RESUMO
Introduction: and importance: An uncommon condition is congenital unilateral agenesis of the internal carotid artery (ICA). Most instances are asymptomatic due to adequate collateral circulation via the circle of Willis, but individuals might potentially manifest (or show) ischemic or aneurysmal dilatation hemorrhagic cerebrovascular lesions. The bony carotid canal must be absent from distinguishing this abnormality from chronic ICA blockage. Neuroradiologists must be aware of this condition since these patients have a higher risk of developing numerous intracranial diseases. Case presentation: This report focuses on the case of 39 years male with an absent right internal carotid artery with posterior cerebral artery aneurism whose main symptoms were on and off headaches. In a discussion that includes demographic characteristics, clinical manifestations, radiologic findings, and an assessment of the risks associated with ICA agenesis. Conclusion: Congenital agencies absence of carotid artery is rare variant anatomy although most of the time they are asymptomatic, it is known to increase the risk of aneurism and therefore, they need screening and close follow up.