The abnormal formation or development of blood vessels is generally referred to as vascular malformation. Abnormal blood vessel structure is usually congenital, meaning it is present at birth.Abnormal blood vessels can create problems with the normal flow of blood by preventing enough oxygenated blood from filling capillaries, the tiny blood vessels that connect the body’s arteries and veins. In some people with vascular malformations, blood travels directly from the arteries into the veins without ever having reached the capillary system. When blood does not fill some capillaries, it creates a lack of oxygen and a build up of wastes in the body tissue that would normally get blood from those capillaries. These potentially dangerous malformation are called arteriovenous malformations, or AVMs.
Other, rarer vascular malformations are:
- Venous angiomas, abnormally formed veins that usually appear as a mass or tangle of veins;
- Cavernous angiomas, or a cluster of tightly packed, enlarged, capillary-like blood vessels that may resemble a raspberry;
- Telangiectasis, or a clump of enlarged capillary-sized vessels; and
- Arteriovenous fistulae, blood vessel malformations that arise because of an injury.
What are the symptoms?
Most people with AVMs experience few, if any, symptoms. Though a malformation may be present at birth, symptoms often do not appear until a person is 20 or older.
Unfortunately, many people with an AVM do not know they have it until they experience a hemorrhage, or the sudden escape of blood from a ruptured blood vessel, or a hemorrhagic stroke, which may occur when an AVM bursts inside the brain and can result in paralysis, loss of vision or speech, and even death.
Less severe symptoms include:
- Headaches; and
- Neurological problems, such as learning disorders, or ischemia, or lack of oxygen, which can affect muscle control, vision, or speech.
Causes And Risk Factors
Vascular malformations are almost always congenital. No genetic, demographic, or environmental risk factors for vascular malformations have been clearly identified.
In rare instances, vascular malformations can be caused by trauma or are associated with inherited neurological disorders such as Sturge-Weber disease.
Though some AVMs are found when a person consults a physician with concerns about seizures or headaches, about half of all AVMs are not found until they hemorrhage. However, in other cases, the physician can diagnose malformations after performing a careful medical history and physical examination, which includes listening to a person describe symptoms.
Some large cerebral (brain) AVMs may produce audible bruits, or abnormal whooshing sounds made by the turbulent flow of blood.
To confirm a suspected vascular malformation in the brain, physicians use one or more of the following tests:
- Computed tomography (CT) scans;
- Magnetic resonance imaging (MRI);
- Magnetic resonance angiography (MRA); or
In making treatment decisions, physicians evaluate the highly individual nature of AVMs and make recommendations case-by-case based on the exact location of any malformation and the specific symptoms and risks posed by the malformation.
People diagnosed with a vascular malformation may only require a physician monitoring them closely for any signs of a hemorrhage; this type of management is often called watchful waiting. Stable AVMs may never require treatment.
Generally, AVMs are treated with:
- Surgery (the surgeon ties off and removes the arteries that feed blood into the malformation and then removes the malformation);
- Embolization (using a thin, flexible tube called a catheter, a physician introduces a substance into a blood vessel to cause a clot and permanently block off that blood vessel); and
- Radiosurgery (the physician aims highly focused radiation directly through the skull and brain and into the malformation itself to damage the blood vessels that comprise the malformation and eventually cause them to close).
Frequently, AVMs are being treated with a combination of these three therapies.