Could you describe a brain aneurysm to me?

Vessel swelling: Aneurysms are swellings of arteries which cannot withstand the internal pressure. A brain aneurysm is such a thing in an artery of the brain. Some are inherited. The risk is that the swelling gets too big and pushes things around or breaks through the wall pouring blood under pressure into the brain and causing damage or death depending upon which vessel has the aneurysm.