World Journal of Neuroscience, 2011, 1, 45-48
doi:10.4236/wjns.2011.13007 Published Online November 2011 (http://www.SciRP.org/journal/wjns/ WJNS ).
Published Online November 2011 in SciRes. http://www.scirp.org/journal/WJNs
Enterprise stent-within-stent embolization of a basilar artery
perforator aneurysm
Eric M. Deshaies1, Walte r Jacobsen2, Satish Krishnamurthy3
1Director of the SUNY Upstate Neurovascular Center; Director of Cerebrovascular, Endovascular, and Skull Base Neurosurgery.
Assistant Professor of Neurosurgery, Neuroscience and Physiology; SUNY Upstate Medical University, Syracuse NY;
2Department of Neurosurgery, SUNY Upstate Medical University, Syracuse NY;
3MCh; Professor of Neurosurgery; Director of Minimally Invasive Neurosurgery, Department of Neurosurgery, SUNY Upstate Medi-
cal University, Syracuse NY.
Received 11 August 2011; revised 22 September 2011; accepted 15 October 2011.
ABSTRACT
Objective and Importance—Vertebrobasilar artery
aneurysms can be very challenging to treat and are
preferentially dealt with using endovascular techni-
ques, since they are associated with lower risk than
surgical clipping. Small aneurysms located on perfo-
rating arteries can pose problems though, as their di-
mensions may not be favorable for coiling and leave
the endovascular surgeon without many options. We
present a basilar perforating artery aneurysm that
was successfully embolized using a stent-within-stent
technique. Clinical Presentation—A 47 year old fe-
male presented with a Hunt-Hess 3, Fisher Grade-3
subarachnoid hemorrhage with blood in the pre-pon-
tine cistern. Initial imaging (CT angiogram and digi-
tal subtraction angiography) did not reveal an aneu-
rysm. Follow-up angiography on post-bleed day eight
demonstrated a three-millimeter basilar perforating
artery aneurysm. After an unsuccessful coiling attempt
a closed-cell stent-within-stent technique was used to
divert flow away from the aneurysm neck to induce
aneurysm thrombosis. Intervention (or Tech-
nique)—Multiple attempts were made to access and
stabilize a microcatheter in the small basilar perfo-
rator artery aneurysm in order to deliver coils for
endovascular embolization; this could not be done
safely. Therefore a closed-cell 4.5 × 22 mm Enterprise
stent (Cordis Neurovascular, Inc., Miami Lakes,
Florida) was deployed in the basilar artery across the
origin of the perforator aneurysm in order for the stent
tines to divert flow away from the aneurysm neck and
induce thrombosis. Persistant brisk flow within the
aneurysm continued however, and a second closedcell
4.5 × 22 mm Enterprise stent was placed within the
first one to increase the stent metal surface area
across the aneurysm neck to further reduce flow into
the aneurysm. Subsequently, angiography demon-
strated stagnant blood flow in the aneurysm dome
an d the aneurysm spontaneously thrombosed, sparing
all associated vessels. Conclusion—Stent-within-stent
technique should be considered as a possible endovas-
cular treatment option for small side-wall and perfo-
rator artery aneurysms that can’t be safely treated
with coils or embolic agents.
Keywords: Aneurysm; Basilar, Enterprise; Stent; Su-
barachnoid Hemorrhage
1. OBJECTIVE AND IMPORTANCE
Aneurymal subarachnoid hemorrhage affects 11 patients
per 100,000 population each year (27,000 aneurysm rup-
tures in the United States alone, annually) [1,2]. Aneu-
rysms can form on any intracranial artery, but most com-
monly occur in the Circle of Willis. Most of the aneury-
sms of the vertebrobasilar system are found at the basilar
artery bifurcation, but can also occur at the origin of other
arteries at their bifurcation points [3]. One example is an
aneurysm arising from the origins of the basilar perfo-
rating arteries. Aneurysms in the vertebrobasilar territory
are preferably treated with endovascular coiling because
the risks of treatment are lower than surgical clip liga-
tion [4,5] .
