ABSTRACT NUMBER: ESOC2026YS251 IMPACT OF ANTERIOR CIRCULATION ARTERIAL BRANCHING VARIATIONS ON ISCHAEMIC STROKE TERRITORIES AND CLINICAL ASSESSMENT: A SYSTEMATIC INTEGRATION AND RETROSPECTIVE COHORT STUDY PROTOCOL

Abstract Background and aims The Circle of Willis exhibits significant anatomical variations in most individuals. As ischaemic stroke predominantly affects the anterior circulation, understanding variations in the anterior cerebral artery (ACA) and middle cerebral artery (MCA) is crucial. These anomalies alter territorial supply, potentially complicating CT angiography (CTA) interpretation and the assessment of atypical stroke patterns. Methods This research project employs a two-stage design. Firstly, a systematic review of published anatomical data established the prevalence of specific vascular anomalies. Secondly, a planned retrospective cohort study (patients aged 18–85 years) will evaluate these variants in acute ischaemic stroke confirmed by DWI-MRI. The study will use CTA to map specific vascular variants against observed infarct topography. Results Systematic evaluation of existing literature reveals a high prevalence of variants that mechanistically imply major clinical consequences. Hypoplasia of the unilateral A1 segment theoretically predisposes to severe, bihemispheric ACA infarction following contralateral A1 occlusion. Accessory ACA may sustain perfusion during primary vessel occlusion, resulting in atypically small infarcts that risk misclassification. Regarding the MCA, primary trunk variant occlusion is anticipated to lead to total ipsilateral MCA-territory infarction due to a lack of M2 divisions. In contrast, trifurcated MCAs may create complex embolic lodging sites, potentially complicating mechanical thrombectomy. Preliminary analysis demonstrates that these variations frequently deviate from standardised stroke templates. Precise identification of these specific vascular configurations is essential for improving prognostic accuracy and tailoring interventions to individual anatomical profiles. Conflict of interest Sebastião Branca: nothing to disclose; Trevor Decker: nothing to disclose; Edson de Oliveira: nothing to disclose; Juan Tejada: nothing to disclose