Intracranial atherosclerotic plaques identified on vessel wall imaging are associated with increased risk of first‐ever stroke in a large Chinese cohort

Intracranial atherosclerotic disease (ICAD) is a major cause of ischemic stroke worldwide, especially in China and Asia. The prevalence of ICAD in stroke-free individuals ranges from 3.5% to 45% across different studies, depending on the definition, characteristics of the study population, and diagnostic methods [1]. Computed tomography angiography (CTA) or magnetic resonance angiography (MRA) are popular diagnostic imaging methods for ICAD by identifying luminal stenosis. However, plaques can present without causing significant stenosis due to outward remodeling, and angiographic imaging may miss plaques with low or zero degree of stenosis [2]. High-resolution magnetic resonance imaging (HR-MRI) provides a unique chance to directly assess the intracranial artery wall, which has been increasingly used to study atherosclerotic plaques [2]. A few studies have investigated the prognosis value of HR-MRI to predict recurrent stroke in acute stroke patients [3] [4], but the value of HR-MRI in predicting first-ever stroke is still unknown. In this Journal issue, the article by Li et al. describes a community-based prospective cohort study that included 1060 stroke-free participants evaluated by HR-MRI that found ICAD detected using HR-MRI increases the long-term risk of a first-ever ischemic stroke by 2.5 times in a stroke-free Chinese population, after adjusting for other risk factors [5]. This is the largest sample size study using HR-MRI on ICAD with a long follow-up duration of more than 4 years on average. The first-ever stroke rate was 5.2% during about 4.5 years' follow-up in patients with ICAD, and the stroke rate increased significantly to 12.5% if the area of stenosis of the intracranial artery was more than 70%, considered very high in such stroke-free individuals. How can we prevent these first-ever strokes in this subcohort of patients? Nearly all the included individuals received medication for risk factor control, but such a high rate of stroke indicates that the current medical management awaits further optimization. In patients with ICAD, especially those with a high degree of stenosis, more aggressive medication may be beneficial to these patients, including high-dose statin treatment, more strict blood pressure control, and so on. The screening of such high-risk patients using HR-MRI may be beneficial, pending future cost-effectiveness studies. With the aid of HR-MRI, this study is the first to identify the features of high-risk intracranial plaques (plaque burden, length, high signal, etc.) in stroke-free participants, which provides baseline data for future stroke-prevention strategies. However, in order to interpret the prevalence and prognosis of asymptomatic ICAD detected in this study, a few critical aspects need to be considered carefully. First, only the middle cerebral artery (MCA) and basilar artery (BA) were assessed in this study using HR-MRI, and other intracranial arteries were only assessed using luminal imaging, which might decrease the rate of ICAD. Future studies are needed to evaluate the major intracranial arteries in the whole brain using HR-MRI. Second, the stenosis was defined as luminal area stenosis, and not the traditionally used diameter stenosis, which should be interpreted with caution. Assuming a circular lumen, a 50% diameter stenosis (the narrowest lumen is half the diameter of the normal artery) is equal to 75% area stenosis. Previous studies have shown that three-dimensional HR-MRI can quantify the diameter stenosis of the intracranial artery accurately and reproducibly [6]. Diameter stenosis is still the most widely used parameter in clinical practice and it is used in the current clinical guidelines. Third, the resolution of HR-MRI used in this study was low compared to the state-of-the-art technique, and only pre-contrast HR-MRI sequences were acquired, which might lead to a missed diagnosis of small plaques, especially non-stenotic ICAD. Also the plaque enhancement feature was not evaluated. The use of higher-resolution HR-MRI sequences, or a higher field strength, can potentially further improve the accuracy of detecting asymptomatic ICAD [7]. Chengcheng Zhu: Conceptualization; writing – review and editing; writing – original draft. Bing Tian: Conceptualization; writing – original draft; writing – review and editing. The authors declare there is no conflict of interest. Data sharing not applicable to this article as no datasets were generated or analysed during the current study.