Aneurysms arising from the sides of arteries, called side-
walled aneurysms, can pose a particular challenge to trea t
with endovascular techniques because the microcatheter
may not naturally take the conformation needed to ac-
cess the aneurysm so that coils can be delivered into the
lesion. When confronted with a ruptured side-walled an eu -
rysm that can’t be accessed and secured with coil em-
bolization, other endovascular options are not typically
*Dr. Eric M. Deshaies is a Physicia n Consultant to eV3, Microvention,
and Integra Corporations.

E. M. Deshaies et al. / World Journal of Neuroscience 1 (2011) 45-48 46
available, meaning that the aneurysm can’t be secured
without putting the patien t through the high risks of sur-
gical intervention near the brainstem.
Here, we present the successful tre atment of a ruptured
three-millimeter side-walled basilar perforating artery aneu-
rysm that could not be secured with traditional endovas-
cular means. Given that the location was not optimal for
surgical intervention, and endovascular treatment was
thought to be the better option, the author (EMD) per-
formed a novel endovascular intervention to successfully
divert blood flow away from the aneurysm neck and oc-
clude the aneurysm, using a stent-within-stent techniqu e.
2. CLINICAL PRESENTATION
A 47-year old female presented with a Hunt-Hess 3, Fi-
sher Grade-3 subarachnoid hemorrhage (SAH) in the
pre-pontine cistern. Initial CT angiogram and digital sub-
traction angiography did not reveal an aneurysm or vas-
cular malformation. On the follow-up angiogram eight days
later, a three-millimeter basilar perforating artery aneu-
rysm was identified (Figure 1). Due to the high morbid ity
and mortality associated with surgical intervention, en-
dovascular intervention was deemed safer and the pa-
tient was brought to the endovascular suite for emboliza-
tion of the aneurysm.
3. INTERVENTION
Coil embolization was attempted numerous times but
could not be performed successfully secondary micro-
catheter instab ility within the aneurys m neck. Each of the
six times the aneurysm was catheterized and coil inser-
tion was attempted, the microcatheter disp laced from the
aneurysm. At this point, coil embolization was abandoned
as a potentially safe treatment option for this aneurysm
because multiple attempts increase the risk of aneurysm
Figure 1. 3D digital subtraction cerebral angiogram (mid-arterial
phase) of the basilar artery demonstrating a < 3mm dorsal basi-
lar perforator artery aneurysm (arrow).
re-rupture from difficult access. At that point, a 4.5 × 22
mm closed-cell Cordis Enterprise stent was deployed in
the basilar artery across the perforating aneurysm ori-
gin. A closed cell stent configuration was chosen by the
endovascular neurosurgery (EMD) because it would po-
tentially provide better surface coverage of the aneurysm
neck, with the intent that it would divert blood flow from
the aneurysm neck and induce thrombosis. Additionally,
there was concern of a theoretical risk that the stent tines
of an open cell stent could bend into the aneurysm and
cause a perforation and re-rupture. After placement of the
st ent, angiography still showed persistent brisk flow withi n
the aneurysm, so a second stent was placed inside the
first one to further reduce the total surface area of the
inflow zone of the aneurysm neck. After both Cordis En-
terprise stents were deployed acros s the aneurysm origin,
angiography demonstrated that the blood flow into the
aneurysm was diminished and the outflow was signify-
cantly delayed (Figure 2(a) and (b)).
(a)
(b)
Figure 2. (a) 2D digital subtraction cerebral angiogram of the
basilar artery after completing the Enterprise stent-within-stent
technique. There is reduced flow into the aneurysm and de-
layed emptying of the contrast in the late arterial phase. (b) 3D
digital subtraction angiogram demonstrating the residual an-
eurysm (arrow).
