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

Advancements in Imaging for the Diagnosis of Wake-up Stroke

BACKGROUND

The concept of wake-up stroke (WUS) as a distinct subtype of acute ischaemic stroke, characterized by an uncertain onset time, traditionally resulted in the exclusion of patients from intravenous thrombolysis treatment.

REVIEW SUMMARY

Advancements in neuroimaging have prompted a shift in the approach to intravenous thrombolysis treatment, moving away from a strict focus on the onset time window toward consideration of the tissue time window. This paradigm shift has expanded the opportunity for a larger cohort of patients with WUS to receive timely and effective treatment, ultimately leading to improved prognosis.

CONCLUSIONS

This study reviews the WUS pathogenesis and the progress of various imaging diagnostic techniques to clarify the WUS onset time and select the optimal treatment plan.

Advances in the management of acute ischemic stroke

PURPOSE OF REVIEW

This review aims to summarize the therapeutic advances and evidence in the medical management of acute ischemic stroke (AIS). Recent evidence comparing the efficacy and safety of tenecteplase (TNK) with alteplase for intravenous thrombolysis (IVT) in AIS will be highlighted. Recent advances and evidence on improving micro-circulation following endovascular procedures and neuroprotection will be reviewed.

RECENT FINDINGS

A significant number of randomized control studies now support the use of tenecteplase for IVT in AIS. TNK 0.25 mg/kg single bolus is as effective and well tolerated as alteplase 0.9 mg/kg infusion for IVT in AIS. Evidence from randomized control trials (RCTs) has shown effective and well tolerated expansion of the therapeutic window of IVT in the wake-up stroke and up to 9 h after last seen well, using advanced neuroimaging with computed tomography perfusion/MRI. Early evidence suggests that intra-arterial alteplase may help improve microcirculation in patients with large vessel occlusion following successful thrombectomy. However, more trials are required to confirm the results. Similarly, early evidence from a recent RCT showed that remote ischemic conditioning confers potential neuroprotection and improves outcomes in AIS.

SUMMARY

Converging evidence has demonstrated that for patients with ischemic stroke presenting at under 4.5 h from the onset, TNK is comparable to alteplase. These data along with the practical advantages of TNK have resulted in a shift to replace intravenous TNK as the standard for thrombolysis. Ongoing studies of IVT with TNK are focussed on defining the optimal dose, expanding the time window with multimodal imaging and defining the role of thrombolysis for bridging patients with stroke due to large vessel occlusion.

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.

MRI radiomic features-based machine learning approach to classify ischemic stroke onset time

PURPOSE

We aimed to investigate the ability of MRI radiomics features-based machine learning (ML) models to classify the time since stroke onset (TSS), which could aid in stroke assessment and treatment options.

METHODS

This study involved 84 patients with acute ischemic stroke due to anterior circulation artery occlusion (51 in the training cohort and 33 in the independent test cohort). Region of infarct segmentation was manually outlined by 3D-slicer software. Image processing including registration, normalization and radiomics features calculation were done in R (version 3.6.1). A total of 4312 radiomic features from each image sequence were captured and used in six ML models to estimate stroke onset time for binary classification (≤ 4.5 h). Receiver-operating characteristic curve (ROC) and other parameters were calculated to evaluate the performance of the models in both training and test cohorts.

RESULTS

Twelve radiomics and six clinic features were selected to construct the ML models for TSS classification. The deep learning model-based DWI/ADC radiomic features performed the best for binary TSS classification in the independent test cohort, with an AUC of 0.754, accuracy of 0.788, sensitivity of 0.952, specificity of 0.500, positive predictive value of 0.769, and negative predictive value of 0.857, respectively. Furthermore, adding clinical information did not improve the performance of the DWI/ADC-based deep learning model. The TSS prediction models can be visited at: http://123.57.65.199:3838/deeptss/ .

CONCLUSIONS

A unique deep learning model based on DWI/ADC radiomic features was constructed for TSS classification, which could aid in decision making for thrombolysis in patients with unknown stroke onset.

