Treatment Options for Cerebral Aneurysms
Updated August, 2009
By Deepa Soni, MD (updated by Jeffrey E. Thomas, MD, FACS)
What is an aneurysm?
A cerebral or intracranial aneurysm is a dilation of an artery in
the brain that results from a weakening of the inner muscular layer
(the intima) of a blood vessel wall. The vessel develops a
"blister-like" dilation that can become thin and rupture without
warning. The resultant bleeding into the space around the brain is
called a subarachnoid hemorrhage (SAH). This kind of hemorrhage can lead
to a stroke, coma, and/or death.
The exact mechanisms by which cerebral aneurysms develop, grow,
and rupture are unknown. However, a number of factors are believed to
contribute to the formation of cerebral aneurysms. These include: 1)
hypertension (high blood pressure); 2) cigarette smoking; 3) congenital
(genetic) predisposition; 4) injury or trauma to blood vessels; 5)
complication from some types of blood infections.
Types of Aneurysms:
An unruptured aneurysm is one whose sac has not previously
leaked. An aneurysm ruptures when a hole develops in the sac of the
aneurysm. The hole can be small, in which case only a small amount of
blood leaks, or large, leading to a major hemorrhage. Every year
approximately 30,000 patients in the United States suffer from a
ruptured cerebral aneurysm, and up to 6 percent of the population may
have an unruptured cerebral aneurysm. The management of both ruptured
and unruptured cerebral aneurysms poses a significant challenge for
patients and their treating physicians.
Today there are three treatment options for people with the
diagnosis of cerebral aneurysm: 1) medical (non-surgical) therapy; 2)
surgical therapy or clipping; and 3) endovascular therapy or coiling.
Medical therapy is usually only an option for the treatment of
unruptured intracranial aneurysms. Strategies include smoking cessation
and blood pressure control. These are the only factors that have been
shown to have a significant effect on aneurysm formation, growth, and/or
rupture. You and your doctor can work together to design an
individualized smoking cessation program that is both practical and
feasible for your lifestyle. In addition, if you suffer from high blood
pressure, your doctor may choose to start you on an antihypertensive
(blood pressure lowering) medication and/or diet and exercise program.
Finally, periodic radiographic imaging (either MRA, CT Scan or conventional angiography)
may be recommended at intervals to monitor the size and/or growth of
the aneurysm. Because the mechanisms of aneurysm rupture are
incompletely understood, and because even aneurysms of very small size
may rupture, the role of serial imaging for cerebral aneurysm is
In 1855, Victor Horsley, MD, was the first to surgically treat
a brain aneurysm. In 1937, Walter Dandy, MD, introduced the method of
"clipping" an aneurysm when he applied a V-shaped, silver clip to the
neck of an internal carotid artery aneurysm. Since that time, aneurysm
clips have evolved into hundreds of varieties, shapes, and sizes. The
mechanical sophistication of available clips, along with the advent of
the operating microscope in the 1960s have made surgical clipping the
gold standard in the treatment of both ruptured and unruptured cerebral
aneurysms. In spite of these advances, surgical clipping remains an
invasive and technically challenging procedure.
How is an aneurysm surgically clipped?
An aneurysm is clipped through a craniotomy, which is a
surgical procedure in which the brain and the blood vessels are accessed
through an opening in the skull. After the aneurysm is identified, it
is carefully dissected (separated) from the surrounding brain tissue. A
small metal clip (usually made from titanium) is then applied to the
neck (base) of the aneurysm. Aneurysm clips come in all different shapes
and sizes, and the choice of a particular clip is based on the size and
location of an aneurysm. The clip has a spring mechanism which allows
the two "jaws" of the clip to close around either side of the aneurysm,
thus occluding (separating) the aneurysm from the parent (origin) blood
vessel. In the ideal clipping, normal blood vessel anatomy is physically
restored by excluding the aneurysm sac from the cerebral circulation.
Endovascular techniques for treating aneurysms date back to
the 1970s with the introduction of proximal balloon occlusion by Fjodor
A. Serbinenko, MD, a Russian neurosurgeon. During the 1980s,
endovascular treatment of aneurysms with balloon angioplasty was
associated with high procedural rate of rupture and complications. Guido
Guglielmi, MD, an American-based neuroradiologist, invented the
platinum detachable microcoil, which was used to treat the first human
being in 1991. The development of Guglielmi detachable coils (GDCs) and
their FDA approval in 1995, revolutionized endovascular treatment of
The common goal of both surgical clipping and endovascular
coiling is to eliminate blood flow into the aneurysm. Efficacy
(long-term success or effectiveness of the treatment) is measured by
evidence of aneurysm obliteration (failure to be demonstrated by
conventional or noninvasive angiography), without evidence of
recanalization (any blood flow into the aneurysm) or recurrence
How is an aneurysm endovascularly coiled?
Guglielmi detachable coils, known as GDCs, are soft wire
spirals originally made out of platinum. These coils are deployed
(released) into an aneurysm via a microcatheter that is inserted through
the femoral artery of the leg and carefully advanced into the brain.
