Blister. Weak spot in vessel where a blister forms. This is called an aneurysm. Often treated with coil embolization or surgical clipping. Can be life threatening. Needs to be followed with cta or mra.
Weak blood vessel. Cerebral aneurysms are outpouchings off of a brain blood vessel. If they rupture, they cause a subarachnoid hemorrhage, a life-threatening kind of brain bleed. Unruptured aneurysms can be treated by surgical clipping or endovascular coiling, which is much less invasive. He should have the pros and cons of each explained by a neurosurgeon.
Cerebral aneurysm. An cerebral aneurysm is a focal outpouching or dilation of a portion of an artery providing blood to the brain.