Procedure allows safer treatment of vessel condition

The new system is called the Onyx Liquid Embolic System, through which liquid onyx is injected in patients to aid in the treatment of the vessel condition.

Normally, arteries, which carry oxygenated blood to the body’s cells, are connected by capillaries to veins that carry oxygen-depleted blood back to the lungs and heart.

AVM, however, is a condition in which the veins and arteries in a small area of the body form a tangled mass. Arteries are connected directly to the veins, with no go-between vessels to regulate blood pressure.

The result is areas of the circulatory system that are weakened and can easily rupture. If the formation happens to be in the brain or spinal area, patients can suffer symptoms ranging from headaches and seizures to paralysis and stroke.

There used to be only two ways to treat the condition, according to SNSI’s Dr. Edwin Cunningham.

“The way we’ve treated them historically was to either excise them – cut them out surgically – or more recently, to use radio surgery, which is a form of focused radiation,” Cunningham said. “The radiation isn’t all that effective – it only works about 70 percent of the time and takes two or three years to work if it’s going to at all.”

The surgery also has serious risks due to the amount of blood flowing through the vessels to be removed. Cunningham said patients can risk death or serious injury due to blood loss during the procedure.

The new system involves inserting a catheter into the blood vessel feeding the tangle of vessels, called the nidus, and injecting the substance, called onyx, to close off the vessel. Surgery is still necessary to remove the tangled mass, but there is less risk of blood loss because the nidus has been closed off.

The injection process has been used in the past, except that the previous system involved injecting NBCA glue –N-butyl cyanoacrylate – which created the potential for problems.

“It’s a very difficult-to-use product,” said Dr. Matthew Burry of St. John’s Clinic-Neurosurgery, of the glue. “It’s difficult to control where it goes, and you only have a few seconds to deal with it before it hardens. You could accidentally glue your catheter in. There’s a lot of anxiety around it.”

Drs. Burry and Cunningham completed classes in March to use the new Onyx Liquid Embolic System.

The new substance is more usable because instead of being adhesive, sticking to everything from the catheter to the vessel, it’s cohesive – sticking only to itself.

“With the onyx, you can literally inject it for hours, and in a much more controlled fashion,” Burry said. “It’s more of a cast of material that just gets blocked in there. That’s where the safety comes from – it’s not a five-alarm fire panic.”

And while the U.S. Food and Drug Administration has approved the substance only for use as preparatory step before surgery to correct AVM, both Cunningham and Burry said that the system could eventually be used as a treatment for smaller AVMs, avoiding surgery altogether. Cunningham pointed out that cases in Europe have already used the procedure in a curative fashion.

“The nice thing about the procedure is that the patient can come in, stay in the hospital a day or two and potentially be back at work a week later,” he added. “Before, with brain surgery, it would take months to recover, even if everything goes well.”

Cunningham has performed the procedure twice; a third procedure was scheduled for June 14. Burry said he has not yet performed the procedure, though he is scheduled to do so in the coming months.