Intracranial fat

An intracranial aneurysm, also known as a 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. [Source: Wikipedia ]

May Be Caused by
 Common
Corpus callosum lipoma
 Uncommon
Dermoid
Epidermoid
Mature teratoma