For patients with acute ischemic stroke (AIS) due to large-vessel occlusion (LVO), endovascular thrombectomy (EVT) is the most effective way to restore cerebral hypoperfusion. In recent years, the factors related to the clinical prognosis after EVT have been a hot topic. More convenient and reproducible imaging markers can help to evaluate the prognosis more accurately based on clinical indicators. The fluid-attenuated inversion recovery vascular hyperintensity (FVH) sign on fluid-attenuation inversion recovery (FLAIR) has received considerable attention [1]. FLAIR is a commonly used sequence in routine MRI of patients with stroke. Therefore, the FVH sign on the FLAIR sequence satisfies the needs of convenience and repeatability.

From the mechanism underlying FVH presentation, it has been known that FVH indicates slow retrograde flow in the leptomeningeal collateral, which is related to abnormal cerebral hemodynamics. Good collateral circulation is beneficial to the prognosis and functional recovery of patients with stroke. Based on this, numerous studies have investigated FVH to predict the prognosis in recent years; it has been reported as a surrogate marker to predict collateral status and patient outcomes [1, 2].

Most previous studies on the relationship between FVH and prognosis generally focused on the pre-treatment of stroke, including intravenous thrombolysis (IVT) and EVT. The latest research found that among various baseline clinical factors, only the FVH score has implications for the 3-month outcome and 6-month survival of AIS patients with LVO after IVT. The baseline FVH score showed great potential to predict the prognosis of acute stroke patients [3] and is associated with prognosis in patients with AIS before-treatment EVT [2, 4]. In this article published in European Radiology, Xu XQ et al [5] innovatively focused on FVH in AIS patients with LVO post-treatment EVT. Based on a dichotomized FVH status, this study established two combined models (model_1: recanalization + NIHSSpre; model_2: recanalization + NIHSSpre + post-treatment FVH) to explore the value of FVH in predicting prognosis. It proved that a post-treatment FVH sign might be associated with poor clinical outcome. This study may offer an additional imaging biomarker for the prognosis evaluation of EVT patients. However, the author did not use the widely used FVH-ASPECTS rating system (score ranging from 0 [no FVH] to 7 [FVHs abutting all ASPECTS cortical areas]) [6] for analysis, which is one of the limitations of this paper.

When analyzing the FVH sign, MRI examination time is an important factor to be considered. It is known that the FVH sign is a transient MRI phenomenon and typically disappears by 36 h post-stroke. In the cohort of this study, all patients underwent MRI scans within an entire week post-treatment EVT. While only four patients (4/84, 4.8%) underwent follow-up MRI scans within 36 h, one patient was observed to have the FVH sign. By analyzing the time distribution of FVH and recanalization in the remaining 80 patients, the author did not retrospectively observe a descending tendency of post-treatment FVH along with the increased time interval between EVT and MRI scan. However, FVH may dynamically change within the process of stroke. Grosch et al [7] reported a decrease in the presence and extent of FVH on follow-up MRI as compared with the baseline, and this effect was much more pronounced in patients who achieved successful recanalization. In the present article, the author’s views are consistent with the previous study, because many patients with recanalization still have the FVH sign, and some patients have not lost the FVH sign anyway. This makes us realize that the evolution (appearance and final disappearance) of FVH seems to be dynamic. The existence and extent of FVH may not represent the same information throughout the stroke process. It may have a protective effect in the early stage of stroke, but if it persists post-treatment EVT, it may indicate that the tissue perfusion cannot return to equilibrium.

In the future, FVH topography (FVH-ASPECTS, positional relationship between FVH and diffusion-weighted imaging (DWI) lesions) and clinical outcomes post-treatment EVT will be valuable. A relevant study has confirmed that FVH is associated with varying outcomes with different lesion patterns on DWI in patients with post-treatment IVT [8]. Moreover, a further attempt to explore the dynamic change and potential mechanism of the FVH sign before- and post-treatment EVT will be more interesting and valuable by prospective research.