Arteriovenous Malformation

Treatment

While studies show that the day-to-day risk of hemorrhage or other problems from an intracranial arteriovenous malformation (AVM) is small, this risk persists over a person's lifetime. Therefore, treatment may be recommended for otherwise healthy young people who have AVMs. The treatment for any AVM has to be carefully individualized to minimize risk and maximize the chance for removing or obliterating the lesion. Treatment decisions require the expertise of a team of neurosurgeons, neurologists and neuroradiologists familiar with AVMs and the treatment options. Generally, a neurologist with expertise in vascular problems will serve as the "quarterback" of the care team, coordinating the care and serving as the main contact for the patient.

An arteriovenous malformation is treated in three main ways:

• Surgical removal
• Radiation (stereotactic radiosurgery)
• Endovascular embolization

Surgical Removal (Resection)

Advances in surgical technique have made surgical treatment relatively safe and effective. A section of skull is removed temporarily to gain access to the AVM. The neurosurgeon, aided by a high-powered intraoperative microscope, seals off the AVM with special clips and, using small cautery tools, carefully removes it from surrounding brain tissue. Sometimes the instrument of choice is a laser. The skull bone is then reattached, and the incision in the scalp is closed.

Occasionally, the surgery is performed while the patient is awake (awake brain surgery). The patient's responses to questions during the procedure help the surgeon avoid injuring critical areas of the brain that control speech or movement.

In almost all cases, an immediate intraoperative or postoperative angiogram to confirst complete removal of the AVM is obtained while the patient is under general anesthesia. If removal appears incomplete, the patient is immediately returned to the operating room for further surgery.

Stereotactic Radiosurgery

Stereotactic radiosurgery uses precisely focused radiation to destroy the AVM. This procedure does not require general anesthesia or an incision. The radiation causes the AVM vessels to slowly clot off from one to three years after the treatment until the AVM is obliterated. This treatment works best for small AVMs and those that have not caused a life-threatening hemorrhage. In a 2003 study, Mayo neurosurgeons reported on results of radiosurgery treatment in 144 patients who were followed for five to 14 years. They reported that most AVM patients are protected from the risk of future hemorrhage. Seventy-three percent had excellent to good results; 14 percent had major neurological injuries or died and 11 percent were unchanged. See abstract.

Another study looked at results of radiosurgery to treat AVMs in more inaccessible deep brain locations. The reseachers found that less than half of the 56 patients with deeply located AVMs were cured of the future risk of hemorrhage without new neurological deficits. This experience emphasizes the difficulty in treating patients with deeply located AVMs, the majority of whom are not good candidates for resection or embolization. See abstract.

In a 2006 paper, Mayo Clinic physicians reported on results of radiosurgery to treat AVMs in children . Twenty-six patients (68 percent) had excellent outcomes (as defined by complete obliteration of the AVM with no new neurological deficit) after treatment Twelve patients (32 percent) remained unchanged (incomplete obliteration but no new deficit). See abstract.

Endovascular Embolization

This procedure is similar to a cerebral arteriogram. A catheter is inserted into a leg artery and threaded through the body to the brain arteries. The catheter is positioned in one of the feeding arteries to the AVM and small particles of a gluelike substance are injected to block the vessel and reduce blood flow into the AVM. Embolization alone does not often cure an AVM so it is usually not the primary treatment. Embolization is often done before surgery to reduce the chance of bleeding during the operation, or to reduce the size of the AVM so stereotactic radiosurgery or conventional surgery can be more effective. In some large AVMs that appear inoperable, embolization may reduce strokelike symptoms by redirecting blood back to the normal brain tissue.