Abstract TP379: Incidence and 5-Year Risk of Cerebrovascular Events and Mortality in Vertebrobasilar Dolichoectasia: A Bayesian and Classical Meta-Analysis

Background: Vertebrobasilar dolichoectasia (VBD) is a rare vascular anomaly of the posterior circulation associated with increased risk of ischemic and hemorrhagic stroke, transient ischemic attack (TIA), and mortality. Quantitative estimates of event rates and long-term risk are scarce, limiting evidence-based management and counseling. We performed a comprehensive meta-analysis integrating classical and Bayesian methods to quantify incidence rates and 5-year cumulative risks in patients with VBD. Methods: We systematically searched PubMed, Scopus, Embase, and the Cochrane Library through September 2025 for observational studies reporting cerebrovascular events and all-cause mortality in adults with VBD. Random-effects meta-analyses using maximum-likelihood estimation accounted for between-study heterogeneity. Bayesian Poisson multilevel models were fitted to estimate study-level incidence rates per 100 person-years (PY) and 5-year predicted risks. Language refinement was assisted by ChatGPT (OpenAI, GPT-5). Results: A total of nine studies were included. In the classical random-effects meta-analysis, the pooled incidence rates per 100 person-years were: ischemic stroke (IS) 6.04 (95% CI 3.67–9.95), transient ischemic attack (TIA) 2.18 (1.66–2.87), intracerebral hemorrhage (ICH) 1.68 (0.66–4.32), any stroke 7.22 (4.70–11.09), and all-cause mortality (ACM) 5.58 (2.06–15.11). Substantial heterogeneity was observed for IS (I^2 = 75.8%), any stroke (I^2 = 83.6%), and ICH (I^2 = 88.6%), while heterogeneity for TIA was low (I^2 = 0%). Bayesian models produced consistent incidence estimates and further provided 5-year cumulative risk predictions: IS 25.8% (95% CI 14.4–44.6%), ICH 8.2% (2.2–22.3%), any stroke 30.3% (19.7–45.9%), and ACM 24.6% (7.7–61.2%). Conclusions: Patients with VBD face considerable risks of ischemic and hemorrhagic stroke and elevated all-cause mortality, with comparatively lower rates of TIA. Reporting incidence per 100 PY alongside Bayesian 5-year risk estimates provides clinically useful metrics for counseling, individualized risk assessment, and planning future studies. Larger prospective cohorts are needed to more precisely define predictors of adverse outcomes and guide management in this rare population. Keywords: Vertebrobasilar dolichoectasia, ischemic stroke, TIA, incidence rate, Bayesian meta-analysis