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E. M. Deshaies et al. / World Journal of Neuroscience 1 45-48 47
The patient was placed on aspirin therapy alone to
simultaneously lower the risk of in-stent thrombosis yet
allow the aneurysm to thrombose, and also allow for
potentially needed external ventricular drain placement
in the future if needed. Repeated cerebra l angiography the
next day demonstrated that the aneurysm dome was al-
most completely thrombosed. At this point she was placed
on an intravenous drip of abciximab (ReoPro, Centocor,
Philadelphia, PA), a sho rt-acting glycoprotein IIb /IIIa re-
ceptor antagonist, to minimize the risk of in-stent throm-
bosis. A second angiogram on day three showed that the
aneurysm was filling again, likely secondary to the ab-
ciximab. Hence abciximab was stopped again and she
was continued on aspirin alone until it was decided that a
ventriculosotomy was not needed, after which time clopi-
dogrel (Plavix 75 mg oral, daily) was added to her anti-
platelet regimen. The patient recovered well and CT an-
giogram performed prior to discharge showed no resid-
ual aneurysm dome filling. The patient was discharged
home on post-bleed day 20 with a standard antiplatelet
regimen of aspirin (325 mg oral, daily) and clopidogrel
(75 mg oral, daily) therapy for 12 weeks. Six month fol-
low-up digital subtraction angiography showed that the
aneurysm had thrombosed and the stents remained pat-
ent without any evidence of stent migration or stenosis
(Figure 3).
4. CONCLUSIONS
Ruptured basilar perforating artery aneurysms can pose
challenges both in diagnosis and treatment. We could find
three articles that reported four patients with similar an-
eurysms [6-8]. All five patients (including the present
Figure 3. Six month follow-up 3D digital subtraction cerebral
angiogram (mid-arterial phase) of the basilar artery demon-
strating complete occlusion of the basilar perforator artery
aneurysm (arrow), no in-stent stenosis, and no stent migration
(gray).
one reported here) had no aneurysm found on the initial
angiogram and the aneurysms were demonstrated on a
subsequent study. A perimesencephalic location of the SAH,
particularly in conjunction with an angiographically ne-
gative study, may lull the treating neurosurgeon into
thinking that these patients have non-aneurysmal SAH.
Furthermore, all of the reported cases treated prior to our
report, were treated surgically as endovascular coiling
was not possible. Flow diverting sten ts, such as the Pipe-
line Embolization Device (eV3, Irvine, California) and
the Silk Stent (Balt, Montmorency, France), have been
shown to be unsafe for use in the basilar artery since
they are associated with a high risk of basilar perforating
artery occlusion and brainstem stroke.
Traditional intracranial arterial stents can b e divided into
“open” and “closed” cell designs. The “open” cell design
has holes in the stent wall that do not have metal around
the entire circumference of the cells, whereas the
“closed” cell stent has metal e ncircling the entire cell cir-
cumference (Figure 4(a) and (b)). The Cordis Enterprise
stent is a closed-cell nitinol stent, with each cell diameter
measuring less than 1.3 French. We had postulated that
placing the closed-cell stent across the aneurysm neck
would divert flow away from the aneurysm neck and
impede outflow of blood from the aneurysm, both pro-
moting thrombosis [9]. An additional theoretical advantage
of using the closed-cell design is th at is would lessen the
risk of the stent tines perforating th e aneurysm. A second
stent was placed within the first to further reduce the
total stent cell size and hence, the cross-sectional area of
the aneurysm inflow zone.
In vitro and in vivo studies on aneurysm hemodynam-
ics after stent placement have consistently demonstrated
reduced flow and shear-stress inside the aneurysm after
stent placement [9-15]. Stents also reduce the pressure in
the distal zone of the aneurysm neck and dome [10]. All
of these hemodynamic changes are favorable for pro-
moting intra-aneurysmal flow stasis and thrombosis. The
(a) (b)
Figure 4. (a) Enterprise (Cordis, Corporation, Johnson and John-
son) stent with closed-cell technology. (b) Neuroform microde-
livery stent (Boston Scientific) stent with open-cell technology.
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E. M. Deshaies et al. / World Journal of Neuroscience 1 (2011) 45-48 48
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In conclusion, stent-within-stent placement across the
neck of a side-walled aneurysm should be considered an
alternative treatment for aneurysms that cannot be treated
with coil embolization, flow-div erting stents, or embolic
glue agents. This technique may also apply to endovas-
cular treatment of small blister aneurysms in other arte-
rial locations that are difficult to coil within the Circle of
Willis. Acute in-stent thro mbosis fro m the metal-to-blo od
interface and delayed in-stent stenosis from neointimal
hyperplasia, are real risks that must be monitored closely.
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