Arteriovenous malformation (AVM) is a congenital vascular anomaly in which the feeding arteries are directly connected to a venous drainage network without interposition of a capillary bed.

A brain aneurysm is a bulging, weakened area in a blood vessel in the brain. If the brain aneurysm expands and the blood vessel wall becomes too thin, the aneurysm will rupture and bleed into the space around the brain, called a subarachnoid hemorrhage.

Cavernous malformations (CMs), also known as cavernomas, are vascular abnormalities of the brain that are comprised of clusters of abnormal, hyalinized capillaries.