Endovascular Aneurysm Treatment

To begin the process of endovascular aneurysm repair, doctors access the body’s system of blood vessels. The most common access location is the femoral artery in the leg. However, other locations such as the wrist, the elbow or underarm are also possible and can be used when necessary. Patients sometimes ask, “Why the leg, when it is so far from the head?” The answer is the safety of access.

Doctors pass a small catheter, usually measuring around 2 mm, through the arteries until the tip of the catheter reaches the origin of the aneurysm. (Remarkably, it takes only seconds to safely pass the catheter all the way from the femoral artery to the head and neck.)

Then the catheter is used as the pathway to place the prosthesis to occlude the aneurysm. For many patients, a variety of prosthesis options are available; these options should be discussed with the doctor.

The most longstanding option is a system of micro coils. Micro coils made of platinum have been commercially available since 1991. Placing these coils gently into the aneurysm prevents blood from entering the aneurysm—and therefore removes the risk that blood will later leak out. These coils were first proven effective for treatment of surgically challenging and inaccessible aneurysms in 1995. In 2002 they were proven effective for preferential treatment of most ruptured aneurysms. Coils are also used with proven success to treat unruptured aneurysms, blocking the flow of blood through the aneurysm and preventing future hemorrhage.

However, not every aneurysm has a shape that allows it to be treated by the placement of coils alone. For example, an aneurysm may have a wide “neck.” In this case, a stent may be needed to redirect blood flow away from the aneurysm as well as to make sure the coils stay inside the aneurysm.

A liquid embolic agent called Onyx HD-500 has been approved for treatment of cerebral aneurysms under special circumstances. This substance solidifies on contact with blood. Liquid embolization with this product is sometimes chosen instead of coiling. The liquid embolic agent is injected into the aneurysm, where it hardens. A temporary tube or balloon placed in the blood vessel below the aneurysm makes sure the injected “glue” cannot leak into the healthy vessel. Although we have access to this product, in most cases it is not the preferred treatment.

Research has shown that redirection of blood flow away from a cerebral aneurysm can cause the aneurysm to regress and even heal completely in some cases. One way to accomplish this is with a surgical bypass via conventional “open” surgery. In 2008, an endovascular solution was approved by the FDA. High surface area stents called “flow diverters” are approved for treatment of large or giant aneurysms of the internal carotid artery. These devices immediately cause a significant reduction in blood flow into the aneurysm. Then, over weeks or months, the endothelium grows across the flow diverter. This essentially “walls off” the aneurysm, causing the aneurysm to wither and resolve.

Since all endovascular procedures are minimally invasive, another system is needed to direct progress of the procedure. Generally, these procedures are performed under fluoroscopy using specialized angiography equipment. Fluoroscopy is low-dose continuous X-ray that allows the physicians to see in real time how and where to direct the catheters and place the aneurysm treatment equipment. Angiography is the picture-taking capability used to document the aneurysm, make any measurements needed to select the appropriate treatment and then complete the treatment procedure. These are multi-million dollar pieces of equipment. Only hospitals invested in the treatment of cerebrovascular disease generally purchase this type of specialized equipment as well as the vast inventory of implantable and disposable tools needed to accomplish these procedures safely.

The doctors who perform endovascular aneurysm repair must have excellent command both of neurosurgery and of radiologic techniques such as fluoroscopy and CT guidance. Depending on the paths they took to get this double expertise, the doctors may be called endovascular neurosurgeons (neurosurgeons with specialized training in real-time radiology) or interventional neuroradiologists (neuroradiologists with specialized training in endovascular surgical neuroradiology, also known as endovascular neurosurgery).