An aneurysm is an abnormal bulge or ballooning in the wall of a blood vessel. An aneurysm can burst. This is called a rupture. A ruptured aneurysm causes bleeding inside the body and often leads to death. Some aneurysms may not cause symptoms. You might not know you have an aneurysm even if it is large.

A brain aneurysm is a weak spot in the wall of a blood vessel inside the brain that can sometimes burst and cause a subarachnoid hemorrhage (SAH).Think of a weak spot in a balloon and how it.