Acta Neurochir (2015) 157:1849–1854
DOI 10.1007/s00701-015-2579-1

CASE REPORT - VASCULAR

Specific and helpful intraoperative indocyanine green
videoangiography finding of blood blister-like aneurysm
of internal carotid artery
Moon-Soo Han 1 & Sung-Pil Joo 1 & Seung-Hoon Jung 1 & Tae-Sun Kim 1

Received: 23 March 2015 / Accepted: 3 September 2015 / Published online: 16 September 2015
# Springer-Verlag Wien 2015

Abstract
Background Blood blister-like aneurysms (BBAs) account
for 0.5–2.0 % of ruptured intracranial aneurysms. Because
of their rarity, the natural history and pathophysiology of such
aneurysms are not fully understood. We present two patients
with BBAs treated with Bemsheets-covered clipping and discuss their pathophysiological characteristics, through the intraoperative and specific indocyanine green (ICG) video angiography (VA) findings.
Case report A 34-year-old male and a 53-year-old female
were admitted to our emergency room with suddenly reduced
levels of consciousness. Brain imaging studies demonstrated a
blood blister-like aneurysm of the supraclinoid segment of the
right ICA. Craniotomy and an attempt of surgical clipping
were performed. ICG-VA showed the filling defect of dye in
aneurysm in the operative field. The BBAs were clipped after
being covered by Bemsheets (Kawamoto Corporation, Osaka,
Japan) and then confirmed by the ICG-VA. Postoperatively,
both patients showed transient neurological deficit due to vasospasms and recovered to their normal statuses within a few
months after their respective operations.
Conclusions ICG-VA showed the filling defect of dye in
BBAs, w hich sup ported that BBAs have been a
pseudoaneurysm. In addition, although not routinely recommended in the treatment of BBAs, we believe that Bemsheetcovered clipping is a safe and effective treatment option for
BBAs.
* Tae-Sun Kim
taesun1963@yahoo.co.kr
1

Department of Neurosurgery, Chonnam National University
Research Institute of Medical Sciences, Chonnam National
University Hospital & Medical School, 42, Jebong-ro, Donggu
Gwangju 501-757, Republic of Korea

Keywords Blood blister-like aneurysm . Pseudoaneurysm .
Indocyanine green . Internal carotid artery . Surgery

Background
Blood blister-like aneurysms (BBAs) account for 0.5–2.0 % of
ruptured intracranial aneurysms and unusually lead to high
morbidity and mortality rates as compared with typical ruptured saccular aneurysms of the internal carotid artery (ICA)
[10, 14, 17, 23]. Because of their rarity, the natural history and
pathophysiology of BBAs are not fully understood. The main
hypothesis is that BBAs arise from dissection of vessel walls
[4, 6], but the pathophysiological studies should be performed
through biopsy or autopsy. Most often, these lesions appear on
the dorsal wall of the supraclinoid portion of the ICA, which
presents as a fragile wall with a poorly defined, broad-based,
ambiguous neck. Given these characteristics, BBAs have been
considered as pseudoaneurysms [6, 24], so the treatment of
BBAs is always challenging. Although the use of endovascular
treatment is increasing, endovascular coil embolization alone
may be insufficient to prevent the recurrence or re-bleeding of
BBAs [14, 17]. Also, surgical clipping has remained challenging, resulting in significant rates of morbidity and mortality.
Recently, microscope-integrated near-infrared indocyanine
green (ICG) videoangiography (VA) has been introduced in
neurosurgery. It has been proven that intraoperative ICG-VA
may help surgeons to evaluate cerebral vessels visible in the
surgical field. In addition, ICG-CA helps surgeons to obtain a
real-time diagnosis of the degree of aneurysm occlusion and
vessel patency, including perforating arteries based on the
timing of fluorescence with the dye [2, 3, 5, 13, 18, 19, 25].
In this paper, we describe two patients with subarachnoid
hemorrhage (SAH) caused by ruptured BBAs that were treated with Bemsheets-covered clipping. In addition, this is the

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first report of specific finding of ICG-VA of BBAs, which can
help reveal the pathophysiology and establish the neurosurgical strategy in treating BBAs.

