Spinal Arteriovenous Malformation (AVM)

A spinal arteriovenous malformation (AVM) is a tangle of blood vessels on or near your spinal cord. This happens when an artery connects directly to a vein, bypassing your capillaries.

Capillaries play an important role in moving blood through your body. Usually, your arteries carry oxygen-rich blood from your heart to your spine. Capillaries branch out of arteries to take blood to your spinal cord and tissues. Your spinal cord removes oxygen from your blood. Your blood then moves away from your spinal cord in your veins, back to your heart.

The rerouting of blood affects how much oxygen is delivered to cells, and it’s usually less than what they need. It can cause blood vessels to enlarge, change in pressure and burst, leading to a hemorrhage (excessive bleeding). This is life-threatening. Treatment is available to prevent this complication.

You might hear your healthcare provider refer to a spinal AVM as a “spinal arteriovenous shunt.”

What are the types of spinal AVM?

There are five types of spinal vascular (blood vessel) malformations, including both spinal arteriovenous malformations (AVM) and spinal arteriovenous fistulas (AVF). Both AVMs and AVFs are abnormal connections between an artery and a vein. AVMs happen in spinal cord tissue. AVFs happen in the dura mater. This is the material that surrounds your spinal cord.

The five types include:

• Type I: Dural AVF: Located in the dura mater, or the outer layer of your spinal cord.
• Type II: Intramedullary glomus AVM: Located inside of your spinal cord.
• Type III: Intramedullary juvenile AVM: Located inside of your spinal cord and outside, involving surrounding tissue. This most often affects children and young adults.
• Type IV: Perimedullary AVF: Located in the tissue surrounding your spinal cord.
• Type V: Extradural AVF: Located in the space outside the dura mater.

To note: An AVM rupture may cause more severe symptoms, as there isn’t a covering (the rupture goes directly into tissue) versus AVFs, which usually have a covering, as they reside in the dura matter.

How common is a spinal AVM?

A spinal AVM is the most common spinal blood vessel condition. The exact rate of occurrence is unknown because many people don’t know they have a spinal AVM unless they have symptoms or an unrelated medical test detects it. AVMs are considered uncommon.