Congenital Absence of the Internal Carotid Artery Associated With Contralateral Middle Cerebral Artery Occlusion in a Young Female Patient: Embryology, Multimodal Imaging Findings, and Clinical Implications.

Congenital absence of the left internal carotid artery (ICA) is a rare condition associated with contralateral occlusion of the right middle cerebral artery (MCA) in a young female patient, highlighting the imaging findings and clinical characteristics of this anatomical variation. We describe the embryological basis, clinical presentation, multimodal imaging findings, and the relevance of collateral circulation development in a patient with a left congenital absence of the ICA associated with contralateral MCA occlusion. In this case, we present a 32-year-old woman with signs and symptoms compatible with a right MCA stroke. The initial multimodal imaging workup revealed an absent left ICA and a left common carotid artery originating from the arterial brachiocephalic trunk. This case highlights a thorough and updated perspective of developmental ICA congenital absence associated with contralateral MCA occlusion, emphasizing key differentiators from other acute cerebrovascular conditions and the potential clinical implications of this anatomical variant.