An endovascular approach to the treatment of intracranial ...
46 JAAPA VOL.19, NO. 11 NOVEMBER 2006 www.jaapa.com
Although aneurysms occurring anywhere in the body
can be problematic, aneurysms within the cere-
brovasculature are especially problematic because the
brain is the end organ. Subarachnoid hemorrhage (SAH)
caused by rupture of an intracranial aneurysm occurs at
a rate of 6 to 8 per 100,000 population,1 and aneurysms
that rupture cause significant disability or mortality in
up to 50% of affected patients.2 The effects of blood flow
disruption within the brain vary according to the vascu-
lar territory affected. Aneurysm size and location are
important variables in that morbidity and mortality
rates are higher when the aneurysm is larger or when it
is located within the posterior circulation.3
Aneurysms arising within the intracranial circulation
occur in the general population with an incidence of
0.2% to 8.1%.4-7 Men and women are affected almost
equally.8 Most aneurysms are diagnosed when patients
are 40 to 59 years old.9 Intracranial aneurysms are un-
common in the pediatric population and rare in those
younger than 5 years.10
The etiology is not well understood, but epidemiolog-
ic studies have identified certain factors that may con-
tribute both to incidence and to risk of rupture. Uncon-
trolled hypertension and current cigarette smoking are
associated with an increased risk of rupture.8 There
appears to be a genetic predisposition as well, especial-
ly in persons with two or more family members who
have had an intracranial aneurysm.11 Diseases such
as Ehlers-Danlos syndrome, Marfan syndrome, and
polycystic kidney disease can increase the likelihood.12
Patients who have had one aneurysm have a 15% to 45%
chance of having additional aneurysms.13
Treatment is aimed at removing the aneurysm while
preserving blood flow in the parent vessel. The primary
Bryan Walker works in the Section of Interventional Neuro-
radiology, Georgetown University Hospital, Washington, DC, and
has no relationships to disclose relating to the content of this arti-
cle. John Deveikis works in the Section of Interventional Neuro-
radiology, Medical University of South Carolina, Charleston, and is
a consultant for Boston Scientific. Steve Wilson works in cardiac,
thoracic, and vascular surgery at the Heart Center, Peninsula
Regional Medical Center, Salisbury, Md, and is a member of the
editorial board of JAAPA.
THE SURGICAL PATIENTTHE SURGICAL PATIENT
Steve Wilson, PA-C, DEPARTMENT EDITOR
An endovascular approach to the
treatment of intracranial aneurysms
Bryan D. Walker, MHS, PA-C; John P. Deveikis, MD
This cerebral angiogram in the anterior-posterior
(AP) projection (left internal carotid artery
injection) shows an aneurysm at the anterior
In and around the OR
A cerebral angiogram in the AP projection
(vertebral artery injection) demonstrates an
aneurysm at the summit of the basilar artery.
48 JAAPA VOL.19, NO. 11 NOVEMBER 2006 www.jaapa.com
objective is to prevent aneurysm rupture, which can be
accomplished using a traditional neurosurgical approach
(craniotomy followed by placement of a clip across the
base of the aneurysm) or using an endovascular ap-
proach (filling the aneurysm sac with metallic coils). This
article discusses the endovascular treatment of intracra-
nial aneurysms as an emerging option.
Pathophysiology and diagnosis
The structural composition of the arterial wall in ves-
sels within the dura is different from that of vessels
elsewhere in the body. Vessels within the dura lack an
external elastic lamina, and the adventitia and media
are thin. Congenital thinning may be present at vessel
branch points. These structural differences render ves-
sels within the dura at increased risk for aneurysm for-
mation due to an altered hemodynamic state, including
those resulting from hypertension, arteriovenous mal-
formation, and polycystic kidney disease. Other risk fac-
tors for aneurysms include smoking, IV drug use, dam-
age caused by radiation therapy, atherosclerosis, trau-
ma, and infection.2
Approximately 90% of aneurysms occur within the
anterior (carotid) circulation; the remainder occur
within the posterior (vertebrobasilar) circulation. In
the anterior circulation, ruptured aneurysms are most
commonly found at the anterior communicating artery
(see Figure 1, page 46), then at the posterior communi-
cating artery, the middle cerebral artery bifurcation,
and the internal carotid artery bifurcation. In the pos-
terior circulation, most aneurysms are seen at the basi-
lar artery bifurcation (see Figure 2, page 46), then at
the vertebrobasilar junction and the posterior-inferior
The most common clinical manifestation of a rup-
tured aneurysm is SAH; 70% to 80% of cases of non-
traumatic SAH are due to a ruptured aneurysm.2,17
Patients may present with severe headache, neurologic
deficits, or seizures. Emergent noncontrast CT of the
head is usually ordered because this test has a high sen-
sitivity (around 90%) for subarachnoid blood.13
Once SAH is diagnosed, the suspicion of intracranial
aneurysm is high and further neuroimaging is done.
