A Rare Arterial Congenital Variant: The Internal Carotid Artery Agenesis.

The cerebral arterial circle has been extensively investigated in recent literature. A scarce congenital arterial variant is considered the internal carotid artery (ICA) agenesis. The computed tomography angiogram of a 65-year-old female patient is reported. The left ICA was absent in the head and neck region. Intracranially, the left middle cerebral artery derived from a hyperplastic posterior communicating artery, and the first segment of the left anterior cerebral artery was absent. This variant corresponds to Lie's type A agenesis of the ICA that coexisted with an aneurysm on the anterior communicating artery. Overall, the absence of ICA has a prevalence of <0.01%. It was associated with clinical symptoms of cerebrovascular insufficiency or intracranial aneurysm. Although extremely rare, the congenital variant is important for radiologists and neurosurgeons planning a surgical procedure in the area.