Predictive value of DWI-FLAIR Mismatch in patients with Ischemic Stroke and receiving Endovascular treatment beyond Time Window

Objective:

To investigate the efficacy and safety of endovascular treatment in patients having acute ischemic stroke with over-time window under DWI-FLAIR mismatch.

Methods:

From January 2018 to January 2020, 80 patients who met the research criteria in the First Central Hospital of Baoding, China were selected. According to the time of onset, they were divided into test group and control group, with 40 cases in each group. Forty patients in the test group were beyond time window (6~24h) and the MRI showed a DWI-FLAIR mismatch. Forty patients in the control group were within the time window (< 6h). All patients received endovascular treatment (EVT). The mRS, NIHSS and infarct volume of patients in the test group were compared and analyzed before and 30 and 90 days after treatment, as well as the indicators of both groups of patients before and after treatment, to determine therapeutic effect in patients receiving EVT beyond time window. Meanwhile, the recanalization of the blood vessel and the incidence of cerebral hemorrhage of patients in both groups were compared to determine the safety in patients receiving EVT beyond time window under DWI-FLAIR mismatch.

Results:

The mRS, NIHSS and infarct size in the test group were significantly improved before and 30 and 90 days after treatment (p<0.05). The test group showed no significant difference in mRS, NIHSS and other indicators when compared with the control group (p>0.05). There was no significant difference in the rate of recanalization of the blood vessel and intracranial hemorrhage after treatment between both groups (p>0.05).

Conclusion:

DWI-FLAIR mismatch can be used as an objective imaging basis for intravascular interventional therapy in patients with stroke with over-time window and large vessel occlusion. It has the advantages of short examination time, non-invasiveness, no need for contrast agents, simple implementation, clear guidance.

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 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.

Clinical characteristics of unknown symptom onset stroke patients with and without diffusion-weighted imaging and fluid-attenuated inversion recovery mismatch

Background Diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) mismatch was suggested to identify stroke patients with unknown time of symptom onset likely to be within the time window for thrombolysis. Aims We aimed to study clinical characteristics associated with DWI-FLAIR mismatch in patients with unknown onset stroke. Methods We analyzed baseline MRI and clinical data from patients with acute ischemic stroke proven by DWI from WAKE-UP, an investigator-initiated, randomized, placebo-controlled trial of MRI-based thrombolysis in stroke patients with unknown time of symptom onset. Clinical characteristics were compared between patients with and without DWI-FLAIR mismatch. Results Of 699 patients included, 418 (59.8%) presented with DWI-FLAIR mismatch. A shorter delay between last seen well and symptom recognition (p = 0.0063), a shorter delay between symptom recognition and arrival at hospital (p = 0.0025), and history of atrial fibrillation (p = 0.19) were predictors of DWI-FLAIR mismatch in multivariate analysis. All other characteristics were comparable between groups. Conclusions There are only minor differences in measured clinical characteristics between unknown symptom onset stroke patients with and without DWI-FLAIR mismatch. DWI-FLAIR mismatch as an indicator of stroke onset within 4.5 h shows no relevant association with commonly collected clinical characteristics of stroke patients. Clinical Trial Registration URL: http://www.clinicaltrials.gov . Unique identifier: NCT01525290; URL: https://www.clinicaltrialsregister.eu . Unique identifier: 2011-005906-32.

Clinical Outcomes of Posterior Versus Anterior Circulation Infarction With Low National Institutes of Health Stroke Scale Scores

Background and Purpose—

We compared baseline characteristics and outcomes at 3 months between patients with minor anterior circulation infarction (ACI) versus minor posterior circulation infarction (PCI), including the influence of large vessel disease on outcomes.

