Neurointerventional Reports
Leo Stent-Assisted Coil Embolization of a Giant Middle
Cerebral Artery Aneurysm
Jung Yong Ahn, MD, Chang Ki Hong, MD, Sang Hyun Suh, MD, Jun Hyung Cho, MD, Yo Shik Shim, MD,
Ji Soon Huh, MD
From the Department of Neurosurgery, Brain Research Institute, Yonsei University College of Medicine, Seoul, Republic of Korea (JYA, CKH, JHC, YSS); Department of
Radiology, Yonsei University College of Medicine, Seoul, Republic of Korea (SHS); and Department of Neurosurgery, College of Medicine, Cheju National University Hospital,
Jeju, Republic of Korea (JSH)

ABSTRACT
We report a case of a 70-year-old man harboring a wide-necked thrombosed giant
aneurysm of the left middle cerebral artery (MCA) on the M1 segment. The patient presented with generalized tonic-clonic seizures. A computerized tomography scan showed
a calcified aneurysmal wall with perianeurysmal swelling. The aneurysm was successfully
embolized using closed-cell nitinol stent-assisted coiling (Leo, BALT Co., Montmorency,
France).

Keywords: Endovascular treatment, intracranial aneurysms, intracranial stent,
middle cerebral artery.
Acceptance: Received August 23,
2007, and in revised form June 30, 2007.
Accepted for publication October 22,
2007.
Correspondence: Address correspondence to Jung Yong Ahn, MD, Department of Neurosurgery, 146–92, Dogokdong, Kangnam-gu, Seoul, 135-720, Republic of Korea. E-mail: jyahn@yumc.
yonsei.ac.kr
J Neuroimaging 2008;18:332-335.
DOI: 10.1111/j.1552-6569.2007.00221.x

Introduction
Giant intracranial aneurysms, defined as those with a maximum
diameter exceeding 2.5 cm. The natural history of these lesions,
once it is diagnosed, is very unfavorable.1 Giant aneurysms
have a body and fundus that exceed the size of the parent artery
incorporating almost invariably a significant proportion of the
parent vessel either in a saccular aneurysm with wide neck or
in a fusiform dilatation. Also, the disproportion between the
size of the aneurysm and the parent artery may include several
branches of the parent artery either in the fundus or neck of
the aneurysm. These peculiarities have significant impact in
both the surgical and endovascular treatment. Their location,
morphological features, size, and type of associated symptoms
may dictate different strategies for their appropriate treatment.
Direct surgical clipping of giant aneurysms poses substantial
risks.1-3 An effective and safe alternative to clipping is endovascular parent vessel occlusion, which can be preceded by bypass
surgery if necessary.4-6 Besides clipping and parent vessel occlusion, selective endovascular treatment with detachable coils
can be considered.7,8 However, the endovascular treatment of
a giant aneurysm is difficult and is often associated with a high
rate of complication and failure.8
Little has been published with regard to the endovascular
treatment of giant middle cerebral artery (MCA) aneurysms.

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Giant MCA aneurysms, which have a wide-necked, thrombosed fundus, or efferent vessels protruding from the aneurysm,
may not be amenable to coil embolization. Stent-assisted coil
embolization of wide-necked intracranial aneurysms using selfexpanding stents is safe and effective, but technical improvements related to various mechanical difficulties during stent
deployment are necessary.9-12 Here, we present a case of a
thrombosed MCA giant aneurysm that was successfully coiled
using a new, self-expandable stent manufactured with braided
nitinol wires (Leo, BALT Co., Montmorency, France).

