What is an AVM?
An AVM is a cluster or nest of blood vessels that create a direct connection between arteries and veins of the brain. This direct connection creates what is called a shunt where the oxygenated blood by-passes brain tissue due to the improper connection of arteries and veins. The blood then flows directly back to the heart never having the opportunity to feed the brain the proper nourishment it needs from the oxygen rich blood.
In a normal circulatory system, arteries and veins are connected between a network of capillaries. Capillaries are extremely small vessels which have very thin walls that allow for an exchange of newly oxygenated blood to tissues and to pick up deoxygenated blood for veins to take back to the heart and lungs for re-oxygenation.
AVMs can be located virtually anywhere in the body, but are common to form in the vascular system of the brain. AVMs are said to be congenital and are formed either during the gestation period or during birth.
Symptoms?
Most people do not display symptoms but the more generalized symptoms can be seizures and headaches. Symptoms are not the same for each individual and are dependent on the location of the AVM within the brain due to the fact that each part of the brain is responsible for different functions of the body. Diagnosing an AVM can be tricky due to the fact that symptoms are not consistent from patient to patient and it is not uncommon to find that most times AVM's are found incidentally on studies that are being done for other health issues. AVMs are also detected when the individual is actively bleeding or hemorraging at the AVM site.
Complications?
AVMs can damage the brain in three major ways:
- reduction of the proper amount of oxygen to brain tissue
- bleeding or hemorrage into the tissues of the brain
- compressing parts of the brain or spinal cord due to the enlarged mass of blood vessels taking
up space that would normally house normal brain tissue or spinal cord
Where do AVMs form in the brain?
They can basically form wherever arteries and veins are located deep within or on the surface of the brain. They can also form on the spinal cord. Typically though, they form either in the dura or pia mater layers of the brain.
Treatment?
Depending on the size, location, and the factors of each individual's case there are a few options for treatment of AVMs.
- Conventional Surgery is used to completely remove the AVM.
- Endovascular Embolization where a surgeon inserts a catheter through an artery to the
AVM site and inserts a substance to occlude or plug the AVM.
- Radiosurgery where localization of the AVM is achieved and then a beam of highly focused
radiation is aimed directly over the AVM. This highly intense beam of radiation damages the
vessel walls and gradually the vessels of the AVM will degenerate and close to resolve the
AVM.
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