Flow Diversion for Brain Aneurysms

What Is Flow Diversion?

A flow diverter is a soft, flexible tube of finely woven metal mesh that is placed inside the artery that carries the aneurysm, called the parent artery. The device spans the opening, or neck, of the aneurysm. Its mesh is dense enough to slow the blood entering the aneurysm, while still letting blood flow normally through the artery and into its branches.

With blood flow slowed, the aneurysm gradually clots off. Over the following months, the lining of the artery grows across the mesh and rebuilds the vessel wall where the aneurysm used to begin. Instead of filling the aneurysm, flow diversion repairs the artery itself. For many aneurysms that were once treatable only with high-risk open surgery, this has changed what is possible.

Flow diversion is one of several ways to treat a brain aneurysm. Others include coiling, intrasaccular devices, and microsurgical clipping. Because I perform all of these, my recommendation is based on what fits your aneurysm best.

The Technique Matters More Than the Brand

Several flow diverters are available, and I use more than one, including the Pipeline and FRED devices, adding new options as they become available. They differ in mesh design, sizing, and how they are delivered. Choosing the right device and size for the shape of your artery, positioning it precisely across the aneurysm neck, and making sure it opens fully against the vessel wall are what drive a good result. I would rather match the device to the aneurysm than fit every aneurysm to one manufacturer's product.

Careful planning starts before the procedure. I study three-dimensional angiography to measure the artery above and below the aneurysm, map nearby branches, and decide exactly where the device should land.

Which Aneurysms Are Treated with Flow Diversion?

• Large and giant aneurysms
• Wide-necked aneurysms that are difficult to coil
• Fusiform aneurysms, which balloon out the full circumference of the artery
• Aneurysms that have come back after coiling or clipping
• Many aneurysms along the internal carotid artery, including those near the eye

In the United States, flow diverters are FDA-approved mainly for aneurysms of the internal carotid artery. Using them in other locations is off-label and decided case by case.

Flow diversion is used less often for aneurysms that have just ruptured, because it requires blood-thinning medication while the artery heals and does not seal the aneurysm right away. I have published on both the use of flow diversion and the concerns about using it after rupture, and I weigh those trade-offs carefully for each patient.

What to Expect

Before the Procedure

Because a device is placed inside the artery, you will start two antiplatelet medications, usually aspirin plus a second medication, several days beforehand. A blood test is often used to confirm that the medication is working, to lower the risk of clots forming on the device.

The Procedure

The procedure is performed under general anesthesia in the angiography suite. Through a small puncture in an artery in the wrist or groin, I guide a series of catheters into the brain and deploy the flow diverter across the aneurysm. There is no incision in the scalp or skull. Most patients spend one night in the hospital.

Afterward

Most people return to normal activities within about a week. You will continue both antiplatelet medications for several months, then usually aspirin alone long term. Follow-up imaging, typically at six to twelve months, checks how well the aneurysm has closed.

How the Aneurysm Heals

Unlike clipping or coiling, flow diversion does not close the aneurysm immediately. Healing happens gradually over months. Most treated aneurysms close completely, but some take longer, and a small number need additional treatment. That is why follow-up imaging is part of every treatment plan.

Risks

Every procedure carries risks. With flow diversion, the most important are stroke from a clot forming on the device, bleeding, which can be related to the blood-thinning medication, and, rarely, delayed rupture of the aneurysm before it has fully healed. There are also small risks at the puncture site. Less common risks include blockage of a small branch artery covered by the device and delayed bleeding in the brain. Serious complications, including permanent disability or death, are uncommon but possible, and the risk is higher for giant aneurysms and those in the back of the brain. I review your individual risks in detail before we decide on treatment.

Why Choose Dr. Walcott for Flow Diversion?

• Published Expertise: Author of a review of flow diversion in JAMA Surgery and co-author of published work on flow diversion after aneurysm rupture
• Multiple Devices: Experienced with more than one flow diverter, so the device is matched to the aneurysm
• The Full Range of Options: Fellowship training in both endovascular neurosurgery (USC) and open cerebrovascular surgery (UCSF), so clipping, coiling, and intrasaccular devices are all on the table
• Experience: Over 750 brain aneurysms treated
• Comprehensive Stroke Center: Treatment and neurocritical care at Santa Barbara Cottage Hospital