FLAIR hyperintensities-DWI mismatch in acute stroke: associations with DWI volume and functional outcome

Fluid-attenuated inversion recovery vascular hyperintensity-diffusion-weighted imaging mismatch and functional outcome after endovascular reperfusion therapy for acute ischemic stroke

BACKGROUND

Fluid-attenuated inversion recovery vascular hyperintensity (FVH) outside of the diffusion-weighted imaging (DWI) lesion, termed FVH-DWI mismatch, may represent penumbral tissue with good collateral status.

METHODS

Consecutive patients who underwent endovascular reperfusion therapy (EVT) for acute internal carotid artery (ICA) or middle cerebral artery (MCA)-M1 occlusion were enrolled. FVH-DWI mismatch score was defined as the number of cortical Alberta Stroke Program Early CT Score areas (I and M1 to M6) that involved FVH but no DWI lesion (0 to 7 points). The outcome measure was set as good functional outcome, defined as a modified Rankin Scale score of 0 to 2, at 90 days after onset.

RESULTS

Of 196 consecutive patients who underwent EVT for acute ICA or MCA-M1 occlusion, 32 without brain MRI before EVT were excluded, and the remaining 164 were analyzed. The median FVH-DWI mismatch score was 2 (interquartile range, 0 to 4). At 90 days after EVT, 2 patients were lost-to follow-up, and 73 had good functional outcome. The frequency of good functional outcome at 90 days after EVT increased significantly with increasing FVH-DWI mismatch score (P for trend <0.001). FVH-DWI mismatch score was independently associated with good functional outcome at 90 days after onset (adjusted odds ratio per 1 point,1.46; 95% confidence interval, 1.15-1.89).

CONCLUSIONS

Patients with large FVH-DWI mismatch had good functional outcome after EVT for acute ICA or MCA-M1 occlusion.

FLAIR vascular hyperintensity combined with asymmetrical prominent veins in acute anterior circulation ischemic stroke: prediction of collateral circulation and clinical outcome

BACKGROUND

To investigate the value of fluid-attenuated inversion recovery vascular hyperintensity (FVH) within asymmetrical prominent veins sign (APVS) on susceptibility-weighted imaging predicting collateral circulation and prognosis in patients with acute anterior circulation ischemic stroke.

METHOD

Patients with severe stenosis or occlusion of ICA or MCA M1, who underwent MRI within 72 h from stroke onset were reviewed. The Alberta Stroke Program Early CT Score was used to evaluate the volume of infarction on DWI, the degree of FVH and APVS. Spearman correlation analysis was used to evaluate the correlation between FVH and APVS. All patients were divided into the good prognosis group and the poor prognosis group according to the score of the modified ranking scale (mRS) 90 days after the stroke. Logistic regression analysis was used to explore the relationship between FVH and APVS and functional prognosis, while receiver operating characteristic (ROC) curves were plotted to assess the value of FVH and APVS in predicting prognosis.

RESULTS

Spearman correlation analysis revealed moderate positive correlations between FVH and APVS (r = 0.586, P < 0.001). The poor prognosis group had a higher rate of a history of atrial fibrillation, a larger cerebral infarction volume, a higher NIHSS score at admission, and a higher FVH and APVS score compared with the good prognosis group (all P < 0.05). A further logistic regression indicated that the NIHSS score, cerebral infarction volume, FVH and APVS were independent risk factors for a poor functional prognosis. In terms of FVH, APVS, alone and their combination for the diagnosis of poor prognosis, the sensitivity, specificity, area under the ROC curve (AUC), and 95% confidence interval (CI) were 86.8%, 83.3%, 0.899 (95% CI 0.830-0.968); 60.5%, 93.7%, 0.818 (95% CI 0.723-0.912); 86.8%, 89.6%, 0.921 (95% CI 0.860-0.981), respectively.

CONCLUSION

The presence of FVH and APVS can provide a comprehensive assessment of collateral circulation from the perspective of veins and arteries, and the correlation between the two is positively correlated. Both of them were independent risk factors for poor prognosis, their combination is complementary and can improve the predictive value.

Individualized interpretation for the clinical significance of fluid-attenuated inversion recovery vessel hyperintensity in ischemic stroke and transient ischemic attack: A systematic narrative review

Fluid-attenuated inversion recovery (FLAIR) vessel hyperintensity（FVH）refers to the hyperintensity corresponding to the arteries in the subarachnoid space. It is caused by critically slowed blood flow and is commonly encountered in patients with large artery steno-occlusions. Quite a few studies have focused on the clinical significance of FLAIR vessel hyperintensity in terms of its relationship to the prognosis of transient ischemic attack (TIA), baseline severity or infarction volume, early neurological deterioration or infarction growth, and functional outcomes in acute ischemic stroke (AIS). However, inconsistent or conflicting findings were common in these studies and caused confusion in the clinical decision-making process guided by this imaging marker. Through reviewing the available studies on the etiologic mechanism of FVH and investigating findings on its clinical significance in AIS and TIA, this review aims to elucidate the key factors for interpreting the clinical significance of FVH individually.

