Abstract A061: High-resolution Vessel Wall Imaging-Based Classification of Pediatric Intracranial Arteriopathies: A Multicenter Cohort Study

Background: Pediatric intracranial arteriopathy is a leading cause of childhood arterial ischemic stroke. Conventional luminal imaging often fails to depict underlying vessel wall pathology, resulting in diagnostic uncertainty. High-resolution vessel wall imaging (HR-VWI) directly visualizes mural characteristics, potentially overcoming this limitation. We aimed to characterize the HR-VWI phenotypes of pediatric arteriopathy and evaluate their prognostic significance. Methods: In this retrospective multicenter cohort study, we analyzed data from an HR-VWI registry across nine tertiary hospitals (January 2014-January 2025). Patients aged 29 days to 18 years with radiologically confirmed intracranial arteriopathy were included. We assessed HR-VWI-based etiologic classification, treatments, outcomes, and their associations. Results: Among 224 enrolled patients (median age 13 years IQR 10-15; 47.9% female), the HR-VWI classification system demonstrated substantial interobserver (κ=0.726) and intraobserver (κ=0.757) agreement. Nine etiological phenotypes were delineated: moyamoya arteriopathy (n=129, 57.6%), possible vasculitis (n=57, 25.4%), arterial dysplasia (n=6, 2.7%), clot (n=6, 2.7%), web (n=5, 2.2%), atherosclerosis (n=5, 2.2%), aneurysm (n=3, 1.3%), dissection (n=1, 0.4%), and occlusion with undetermined cause (n=12, 5.4%). Compared with the Childhood Arterial Ischemic Stroke Standardized Classification and Diagnostic Evaluation (CASCADE) system, HR-VWI revealed marked etiological heterogeneity within the CASCADE “unifocal cerebral arteriopathy” category: possible vasculitis (54.2%), moyamoya arteriopathy (19.4%), atherosclerosis (6.9%), and web (5.5%). Follow-up vascular imaging (n=47; median 11.5 months) showed disease stability (68.1%), improvement (19.1%; mainly vasculitis and atherosclerosis), or worsening (12.8%; predominantly moyamoya arteriopathy). Over a median follow-up of 13 months (IQR 5.5–24), new-onset stroke occurred in 11 (10 ischemic, 1 hemorrhagic), primarily in moyamoya arteriopathy (n=6) and possible vasculitis (n=4), yielding a cumulative incidence of 5.8% and an incidence rate of 3.12 per 100 person-years. Conclusions: HR-VWI reveals distinct vessel-wall phenotypes reflecting diverse underlying etiologies in pediatric arteriopathy. Compared to conventional luminal imaging, HR-VWI potentially enables more precise classification and supports more individualised management strategies.