Case Report

Complete Spontaneous Thrombosis and
Recanalization of a Ruptured Posterior Cerebral
Artery Aneurysm
Rüptüre Posterior Serebral Arter Anevrizmasının Tam Spontan
Trombozu ve Rekanalizasyonu
Du Weı1,2, Zhou Jıngru2, Fan Cungang2, Xue Yake1, Wang Donglıang2, Wei Zhengmao2,
Wei Xıntıng1, Zhang Qıngjun2
1The First Affiliated Hospital of Zhengzhou University, Department of Neurosurgery, Zhengzhou, Henan, China
2Peking University People’s Hospital, Department of Neurosurgery, Beijing, China

Corresponding Author: Zhang Qıngjun / E-mail: [email-masked]

ABSTRACT
Complete spontaneous thrombosis followed by recanalization of non-giant aneurysms is a rare event that can be discovered incidentally on
advanced neural images. In this case report, the authors described a woman who presented with subarachnoid hemorrhage (SAH) and left
posterior cerebral artery (PCA) territory ischemic stroke. Cerebral angiography revealed a left PCA aneurysm at the P1-P2 junction. The patient
received conservative treatment and repeated cerebral angiography 4 weeks later demonstrated the disappeared aneurysm. Subsequent
magnetic resonance imaging (MRI) and contrast-enhanced computed tomography (CT) demonstrated the totally thrombosed aneurysm with
hydrocephalus. Ventriculo-peritoneal shunt surgery for hydrocephalus was performed and the patient noted a great improvement of the
neurological deficit. Follow-up contrast-enhanced CT after 10 weeks revealed recurrence of the aneurysm. This case provides insight into the
natural dynamic process of intracranial aneurysm, and a complete thrombosed aneurysm has the potential for recanalization.
Keywords: Intracranial aneurysm, Subarachnoid hemorrhage, Spontaneous thrombosis, Recanalization

ÖZ
Dev olmayan anevrizmalarda rekanalizasyonla birlikte tam spontan tromboz nadirdir ve gelişmiş nöral görüntülerde tesadüfen bulunabilir.
Bu olgu raporunda yazarlar subaraknoid kanama (SAK) ve sol posterior serebral arter (PSA) bölgesinde iskemik inmeyle gelen bir hastayı
sunmaktadır. Serebral anjiyografi P1-P2 bileşkesinde bir sol PSA anevrizması göstermiştir. Hastaya konservatif tedavi verilmiş ve 4 hafta sonra
tekrarlanan serebral anjiyografi anevrizmanın kaybolduğunu ortaya koymuştur. Daha sonraki manyetik rezonans görüntüleme (MRG) ve
kontrastlı bilgisayarlı tomografi (BT) total tromboze olmuş anevrizma ve hidrosefali göstermiştir. Hidrosefali için ventriküloperitoneal şant
cerrahisi yapılmış ve hastanın nörolojik defisinde büyük bir düzelme görmüştür. 10 hafta sonra takip kontrastlı BT anevrizmanın tekrarladığını
göstermiştir. Bu olgu bir intrakraniyal anevrizmanın doğal dinamik süreci konusunda bilgi sağlamaktadır ve tam trombozlu bir anevrizmada
rekanalizasyon potansiyeli mevcuttur.
ANAHTAR SÖZCÜKLER: İntrakraniyal anevrizma, Subaraknoid kanama, Spontan tromboz, Rekanalizasyon

Introduction
Cerebral aneurysm is the principle cause of nontraumatic
subarachnoid hemorrhage due to rupture. Spontaneous
thrombosis of a giant intracranial aneurysm is not an
uncommon event and could be followed by a parent artery
thrombosis, ischemic stroke and focal neurological deficits
(10,2). There are many reports of spontaneous thrombosis
of giant aneurysms, and various factors have been discussed
in literature. These partially or completely thrombosed
aneurysms are considered unstable lesions that may either
grow, compress, recanalize or give rise to rupture events (3).
However, in non-giant aneurysms, the process of complete
thrombosis and recanalization has been rarely reported and
in general, is poorly understood.

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We describe a rare case of recanalization of a totally
thrombosed non-giant ruptured posterior cerebral artery
aneurysm and review the possible pathogenic mechanisms.
Case report
A 36-year-old woman was admitted to a local hospital
with sudden bursting headache and deterioration of
consciousness. Until her present illness, there was no past
medical history and no noticeable physical anomalies. Urgent
computed tomography (CT) scan of brain demonstrated
diffuse subarachnoid hemorrhage (SAH) with cerebral
infarction in the left posterior cerebral artery (PCA) territory
(Figure 1A,B). Cerebral angiography revealed a left PCA
aneurysm arising from the P1-P2 junction with vasospasm of

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A

b

A

b

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d

Figure 1: Axial plain CT scans
of brain (A, B) on admission
demonstrated subarachnoid
hemorrhage (SAH) with the
hypodensity in the left posterior
cerebral artery (PCA) territory.

Figure 2: Anteroposterior
angiogram (A), lateral angiogram
(B) and 3D reconstruction of
dynamic DSA (C, D) showed a left
PCA aneurysm arising from the P1P2 junction with vasospasm of the
parent artery.

