Arteriovenous malformations (AVMs) are blood vessel defects that occur before birth when the fetus is growing in the uterus (prenatal development). The blood vessels appear as a tangled mass of arteries and veins.

They are usually benign. Your eye doctor will monitor them.

AVMs can occur anywhere in the body and have been found in the arms, hands, legs, feet, lungs, heart, liver, and kidneys. However, 50% of these malformations are located in the brain, brainstem, and spinal cord.

Barbiturate comas are used to protect the brain during major brain surgery, such as the removal of arteriovenous malformations or aneurysms

Telangiectasias-- Very small arteriovenous malformations, or connections between the arteries and veins. The result is small red spots on the skin known as "spider veins."