Fluid-Attenuated Inversion Recovery Vascular Hyperintensities in Transient Ischemic Attack within the Anterior Circulation

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.

Ultrafast MRI using deep learning echoplanar imaging for a comprehensive assessment of acute ischemic stroke

OBJECTIVES

Acute ischemic stroke (AIS) is an emergency requiring both fast and informative MR sequences. We aimed to assess the performance of an artificial intelligence-enhanced ultrafast (UF) protocol, compared to the reference protocol, in the AIS management.

METHODS

We included patients admitted in the emergency department for suspected AIS. Each patient underwent a 3-T MR protocol, including reference acquisitions of T2-FLAIR, DWI, and SWI (duration: 7 min 54 s) and their accelerated multishot EPI counterparts for T2-FLAIR and T2*, complemented by a single-shot EPI DWI (duration: 1 min 54 s). Two blinded neuroradiologists reviewed each dataset, assessing DWI (detection, location, number of acute lesions), FLAIR (vascular hyperintensities, visibility of acute lesions), and SWI/T2* (hemorrhagic transformation, thrombus). We compared the agreement between the diagnoses obtained with both protocols using kappa coefficients.

RESULTS

A total of 173 patients were included consecutively, of whom 80 with an AIS in DWI. We found an almost perfect agreement between the UF and reference protocols regarding the detection, distribution, number of AIS in DWI (κ = 0.98, 0.98, and 0.87 respectively), the presence of vascular hyperintensities, and the presence of a parenchymal hyperintensity in the AIS region in FLAIR (κ = 0.93 and 0.89 respectively). Agreement was substantial in T2*/SWI for thrombus detection, and fair for hemorrhagic transformation detection (κ = 0.64 and 0.38 respectively). Differential diagnoses were similarly detected by both protocols (κ = 1).

CONCLUSIONS

Our AI-enhanced ultrafast MRI protocol allowed an effective detection and characterization of both AIS and differential diagnoses in less than 2 min.

KEY POINTS

• The AI-enhanced ultrafast MRI protocol allowed an effective detection of acute stroke. • Characterization of stroke features with the UF protocol was equivalent to the reference sequences. • Differential diagnoses were detected similarly by the UF and reference protocols.

Laser Speckle Flowmetry for the Prognostic Estimation Study of Permanent Focal Ischemia in Mice

The distal middle cerebral artery occlusion (dMCAO) model that mainly targets the cortex and causes low mortality is developed for the study of permanent focal ischemia, and it is highly appropriate for the study in the aged population. The two most common methods used to establish dMCAO models are dMCAO alone and dMCAO plus ipsilateral common carotid artery occlusion (CCAO). Up to now, studies on the prognosis of the two types of dMCAO models and the accuracy of cerebral blood flow (CBF) in predicting prognosis have not yet been reported. In the present study, we established permanent focal ischemia models in two groups of aged mice by dMCAO alone or by dMCAO plus ipsilateral common carotid artery occlusion (CCAO). CBF was evaluated by laser speckle flowmetry (LSF) before and after surgery. Cerebral infarction was assessed by TTC staining at day 2 after surgery and MAP2 staining at day 21 after surgery. In addition, behavioral outcomes were evaluated using the modified Garcia scoring system, adhesive removal test, and foot-fault test. Our results showed that compared with those in the dMCAO alone group, the mice in the dMCAO plus CCAO group had a larger cerebral infarct size and more severe neurological deficits. According to the results of the correlation analysis, the area of the ischemic core region on CBF imaging in the dMCAO group was helpful in predicting the infarct volume. In addition, the total CBF of the ischemic area in the dMCAO plus CCAO group showed a significant correlation with Garcia scores 3 days after surgery, but there was no significant correlation of CBF imaging with the foot-fault test 7 days after surgery. These results suggest that the total CBF of the ischemic area might be helpful to predict the severity of neurological damage at the acute stage.

FLAIR Vascular Hyperintensity: An Important MRI Marker in Patients with Transient Ischemic Attack

Purpose

We aimed to investigate the prevalence of fluid-attenuated inversion recovery (FLAIR) vascular hyperintensities (FVHs) and the clinical-radiological correlation in transient ischemic attack (TIA) patients.

Materials and Methods

We performed a retrospective analysis of TIA patients who had undergone magnetic resonance imaging (MRI) within 24 h of symptom onset. Two independent neuroradiologists investigated the presence of FVHs, large-artery severe stenosis or occlusion (LASO) in magnetic resonance angiograms, and the nature of factors associated with FVH.

Results

A total of 207 patients were enrolled in this study. FVHs were detected in 42 (20.3%) patients, in whom atrial fibrillation (AF) was confirmed in 25 (59.5%) cases and LASO was confirmed in 30 (71.4%) cases. The corresponding figures were 33 (20.0%) and 10 (6.1%), respectively, for the 165 FVH-negative patients. Logistic regression analysis showed that time from symptom onset to MRI (odds ratio [OR] = 0.82, 95% CI 0.76-0.97, p = 0.042), previous stroke (OR = 2.95, 95% CI 1.58-6.74, p = 0.002), AF (OR = 5.83, 95% CI 2.24-9.46, p < 0.001), and LASO (OR = 4.28, 95% CI 2.96-10.28, p < 0.001) were independently associated with FVH. Overall, the sensitivity and specificity of FVH for predicting LASO were 0.75 and 0.93, respectively, and the positive predictive value, negative predictive value, and accuracy were 0.71, 0.94, and 0.89, respectively. The area under the receiver operating characteristic curve was 0.839. FVH-positive TIA patients with LASO had less AF (14 [46.7%] versus 11 [91.7%], p = 0.019) and longer times from symptom onset to MRI (6.8 ± 2.8 h versus 4.8 ± 1.3 h, p = 0.004) than those without LASO.

Conclusion

The presence of FVH could be an important marker in TIA patients. Many factors, including LASO, AF, and time from symptom onset to MRI, are associated with the detection of FVH.

Fluid-Attenuated Inversion Recovery Vascular Hyperintensity as a Potential Predictor for the Prognosis of Acute Stroke Patients After Intravenous Thrombolysis

Background

Fluid-attenuated inversion recovery vascular hyperintensity (FVH) can reflect the collateral status, which may be a valuable indicator to predict the functional outcome of acute stroke (AS) patients.

Methods

A total of 190 AS patients with large vessel occlusion (LVO) were retrospectively investigated. All patients completed a 6-month follow-up and their modified Rankin Scale (mRS) scores were recorded at 1, 3, and 6 months after intravenous thrombolysis (IVT). Based on their mRS at 3 months, patients were divided into two groups: poor prognosis (131 patients; 68.9% of all subjects) and favorable prognosis (59 patients; 31.1% of all subjects). The death records of 28 patients were also analyzed in the poor prognosis group.

Results

(1) Univariate and multivariate analyses showed that the higher National Institutes of Health Stroke Scale (NIHSS) score at admission, higher fasting blood glucose, and lower FVH score were independent risk factors to predict the poor prognosis of IVT. (2) Survival analysis indicated that FVH score was the only baseline factor to predict the 6-month survival after IVT. (3) Baseline FVH score had great prediction performance for the prognosis of IVT (area under the curve = 0.853). (4) Baseline FVH score were negatively correlated with the NIHSS score at discharge and mRS score at 1, 3, and 6 months.

Conclusion

Among various baseline clinical factors, only the FVH score might have implications for 3-month outcome and 6-month survival of AS patients after IVT. Baseline FVH score showed great potential to predict the prognosis of the AS patients.

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.

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.