The microcatheter is selectively advance into the aneurysm itself, and
the microcoils are released in a sequential manner. Once the coils are
released into the aneurysm, the blood flow pattern within the aneurysm
is altered, and the slow or sluggish remaining blood flow leads to a
thrombosis (clot) of the aneurysm. A thrombosed aneurysm resists the
entry of liquid blood, providing a seal in a manner similar to a clip.
Endovascular coiling is an attractive option for treating
aneurysms because it does not require opening of the skull, and is
generally accomplished in a shorter timeframe, which lessens the
anesthesia given. Nevertheless, important differences remain between
clipping and coiling, including the nature of the seal created. Because
coiling does not physically reapproximate the inner blood vessel lining
(endothelium), recanalization may occur through the eventual compaction
of the coils into the aneurysm by the bloodstream.
The long-term durability of coiling is still unknown and not all
aneurysms are suitable for coiling. As experience with coiling grows,
the indications and pitfalls continue to be refined. Endovascular and
coil technology continue to improve: endovascular adjuncts, such as
intracranial stents, are now available to assist in coiling procedures;
the original platinum microcoil has been refined with ever-improving
features such as biological coating and microengineering for efficiency
Who performs the procedure?
Surgical clipping of a cerebral aneurysm is always performed
by a neurosurgeon, often one with expertise in cerebrovascular disease.
Most cerebrovascular neurosurgeons have had 5-7 years of general
neurosurgery training and an additional 1-2 years of specialized
Endovascular coiling is done either by a neurosurgeon or by an
interventional neuroradiologist. An interventional radiologist has
undergone extensive training (3-5 years) in both radiology and
interventional (invasive) procedures involving the brain and spinal
cord. All neurosurgeons that perform endovascular coiling have undergone
additional training in endovascular techniques in addition to full
neurosurgery training (5-7 years of residency).
Safety and Common Complications.
Although the frequencies of certain complications vary
according to the intervention, both clipping and coiling share the same
complications. Rupture of the aneurysm is one of the most serious
complications seen in either procedure. Exact frequencies of ruptures
are not well documented, but reported rupture rates range from 2 percent
to 3 percent for both coiling and clipping. Rupture can cause massive
intracerebral hemorrhage (hemorrhagic stroke, or bleeding into the
brain) and subsequent coma or death. Although rupture can have
catastrophic consequences during either procedure, surgery probably
provides a better opportunity to control hemorrhage because of direct
access to the ruptured aneurysm and the supplying vessels.
Ischemic stroke (stroke secondary to decreased blood oxygen) is
another serious complication frequently encountered in both clipping and
coiling. The pattern and distribution of strokes varies according to
the aneurysm location and procedure type.
The actual length of the procedure, the associated risks, the
projected recovery time, and the expected prognosis (outcome) depend on
both the location of the aneurysm, the presence and severity of
hemorrhage, and the patient's underlying medical condition. Therefore,
each individual case should be discussed with the treating
Review of Current Literature
Comparing the safety, effectiveness, and long-term outcome of
endovascular coiling to surgical clipping of cerebral aneurysms is a
major research initiative in neurosurgery. A randomized, controlled
trial (what is a randomized control trial?)
is needed to compare the safety and long-term outcome of surgical
clipping to endovascular coiling for the treatment of cerebral
Results from the International Subarachnoid Aneurysm Trial
(ISAT), a randomized control trial which compared surgical clipping to
endovascular coiling in the treatment of ruptured aneurysms, were
published in the Lancet in 2002. The results indicated that endovascular
coiling is slightly less risky (6.9 percent) than surgical clipping.
These results are informative, but they must be interpreted with caution
(AANS/CNS position statement)
because this study was the first of its kind, and the follow-up period
for the patients was short (one year). The durability or long-term
permanence of endovascular coiling has yet to be established. As far as
the safety of clipping or coiling, the study showed no difference in the
mortality (death) rate between clipping and coiling. Therefore, no
definite conclusions can be made regarding the superiority of one
treatment over the other.
A more recent, large study has shown that for ruptured aneurysms
suitable for both clipping and endovascular coiling, patients who
underwent endovascular coiling had better outcomes at least in the short
term (chance of death or disability at one year of 23.5 percent in
patients who were coiled versus 30.9 percent in those who underwent
clipping). While this study has firmly established endovascular coiling
of ruptured aneurysms as an acceptable treatment option, there were
limitations inherent to this study.
How do I decide what procedure to have if I have a cerebral
The treatment of choice for an intracranial aneurysm, like all
medical decisions, should be agreed upon by both the physician and the
patient. In the case of either ruptured or unruptured intracranial
aneurysms, the treating physician should discuss the risks and benefits
of each available treatment option. The physician will usually make
recommendations for one treatment over another, depending on the facts
of each individual case. Seeking a second opinion, when possible, is
Although unresolved controversies remain as to the best treatment
option for an individual patient, both surgical clipping and
endovascular coiling are considered to be viable treatment options in
the management of cerebral aneurysms today.