Arteriovenous Malformation (AVM)
An AVM is a tangle of abnormally formed blood vessels (arteries and veins), where blood flows directly from the arterial system to the venous system without passing through a capillary system. AVMs can result in bleeds, seizures, stroke-like symptoms (vascular steal phenomenon), and mass effect on surrounding structures. An AVM can occur anywhere in the body, but brain and spinal AVMs present substantial risks when they bleed. AVMs can also be associated with aneurysms, which increases the risk of bleeding.
Some 12% percent of people with AVMs will experience symptoms varying in severity. AVMs can irritate the surrounding brain and cause seizures or headaches. They can also result in hemorrhage from stress on the abnormal blood vessels. Any of the following symptoms may occur:
- Seizures, new onset
- Muscle weakness or paralysis
- Loss of coordination
- Difficulties carrying out organizational tasks
- Visual disturbances
- Language problems
- Abnormal sensations such as numbness, tingling or spontaneous pain
- Memory deficits
- Bowel/bladder dysfunction
AVMs are usually diagnosed through a combination of magnetic resonance imaging (MRI), magnetic resonance angiography (MRA) and cerebral catheter angiography. These tests may need to be repeated to analyze a change in the size of the AVM, recent bleeding or the appearance of new lesions.
Treatment options for AVMs include microsurgery, stereotactic radiosurgery (SRS), endovascular treatment, and conservative monitoring with serial imaging. While surgery is the most invasive treatment, it provides the most conclusive removal of the AVM. SRS is a minimally invasive modality that applies focused radiation to the abnormal vessels. However, SRS can take up to two years for the effect to occur, there is no guarantee of obliteration, and during the two year time period there is increased risk of bleeding. Endovascular treatment is not considered a mainstay, stand-alone treatment. It is usually used as an adjunct to surgery, and sometimes radiation. Endovascularly treated lesions have a high risk of recurrence if treated by only this modality. Patients should have an in-depth discussion with their surgeon regarding the best treatment algorithm for their particular situation.
Patient outcome depends on the size and location of the AVM, severity of bleeding, and the extent of neurological symptoms on presentation. Many patients undergoing microsurgery make an excellent and quick recovery after several days of hospitalization. Following or during surgery, an angiogram is performed to assure complete removal of the AVM. If the AVM is completely removed, the patient is considered cured.