ARTICLE IN BRIEF
Experts discuss the risks and benefits of two types of intervention for people with cerebral aneurysms and arteriovenous malformations.
Aneurysms or arteriovenous malformations (AVMs) that are discovered incidentally in healthy people pose a treatment dilemma for physicians — how and when should they intervene?
These issues were the focus of debate for a November meeting sponsored by North Shore University Hospital's Harvey Cushing Institute for Neuroscience and Columbia University Medical Center.
The understanding of the natural history of AVMs, a tangle of abnormal vessels in the brain, is controversial, according to David Chalif, MD, chief of neurovascular neurosurgery and co-director of the North Shore-Long Island Jewish Brain Aneurysm Center. The question is whether the benefits of intervention outweigh the risks.
BENEFITS-RISKS OF TREATMENT
Roberto C. Heros, MD, a neurosurgeon at the University of Miami, said the benefits of intervention should be carefully considered when the unruptured AVM is small (under 3 centimeters) and located deep in the brain.
“We know that we can do well if we select the right patients,” said Dr. Heros. He said that embolization works to cure AVMs but only if the AVM is totally obliterated. Only about 15 percent of AVMs are completely obliterated with embolization. Microsurgery and radiosurgery may also be effective as adjunctive treatments with embolization for treating selective AVMs. Radiosurgery could be used for small AVMs without the need for pre-treatment embolization.
Much of the symposium discussion focused on aneurysms. According to Columbia University's E. Sander Connelly, MD, associate professor of neurological surgery and surgical director of the neuro-intensive unit, an aneurysm larger than 5 to 7 millimeters and its location increase the risk for a rupture. Other risk factors for aneurysmal rupture and bleeding include age, hypertension, cigarette smoking, family history, and certain kidney diseases. The data were reported with results of a 2008 study in the journal Neurosurgery.
It is not clear how many people will develop symptoms or how many aneurysms will rupture, Dr. Chalif said. He suspects that 3 to 5 percent of all adults may be walking around with a brain aneurysm. In the US, about 30,000 to 50,000 people have ruptured aneurysms at an average age of 55; one-third die before they reach a hospital, and almost another third arrive at the hospital close to death.
Numerous studies have shown a strong correlation between a large size of an unruptured aneurysm and the hazard of bleeding.
Those who survive require urgent intervention. A growing number of centers, including North Shore and Columbia, offer a less invasive technique called endovascular coiling. A micro-catheter is threaded through the carotid artery, and through this catheter, platinum coils are directed into the aneurysm dome.
The efficacy of coiling versus clipping for ruptured aneurysms was discussed by Cameron G. McDougall, MD, chief of endovascular surgery at the Barrow Institute in Arizona. Dr. McDougall and his colleagues enrolled 500 aneurysm patients into a randomized trial where they were treated with either clipping or coiling.
Once a patient was enrolled in a particular treatment group, the neurosurgeon evaluated the patient to determine whether the treatment was appropriate. If it wasn't, that patient was crossed over into the other treatment group. Almost 80 of the 500 patients were reassigned following the assessment.
“Large aneurysms are generally not good for coiling,” said Dr. McDougall. A year after the intervention, they followed up on 86 percent of the patients in both study groups. Sixty-five percent of the 203 patients who had surgical clipping had a good outcome at one year compared to 74.2 percent of the 198 patients who had a coiling procedure. The findings of this randomized trial have not been published yet.
At North Shore, Dr. Chalif works closely with interventional neuroradiologist Avi Setton, MD, an expert in the coiling technique. They study each case and determine what would be the best treatment. They also combine both techniques when necessary.
Investigators of the multicenter International Subarachnoid Aneurysm Trial (ISAT) reported in Lancet in 2002 that coiling had lower morbidity and mortality than clipping. But the neurosurgical community has challenged the data and other studies are now underway to come to a consensus, Dr. Chalif said.
Columbia's Byron Stookey Professor of Neurosurgery Robert A. Solomon, MD, said that the historical importance of endovascular surgery for cerebral aneurysms rivals the introduction of the microscope, but it is still not the answer for most complicated giant aneurysms. Aneurysms of the middle cerebral artery are still the domain of vascular neurosurgeons and microsurgery remains a viable option for some aneurysms in other locations, he said. Also, the long-term durability of the coiling material remains a concern. Therefore, he added, in young patients with unruptured aneurysms, surgical clipping by a surgeon that specializes in aneurysm surgery, may still be preferable to endovascular treatment.
“I think this (coiling) is the future,” Dr. Chalif said, demonstrating the procedure in real-time on a computer screen. Dr. Setton agreed. “Patients should be exposed to both options,” he said.
THE COILING TECHNIQUE
The less invasive coiling technique, which is done under anesthesia, was developed more than a decade ago, with instruments borrowed from interventional cardiologists.
A hair-thin catheter is introduced through the groin and sent up into the neck through the artery and into the base of the aneurysm. Coiling works best if the neck of the aneurysm is small, like the opening of a balloon. Once the flexible catheter is in place, the radiologist carefully guides a platinum coil into the aneurysm, gliding it round and round until it fills up the space — thus cutting it off from the normal brain blood vessel and preventing another rupture.
“Coiling of an aneurysm depends on size, configuration, and neck width. These anatomical factors dictate feasibility to completely obliterate an aneurysm, as well as the risk and the complexity of the procedure. The main risk is an embolic event, inducing stroke and rupture during coiling. We have techniques to reduce these hazards,” said Avi Setton, MD, an interventional radiologist at the Harvey Cushing Institute of Neuroscience at the North Shore-LIJ Health System. “It is important to note that aneurysm post coiling requires imaging monitoring to confirm persistent obliteration or reveal recanalization. This is why proper selection is so important.”
FOR MORE ABOUT ANEURYSMS AND ARTERIOVENOUS MALFORMATIONS
See www.neurotodayonline.com for these Neurology Today articles:
* “Surgical Treatment of Unruptured Aneurysms Reduces Mortality But Long-Term Follow-Up Needed,” July 17, 2008.
* ”A Senator's Illness and New Studies Focus Attention on How to Treat Brain AVMs,” Jan. 16, 2007.
* “Endovascular Coiling Favored in New Analysis of ISAT Aneurysm Data,” November 2005.