The effects of cerebral artery variations on the occurrence of intracranial atherosclerosis : serial hospital-based clinical research

Abstract

Background: Ischemic stroke (IS) is a major cause of adult disability and death all over the world. Intracranial atherosclerosis (ICAS) is the most common etiology of IS among Chinese stroke patients, and involves the major cerebral large arteries growing atherosclerotic plaques. The current advances in imaging technology have greatly facilitated the detection of the cerebral artery anatomical variations and the intracranial atherosclerotic plaques among the general populations. Nonetheless, few studies investigated the underlying influence of the cerebral artery variations on ICAS, including the common variability in the circle of Willis (COW) structure and in the vertebrobasilar junction (VBJ) angle magnitude. Purpose: Our research aimed to explore the effects of the cerebral vascular variations, namely the COW structural anomaly and the varying VBJ-angle degrees, on the occurrence and progression of ICAS among stroke patients, via using high-resolution magnetic resonance imaging (HR-MRI). Methods and materials: This hospital-based research consecutively recruited adult patients with acute IS or transient ischemic attack, who were scanned by both routine cerebral MRI and intracranial vessel-wall 3.0-Tesla MRI sequences. Magnetic resonance angiography was used to assess the anatomical completeness of the COW and the degrees of the VBJ angle. The COW consists of the anterior COW (A-COW) and the posterior COW (P-COW). The VBJ angle was stratified into the angle above 90° or the angle below 90°. HR-MRI was utilized to evaluate the plaque imaging features quantitatively and qualitatively. The intracranial atherosclerotic lesions were categorized as asymptomatic or symptomatic, based on acute cerebral infarction on diffusion-weighted imaging and/or acute stroke symptoms. Results: This research enrolled a total of 125 acute stroke patients with intracranial large artery atherosclerosis between 2014 and 2020, among whom 96 patients had the complete imaging scan covering the intracranial vertebral artery segments. Besides, 107 patients had the atherosclerotic lesions in the middle cerebral artery (MCA) detected by HR-MRI, and 68 patients with vertebrobasilar atherosclerotic lesions were included in the subsequent analyses. Firstly, among 96 patients with intracranial large artery atherosclerosis (mean age = 63.41 ± 10.31 years old; 60 were male), the incomplete COW subtypes were prevalent (the incomplete A-COW, 44.8%; the incomplete P-COW, 83.3%). Two hundred and ninety-two intracranial atherosclerotic plaques were detected in patients with intracranial large artery atherosclerosis (224 were asymptomatic and 68 were symptomatic). The prevalence of the symptomatic plaques in the first segment of the MCA was observed to be 82.8% in the incomplete A-COW subtype, and significantly higher than 48.7% in the complete A-COW subtype (P = 0.005). Yet, no significant difference in the location of the symptomatic plaques within the second segment of the MCA, the basilar artery, or the vertebral artery was found between the complete and incomplete A-COW subtypes (all P values > 0.05/4 times of the repeated comparisons). Secondly, among 107 patients with MCA atherosclerosis (mean age = 62.50 ± 11.69 years old; 67 were male), the prevalence of the incomplete A-COW subtype was 43.0%, while that of the incomplete P-COW subtype went up to 85.0%. One hundred and fifty-eight MCA plaques were detected in patients with MCA atherosclerosis (96 were asymptomatic and 62 were symptomatic). Compared to the complete A-COW, the incomplete A-COW had more inferior-wall plaques, but fewer ventral-wall plaques in the MCAs, regardless of whether the MCA plaques were symptomatic or not (P values < 0.05). Besides, the dysplasia or absence of the posterior communicating artery (80.4%) was the most prevalent among patients with MCA atherosclerosis, followed by the dysplasia or absence of the anterior cerebral artery (34.6%), the anterior communicating artery (ACoA) (29.9%), and the posterior cerebral artery (27.1%). The dysplasia or absence of ACoA, as a typical incomplete A-COW pattern, was then found in independent association with symptomatic MCA atherosclerosis (odds ratio, 3.132, [95%CI, 1.412-6.946]; P = 0.005) after controlling the potential confounders. Thirdly, among 68 patients with vertebrobasilar artery atherosclerosis (mean age = 63.53 ± 9.42 years old; 63.2% were male), the VBJ angles ranged in magnitude between 29.45° and 124.20°. 48.5% of patients with vertebrobasilar atherosclerosis had the VBJ angles ≥ 90°, while 51.5% possessed the VBJ angles < 90°. One hundred and thirty-one vertebrobasilar plaques were detected in patients with vertebrobasilar artery atherosclerosis. The VBJ angles ≥ 90° had more vertebrobasilar plaques on the ventral walls (50.14% versus 25.49%, P = 0.003), but fewer vertebrobasilar plaques on the dorsal walls (7.32% versus 40.34%, P < 0.001) than the VBJ angles < 90°. Additionally, the values of wall thickness, luminal stenosis and plaque burden in vertebrobasilar artery atherosclerosis were significantly increased in the VBJ angles ≥ 90°, rather than the VBJ angles < 90° (all P values < 0.05). The VBJ angles ≥ 90° also possessed more vertebrobasilar plaques with hypointensity signal, intraplaque hemorrhage, and symptomatic status (all P values < 0.05). Conclusion: In our research, 1) the incomplete A-COW subtype was significantly associated with the occurrence of the symptomatic atherosclerotic lesions in the MCA-M1 segment among patients with intracranial large artery atherosclerosis. 2) The incomplete A-COW structure might strongly influence the MCA plaque location on the vessel walls in patients with MCA atherosclerosis. 3) The ACoA dysplasia or absence might serve as an independent risk factor for developing symptomatic MCA atherosclerotic lesions in patients with MCA atherosclerosis. 4) The structure of the VBJ angles ≥ 90° might robustly affect the vertebrobasilar plaque location on the vessel walls among patients with vertebrobasilar artery atherosclerosis. 5) The VBJ angles ≥ 90° were significantly related to the progressive vertebrobasilar atherosclerotic lesions in patients with vertebrobasilar artery atherosclerosis. Accordingly, our findings highlight the important roles of the cerebral artery variations in the occurrence and progression of ICAS among stroke patients.