Types of disorders
Types of disorders | Arteriovenous malformation (AVM)
An arteriovenous malformation (AVM) is a congenital malformation of the vascular system, in which an abnormal short circuit (vascular malformation) occurred between arteries and veins during the development of the blood vessels. The result is a tangle of dilated blood vessels (vascular tangle) in the brain.
Normally an artery carries blood with high oxygen from the lungs to the various organs in the body. This goes with high blood pressure by the cardiac pump function. The arteries branch out (like a tree) to smaller and smaller blood vessels with decreasing pressure until finally the smallest blood vessels, capillaries (capillaries) are reached in the organs. In the capillaries oxygen delivery takes place to the tissues. Then the oxygen poor blood goes under low pressure via the veins to the lungs, where the blood is again oxygenated.
In case of an AVM, the network of the smallest blood vessels (capillaries) is missing. As a result there is a direct connection between the arteries and veins, so no oxygen transfer occurs (short circuit or malformation). The second consequence is that the local high pressure in the arteries is transferred directly to the veins, resulting in dilatation of these veins. This has consequences both locally in the brain as well as to the heart because of the increased amount of circulating blood to needs to be pumped through the body. Therefore, an AVM, both can have an effect in the brain as well as on the entire vascular system and the heart.
The cerebral AVM is seen especially in younger people, because it is a congenital vascular disease. Usually, an AVM causes symptoms in the course of one’s life. Most patients are seen for the first time at the age of 20 to 40 years old. The symptoms from a cerebral AVM are cerebral hemorrhage, epilepsy, headache and neurological symptoms (paralysis, speech problems, vision problems, etc.). Sometimes an AVM is discovered by accident on a scanner (CT or MRI).
Only a very small portion of cerebral AVMs makes no complaints during the course of one’s life. In our team every patient with an AVM is discussed individually. The treatment or combination of treatments with the lowest risk and most optimal result is advised. These treatments are usually done in several steps (phases). At intervals of several months a patient repeatedly undergoes his/her treatment to gradually reduce the AVM. For the specific treatments please read the chapter endovascular and surgical treatment.
The diagnosis of an AVM is made by means of a CT-scan or MRI. Subsequently, angiography (blood vessel examination) has to unravel the tangle of vessels. The angiography study is described in the chapter endovascular examinations.