Treatment is offered is to try to prevent bleeding from the AVM. Bleeding may injure the surrounding brain resulting in a stroke , with possible permanent disability or even death. The risk of bleeding is 4% per year, which means that 4 out of every 100 people with an AVM will have a bleed (hemorrhage) during any one year. AVM's may also produce headaches, seizures and progressive paralysis, and the treatment may alleviate these symptoms.
Anyone can be born with a brain AVM, but these factors may be a risk:
- Being male. AVMs are more common in males.
- Having a family history. Cases of AVMs in families have been reported, but it's unclear if there's a certain genetic factor or if the cases are only coincidental. It's also possible to inherit other medical conditions that predispose you to having vascular malformations such as AVMs.
Complications of a brain AVM include:
- Bleeding in the brain (hemorrhage). Walls of the affected arteries and veins may become thin or weak. An AVM puts extreme pressure on these walls, since no capillaries are available to slow down the blood flow. A hemorrhage may result. A very small (microscopic) hemorrhage causes limited damage to surrounding tissues and is unlikely to produce noticeable symptoms. A larger hemorrhage, however, can cause brain damage and is known as an intracerebral hemorrhage when bleeding occurs in the brain tissue.
- Reduced oxygen to brain tissue. With an AVM, blood bypasses the network of capillaries and flows directly from arteries to veins. Blood rushes quickly through the altered path because it isn't slowed down by channels of smaller blood vessels. Surrounding brain tissues can't easily absorb oxygen from the fast-flowing blood. Without enough oxygen, brain tissues weaken or may die off completely. This results in stroke-like symptoms, such as difficulty speaking, weakness, numbness, vision loss or severe unsteadiness.
- Thin or weak blood vessels. An AVM puts extreme pressure on the thin and weak walls of the blood vessels. A bulge in a blood vessel wall (aneurysm) may develop and become susceptible to rupture.
- Brain damage. As you grow, more arteries may be "recruited" to supply blood to the fast-flowing AVM. As a result, some AVMs enlarge, which displaces or compresses portions of the brain. This may prevent protective fluids from flowing freely around the hemispheres of the brain. If fluid builds up, it can push brain tissue up against the skull — a condition known as hydrocephalus.