Types of Brain Aneurysms

There are several types of brain aneurysms classified by shape. These are saccular (also called berry) aneurysms, which are by far the most common. Less common are the fusiform and dissecting types. Brain aneurysms may also be classified by:

  • Size (small, large, and giant)

  • Location

  • Cause (such as a mycotic aneurysm, caused by an infection)

Most aneurysms occur where an artery branches, often at the base of the brain. The risk of an aneurysm bursting (rupturing) can be affected by the shape and location of the aneurysm. The treatment options vary, depending on the type of aneurysm, its size, and its location.

Brain viewed from bottom showing brain stem, cerebellum, and arteries.
Using this picture, the surgeon may mark the site of the aneurysm.

A saccular (berry) aneurysm bulges from 1 side of an artery. A neck leads to it.

Closeup of brain showing artery with saccular aneurysm.

A fusiform aneurysm bulges from all sides of an artery. It rarely has a neck.

Closeup of brain showing artery with fusiform aneurysm.

A giant aneurysm can affect more than 1 artery. It's over 2.5 centimeters (cm) wide.

Closeup of brain showing giant aneurysm involving two arteries.

A mycotic aneurysm is caused by an infected artery wall. This type of aneurysm is fairly rare.

Closeup of brain showing mycotic aneurysm on artery.

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