Arteriovenous malformations

An arteriovenous malformation (AVM) is a congenital disorder (one present at birth) of blood vessels in the brain, brainstem, or spinal cord that is characterized by a complex, tangled web of abnormal arteries and veins connected by one or more fistulas (abnormal communications). AVM's can be silent for many years and typically cause problems before the age of 40. The most common symptoms of AVM include hemorrhaging (bleeding), seizures, headaches, and neurological problems such as paralysis or loss of speech, memory, or vision. The frequency of hemorrhage in various series ranges from 30-82%. AVM rupture accounts for 2% of all strokes.

William Beaumont Hospital employs a multidisciplinary approach for treating AVM's involving both radiation oncologists and neurologists to determine the best course of treatment for each individual patient. The various treatment options for AVM's include embolization, microsurgery and Gamma Knife radiosurgery.

Prior to microsurgery or radiosurgery, patients with multiple AVM's or lesions larger than 3 cm usually require embolization. Embolization is the obstruction of a blood vessel. The goal is to reduce the amount of blood flowing into the AVM by filling it with specially designed particles, coil or glue. The clots formed by these agents plug the vessels of the AVM making it more manageable during subsequent procedures by reducing the amount of bleeding during surgery or reducing the target for radiosurgery.

If a patient has already suffered a bleed surgery is often recommended to quickly eliminate the risk of another hemorrhage. The neurosurgeon will expose the AVM and removes its nidus (nest of the AVM). Sometimes removing all the vessels that feed the AVM may be cause too great a risk of bleeding and the residual AVM may then be treated with microsurgery.

As stated above, Gamma Knife radiosurgery may be used to treat residual AVM's following microsurgery or in patients with deep-seated AVM's, where surgery would be difficult, or brain stem AVM's. Gamma Knife treatment is performed by delivering a high dose of radiation in a single treatment session using multiple beams of radiation. Research suggests that the obliteration of small AVM's treated with radiosurgery is 80-90% at 2 years follow up.

Gamma Knife vs. Cyberknife