Arteriovenous malformations, (AVMs) are abnormalities in the development of the arteries and veins. AVMs are a congenital condition, and therefore present at the time of birth. These abnormalities are often not found until later in life when the individual might present with hemorrhage (bleeding) into the brain. Patients also may present with seizures. Both hemorrhage and/or seizure, can affect the patient’s neurological or brain function including impairment in thinking capacities, consciousness, vision, hearing, walking and balance to name a few.
Treatment of AVMs can represent a surgical emergency depending on the severity of the hemorrhage. Without treatment, the arteriovenous malformations have an estimated annual rate of hemorrhage of approximately 1- 2% per year. This risk of hemorrhage is increased in the year or so after a hemorrhage.
Gamma Knife radiosurgery can obliterate an arteriovenous malformation by damaging the abnormal vessels so that they occlude over time. The response of an AVM to Gamma Knife is a delayed process and the ultimate obliteration of the AVM may take one to two-years, or more.
Treatment strategies for AVMs include: open microsurgery to remove them; embolization (a procedure by which particles are injected into the arteries of the AVM) can be performed as well in certain circumstances, and is usually used in preparation for ultimate surgical removal; or Gamma Knife radiosurgery.
Complications and Outcomes
There are typically no immediate side-effects of the Gamma Knife treatment. Over the year or more that it causes obliteration of the AVM, the radiation from the Gamma Knife also may cause some neurological adverse events including irritation or swelling of the surrounding brain and nerves. Most commonly, these are temporary lasting to weeks to months, and sometimes are treated with steroid medications to alleviate the swelling.
In general, the outcome for patients with arteriovenous malformations treated with Gamma Knife are excellent. Some sub-types of AVMs have an obliteration rate of 80 to 90 percent by two-years. Patients undergoing Gamma Knife do have a continued risk of possible hemorrhage from the AVM until that time point which the AVM has been obliterated altogether, which again may be a year or more after the treatment procedure.