
Brain aneurysms are described by shape, size, and location. The three most common shapes are saccular, fusiform, and dissecting. A saccular aneurysm has a neck or stem with a bulge at the end resembling a berry and is often called a berry aneurysm. This type of aneurysm represents 90% of all brain aneurysm cases, according to the Columbia University Department of Neurology. A fusiform aneurysm bulges circumferentially on all sides of the artery. And, dissecting aneurysms are usually associated with traumatic injury. These aneurysms present when there is a tear in the inner layer (of three layers) of the artery wall causing blood to seep between the artery wall layers.
The size of a brain aneurysm is generally measured in millimeters. An aneurysm is considered an increased risk for rupture when its size is 10 mm or greater. However, aneurysms can rupture at any size.
Although they can occur in any artery in the brain, aneurysms most frequently occur in the front part of the brain which supplies oxygen-rich blood to brain tissue.
In all cases, size, shape, and location of the aneurysm determine treatment. Click here to read about common treatment procedures.