In Mild and Moderate Acute Ischemic Stroke, Increased Lipid Peroxidation and Lowered Antioxidant Defenses Are Strongly Associated with Disabilities and Final Stroke Core Volume

In acute ischemic stroke (AIS), there are no data on whether oxidative stress biomarkers have effects above and beyond known risk factors and measurements of stroke volume. This study was conducted in 122 mild-moderate AIS patients and 40 controls and assessed the modified ranking scale (mRS) at baseline, and 3 and 6 months later. We measured lipid hydroperoxides (LOOH), malondialdehyde (MDA), advanced oxidation protein products, paraoxonase 1 (PON1) activities and PON1 Q192R genotypes, high density lipoprotein cholesterol (HDL), sulfhydryl (-SH) groups), and diffusion-weighted imaging (DWI) stroke volume and fluid-attenuated inversion recovery (FLAIR) signal intensity. We found that (a) AIS is characterized by lower chloromethyl acetate CMPAase PON1 activity, HDL and -SH groups and increased LOOH and neurotoxicity (a composite of LOOH, inflammatory markers and glycated hemoglobin); (b) oxidative and antioxidant biomarkers strongly and independently predict mRS scores 3 and 6 months later, DWI stroke volume and FLAIR signal intensity; and (c) the PON1 Q192R variant has multiple effects on stroke outcomes that are mediated by its effects on antioxidant defenses and lipid peroxidation. Lipid peroxidation and lowered -SH and PON1-HDL activity are drug targets to prevent AIS and consequent neurodegenerative processes and increased oxidative reperfusion mediators due to ischemia-reperfusion injury.

FLAIR Vascular Hyperintensities as a Surrogate of Collaterals in Acute Stroke: DWI Matters

BACKGROUND AND PURPOSE

FLAIR vascular hyperintensities are thought to represent leptomeningeal collaterals in acute ischemic stroke. However, whether all-FLAIR vascular hyperintensities or FLAIR vascular hyperintensities-DWI mismatch, ie, FLAIR vascular hyperintensities beyond the DWI lesion, best reflects collaterals remains debated. We aimed to compare the value of FLAIR vascular hyperintensities-DWI mismatch versus all-FLAIR vascular hyperintensities for collateral assessment using PWI-derived collateral flow maps as a reference.

MATERIALS AND METHODS

We retrospectively reviewed the registries of 6 large stroke centers and included all patients with acute stroke with anterior circulation large-vessel occlusion who underwent MR imaging with PWI before thrombectomy. Collateral status was graded from 1 to 4 on PWI-derived collateral flow maps and dichotomized into good (grades 3-4) and poor (grades 1-2). The extent of all-FLAIR vascular hyperintensities and FLAIR vascular hyperintensities-DWI mismatch was assessed on the 7 cortical ASPECTS regions, ranging from 0 (absence) to 7 (extensive), and associations with good collaterals were compared using receiver operating characteristic curves.

RESULTS

Of the 209 included patients, 133 (64%) and 76 (36%) had good and poor collaterals, respectively. All-FLAIR vascular hyperintensity extent was similar between collateral groups (P = .76). Conversely, FLAIR vascular hyperintensities-DWI mismatch extent was significantly higher in patients with good compared with poor collaterals (P < .001). The area under the curve was 0.80 (95% CI, 0.74-0.87) for FLAIR vascular hyperintensities-DWI mismatch and 0.52 (95% CI, 0.44-0.60) for all-FLAIR vascular hyperintensities (P < .001 for the comparison), to predict good collaterals. Variables independently associated with good collaterals were smaller DWI lesion volume (P < .001) and larger FLAIR vascular hyperintensities-DWI mismatch (P = .02).

CONCLUSIONS

In acute ischemic stroke with large-vessel occlusion, the extent of FLAIR vascular hyperintensities does not reliably reflect collateral status unless one accounts for DWI.

