Agenesis of the Left Internal Carotid Artery Associated with Dolichoectatic Intracranial Arteries.

A 28-year-old man without a significant medical history visited our hospital complaining of a headache. Computed tomography (CT) demonstrated thick, calcified vertebral artery (VA) and basilar artery (BA), despite the patient being young. Magnetic resonance angiography demonstrated the absence of the left internal carotid artery (ICA). The right ICA, the bilateral VA, and the BA were well developed and dolichoectatic. CT revealed the absence of the carotid canal on the left side. The condition was diagnosed as congenital agenesis of the left ICA with dolichoectatic changes in 3 other arteries. In a young patient with thick, calcified intracranial arteries, close examination is necessary, because vascular anomalies such as ICA agenesis may exist.