Abstract 127: Persistent Primitive Anastomoses in Stroke: From Incidental Finding to Hemodynamic Culprit ; A Case Based Discussion

Introduction Persistent primitive anastomoses (PPAs), including the trigeminal artery (PTA) and hypoglossal artery (PHA), are rare embryologic connections between the carotid and vertebrobasilar circulations. They are most often identified incidentally, with reported prevalence ranging between 0.1‐0.6% in angiographic studies. Although historically regarded as benign anatomic variant, more recent reports suggest that PPAs can alter cerebral hemodynamics, mimic pathology, and impact both ischemic stroke presentation and interventional strategy. Methods We describe two patients in whom PPAs were identified on neurovascular imaging—one incidental and one during acute stroke intervention—to illustrate both diagnostic pitfalls and hemodynamic significance. Results A 63‐year‐old woman with vascular risk factors presented with subacute dizziness and imbalance. Brain CT was unremarkable, but CTA demonstrated a PHA arising from the cervical ICA and traversing the hypoglossal canal into the posterior circulation. While asymptomatic, recognition of this variant was essential to avoid misinterpretation as vascular loop pathology and to anticipate potential implications in surgical approach such as skull base surgery or endovascular procedures.A 65‐year‐old man with hypertension, hyperlipidemia, and carotid stenosis presented with acute right hemiparesis and unresponsiveness. CTA revealed a left M1 occlusion. During thrombectomy, angiography identified a PTA connecting the cavernous ICA to the basilar artery. This vessel provided ipsilateral collateral flow to the MCA territory via posterior circulation channels, partially preserving perfusion despite proximal occlusion. Such collateral contribution from PTA has been rarely documented but highlights its potential role as a hemodynamic modifier in stroke. Conclusion PPAs are more than incidental embryologic remnants. The PTA may serve as a critical collateral lifeline in the setting of LVO, while the PHA, if unrecognized, may masquerade as pathology. Awareness of these variants improves diagnostic accuracy, enhances interpretation of collateral flow in stroke imaging, and informs safe neurointerventional planning. image