Predicting the Severity of Neurological Impairment Caused by Ischemic Stroke Using Deep Learning Based on Diffusion-Weighted Images

Purpose: To develop a preliminary deep learning model that uses diffusion-weighted imaging (DWI) images to classify the severity of neurological impairment caused by ischemic stroke. Materials and Methods: This retrospective study included 851 ischemic stroke patients (711 patients in the training set and 140 patients in the test set). The patients’ NIHSS scores, which reflect the severity of neurological impairment, were reviewed upon admission and on Day 7 of hospitalization and were classified into two stages (stage 1 for NIHSS < 5 and stage 2 for NIHSS ≥ 5). A 3D-CNN was trained to predict the stage of NIHSS based on different preprocessed DWI images. The performance in predicting the severity of anterior and posterior circulation stroke was also investigated. The AUC, specificity, and sensitivity were calculated to evaluate the performance of the model. Results: Our proposed model obtained better performance in predicting the NIHSS stage on Day 7 of hospitalization than that at admission (best AUC 0.895 vs. 0.846). Model D trained with DWI images (normalized with z-score and resized to 256 × 256 × 64 voxels) achieved the best AUC of 0.846 in predicting the NIHSS stage at admission. Model E rained with DWI images (normalized with maximum−minimum and resized to 128 × 128 × 32 voxels) achieved the best AUC of 0.895 in predicting the NIHSS stage on Day 7 of hospitalization. Our model also showed promising performance in predicting the NIHSS stage on Day 7 of hospitalization for anterior and posterior circulation stroke, with the best AUCs of 0.905 and 0.903, respectively. Conclusions: Our proposed 3D-CNN model can effectively predict the neurological severity of IS using DWI images and performs better in predicting the NIHSS stage on Day 7 of hospitalization. The model also obtained promising performance in subgroup analysis, which can potentially help clinical decision making.

Fluid-Attenuated Inversion Recovery Vascular Hyperintensity in Cerebrovascular Disease: A Review for Radiologists and Clinicians

Neuroradiological methods play important roles in neurology, especially in cerebrovascular diseases. Fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH) is frequently encountered in patients with acute ischemic stroke and significant intracranial arterial stenosis or occlusion. The mechanisms underlying this phenomenon and the clinical implications of FVH have been a matter of debate. FVH is associated with large-vessel occlusion or severe stenosis, as well as impaired hemodynamics. Possible explanations suggested for its appearance include stationary blood and slow antegrade or retrograde filling of the leptomeningeal collateral circulation. However, the prognostic value of the presence of FVH has been controversial. FVH can also be observed in patients with transient ischemic attack (TIA), which may have different pathomechanisms. Its presence can help clinicians to identify patients who have a higher risk of stroke after TIA. In this review article, we aim to describe the mechanism and influencing factors of FVH, as well as its clinical significance in patients with cerebrovascular disease.

Interpretation of fluid-attenuated inversion recovery vascular hyperintensity in stroke

Fluid-attenuation inversion recovery (FLAIR) vascular hyperintensity (FVH) is a common presentation on brain magnetic resonance images of patients with acute ischemic stroke. This sign is known as a sluggish collateral flow. Although FVH represents the large ischemic penumbra and collateral circulation, the clinical significance of FVH has not been established. Varying protocols for FLAIR, treatment differences, and heterogeneity of endpoints across studies have complicated the interpretation of FVH in patients with acute stroke. In this review article, we describe the mechanism of FVH, as well as its association with functional outcome, perfusion-weighted images, and large artery stenosis. In addition, we review the technological variables that affect FVH and discuss the future perspectives.

The impact of FLAIR vascular hyperintensity on clinical severity and outcome : A retrospective study in stroke patients with proximal middle cerebral artery stenosis or occlusion

BACKGROUND

The clinical significance of fluid-attenuated inversion recovery vascular hyperintensity (FVH) has not been clarified. The aim of this study was to clarify the effects of FVH on the clinical severity and long-term prognosis of patients with proximal middle cerebral artery (MCA) occlusion or severe stenosis.

METHOD

Because their clinical and imaging data is not accessible, we excluded the patients being treated with IV thrombolysis or mechanical thrombectomy. Clinical and imaging characteristics were documented in 282 consecutive AIS patients with proximal MCA occlusion or severe stenosis. We assessed clinical severity using the National Institutes of Health Stroke Scale (NIHSS) score and clinical outcomes using mRS scores. The average time interval between symptom onset and imaging was 16-18 h. The FVH score according to FVH-ASPECTS ranged from 0 to 7, based on the numbers of territories where FVH is positive.

RESULTS

FVH was observed in 235 (83.33%) of the AIS patients. The FVH(+) group tended to have more alcoholics (65 [27.66%] vs 6 [12.77%], P = 0.032), a higher NIHSS score on the 7th day (3 [1-6] vs 2 [1-3], P = 0.039), more instances of early neurological deterioration (END) (27 [11.4%] vs 1 [2.12%], P = 0.05), and more patients with MCA occlusion (94 [40.00%] vs 3 [6.38%]). Among the patients with positive FVH, a high FVH score represented severe clinical impairment (higher NIHSS score on admission [P = 0.009] and 7th day since admission [P = 0.02]) and poor clinical outcomes. Spearman's rank correlations showed that FVH scores were positively correlated with NIHSS scores on admission and NIHSS scores on the 7th day (P = 0.039; P = 0.017, respectively).