Methods—

This study is an analysis of a prospective multicenter registry database in South Korea. Eligibility criteria were patients with ischemic stroke admitted within 7 days of stroke onset, lesions in either anterior or posterior circulation, and National Institutes of Health Stroke Scale score of ≤4 at baseline. Patients were divided into 4 groups for further analysis: minor ACI with and without internal carotid artery/middle cerebral artery large vessel disease and minor PCI with and without vertebrobasilar large vessel disease.

Results—

A total of 7178 patients (65.2±12.6 years) were analyzed in this study, and 2233 patients (31.1%) had disability (modified Rankin Scale score 2–6) at 3 months. Disability was 32.3% in minor PCI and 30.3% in minor ACI ( P =0.07), and death was 1.3% and 1.5%, respectively ( P =0.82). In a multivariable logistic regression analysis, minor PCI was significantly associated with disability at 3 months when compared with minor ACI (odds ratio, 1.23; 95% confidence interval, 1.09–1.37; P <0.001). In pairwise comparisons, minor PCI with vertebrobasilar large vessel disease was independently associated with disability at 3 months, compared with the other 3 groups.

Conclusions—

Our study showed that minor PCI exhibited more frequent disability at 3 months than minor ACI. Especially, the presence of vertebrobasilar large vessel disease in minor PCI had a substantially higher risk of disability. Our results suggest that minor PCI with vertebrobasilar large vessel disease could require more meticulous care and are important targets for further study.

Simple quantitative measurement based on DWI to objectively judge DWI-FLAIR mismatch in a canine stroke model

PURPOSE

Diffusion-weighted imaging (DWI) - fluid attenuated inversion recovery (FLAIR) mismatch was proven useful to time the onset of wake-up stroke; however, identifying the status of FLAIR imaging has been mostly subjective. We aimed to evaluate the value of relative DWI signal intensity (rDWI), and relative apparent diffusion coefficient (rADC) in identifying the FLAIR status in the acute period.

METHODS

Autologous clot was used to embolize left middle cerebral artery in 20 dogs. Magnetic resonance imaging was performed 3-6 hours and 24 hours after embolization. DWI-FLAIR mismatch was defined as hyperintense signal detected on DWI, but not on FLAIR. The mean values of rDWI or rADC of FLAIR- and FLAIR+ lesions were compared and the critical cutoff values of rDWI and rADC for identifying the FLAIR status were determined.

RESULTS

Stroke models were successfully established in all animals. DWI+ lesions were found in all 20 dogs from three hours, while FLAIR+ lesions were found in three, 11, 16, 19, and 20 dogs at five time points after embolization, respectively. The mean rDWI values were significantly different between FLAIR- and FLAIR+ lesions (P < 0.001), but rADC values were not (P = 0.73). Using rDWI=1.90 as the threshold value, excellent diagnostic efficacy was achieved (AUC, 0.88; sensitivity, 0.77; specificity, 0.88). However, rADC appeared not useful (AUC, 0.48; sensitivity, 0.52; specificity, 0.58) in identifying the FLAIR status.

CONCLUSION

In our embolic canine stroke model, rDWI was useful to identify FLAIR imaging status in the acute period, while rADC was not.

MRI based thrombolysis for FLAIR-negative stroke patients within 4.5-6h after symptom onset

To investigate the feasibility of DWI-FLAIR mismatch in identifying patients who might benefit from thrombolytic therapy within 4.5-6h, we analyzed the data of 105 ischemic stroke patients with known time of symptom onset who underwent MRI within 6h of stroke and thrombolysis between December 2006 and December 2013. They were divided into three groups: symptom onset within 4.5h (n=66); 4.5-6h and FLAIR images negative (n=9); and 4.5-6h and FLAIR images positive (n=30). Outcome of thrombolysis was assessed for each group by recanalization rate, National Institutes of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS) scores. The results showed that mismatch between positive DWI and negative FLAIR images identified patients within 4.5h of symptom onset with sensitivity, specificity, positive predictive value and negative predictive value of 40.9%, 76.9%, and 75% and 43.5%. Recanalization rate, NIHSS score and mRS score were all better in both the 0-4.5h and 4.5-6h FLAIR-negative groups than in the 4.5-6h FLAIR-positive group (p<0.05). These data demonstrate that within 4.5-6h of symptom onset, patients with negative FLAIR images may benefit from thrombolysis therapy.

