Brain aneurysms are the result of areas of weakness in the normally muscular wall of an artery supplying the brain, combined with the pressure transmitted to the artery by the pumping of the heart. This causes stretching or ballooning of the artery wall to form an aneurysm. Typically, these take many years to develop. A typical aneurysm can be seen in this video:

Aneurysms can be repaired in 2 ways. The first more conventional, is with brain surgery, in which a metallic, spring-loaded clip is placed across the neck of the aneurysm, seen in this figure:

The second, more recently developed non-surgical approach is with the use of coils placed into the aneurysm through a micro-catheter [ Excelsior SL-10 Microcatheter], which is placed into the aneurysm using x-ray or fluoroscopic guidance, from a femoral (groin) artery approach. An illustration of a coil can be seen below:

Videos from actual aneurysm coiling under fluoroscopy can be seen below:

An angiogram done after the aneurysm has been occluded with coils can be seen here:

Sometimes, aneurysms have very wide necks:

(wide neck aneurysm)

Because of the wide necks, coils placed in them may not stay within the aneurysm, but instead migrate out of the aneurysm into a normal brain artery (see figure 7a under illustrative cases), where it can potentially cause a blockage and perhaps stroke. This problem has been overcome by the use of a stent, which can be placed across the neck of an aneurysm to help hold the coils in place.

(stenting deployment)

(stenting deployed)

With the stent in place, the microcatheter is advanced through the stent into the aneurysm

(stenting aneurysm access)

and the coils advanced through the microcatheter.

(stenting aneurysm coiling)

Another illustration of this can be seen here:

(aneurysm with stent)

Here are videos of the stent being deployed:

and the coils being placed: