AVM: Types & Stages
Are there different types of brain AVMs?
All blood vessel malformations involving the brain and its surrounding structures are commonly referred to as AVMs. But several types exist:
- True arteriovenous malformation (AVM).This is the most common brain vascular malformation. It consists of a tangle of abnormal vessels connecting arteries and veins with no normal intervening brain tissue.
- Occult or cryptic AVM or cavernous malformations.This is a vascular malformation in the brain that doesn’t actively divert large amounts of blood. It may bleed and often produce seizures.
- Venous malformation.This is an abnormality only of the veins. The veins are either enlarged or appear in abnormal locations within the brain.
- Hemangioma.These are abnormal blood vessel structures usually found at the surface of the brain and on the skin or facial structures. These represent large and abnormal pockets of blood within normal tissue planes of the body.
- Dural fistula.The covering of the brain is called the “dura mater.” An abnormal connection between blood vessels that involve only this covering is called a dural fistula. Dural fistulas can occur in any part of the brain covering. Three kinds of dural fistulas are:
- Dural carotid cavernous sinus fistula.These occur behind the eye and usually cause symptoms because they divert too much blood toward the eye. Patients have eye swelling, decreased vision, redness and congestion of the eye. They often can hear a “swishing” noise.
- TransverseSigmoid sinus dural fistula.These occur behind the ear. Patients usually complain of hearing a continuous noise (bruit) that occurs with each heartbeat, local pain behind the ear, headaches and neck pain.
- Sagittal sinus and scalp dural fistula.These occur toward the top of the head. Patients complain of noise (bruit), headaches, and pain near the top of the head; they may have prominent blood vessels on the scalp and above the ear
Physicians do not categorize states of arteriovenous malformation (AVM) as it is not a progressive disease. The condition is congenital – occurring at birth – and continues through life unless treated. In many cases, symptoms never appear and the person leads a normal life unaware of the condition. However, an AVM can grow, creating pressure on surrounding areas of the brain, leading to headaches, dizziness and confusion. In addition, the AVM can reach a stage of development where it may burst.