An Arterio-Venous Malformation, or AVM, is a congenital (existing at birth) defect of blood vessels within the brain. In healthy brains, oxygen-rich blood is brought into the brain through various arteries, and is passed through smaller and smaller vessels until it reaches capillaries, at which point it can diffuse out into the brain tissue itself. After the brain is done with the blood, it is brought back to the heart via networks of veins. Imagine a city planner, who plans to route cars through networks of freeways and parkways into smaller and smaller residential streets. Everybody eventually gets to the correct location, and everybody is happy.
This does not necessarily happen in the case of AVMs. Instead of the oxygen-rich blood getting to the brain tissue properly through capillaries, it instead routes directly to the system of veins in a short-circuiting of the nearby brain tissue. To bring back the city planner analogy, in this case, our city planner has neglected to provide exits for the cars to get to the residential streets. Nobody is happy.
Symptoms and Diagnosis
Usually, the patient will encounter no adverse effects to let the patient know that they have this issue in their brain. Patients can potentially live normal, healthy lives with this condition, and die of an entirely unrelated cause. However, it is the case that over time, a situation similar to an aneurysm can occur whereby the walls of the AVM will weaken and eventually rupture. As the patient gets older, the chances of such a thing happening increases greatly. Along with the risk of rupture, another risk is that a growing AVM can put pressure on surrounding areas of the brain, as well as the fact that the bypass of blood away from the brain tissue can cause the brain not to function optimally.
As symptoms do not usually manifest until too late, the other way for a patient to discover that they have an AVM is by going in for an unrelated MRI, etc. which would show this development.
Treatment options for AVMs generally fall under embolization, radiation, surgery, and observation. In the case of patients where the risks of treatment far outweigh the benefits, observation is generally the option chosen. For example, an otherwise healthy 90 year old with an AVM that has not ruptured in the past will probably not undergo any type of surgery, as they can be expected to live out the rest of their lives without further issue. However, a younger patient of perhaps 15 would be a far more likely candidate to have some kind of treatment done for the AVM.
Embolization entails placing a foreign object within blood vessels of the AVM to dissuade blood from entering it. This will eventually make the AVM smaller and easier to operate on. In some cases, it has been reported that the AVM has been eliminated through this treatment. The foreign objects used to block the blood vessels can be a special type of glue, metal coils, or other material; these are delivered using a process similar to an angiogram using arteries in the leg to route the needle through the body.
Radiation can also be performed to reduce the size of AVMs. In this case, highly targeted and powerful radiation is focused on the site of the AVM. After the treatment and over a period of months, the AVM will shrink. This potentially has complications: if the radiation is not targeted well, surrounding brain tissue can undergo necrosis. This is not a happy situation.
Surgery to remove the AVM can be performed when the patient is in relatively good health and is stable. A neurosurgeon is potentially able to remove an AVM entirely by removing the arteries and veins responsible for the defect.
Life with an AVM
After a patient discovers that he or she has an AVM, discussion with a neurosurgeon regarding the recommended treatment options is prudent. There are no known triggers for an AVM rupture, so the patient should not feel that they should overly limit their life activities.
If the AVM has ruptured, the patient potentially has a long road to recovery. Including treatment of the AVM itself, deficits in normal brain function can manifest themselves after the patient has completed treatment. This can include, but is not limited to, memory problems, speaking issues, writing issues, weakness, poor muscle control, etc. Much work in terms of rehabilitation will have to be undertaken in order to regain the ability that has been lost. From the reading that I have done, 90% of recovery of brain function that the patient will go through will occur within the first year after the burst; it should be noted, however, that this is not a hard and fast rule.
I am not a doctor, nor do I play one on TV. If you feel that you may have an AVM, please get to the hospital and get yourself checked out as soon as possible. The knowledge presented here has been gleaned from various sources following the discovery that my mother has an AVM, and that it has ruptured. This node is dedicated to her fast recovery.