CONCLUSION

In patients with proximal middle cerebral artery (MCA) occlusion or stenosis ≥ 70%, a high FVH score represented severe clinical impairment and poor clinical outcomes. In acute ischemic stroke (AIS) patients with proximal MCA occlusion, a high FVH score represented favorable clinical outcomes.

Clinical prognosis of FLAIR hyperintense arteries in ischaemic stroke patients: a systematic review and meta-analysis

OBJECTIVE

We performed a systematic review and meta-analysis to determine the association of fluid-attenuated inversion recovery (FLAIR) hyperintense arteries (FLAIR-HAs) on brain MRI and prognosis after acute ischaemic stroke (AIS).

METHODS

We searched Medline, Embase and Cochrane Central Register of Controlled Trials for studies reporting clinical or imaging outcomes with presence of FLAIR-HAs after AIS. Two researchers independently assessed eligibility of retrieved studies and extracted data, including from the Enhanced Control of Hypertension and Thrombolysis Stroke Study (ENCHANTED). Outcomes were unfavourable functional outcome (primary, modified Rankin scale scores 3-6 or 2-6), death, intermediate clinical and imaging outcomes. We performed subgroup analyses by treatment or types of FLAIR-HAs defined by location (at proximal/distal middle cerebral artery (MCA), within/beyond diffusion-weighted imaging (DWI) lesion) or extent.

RESULTS

We included 36 cohort studies (33 prospectively collected) involving 3577 patients. FLAIR-HAs were not associated with functional outcome overall (pooled risk ratio 0.87, 95% CI 0.71 to 1.06), but were significantly associated with better outcome in those receiving endovascular therapy (0.56, 95% CI 0.41 to 0.75). Contrary to FLAIR-HAs at proximal MCA or within DWI lesions, FLAIR-HAs beyond DWI lesions were associated with better outcome (0.67, 95% CI 0.57 to 0.79). FLAIR-HAs favoured recanalisation (1.21, 95% CI 1.06 to 1.38) with increased risk of intracerebral haemorrhage (2.07, 95% CI 1.37 to 3.13) and early neurological deterioration (1.93, 95% CI 1.30 to 2.85).

CONCLUSIONS

FLAIR-HAs were not associated with functional outcome overall but were associated with outcome after endovascular therapy for AIS. FLAIR-HAs were also associated with early recanalisation or haemorrhagic complications, and early neurologic deterioration.

PROSPERO REGISTRATION NUMBER

CRD42019131168.

Diffusion-weighted imaging (DWI) ischemic volume is related to FLAIR hyperintensity-DWI mismatch and functional outcome after endovascular therapy

BACKGROUND

We assessed whether diffusion-weighted imaging (DWI) volume was associated with fluid-attenuated inversion recovery vascular hyperintensities (FVH)-DWI mismatch and functional outcome in patients with acute stroke who received endovascular therapy (EVT).

METHODS

Fifty-three acute stroke patients who received EVT were enrolled. FVH-DWI mismatch, DWI volume on admission, DWI volume on follow-up, DWI volume growth, the functional outcome at 3 months (mRS) and other clinical data were collected. Receiver operating characteristic (ROC) analysis was performed to evaluate the value of DWI volume in predicting functional outcome after stroke.

RESULTS

The FVH-DWI mismatch group had a smaller DWI volume on admission (13.86±19.58 vs. 65.07±52.21; t=-4.301, P=0.000), a smaller DWI volume on follow-up (29.88±33.52 vs. 112.43±87.19; t=-4.143, P=0.000), and a lower DWI volume growth (16.02±19.90 vs. 47.36±40.06; t=-3.326, P=0.003) than those of the no FVH-DWI mismatch group. The good functional outcome group had a smaller DWI volume on admission (13.30±13.26 vs. 68.56±54.28; t=-5.611, P=0.000), a smaller DWI volume on follow-up (27.65±18.80 vs. 120.25±90.37; t=-5.720, P=0.000), lower DWI volume growth (14.35±15.06 vs. 51.69±41.17; t=-4.737, P=0.001) and a higher FVH-DWI mismatch ratio (75.76% vs. 35%; t=8.647; P=0.004) than those of the poor functional outcome group. ROC analysis showed that the sensitivity and specificity of DWI volume on admission for predicting functional outcome were 65% and 96.97%, respectively (the optimal cut-off value: 33.50 mL); DWI volume on follow-up was 48.6 mL, with a sensitivity and specificity of 80% and 87.88%, respectively; DWI volume growth was 22.25 mL, with a sensitivity and specificity of 70% and 87.88%, respectively.

CONCLUSIONS

DWI volume and DWI volume growth can provide the prognostic information of acute stroke patients after thrombectomy.