Aneurysms of the cerebral vasculature are relatively common. A recent systematic review collecting data from many countries reported a prevalence of 0.4% and 3.6% in retrospective and prospective autopsy studies, respectively, and 3.7% and 6.0% in retrospective and prospective angiographic studies, respectively (1). The angiographic studies likely overestimate the true prevalence due to a selection bias, whereas the retrospective autopsy studies likely underestimate the true prevalence due to an inability to review the original material. Eighty-five percent of saccular aneurysms of the cerebral vasculature occur in the circle of Willis (2). Multiple aneurysms are seen in 30% of patients. Most are small and asymptomatic, but each year, approximately 30,000 people in the United States suffer a rupture, peaking in the sixth decade (3). When an intracranial aneurysm ruptures, it may bleed into the brain parenchyma resulting in a parenchymal hemorrhage, or more often, it will bleed into the subarachnoid space, resulting in a subarachnoid hemorrhage (SAH). A SAH is a catastrophic event with a mortality rate of 25% to 50%. Permanent disability occurs in nearly 50% of the survivors, thus, only approximately one-third of patients who suffer a SAH have a positive outcome.