In the past two decades, the diagnosis and management of intracranial aneurysms have
evolved dramatically. With development of sophisticated diagnostic tools such as MR
angiography and CT angiography, it is possible to diagnose most intracranial aneurysms
in noninvasive manner; on the other hand, the improvement of nonoperative endovascular
techniques makes their treatment increasingly safer and more and more effective and
provides a valuable alternative to surgery. First endovascular treatment (EVT) of
intracranial aneurysm was described in the early 1970s by a Russian neurosurgeon,
Fedor Serbinenko, who used vascular catheter with a detachable latex balloon to treat
aneurysms, either by putting the balloon directly into the aneurysm lumen or by occluding
the parent artery. In 1991, Guido Guglielmi, Italian neurosurgeon, was the first to
describe the technique of occluding aneurysms from an endovascular approach with electrolytic
detachable platinum coils, termed Guglielmi detachable coils (GDCs). GDCs are introduced
directly into the aneurysm through a microcatheter and detached from a stainless-steel
microguidewire by an electrical current. The first such EVT was realized in 1991.
godine at UCLA, when the intracranial aneurysm was obliterated by GDC. Since then,
with use of different new materials, the endovascular technique developed revolutionary
that changed completely the attitudes about intracranial aneurysms treatment.
Coiling Alone
The development of coils with controlled detachable system was the first important
step for widespread use of EVT. Initial large series showed acceptable mortality (≈2%)
and morbidity (between 4 and 9%) (Pierrot 2013), related mostly to thromboembolic
complications and intraoperative rupture that are the two most frequent complications
of aneurysm coiling.
Two main disadvantages in this technique are:
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Some aneurysms are difficult to treat because of their shape (large and giant aneurysms,
fusiform aneurysms, large neck aneurysms).
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The durability of aneurysm coil embolization cannot be achieved in all aneurysms.
A systematic review of a large number of studies showed that aneurysm recanalization
occurred in 20.8% of cases, requiring retreatment in 10.3% (Ferns 2009).
This led to development of new techniques, including balloon-assisted coiling (known
as the remodeling technique) and stent-assisted coiling, and more recently introduction
of flow diversion and flow disruption.
Baloon-Assisted Coiling (BAC)
Moret et al (1997) initially described the balloon-assisted coiling (remodeling technique)
for EVT of wide-neck aneurysms. A nondetachable balloon is temporarily inflated in
front of the neck of the aneurysm during each coil placement. This method expanded
a spectrum of, until then, untreatable aneurysms. It was also useful as a rescue in
cases of intraoperative ruptures, but the overall results from many studies did not
bring a clear conclusion whether the results of BAC were better compared to coiling
alone.
Stent-Assisted Coiling (SAC)
This new technique was introduced >10 years ago to overcome some limitations of standard
coiling in the treatment of some complex aneurysms. SAC was also used as rescue approach
in coil herniation or migration of coils into the parent vessel.
Because stents are implanted in the parent artery, over the aneurysm neck, risk of
in-stent thrombosis is higher than with coiling alone, so the preoperative and postoperative
antiplatelet treatment is mandatory. This initially limited SAC to unruptured aneurysms.
However, with the gain of experience during the past years, stenting has been used
in ruptured aneurysms. Stenting is also considered helpful in preventing aneurysm
recanalization.
Flow Diversion and Flow Disruption
In the past 8 years, flow diverters (FDs) were introduced into the clinical practice.
FDs are low-porosity stent-like implants that function in two ways:
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Flow redirection: The FD bridges the aneurysm neck and reduces the blood flow into
the aneurysm sac because of dense mesh of the implant, yet provides blood flow through
adjacent perforators and side branches. This enables a redirection of the blood flow
away from the aneurysm toward the distal parent artery. Reduction of blood circulation
within the aneurysm leads to flow stasis and induces formation of a stable aneurysmal
thrombus.
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Tissue overgrowth: The FD provides a scaffold for neoendothelization across the aneurysm
neck.
FDs are mainly used in large and giant aneurysms (including fusiform), wide-neck aneurysms,
multiple aneurysms within a segmental diseased artery, and recurrent aneurysms. Dual
antiplatelet is recommended, so most aneurysms treated are unruptured. However, some
complications with FDs are observed, not documented with standard coiling or BAC,
such as delayed aneurysm ruptures and remote parenchymal hematomas. Most of those
complications have occurred in large and giant aneurysms that have a high natural
incidence of bleeding or were neither surgically nor endovascularly treatable.
Intrasaccular flow disruption is an endovascular approach similar to the intraluminal
FD method. The mesh of the flow disruptor is placed within the aneurysm sac and creates
blood flow stasis with subsequent thrombosis.
Progress in imaging and device manufacturing is providing more sophisticated tools
that have expanded EVT to aneurysms that were previously neither surgically nor endovascularly
treatable. Randomized trials are still necessary to evaluate the safety and efficacy
of various emerging new technologies for aneurysm treatment.
