What is "intracranial aneurysm"

n. an aneurysm of a cranial artery

An intracranial aneurysm (also called cerebral or brain aneurysm) is a cerebrovascular disorder in which weakness in the wall of a cerebral artery or vein causes a localized dilation or ballooning of the blood vessel.

Aneurysms in the posterior circulation ( basilar artery, vertebral arteries and posterior communicating artery) have a higher risk of rupture. Basilar artery aneurysms represent only 3%-5% of all intracranial aneurysms but are the most common aneurysms in the posterior circulation.