Case Report
A 70-year-old man with a history of hypertension presented
to another hospital with generalized tonic-clonic seizures. A
noncontrast computerized tomography (CT) scan of the head
revealed a 3.5 × 2.8 cm sized thrombosed mass on the left
temporal area with a calcified wall and surrounding edema
(Fig 1A). On a contrast computerized tomography (CT) scan
(Fig 1B), a residual vascular lumen in the thrombosed aneurysmal sac was noted. The initial angiogram demonstrated a residual wide-necked aneurysmal lumen of the left M1 segment
(Fig 2). The patient underwent craniotomy, but aneurysmal
clipping was failed due to hard calcified wall. And then, the

Copyright C 2008 by the American Society of Neuroimaging

Fig 1. (A) A noncontrast CT scan of the head revealed a 3.5 cm × 2.8 cm sized thrombosed mass on the left temporal area with a calcified
wall and surrounding edema. (B) A contrast CT scan showed a residual vascular lumen (arrows) in the thrombosed aneurysmal sac.
patient was referred to our institution for definitive treatment
of the giant thrombosed aneurysm with calcified wall. The options for managing the lesion, including endovascular obliteration and surgical clip ligation with or without bypass surgery,
were discussed in detail with the patient and his family. Previous surgical clipping via craniotomy were unsuccessful and
the patient’s age was old. In addition, the lateral lenticulostriate
artery originated from the base of the wide-necked aneurysm.
The patient was, therefore, scheduled for a stent-assisted coiling
with preservation of the lateral lenticulostriate artery.
Treatment intervention was performed under general anesthesia. The patient was heparinized to an activated clotting
time of 250 to 300 seconds. A 6 French Envoy guide catheter
(Cordis, Johnson & Johnson, Miami, FL, USA ) was inserted
into the left internal carotid artery. A microcatheter was placed
first within the aneurysm lumen to allow for coil delivery. Then,
the endovascular procedure consisted of stent placement across
the aneurysm neck. A Vasco microcatheter (BALT Co., Montmorency, France) was positioned past the aneurysm neck by

different microguidewires (Transend 14, Target Therapeutics,
Fremont, CA, USA ). A 2.5 mm/18 mm Leo self-expanding
stent (BALT, Montmorency, France) was loaded into the Vasco
microcatheter and gently advanced to be placed at the end of
the catheter (Fig 3A). Under road-mapping guiding, the stent
was deposited by slowly moving back the microcatheter while
the pusher was held. Ten Matrix coils (Boston Scientific/Target
Therapeutics, Fremont, CA, USA ) were then delivered into
the aneurysm through the first microcatheter. Near complete
obliteration of the aneurysm cavity was obtained without any
compromise of distal flow (Fig 3B).
The patient was maintained on heparin for 24 hours after
stent placement and coiling. Heparinization was discontinued
24 hours after treatment but was not reversed. The patient was
also given a clopidogrel load of 450 mg and 325 mg of aspirin,
immediately following the procedure. The postoperative course
was uneventful, and the patient remained neurologically intact.
He was discharged home with aspirin (100 mg) for at least 1
year, in combination with clopidogrel (75 mg) for 2 months. A

Fig 2.

The initial angiogram (A: oblique view, B: lateral view) demonstrated a residual wide-necked aneurysmal lumen (arrow) of the left M1
segment with displacement of ipsilateral M2 segment to upward and lateral directions. The lateral lenticulostriate artery originated from the
base of the aneurysm.

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Fig 3. (A) A 2.5 mm/18 mm Leo self-expanding stent was deployed across the neck of the aneurysm in the M1 segment. Two highly
radiopaque helical platinum filaments (arrows) ensured the visibility of the entire stent length. (B) Near complete obliteration of the aneurysm
cavity was obtained without any compromise of distal flow.

6-month follow-up angiogram (Fig 4) revealed continued obliteration of the aneurysm with patency of parent vessels. The
patient’s neurological status continues to remain unchanged,
and there have been no more seizures.