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.

A double-tuned 1H/23Na resonator allows 1H-guided 23Na-MRI in ischemic stroke patients in one session

Background

Established imaging methods are still not confident in the determination of stroke onset. Sodium imaging in animal models and lately in humans implicates that the sodium signal intensity within the ischemic lesion increases in a time-dependent fashion. Sodium imaging usually requires a time-consuming change of resonators or magnetic resonance imaging systems. To avoid this, we used a double-tuned 1H/23Na birdcage head coil in combination with a protocol minimizing T1- and T2*-weighting effects for measurement of sodium intensity in acute stroke patients.

Methods

Multinuclear 1H/23Na data sets were obtained from 16 stroke patients [75 ± 9.9 (standard deviation) years old] 4-130 h after symptom onset. The protocol was acquired on a clinical 3T magnetic resonance imaging site using a double-tuned 1H/23Na birdcage head coil. Sodium signal intensity within the lesion and homologous contralateral side was measured and compared.

Results

With an acquisition time of the complete magnetic resonance imaging protocol of 22 min, a nonlinear sodium signal intensity increase within the lesion over time after stroke onset was acknowledged. Onset time within six-hours showed an increase of only 8% or less, whereas onset time beyond 8.5 h demonstrated increases of 36% or more reaching a maximum of 170% > 120 h. In addition, some patients showed a difference in sodium signal intensity compared with diffusion weighted imaging lesion.

Conclusions

The use of a double-tuned 1H/23Na birdcage head coil in a clinical setting ‘allowed sodium intensity measurements’ in a justifiable time also for acute stroke patients, and heterogenous sodium signal intensity in the diffusion weighted imaging lesion might represent differences in tissue damage or repair.

Efficacy and safety of thrombolysis for stroke of unknown onset time: a meta-analysis

Current stroke treatment guidelines exclude unknown onset stroke (UOS) patients from thrombolytic therapy even though several studies have reported significant treatment efficacy and safety. We performed a meta-analysis of relevant studies retrieved by systematic searches of the PubMed, Embase, and Cochrane databases up to December 31, 2013. Dichotomized modified Rankin Scale (mRS) scores 0-1 at 90 days, mRS 0-2 at 90 days, overall mortality, and symptomatic intracranial hemorrhage (sICH) incidence were collected as primary outcome measures. Fixed effects meta-analytical models were used, and between-study heterogeneity was assessed. Eleven studies encompassing 1,832 patients were included. In case-control studies of UOS patients, thrombolysis was associated with a significant increase in the proportion of patients with mRS scores of 0-1 (OR 2.37; 95% CI 1.20-4.69; P = 0.013) and 0-2 (OR 2.03; 95% CI 1.26-3.30; P = 0.004) without increased mortality or sICH incidence. In studies comparing thrombolysis-treated UOS to thrombolysis-treated known onset stroke, however, fewer UOS patients had mRS scores of 0-1 (OR 0.70; 95% CI 0.51-0.97; P = 0.033) with no change in mortality, sICH incidence, or patients with mRS of 0-2. Subgroup analysis based on imaging criteria and time window of thrombolysis indicated that UOS patients treated within 3 h after first found abnormal and those with early ischemic changes restricted to <1/3 of the middle cerebral artery territory gained more benefit from thrombolysis treatment than the whole UOS population. Randomized controlled trials are warranted to confirm the efficacy of thrombolysis in this UOS subgroup.

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.

