variety of imaging techniques has become available to assess vascular lesions and brain tissue status in acute stroke patients. However, the practical challenge for physicians is to understand the multiple facets of these imaging techniques, including which imaging techniques to implement and how to optimally use them, given available resources at their local institution. Important considerations include constraints of time, cost, access to imaging modalities, preferences of treating physicians, availability of expertise, and availability of endovascular therapy. The choice of which imaging techniques to employ is impacted by both the time urgency for evaluation of patients and the complexity of the literature on acute stroke imaging. Ideally, imaging algorithms should incorporate techniques that provide optimal benefit for improved patient outcomes without delaying treatment.

Reperfusion therapy in unclear-onset stroke based on MRI evaluation (RESTORE): a prospective multicenter study

BACKGROUND AND PURPOSE

Unclear-onset strokes are generally excluded from time-based thrombolytic therapy. We examined the safety and feasibility of magnetic resonance imaging-based reperfusion therapy in unclear-onset stroke.

METHODS

This prospective, multicenter, single-arm study screened consecutive unclear-onset stroke patients within 6 hours of symptom detection. Patients with perfusion-diffusion mismatch>20% and negative or subtle fluid-attenuated inversion recovery changes were treated with intravenous tissue plasminogen activator, intra-arterial therapy, or a combination. The safety outcome was symptomatic intracranial hemorrhage within 48 hours after treatment. The primary efficacy outcome was a 3-month modified Rankin Scale score of 0 to 2. Controls were untreated unclear-onset stroke patients prospectively captured in stroke registries.

RESULTS

Of 430 unclear-onset stroke patients, 83 (19.3%) received reperfusion therapy (mean age, 67.5±10.4 years; males, 66.3%; median baseline National Institutes of Health Stroke Scale, 14). Symptomatic intracranial hemorrhage with any neurological decline developed in 5 patients (6.0%). Symptomatic intracranial hemorrhage with National Institutes of Health Stroke Scale worsening ≥4 developed in 3 patients (3.6%). Thirty-seven patients (44.6%) achieved modified Rankin Scale score of 0 to 2, and 24 (28.9%) had modified Rankin Scale score of 0 to 1. Female, baseline National Institutes of Health Stroke Scale score, no immediate or early recanalization, and more white blood cells were independent predictors of poor outcome. Compared with untreated controls, the treated group was significantly associated with good outcomes of modified Rankin Scale score of 0 to 2 after adjusting for age, sex, and baseline National Institutes of Health Stroke Scale in logistic regression analysis (odds ratio, 2.25; 95% CI, 1.14-4.49).

CONCLUSIONS

In unclear-onset stroke patients, magnetic resonance imaging-based reperfusion therapy was feasible and safe. Randomized controlled trials are warranted to confirm the benefit of reperfusion therapy for unclear-onset stroke.