Case reports
Case 1
In December of 2013, a 34-year-old male who lost consciousness, which was recovered shortly, was admitted to our emergency room. Except for severe a headache, there was no specific history of head trauma or medical illness.
In neurological examination, he showed a confused mentality with a Glasgow Coma Scale (GCS) of 13/15 and a Hunt
and Hess grade of II. There were no abnormal laboratory
findings. A non-contrasted brain computed tomography
(CT) scan showed a subarachnoid hemorrhage (SAH)
(Fig. 1a). Conventional four-vessel angiography confirmed a
4-mm-sized blister-like aneurysm of the supra-clinoid segment of the right ICA (Fig. 1b, c, d). There were no other
aneurysms or vascular malformations that could be related to
the SAH. Endovascular treatment seemed to be unsuitable due
to the broad-based aneurysmal neck and small morphology. A
right fronto-temporal craniotomy and an attempt of surgical
clipping were performed.
Fig. 1 a Initial brain CT showed
SAH. b, c, d Conventional fourvessel angiography and 3D
angiogram demonstrate a blood
blister-like aneurysm dilation at
the dorsal wall of the supraclinoid
segment of right ICA. The size is
4 mm

Acta Neurochir (2015) 157:1849–1854

During the operation, an extremely thin and defective
walled aneurysm was seen and part of the bulging wall
seemed to have a hemorrhage within it (Fig. 2a). Before
clipping, the ICG-VA was performed and revealed the filling defect of dye in aneurysm (Fig. 2b). After the temporary clip was applied on the proximal ICA, the aneurysm
and arterial wall were then covered thinly with Bemsheets
to prevent the clip from slipping, and then a Sugita-6 clip
was applied parallel to the arterial wall (Fig. 2c) so that
the clip blades could cover the arterial wall beyond the
lesion.
ICG-VA was performed again to confirm the patency of
parent artery and perforators (Fig. 2d). After the surgery, the
patient exhibited paraparesis. A follow-up brain CT angiogram showed vasospasms in both ACAs. The patient’s symptoms gradually improved through 3-H therapy.
A follow-up angiography 2 weeks later revealed a good
patency of the ICA and the obliteration of the aneurysm
(Fig. 2e, f). The patient had no residual motor deficit and
had returned to normal activities in 3 months after the
surgery.
Case 2
In February of 2014, a 53-year-old female presented with
SAH. She showed a drowsy mentality, with a Hunt and

Acta Neurochir (2015) 157:1849–1854

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Fig. 2 Intra-operative findings. a
In situ blister-like aneurysm. b
Specific ICG-VA finding of BBA
that has filling defect of dye in
aneurysm (arrow). c Bemsheets
covers the aneurysm before
clipping. d ICG-VA was
performed after clipping,
confirming intact blood flow of
the ICA and perforating arteries.
e, f A follow-up angiography
revealed good patency and no
significant vasospasm

Hess grade of II. Brain CT angiogram scan showed Fisher
grade IV SAH and a 3-mm-sized blister-like aneurysm of
the supraclinoid segment of the left ICA (Fig. 3). The
patient has a humpback, so that the conventional fourvessel angiography could not be performed. A left
fronto-temporal craniotomy was performed to attempt surgical clipping. During the operation, an extremely thin
walled aneurysm having a hemorrhage within it was seen
and an aneurysmal dome was defected (Fig. 4a). Through
the ICG-VA, we were able to see the filling defect of dye
in the aneurysm (Fig. 4b). The aneurysm and arterial wall
were covered thinly with Bemsheets and then a Sugita
clip was applied parallel to the arterial wall using the

same method as in case 1 (Fig. 4c). ICG-VA was performed again, showing the intact blood flow of the ICA
and perforating arteries (Fig. 4d). Five days after the
SAH, the patient suffered aphasia and a confused mental
state. A follow-up brain CT angiogram revealed vasospasms at both ACAs, MCAs, and PCAs. The patient’s
symptoms have gradually improved through the 3-H treatment. A follow-up brain CT angiogram several days later
revealed the obliteration of the aneurysm, no migration of
the aneurismal clip, and improvement of vasospasm
(Fig. 4e, f). At the 3-month follow-up check-up, the patient was doing well and her neurological examination
was normal.

