Four-Dimensional Computed Tomography Angiography Demonstrating a Ruptured Basilar Artery Aneurysm Causing Anterior Cerebral Circulation Arrest.

A 61-year-old woman suffered a pronounced subarachnoid hemorrhage. Conventional computed tomography angiography (CTA) showed no enhancement of the intracranial vasculature, whereas there was normal contrast enhancement of bilateral external carotid artery branches. Subsequent four-dimensional computed tomography angiography (4D-CTA) demonstrated active contrast leakage out of a ruptured basilar tip aneurysm, whereas there was no enhancement of the anterior circulation at any time point, consistent with intracranial anterior circulation arrest. This case illustrates that 4D-CTA is superior to conventional CTA for the evaluation of intracranial flow dynamics and delayed intracranial vascular contrast filling.