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Oxford Researchers Develop New Aneurysm Treatment

by Christine DeGennaro, Writer | May 21, 2010
A new concept for stent
design may make current
models a thing of the past.
Intracranial aneurysms occur in 2-5% of people living in the United States, with 27,000 suffering ruptures of saccular aneurysms each year. Brain aneurysms - localized widening of blood vessels - can be caused by high blood pressure or head injuries. As the vessel widens, its walls weaken and balloon to form a blood-filled cavity. These can rupture and bleed into the brain causing a hemorrhagic stroke, which can be fatal.

Physicians currently look to surgical clipping and endovascular coiling as the gold standard for treating intracranial aneurysms. But clipping requires open-brain surgery, and the clots created during either procedure to prevent and stem bleeding cannot be reabsorbed by the body after the body has healed. This creates permanent pressure on the surrounding brain area.

To combat these problems, Dr. Zhong You at Oxford's Department of Engineering Science and his colleagues in the field of neurosurgery have developed what they call a "flow-diverting intracranial stent."

"The flow-diverting stent works by shielding the aneurysm from arterial pressure, lowering the risk of aneurysm rupture and inducing thrombus formation. The clot is able to break down and be reabsorbed allowing the aneurysm to completely heal," said Dr. Brijesh Roy with Oxford's spin-off company, Isis Innovation, Ltd.

The stent's design presented a number of challenges to Dr. You and his colleagues. It had to be flexible enough for use in the delicate intracranial vasculature, yet strong enough to support the damaged blood vessel. Researchers also needed the stent to have a high surface area suitable for shielding the aneurysm from arterial pressure once it was deployed, but the design also had to collapse into a small enough package for minimally invasive delivery with easy expansion at the aneurysm site.

Dr. You, who has a long history of working on "motion-structures" using origami-type structures, got his design inspiration from the fern plant.

"He noticed that when ferns grow, they begin life as tightly folded stems and then as they grow they unfurl to have very high surface areas producing large amounts of shade, equivalent to the shielding required by the blood vessel wall," Dr. Roy said.

When the stent is in its collapsed state, the leaves are able to overlap, allowing tight packing. The flow-diverting stent can therefore be introduced into the brain using a small plastic tube which is inserted into the femoral artery near the groin, then fed through the patient's vascular system to the site of the aneurysm. This is the same method currently employed to use stents that are inserted at the back of the neck to keep endovascular coils in place during treatment.

The new stent is also made to be cost-effective on the manufacturing end, as its straightforward design uses readily available and biocompatible nitinol, an alloy of nickel and titanium.

In terms of development, the team is currently optimizing the laser cutting of the stent, and will next be choosing a widely available stent delivery mechanism, with animal trials beginning by the year's end. Researchers expect clinical trials to begin within two years.

Dr. Roy believes that, once approved, the device will be a major breakthrough in the way we treat intracranial aneurysms.

"The flow-diverting stent has the potential to remove the need for endovascular coiling, making treatment of aneurysms faster, safer and more effective."