Infarct morphology assessment in patients with carotid artery/middle cerebral artery occlusion using fast fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH)

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.

Hemodynamics derived from computational fluid dynamics based on magnetic resonance angiography is associated with functional outcomes in atherosclerotic middle cerebral artery stenosis

BACKGROUND

To investigate the relationship between fluid-attenuated inversion recovery (FLAIR) vascular hyperintensity (FVH), hemodynamics, and functional outcome in atherosclerotic middle cerebral artery (MCA) stenosis using a computational fluid dynamics (CFD) model based on magnetic resonance angiography (MRA), according to a modified Rankin Scale (mRS) at 3 months.

METHODS

A total of 120 patients with 50-99% atherosclerotic MCA stenosis were included. The training and internal validation groups were composed of 99 participants and 21 participants, respectively. Demographic, imaging data, and functional outcome (mRS at 3 months) were collected. Hemodynamic parameters were obtained from the CFD model. The FVH score was based on the number of territories where FVH is positive, according to the spatial distribution in the Alberta Stroke Program Early Computed Tomography Score (ASPECTS). The prediction models were constructed according to clinical and hemodynamic parameters using multivariate logistic analysis. The DeLong test compared areas under the curves (AUCs) of the models.

RESULTS

The multivariable logistic regression analysis showed that the National Institute of Health Stroke Scale (NIHSS) at admission, hypertension, hyperlipidemia, the ratio of wall shear stress before treatment (WSSR_before), and difference in the ratio of wall shear stress (WSSR) were independently associated with functional outcome (all P<0.05). In the training group before treatment, the AUC of model 1a (only clinical variables) and 2a (clinical variables with addition of WSSR_before) were 0.750 and 0.802. After treatment, the AUC of model 1b (only clinical variables) and 2b (clinical variables with addition of difference in WSSR) were 0.815 and 0.883, respectively. The AUC of models with hemodynamic parameters was significantly higher than the models based on clinical variables only (all P<0.05, DeLong test). In the internal validation group before treatment, the AUC of the model (clinical variables) was 0.782, and that of the model (clinical variables and WSSR_before) was 0.800. After treatment, the AUC of the model (clinical variables) was 0.833, and that of the model (clinical variables and difference in WSSR) was 0.861. There were no significant differences between the good and the poor functional outcome group concerning FVH_before scores before treatment (0.30±0.81 vs. 0.26±0.97; P=0.321) and FVH_after scores after treatment (0.08±0.39 vs. 0.00±0.00; P=0.244).

CONCLUSIONS

Hemodynamics was associated with functional outcomes in patients with ischemic stroke attributed to atherosclerotic MCA stenosis, while FVH was not. Hemodynamic parameters were of great importance in the prediction models.

FLAIR vascular hyperintensity in acute stroke is associated with collateralization and functional outcome

PURPOSE

Fluid-attenuated inversion recovery vascular hyperintensity (FVH) is frequently found in stroke patients after intracranial arterial occlusion, but the prognostic value of FVH findings is unclear. We assessed whether FVH is associated with cerebral collateral status and functional outcome in patients with acute stroke patients receiving endovascular therapy.

METHODS

FVH score, American Society of Interventional and Therapeutic Neuroradiology (ASITN) grade, the functional outcome at 3 months (modified Rankin Scale (mRS)), and other clinical data were collected for 37 acute stroke patients with large vessel occlusion (LVO) receiving MRI before and after endovascular therapy. Statistical analysis was performed to predict functional outcome after stroke.

RESULTS

The good functional outcome group (n = 16) had a higher FVH₁ (FVH before therapy) score (4.63 ± 1.20 vs 3.14 ± 1.15; p = 0.001) and ASITN grade (3.31 ± 0.48 vs 2.00 ± 1.22; p < 0.001) and a lower FVH₂ (FVH after therapy) score than the poor functional outcome group (n = 21; 0.125 ± 0.50 vs 1.44 ± 2.16; p = 0.030). mRS at 3 months was negatively correlated with FVH₁ (r = - 0.525, p = 0.001) and the ASITN grade (r = - 0.478, p = 0.003) and positively correlated with FVH₂ (r = 0.376, p = 0.034). FVH₁ (OR, 0.085; 95% CI, 0.013-0.577; p = 0.012) and FVH₂ (OR, 2.724; 95% CI, 1.061-6.996; p = 0.037) were independently associated with functional outcome in multivariable logistic regression analysis.

CONCLUSIONS

Assessing FVH before and after therapy in acute stroke patients with LVO might be useful for predicting functional outcome after stroke.

KEY POINTS

• Fluid-attenuated inversion recovery vascular hyperintensity is a circular or serpentine brightening in the brain parenchyma or cortical surface bordering the subarachnoid space on MR imaging. • A prospective study showed that fluid-attenuated inversion recovery vascular hyperintensity is associated with cerebral collateral circulation and prognosis. • Fluid-attenuated inversion recovery vascular hyperintensity helps clinicians to predict the prognosis of patients with acute stroke.