Catheter cerebral angiography is the gold standard for
the diagnostic assessment of aneurysmal SAH; it pro-
vides a high degree of anatomic resolution and allows the
angiographer to obtain the best angles and images to sort
out the aneurysmal morphology. Noninvasive CT angiog-
raphy (CTA) or magnetic resonance angiography (MRA)
may be useful as well. CTA can easily be used in the
hyperacute setting when surgery is urgently required
and provides images comparable to those obtained with
conventional angiography (see Figure 3).
Endovascular treatment options
Until a little more than 10 years ago, the only treatment
option for an intracranial aneurysm was open neuro-
surgery with placement of a clip on the aneurysm neck.
With new interventional neuroradiology techniques,
however, many aneurysms can now be treated using an
endovascular approach. Digital fluoroscopy, micro-
catheters, and coils are increasingly being used to
Morphology must be determined before an aneurysm
is treated using an endovascular technique. Aneurysms
are most commonly saccular, with a single, definable
opening to the parent vessel, referred to as the neck of
the aneurysm. The ratio of the top, or dome, of the
aneurysm to the neck determines the stability of the
The surgical patient
A posteriorly projected aneurysm is seen using CT
angiography with 3D reconstruction (A). The same
aneurysm is seen on a cerebral angiogram (B).
coils after they are placed into the aneurysm. If the neck
is too wide, it may be difficult to prevent prolapse of the
coils into the parent artery. A soft balloon may be
employed to serve as a temporary neck to hold coils in
position during placement. Once the coils are properly
positioned, the balloon is deflated and is removed when
the procedure is completed. More recently, stents have
been used to create a scaffold that maintains the coils
positioned in the aneurysm and keeps the parent artery
patent, even in cases of wide-necked aneurysms. After
the morphology, size, location, and number of aneurysms
are known, treatment is planned.
In the angiography suite, the patient is placed in a
supine position on the table, and the femoral artery area
is exposed bilaterally. Biplane fluoroscopy equipment is
mandatory because it allows data acquisition in both the
posterior-anterior and lateral projections simultaneous-
ly. Diagnostic angiography is routinely performed with
local anesthesia and sedation. If the patient is unstable
or unable to cooperate, general anesthesia may be
employed. For endovascular procedures, general anes-
thesia is most commonly used.
The femoral artery is accessed using a modified
Seldinger technique, and an arterial sheath is placed to
aid in catheter placement and exchange. A number of
diagnostic catheter shapes (Berenstein, Simmons, H1H
[Cook], and Newton) are available, depending on vascu-
lar anatomy, to aid in vessel selection. Guidewires are
also used within the catheter to select vessels. The use
of fluoroscopy aids the angiographer in determining the
catheter or guidewire position. The catheter is moved
up the femoral artery to the iliac artery and up the aorta
to the arch, where the great vessels of the neck origi-
nate. The side where the lesion is suspected to be is usu-
ally selected first. Radiographic contrast is injected,
multiple biplane radiographic views are obtained, and
then the rest of the vessels are studied. The entire
intracranial circulation must be examined to determine
whether multiple aneurysms exist.18
Aneurysms in the posterior circulation are more diffi-
cult to approach surgically; therefore, the tendency is to
treat them by coiling.19 Those in the middle cerebral or
posterior communicating territories are easier to access
surgically and have usually been treated with open sur-
gical clipping. Until recently, when experience with bal-
loon-assisted or stent-assisted coil embolization had im-
proved, aneurysms with wide necks tended to be treated
surgically. Patients who are too unstable for craniotomy
and microsurgical clipping are more likely to be able to
tolerate the less invasive endovascular treatment.
