AVM: Multimodal approach for individualized treatment

May 19, 2018

Mayo Clinic has neurosurgeons with expertise in the full range of treatment options for people with arteriovenous malformations (AVMs). That multimodal capability — encompassing microsurgical resection, endovascular embolization, stereotactic radiosurgery and awake surgery, as well as watchful waiting — allows treatment for these complex cases to be individualized to each patient.

"This disease has so many variables that no single strategy would work for all patients. It's important to have all these strategies available, and to be able to perform them in a very advanced way, to ensure that the patient is receiving the best possible care," says Rabih G. Tawk, M.D., a neurosurgeon at Mayo Clinic in Jacksonville, Florida.

Mayo neurosurgeons have pioneered surgical techniques for AVM and stereotactic radiosurgery, and developed the radiosurgery-based AVM grading score to predict outcomes after Gamma Knife treatment. As a major neurosciences center, Mayo has a large group of neurosurgeons with experience in diverse AVM treatments.

"Some of us have expertise in radiosurgery; others have experience in surgery and embolization, or embolization alone," says Giuseppe Lanzino, M.D., a neurosurgeon at Mayo Clinic in Rochester, Minnesota. "We can be comprehensive in our approach but use our individual strengths in various techniques to the patient's advantage."

Broad, team-based care

Mayo Clinic sees more than 300 people with AVM and other vascular malformations every year. The complete integration of Mayo's neurological and neurosurgical services helps ensure efficient patient care.

"Having different specialists working under the same umbrella improves communication and patient flow. Often, patients are given a diagnosis and a therapeutic plan within the same day," Dr. Lanzino says.

Patients typically are evaluated by a neurologist, who might prescribe or adjust medications, particularly if the patient is experiencing seizures. Detailed imaging, including cerebral angiography, is done to assemble the information needed to make treatment decisions.

"We now also use holography, 4D MRI and 3D printing to assess an AVM before treatment," says Bernard R. Bendok, M.D., chair of neurosurgery at Mayo Clinic in Phoenix/Scottsdale, Arizona. "This allows the treating team to think through management options more clearly and to relay the consensus opinion back to the patient in a more comprehensible way."

The treatment team considers the AVM's size, location and blood flow, as well as whether the patient is experiencing symptoms and whether the AVM is robbing adjacent brain tissue of blood. "If the patient is asymptomatic, sometimes it is better to leave the lesion and monitor it," Dr. Tawk says. "But if treatment is needed, we discuss which modality or modalities would be best. The goal is to solve that particular patient's problem, with minimal risk."

If the AVM has bled or is readily accessible, surgical resection is generally recommended. An AVM in a deeper location might be treated with stereotactic radiosurgery, to avoid damaging brain tissue during resection. Endovascular embolization might be used to stem blood flow, with possible follow-up surgery or stereotactic radiosurgery. "If we know the AVM is going to bleed heavily during surgery, we do embolization first to cut the blood supply and make the surgery safer," Dr. Lanzino says.

Large vascular lesions are sometimes treated with volume-staged stereotactic radiosurgery. Staging treatment into multiple radiological sessions allows a higher radiation dose to be delivered to the entire AVM volume while reducing radiation exposure to the adjacent brain. In a retrospective study published in the April 2017 issue of Neurosurgery, Mayo Clinic researchers found that 34 patients with large AVMs treated with volume-staged radiosurgery at Mayo had a low rate of adverse radiation effects. The median follow-up period was eight years.

"In our small study, we found that patients with AVMs typically considered too large for radiosurgery could be safely managed with this approach. Overall, 71 percent of patients achieved AVM obliteration with a low rate of radiation-related complications," says Bruce E. Pollock, M.D., a neurosurgeon at Mayo Clinic's campus in Minnesota.

Stereotactic radiosurgery is sometimes followed by surgical resection. "An AVM treated with radiosurgery might still have a small portion that doesn't respond, even after five years. But then it's relatively easy to do surgery on that smaller AVM," Dr. Lanzino says.

Mayo Clinic has experience with even the most challenging AVMs. Dr. Tawk cites a patient with a ruptured AVM and aneurysm who was initially treated with endovascular embolization to stem the AVM's high blood flow. "Once she recovered good functional outcome, we brought her back in and performed surgery with her in a seated position, to get access to the aneurysm," Dr. Tawk says.

Surgery in the sitting position carries risk, including air embolism. "But with help from our colleagues in anesthesiology, we were able to do this procedure safely," Dr. Tawk says. "The AVM is gone, and the patient is doing great."

Awake surgeries

Mayo Clinic also uses awake surgery for select patients with intracranial neurovascular pathologies. That option can be particularly helpful for patients with an AVM that is causing seizures.

In a retrospective review of nine procedures, published in the September 2017 issue of World Neurosurgery, Mayo Clinic neurosurgeons reported that awake surgery can be safe for these select patients while offering the advantages of greater safety, a shorter hospital stay and reduced cost. Two patients in the study had a Spetzler-Martin grade 2 AVM with seizure activity. One of the AVMs was near Wernicke's area; the other patient's lesion abutted right-sided hand, lip and tongue sensorimotor activity. Language and motor mapping were used in the respective awake surgeries, and both achieved complete AVM resection.

"The functional delineation of tissue surrounding the AVMs permitted the surgeon to more confidently remove the pathologies," Dr. Bendok says. "The patients had no permanent postoperative neurologic deficits, and both are seizure-free."

Dr. Lanzino notes that decisions about whether and how to treat AVM should take into account the patient's long-term likelihood of bleeding. Many people with an AVM are young and face a lifelong risk of bleeding. A Randomized Trial of Unruptured Brain Arteriovenous Malformations (ARUBA) was halted after about three years because of results indicating that the risk of death or stroke was significantly lower in the group of trial participants who received medical management versus the interventional therapy group. That trial had several limitations.

"We don't treat patients with AVM to take away the risk of bleeding for three years — we take the risk away for a lifetime," Dr. Lanzino says. "What ARUBA has shown is that if treatment is undertaken, it must be done safely. At Mayo Clinic, we have a long tradition of research and of treating even the most complex lesions. We have in-depth knowledge of this disease, which guides our treatment decisions."

For more information

Pollock BE, et al. Volume-staged stereotactic radiosurgery for intracranial arteriovenous malformations: Outcomes based on an 18-year experience. Neurosurgery. 2017;80:543.

Aoun RJN, et al. Awake surgery for brain vascular malformations and moyamoya disease. World Neurosurgery. 2017;105:659.