Unruptured intracranial aneurysms are found in ~3–5% of healthy adults, with ~85–90% never becoming symptomatic or rupture. The overall five-year risk of aneurysmal rupture is ~3% and is highly influenced by vascular risk factors such as smoking, hypertension, and psychostimulant use, as well as nonmodifiable risk factors such as aneurysm size, prior aneurysmal subarachnoid hemorrhage, and female sex. Additionally, those with certain genetic and connective tissue disorders such as Ehlers–Danlos syndrome, Marfan syndrome, and polycystic kidney disease are predisposed to the formation of intracranial aneurysms. It is estimated that ~20% of patients with a history of a ruptured aneurysm also have an unruptured aneurysm at a separate location.