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Wei D. et al: Spontaneous Thrombosis and Recanalization of Posterior Cerebral Artery Aneurysm

A

b

the parent artery (Figure 2A-D). The patient was treated with
non-steroidal anti-inflammation and anticonvulsant drugs,
and her level of consciousness improved. Four weeks later,
this patient was transferred to our neurosurgical department
for further treatment. At the moment of the admittance, she
exhibited orientation disturbance, right hemiparesis and
right homonymous hemianopsia. Repeated angiography
was performed on the day of transfer that failed to show the
aneurysm (Figure 3A,B). Sequential head magnetic resonance
imaging (MRI) and contrast-enhanced CT demonstrated the
complete thrombosed aneurysm associated with left PCA
territory infarction and hydrocephalus (Figure 4A-D). These
findings were considered to be complete spontaneous
thrombosis of the aneurysm and microsurgical clipping of the
aneurysm was deferred. The patient underwent a ventriculoperitoneal shunt because of hydrocephalus. Thereafter, she
was noted a great improvement of neurological deficit and
was discharged from our hospital.
Follow-up contrast-enhanced CT after 10 weeks in the district
hospital demonstrated recanalization of the aneurysm (Figure
5A,B). Considering the recanalized aneurysm may rerupture,
the need of surgical clipping or endovascular treatment was
strongly recommended. However, the suggestion was refused
and the patient is receiving rehabilitation therapy.

Figure 3: Anteroposterior (A) and
lateral (B) angiograms taken 4
weeks later showed the aneurysm
disappeared completely.

considered to be the mainly factor for thrombus formation
because of hemodynamic disturbance (1). Intraluminal
thrombosis may occur in aneurysms with a relatively small
neck (8). In addition, other biophysiological factors such
as increased blood coagulability, age of the aneurysm,
hemodymanics in the parent artery, direct distortion of
the parent artery by the aneurysmal sac, turbulent flow
in aneurysms, endothelial damage and increased platelet
aggregation have also been proposed (2,1).
The angiographic procedure itself and contrast media used in
angiography is another factor in spontaneous thrombosis of
intracranial aneurysms. In our patient, follow-up angiogram
after 4 weeks showed disappeared aneurysm. It is estimated
that no more than 1% or 2% of ruptured aneurysms will
show thrombosis completely on subsequent angiography
(4). Although the relation between contrast media used
and clotting mechanism has not been well understood, it is
considered that both of non-ionic media and ionic media may
cause thrombosis of aneurysms by platelet and red blood cell
aggregation, slow flow due to partial obstruction induced by
the catheter, endothelial injury or spasm of the parent artery
(5).

Spontaneous thrombosis of ruptured aneurysms is a
well-documented phenomenon in the natural history of
intracranial aneurysms. While it is more common in giant
intracranial aneurysms, occurring in approximately 50%
of cases, the occurrence of these phenomena in non-giant
aneurysms has been rarely reported (9).

It is also pointed out that an aneurysm may diminish in size
or disappear completely after partial or complete temporary
or permanent occlusion of the parent artery (2). In our case,
clinical and imaging correlation provided evidence that the
aneurysm could have thrombosed and had originated from
occlusion of the parent artery of the aneurysm. The possible
pathogenic mechanisms have been described as local
extension of the luminal thrombi, retrograde development of
a thrombus originating within the aneurysm or secondary to
dislodgement of intra-aneurysm thrombus (7).

Various biophysical and dynamic factors have been suggested
to influence the spontaneous thrombosis of intracranial
aneurysms. The aneurismal volume to neck size ratio has been

Although growth, recanalization, and hemorrhage of the
thrombosed giant aneurysms are well described, similar
events for non-giant aneurysms has been only rarely reported

Discussion

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Wei D. et al: Spontaneous Thrombosis and Recanalization of Posterior Cerebral Artery Aneurysm

A

c

A

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b

d

b

Figure 4: Axial MR image (A), plain
CT scan (B), and enhanced CT scan
(C, D) 4 weeks later indicated the
thrombosed aneurysm (measuring
approximately 20 mm in diameter)
with a left PCA territory infarction
and hydrocephalus.

Figure 5: Ten-week follow-up
axial contrast-enhanced CT
(A) and sagittal contrast-enhanced
CT (B) showed reappearance of
the aneurysm (measuring about
13×11×14 mm).

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Wei D. et al: Spontaneous Thrombosis and Recanalization of Posterior Cerebral Artery Aneurysm

(6). The mechanism of recanalization of spontaneously
thrombosed aneurysm is poorly understood with few
literature reports. As Pritz reported, the thrombosed non-giant
aneurysm behaved similar to a thrombosed giant aneurysm.
Growth or recanalization of this type of non-giant aneurysm
has been attributed to such possible reasons: hemorrhage
into the aneurysm wall, clot retraction or bleeding into the
thrombus itself (6).
The principal message of our study is that spontaneous
aneurysmal thrombosis cannot per se always be considered
a good or safe sign. Even a completely thrombosed non-giant
aneurysms are unstable and has little prognostic significance,
which should be taken carefully into consideration when
discussing the therapeutic management.
Conclusion
The natural history of intracranial aneurysms is a dynamic
process thought to be governed by delicate balance between
thrombogenesis and thrombolysis. Spontaneous thrombosis
of the aneurysms should be considered a possibility dynamic
state. However, even when the angiographically occluded
non-giant aneurysms may not predict a good outcome, there
is still a risk of recanalization and rupture. Therefore, even a
completely clotted, non-giant aneurysm can potentially be
life threatening and requires vigilant monitoring.
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Spontaneous thrombosis of an unruptured anterior
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