Internal carotid absence

Internal carotid absence (also known as agenesis of the internal carotid artery or congenital absence of the internal carotid artery) is a rare vascular anomaly in which one or both internal carotid arteries fail to develop during embryogenesis. The internal carotid arteries are major blood vessels that supply blood to the brain, and their absence requires the development of collateral circulation pathways to maintain adequate cerebral blood flow. This condition primarily affects the cerebrovascular system and may involve the circle of Willis, which often shows compensatory enlargement of other vessels such as the contralateral internal carotid artery, the vertebrobasilar system, or persistent embryonic anastomotic channels (such as a persistent trigeminal artery). Many individuals with internal carotid absence remain asymptomatic throughout life due to adequate collateral blood supply to the brain. However, some patients may present with headaches, transient ischemic attacks (TIAs), stroke, subarachnoid hemorrhage (due to associated intracranial aneurysms that develop from increased hemodynamic stress on collateral vessels), or seizures. The condition is often discovered incidentally during neuroimaging performed for other reasons. A characteristic finding on imaging is the absence or hypoplasia of the carotid canal on CT of the skull base, which distinguishes true congenital absence from acquired occlusion. There is no specific curative treatment for internal carotid absence itself, as it is a congenital anatomical variant. Management focuses on surveillance and treatment of associated complications, particularly intracranial aneurysms, which occur at a higher frequency in affected individuals compared to the general population. Patients may require regular neurovascular imaging to monitor for aneurysm development. When aneurysms are detected, standard neurosurgical or endovascular interventions may be employed. Antiplatelet therapy or other stroke-prevention strategies may be considered in patients who present with cerebrovascular symptoms.

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