When endovascular treatment is chosen, various
coils and delivery systems are available. In 1991, the
Guglielmi detachable coil (GDC) system became avail-
able, allowing safe, effective endovascular occlusion of
aneurysms.20 The coils now come in a variety of gauges
(0.010-0.015 inch), lengths (2-30 cm), shapes (helical,
2D, 3D), and compositions (bare platinum or with bio-
A 5 or 6 French guide catheter is first positioned at a
stable area within the parent artery in the neck (the
common or internal carotid artery or the vertebral
artery). Under fluoroscopy, a microcatheter-microwire
delivery system is introduced through the guide
catheter; the tip of the microwire, and ultimately the
catheter, is placed within the aneurysm.
The coil is attached to a stainless steel introducer wire
or to a thin hypotube, which runs the length of the
microcatheter. The coil is introduced into the catheter
and delivered into the aneurysm sac. When deployed,
the soft platinum coil conforms to the shape of the
aneurysm. Once in position, the coil is detached from an
www.jaapa.com VOL.19, NO. 11 NOVEMBER 2006 JAAPA 51
The surgical patient
In these four images, coils are delivered
sequentially into an aneurysm in the anterior
communicating artery until the aneurysm no
longer fills with contrast.
Aneurysms in the posterior
circulation are more difficult to
approach surgically and tend
to be treated by coiling.
52 JAAPA VOL.19, NO. 11 NOVEMBER 2006 www.jaapa.com
introducer wire by electrolysis following discharge of a
small electrical current through the introducer wire.
Coils mounted on a hypotube are detached by injecting
small quantities of fluid into the tube. Multiple coils are
sequentially delivered into the aneurysm sac until the
flow of blood into the aneurysm has ceased or until no
more coils can be introduced (see Figure 4, page 51).
Complications of diagnostic cerebral angiography
and endovascular treatment include thromboembolic
stroke, aneurysm rupture, bleeding or infection at the
access site, and allergic reactions to the contrast agent.
Overall, major complications from diagnostic cerebral
angiography occur at a rate of 2%.21 Aneurysm rupture
during embolization has been reported to occur in 2% to
5% of cases.22
To minimize the risk of thromboembolic complica-
tions, patients are anticoagulated during the procedure
and for 24 hours after. Those with SAH are kept in the
neurosurgical ICU for continued monitoring and treat-
ment. Patients with unruptured aneurysms often go
home the day after the procedure. Follow-up care con-
sists of clinic visits along with neuroimaging to monitor
whether the aneurysm remains completely occluded.
The usual protocol includes follow-up arteriography at 6
months and high-resolution MRA annually.
Although early neurosurgical intervention was known to
reduce overall mortality in patients with acutely rup-
tured aneurysms,23 until recently, there had been no ran-
domized prospective studies to ascertain the usefulness
of endovascular coil treatment of an acutely ruptured
aneurysm. The International Subarachnoid Aneurysm
Trial (ISAT), which compared neurosurgical clipping ver-
sus endovascular coiling of ruptured aneurysms, demon-
strated encouraging results for the use of endovascular
coil treatment, especially at 1 year.24
ISAT was a multicenter, prospective, randomized
trial conducted at centers offering both neurosurgical
and endovascular treatment. Patients were evaluated
by both neurosurgical and endovascular specialists
and were enrolled if patients and specialists agreed
that an aneurysm could be treated by either means.
Patients were then randomized into a surgical or
endovascular arm for treatment. Follow-up evalua-
tions occurred at 2 months and 1 year to determine the
rates of rebleeding and clinical outcomes. This study
showed that at 1 year, patients who received endovas-
cular coil treatment for a ruptured aneurysm had
fewer poor clinical outcomes (23.7% dead or disabled)
than did those treated with surgical clipping (30.6%
dead or disabled, P = .001). There was a trend toward
more delayed rebleeding in the endovascular group,
but it was not statistically significant.
In summary, endovascular coiling is an evolving ther-
apy that provides new, less invasive treatment options
for patients with intracranial aneurysms. The decision
to treat an aneurysm with coiling or surgical clipping
should be made on a case-by-case basis, after careful
review by the neurosurgical and interventional neuro-
radiology teams, to maximize patient safety and ensure
the best outcomes. ■■
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