Factors Influencing Stroke Severity Based on Collateral Circulation, Clinical Markers and Machine Learning

<b>Background/Objectives:</b> Stroke is a serious neurological disorder that significantly affects patients' quality of life and overall health. The severity of a stroke can vary widely and is influenced by multiple factors, such as clinical presentation, diagnostic findings, and the site of onset. This study aimed to identify and analyze key variables that contribute to stroke severity, with a particular focus on the role of collateral circulation. <b>Methods</b>: This study analyzed clinical, imaging, and biochemical variables-ipsilateral collateral flow on MRA, MRI unilateral-bilateral stroke, systolic blood pressure (SBP), fasting plasma glucose (FPG), and blood urea nitrogen (BUN). Group differences used chi-square and Mann-Whitney U tests. Class imbalance was addressed with SMOTE; Logistic Regression, Random Forest, XGBoost, and SVM were cross-validated, reporting accuracy, precision, recall, and F1 with 95% CIs. <b>Results</b>: Reduced or absent ipsilateral collateral flow and unilateral-bilateral stroke were strongly associated with greater severity (<i>p</i> < 0.001). SBP was significant (<i>p</i> = 0.034), FPG was significant (<i>p</i> = 0.023), and BUN was borderline (<i>p</i> = 0.059). SMOTE improved prediction: Random Forest achieved accuracy 83.3% (CI: 79.1-87.6) and F1 84.0% (CI: 79.1-88.9); XGBoost reached accuracy 80.2% (CI: 71.5-89.0) and F1 81.4% (CI: 73.8-89.0). Logistic Regression improved to F1 70.8% (CI: 55.4-86.2), whereas SVM declined to accuracy 52.2% (CI: 37.5-67.0). <b>Conclusions</b>: Collateral status and unilateral-bilateral stroke are key determinants of severity; SBP and FPG add prognostic value, with BUN borderline. Tree-based ensembles trained on SMOTE-balanced data provide the most reliable predictions for risk stratification. These findings suggest that future work may focus on integrating such predictive models into Clinical Decision Support Systems (CDSSs) to enhance early risk identification, strengthen CDSSs, and enable more personalized care planning for stroke patients.