Discussion
This case report demonstrates the feasibility of stent-assisted
coiling of a wide-necked giant M1 aneurysm. Given the patient’s age, endovascular therapy was considered the primary
therapeutic modality. Current techniques for the endovascular management of giant aneurysms can be grouped in two
categories: deconstructive or reconstructive techniques. In our
case, reconstructive procedure or bypass surgical procedures
were mandatory because of poor retrograde blood flow from
the anterior cerebral artery and posterior cerebral artery to the
MCA.
Recently, the development of intravascular stents represents
a promising advancement that may overcome important technical limitations in the endovascular therapy of giant or wide-

necked aneurysms. In an experimental study, the stent acts as
a scaffold in the parent artery while coils are deposited into the
aneurysmal lumen.13 Experimental models have demonstrated
that stent deployment promotes intraaneurysmal flow stasis,14
reduces wall shear stresses,15 and can prevent regrowth of the
aneurysmal sac.16 The latest developments have led to highly
flexible, self-expanding nitinol stents, including the Neuroform,
its upgraded version (Neuroform2/Treo, Boston Scientific, Fremont, CA,USA ) and the Leo stent. The Neuroform has been
evaluated for the endovascular treatment of wide-necked intracranial aneurysms in several series.9-12 In contrast to the
Neuroform stent, the Leo has a closed-cell design and is made
of braided nitinol wires, giving it high radial force and homogeneous wall structure even in acute curves. Two highly
radiopaque helical platinum filaments ensure the visibility of
the entire stent length. Additionally, the advantage of the Leo
stent is that it can be repositioned, which allows for very precise
placement across the aneurysm neck.17 The stent is attached to
a pusher and introduced inside the lumen of the microcatheter.

Fig 4. A 6-month follow-up angiogram (A: oblique view, B: lateral view) revealed continued obliteration of the aneurysm with patency of
parent vessels.

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Journal of Neuroimaging Vol 18 No 3 July 2008

If the device is not correctly positioned across the aneurysm
neck, the pusher allows for resheathing the repositioning. When
the catheter is fully withdrawn over the pusher, the coupling
wire releases, and the stent is deployed. It has been reported
that the Leo stent-assisted coiling of wide-necked intracranial
aneurysms is feasible and effective.17,18
Recently, Food and Drug Administration (FDA) approved
Enterprise stent (Cordis Neurovascular, Miami, FL, USA ),
which is a new highly flexible nitinol stent designed for use
in the endovascular treatment of intracranial wide-necked
aneurysms.19,20 The main advantage of the Enterprise stent
compared with the Leo stent is its flexibility and in some situations its fixed closed cell design. Even though Leo stent has
also a closed cell design, the gaps between the stent struts are
not fixed and sliding between the stent struts during deployment may lead to difficulties, such as stretched stent, in arterial
curves.20 Thus, there may be no contact between the outer
surface of the stent and the arterial wall.
Coil compaction remains a problem for giant aneurysms;
subsequent treatments are very often necessary in these cases.
Primary complete occlusion with coils of the aneurysmal lumen does not necessarily prevent recanalization, and therefore
regrowth or rebleeding. This is especially relevant for partially
thrombosed aneurysms, because the coils invariably settle into
the thrombus and can cause the aneurysm to recanalize.21,22 In
a recent series of 31 patients with giant or very large aneurysms,
Gruber et al.8 reported 73.3% excellent to good recoveries after
coils embolization with 13.3% procedure-related morbidity rate
and a 6.7% mortality rate. However, in the angiographic followup, complete or almost complete occlusion was observed in
only 71% of patients, and single procedure was definitive treatment for only 12.5% of the giant aneurysms. A very high 6.5%
post-GDC treatment hemorrhage rate was also reported by this
group. In the review of literature, the recanalization rate was
approximately 55% in 164 giant aneurysms with extremely variable follow-up times.23 Close angiographic follow-up is mandatory to permit the timely detection of early recanalization and
of any indication for repeat coiling or other additional therapy.
Numerous challenging issues remain to be resolved in the
treatment of giant aneurysms. Improvements in stent technology, specifically the development of covered stents or less
porous stents with enhanced navigability into the intracranial
circulation, may sufficiently alter the aneurysm inflow, which
may produce complete exclusion of the circulation and thrombosis. The use of a covered stent could allow reconstruction
of the vascular anatomy in a dysplastic segment of the MCA
where no perforating arteries originate.24

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