Interpretation of fluid-attenuated inversion recovery vascular hyperintensity in stroke

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.

Association of fluid-attenuated inversion recovery vascular hyperintensity with ischaemic events in internal carotid artery or middle cerebral artery occlusion

BACKGROUND AND PURPOSE

Individuals with intracranial artery occlusion have high rates of ischaemic events and recurrence. It has been challenging to identify patients who had high-risk stroke using a simple, valid and non-invasive screening approach. This study aimed to investigate whether fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH), a specific imaging sign on the FLAIR sequence, could be a predictor of ischaemic events in a population with internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion.

METHODS

We retrospectively analysed 147 patients (mean 60.43±12.83 years) with 149 lesions, including 37 asymptomatic and 112 symptomatic cases of ICA or MCA occlusion. Symptomatic occlusion was considered if ischaemic events were present in the relevant territory within 90 days. FVH Alberta Stroke Program Early Computed Tomography Score (FVH-ASPECTS: 0-7, with 0 indicating absence of FVH and 7 suggesting prominent FVH) and collateral circulation grade were assessed for each participant. Multivariable logistic regression analysis was performed to detect independent markers associated with symptomatic status.

RESULTS

A lower FVH-ASPECTS was associated with a more favourable collateral circulation grade (rho=-0.464, p<0.0001). The FVH-ASPECTS was significantly lower in the asymptomatic occlusion group than in the symptomatic occlusion group (p<0.0001). FVH-ASPECTS (Odd ratio, 2.973; 95% confidence interval, 1.849 to 4.781; p<0.0001) was independently associated with symptomatic status after adjustment for age, sex, lesion location and collateral circulation grade in the multivariate logistic regression. The area under the curve was 0.861 for the use of FVH-ASPECTS to identify symptomatic occlusion.

CONCLUSIONS

The ability to discriminate symptomatic from asymptomatic occlusion suggests that FVH may be a predictor of stroke. As a simple imaging sign, FVH may serve as a surrogate for haemodynamic impairments and can be used to identify high-risk stroke cases early in ICA or MCA occlusion.

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.

Editorial comment: Prognostic value of post-treatment fluid-attenuated inversion recovery vascular hyperintensity in ischemic stroke after endovascular thrombectomy

KEY POINTS

• The fluid-attenuated inversion recovery vascular hyperintensity (FVH) sign on FLAIR has been reported as a surrogate marker to predict collateral status and clinical outcome in patients with stroke. Most previous studies on the relationship between FVH and prognosis generally focused on the pre-treatment of stroke.• This article focused on FVH in AIS patients with LVO post-treatment EVT. It proved that the post-treatment FVH sign may be associated with poor clinical outcome. It may offer an additional imaging biomarker for the prognosis evaluation of EVT patients.

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.