Wake-up stroke and stroke of unknown onset: a critical review

Patients, who wake up with an ischemic stroke, account for a large number of the total stroke population, due to circadian morning predominance of stroke. Currently, this subset of patients is excluded from revascularization-therapy since no exact time of onset is known. A large group of these patients might be eligible for therapy. In this review, we assessed the current literature about the hypothesis that wake-up-strokes occur just prior on awakening and if this subgroup differs in characteristics compared to the overall stroke population. We looked at the safety and efficacy of thrombolysis and interventional techniques in the group of patients with unknown stroke-onset. We performed a meta-analysis of the diagnostic accuracy of the diffusion-FLAIR mismatch in identifying stroke within 3 and 4.5 h. The different imaging-selection criteria that can be used to treat these patients are discussed. Additional research on imaging findings associated with recent stroke and penumbral imaging will eventually lead to a shift from a rigid time-frame based therapy to a tissue-based individualized treatment approach.

Color-coded fluid-attenuated inversion recovery images improve inter-rater reliability of fluid-attenuated inversion recovery signal changes within acute diffusion-weighted image lesions

BACKGROUND AND PURPOSE

Diffusion-weighted image fluid-attenuated inversion recovery (FLAIR) mismatch has been considered to represent ischemic lesion age. However, the inter-rater agreement of diffusion-weighted image FLAIR mismatch is low. We hypothesized that color-coded images would increase its inter-rater agreement.

METHODS

Patients with ischemic stroke <24 hours of a clear onset were retrospectively studied. FLAIR signal change was rated as negative, subtle, or obvious on conventional and color-coded FLAIR images based on visual inspection. Inter-rater agreement was evaluated using κ and percent agreement. The predictive value of diffusion-weighted image FLAIR mismatch for identification of patients <4.5 hours of symptom onset was evaluated.

RESULTS

One hundred and thirteen patients were enrolled. The inter-rater agreement of FLAIR signal change improved from 69.9% (k=0.538) with conventional images to 85.8% (k=0.754) with color-coded images (P=0.004). Discrepantly rated patients on conventional, but not on color-coded images, had a higher prevalence of cardioembolic stroke (P=0.02) and cortical infarction (P=0.04). The positive predictive value for patients <4.5 hours of onset was 85.3% and 71.9% with conventional and 95.7% and 82.1% with color-coded images, by each rater.

CONCLUSIONS

Color-coded FLAIR images increased the inter-rater agreement of diffusion-weighted image FLAIR recovery mismatch and may ultimately help identify unknown-onset stroke patients appropriate for thrombolysis.

The usefulness of diffusion-weighted/fluid-attenuated inversion recovery imaging in the diagnostics and timing of lacunar and nonlacunar stroke

INTRODUCTION

The DWI/FLAIR mismatch is a potential radiological marker for the timing of stroke onset. The aim of the study was to assess if the DWI/FLAIR mismatch can help to identify patients with both lacunar and nonlacunar acute ischemic stroke within 4.5 h of onset.

METHODS

A retrospective study was performed in which the authors analysed data from 86 ischemic lacunar and nonlacunar stroke patients with a known time of symptom onset, imaged within the first 24 h from stroke onset (36 patients <4.5 h, 14 patients 4.5-6 h, 15 patients 6-12 h, and 21 patients 12-24 h). Patients underwent the admission CT and MR scan. The presence of lesions was assessed in correlation with the duration of the stroke.

RESULTS

The time from stroke onset to neuroimaging was significantly shorter in patients with an ischemic lesion visible only in the DWI (mean 2.78 h, n = 24) as compared to patients with signs of ischemia also in other modalities (mean 8.6 h, n = 62) (p = 0.0001, Kruskal-Wallis ANOVA). The DWI/FLAIR mismatch was characterised by a global sensitivity of 58%, specificity 94%, PPV 87.5%, and NPV 76% in identifying patients in the 4.5 h thrombolysis time window. For lacunar strokes (n = 20), these parameters were as follows: sensitivity 50%, specificity 92.8%, PPV 75 %, and NPV 81.2%.

CONCLUSIONS

The presence of acute ischemic lesions only in DWI can help to identify both lacunar and nonlacunar stroke patients who are in the 4.5 h time window for intravenous thrombolysis with high specificity.