A<unk>  or brain<unk>  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.
A common location of<unk> s is on the arteries at the base of the brain, known as the Circle of Willis. Approximately 85% of<unk> s develop in the anterior part of the Circle of Willis, and involve the internal carotid arteries and their major branches that supply the anterior and middle sections of the brain. The most common sites include  the anterior communicating artery (30-35%), the bifurcation of the internal carotid and posterior communicating artery (30-35%), the  bifurcation of the middle cerebral artery (20%), the bifurcation of the basilar artery, and the remaining posterior circulation arteries (5%).
Cerebral aneurysm
Intracranial aneurysms
Carotid artery dissection
Intracranial berry aneurysm
Subarachnoid hemorrhage
Arterial thrombosis
Cerebral vasculitis
Carotid artery stenosis