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Acta Neurochir (2015) 157:1849–1854

Fig. 3 a Initial CT showed diffuse, Fisher grade IV SAH. b, c Brain CT angiogram showed an irregularity of the anterior wall of the left ICA

Fig. 4 Intra-operative findings. a
In situ blister-like aneurysm (note
the lack of aneurysm dome). b
Specific ICG-VA finding of BBA
that has filling defect of dye in
aneurysm (arrow). c Bemsheets
wraps the aneurysm before
clipping. d ICG-VA was
performed after clipping,
confirming intact blood flow of
the ICA and perforating arteries.
e, f A follow-up brain CT
angiogram revealed no migration
of the aneurismal clip and
improvement of vasospasm

Acta Neurochir (2015) 157:1849–1854

Discussion
BBAs are rare, accounting for 0.5–2.0 % of ruptured intracranial aneurysms, but are clinically important because they can
cause a SAH [10, 14, 17, 23]. The pathophysiology of BBAs
is not fully understood. Some studies suggest that BBAs are
not true aneurysms. BBAs consist of a fragile fibrin layer in a
focal wall defect with the absence of an internal elastic lamina
and media [6, 12]. Merely blood clots of fenestrations found in
the internal elastic lamina of affected carotid arteries [22], and
organization and growth of the blood clots on the focal wall
defect [1]. These segments are believed to undergo major
dynamic changes depending on blood pressure and sheer
stress. Consequentially, these are caused secondary to a
subadventitial dissection of the ICA, which may represent a
possible mechanism of BBAs’ formation. These pathophysiological characteristics are considered as a pseudoaneurysm
[6, 24] and therefore treatment strategies used for other typical
types of aneurysms cannot be applied for BBAs.
In our patients, intraoperative ICG-VA showed the filling
defect of dye in aneurysms. This demonstrates that organized
blood clots were on the focal wall defect. These intraoperative
ICG-VA findings support previous pathophysiological studies
and could support that BBA is a pseudoaneurysm radiologically instead of taking a biopsy of the lesion or performing an
autopsy to confirm the pathophysiological feature.
Treatment of BBAs remains challenging due to their small
size, broad-based morphology, and fragile thin wall, making
them prone to rupture during microsurgery [26]. Various treatment strategies have been developed to deal with BBAs. The
treatment modality should be tailored to not only the
pseudoaneurysm but also the affected ICA vascular wall in
order to prevent re-bleeding and regrowth. Proposed pathogenesis and ICG-VA finding of BBAs support that BBAs are a
pseudoaneurysm, so endovascular coil embolization alone has
been associated with a high intraprocedural rupture rate [17]
and should not be considered as a first option.

Fig. 5 ICG-VA could distinguish
the pseudoaneurysmal wall from
the normal internal carotid artery
wall (line transitional zone)

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Surgical treatment has the advantage of enabling direct
observation of the vascular lesion. Although intraoperative
rupture has been demonstrated to occur during dissection,
during clip closure, and after slipping-off the clip [15, 21],
these problems have been managed using various methods,
including trapping or occlusion, clipping on wrapping material [8, 16], suturing the tear [7, 26], and clipping with an
encircling clip [9, 20]. Some authors have emphasized that
clip blades are applied parallel to the ICA, taking part of
the normal carotid wall beyond the lesion [1, 12, 15, 21].
However, clipping, either directly or on a wrapping material, may compromise the patency of the parent artery and
injure branching vessels and perforators resulting in ischemia [11]. Ogawa et al. [15] reported ischemic complications in a patient with ICA stenosis after BBAs clipping.
As illustrated by our patients, we were able to preserve the
parent artery and perforator arteries through the ICG-VA.
Especially, before BBA clipping, we could distinguish the
pseudoaneurysmal wall from the normal internal carotid
artery wall by using ICG-VA. So, confirming the transitional zone (Fig. 5), we could perform the Bemsheetscovered clipping in the appropriate location, preventing a
slipping-off of the clip and ICA stenosis. After clipping,
through the ICG-VA, we could confirm the intact blood
flow of the ICA and perforating arteries

Conclusions
Intraoperative ICG-VA revealed the filling defect of dye in
aneurysm, supporting that BBAs are pseudoaneurysms. It also
helps to reduce perioperative aneurysm rupture and ischemic
complications, consequently improving patient outcome in
BBA cases. In addition, although not routinely recommended
in the treatment of BBAs, we believe that the Bemsheetscovered clipping is a safe and effective treatment for BBAs..

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Acta Neurochir (2015) 157:1849–1854

Acknowledgments All patients and guardian consent to the submission of case report (IRB of Chonnam National University Hospital).
Conflict of interest None.

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