An Official publication of The Asian Congress of Neurological Surgeons (AsianCNS)

Search Article
Home About us Editorial board Search Ahead of print Current issue Archives Submit article Instructions Advertise Subscribe Contacts Login  Facebook Tweeter
  Users Online: 1603 Home Print this page Email this page Small font sizeDefault font sizeIncrease font size  

   Table of Contents      
CASE REPORT
Year : 2020  |  Volume : 15  |  Issue : 4  |  Page : 1055-1058

Spontaneous disappearance of an intracranial small unruptured aneurysm on magnetic resonance angiography: Report of two cases


1 Department of Neurosurgery, Tsukuba Memorial Hospital, Tsukuba, Ibaraki, Japan
2 Department of Radiology, Tsukuba Memorial Hospital, Tsukuba, Ibaraki, Japan
3 Department of Neurosurgery, Institute of Clinical Medicine, University of Tsukuba, Tsukuba, Ibaraki, Japan

Date of Submission07-Jun-2020
Date of Decision03-Jul-2020
Date of Acceptance13-Jul-2020
Date of Web Publication19-Oct-2020

Correspondence Address:
Dr. Eiichi Ishikawa
Department of Neurosurgery, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575
Japan
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ajns.AJNS_281_20

Rights and Permissions
  Abstract 

Spontaneous radiographic disappearance of cerebral aneurysms is often observed under special conditions such as giant aneurysms. However, spontaneous disappearance of an unruptured and nongiant intracranial saccular aneurysms is rare. We describe two cases of this rare vascular phenomenon. The first patient is a 64-year-old female diagnosed with a small unruptured aneurysm arising from the distal anterior cerebral artery. Spontaneous disappearance of the aneurysm on magnetic resonance angiography (MRA) was observed 5 years after the initial diagnosis. Continuous imaging surveillance also revealed spontaneous reappearance of the aneurysm 2 years later. The second patient is a 57-year-old female harboring a small unruptured saccular aneurysm arising from the M1–M2 bifurcation of the middle cerebral artery. The aneurysm showed spontaneous disappearance on MRA 13 years after the initial diagnosis. These cases provide a new insight into this natural dynamic process even in cases of a small unruptured intracranial saccular aneurysm.

Keywords: Spontaneous disappearance, thrombosis, unruptured cerebral aneurysm


How to cite this article:
Akimoto Y, Yanaka K, Onuma K, Nakamura K, Takahashi N, Ishikawa E. Spontaneous disappearance of an intracranial small unruptured aneurysm on magnetic resonance angiography: Report of two cases. Asian J Neurosurg 2020;15:1055-8

How to cite this URL:
Akimoto Y, Yanaka K, Onuma K, Nakamura K, Takahashi N, Ishikawa E. Spontaneous disappearance of an intracranial small unruptured aneurysm on magnetic resonance angiography: Report of two cases. Asian J Neurosurg [serial online] 2020 [cited 2021 Jan 18];15:1055-8. Available from: https://www.asianjns.org/text.asp?2020/15/4/1055/298565


  Introduction Top


Saccular intracranial aneurysms can often have a variable degree of thrombosis. Although spontaneous thrombosis including partial thrombosis in giant aneurysms is a relatively common vascular event,[1],[2],[3] the occurrence of this phenomenon in nongiant saccular aneurysms is rarely reported.[4],[5],[6] Here, we report two cases of a small unruptured saccular aneurysm showing a radiographic spontaneous disappearance and present a brief literature review related to these cases.


  Case Reports Top


Case 1

A 64-year-old female visited our hospital for a brain checkup in November, 2011. An aneurysm located at the left distal anterior cerebral artery was found on magnetic resonance angiography (MRA) [Figure 1]a. Three-dimensional computed tomography (CT) angiography performed at the same time showed no vessel stenosis around the aneurysm [Figure 2]. The size of the aneurysm was 4.9 mm in diameter. Laboratory tests revealed no abnormalities, including those of the coagulation system. Follow-up MRA, conducted every 6 months, showed no remarkable change of the aneurysm for 3.5 years after the initial diagnosis. MRA performed 4 years after the initial diagnosis showed a slight reduction in the aneurysm size [Figure 1]b. The aneurysm completely disappeared the following year [Figure 1]c. MRA performed 2 years after the disappearance of the aneurysm showed a recurrence at the same site [Figure 1]d. MRA performed 1 year after the recurrence showed a slight enlargement of the aneurysm [Figure 1]e.
Figure 1: (a) Magnetic resonance imaging at first examination showing a small unruptured aneurysm (arrow) arising from the distal anterior cerebral artery. (b) Magnetic resonance imaging performed 4 years after the initial diagnosis showing a slight reduction in aneurysm size. (c) Magnetic resonance imaging performed 5 years after the initial diagnosis showing complete disappearance of the aneurysm. (d) Magnetic resonance imaging performed 2 years after disappearance showing spontaneous recanalization of the aneurysm. (e) Magnetic resonance imaging performed 1 year after recanalization showing a slight enlargement of the aneurysm

Click here to view
Figure 2: Three-dimensional computed tomography angiography performed at the initial diagnosis showing no vessel stenosis around the aneurysm

Click here to view


Case 2

A 57-year-old female visited our hospital for a brain checkup in October, 2006. A saccular aneurysm located at M1–M2 bifurcation of the right middle cerebral artery was found on MRA [Figure 3]a. The size of the aneurysm was 2.4 mm in diameter. Laboratory tests revealed no abnormalities including those of the coagulation system. Follow-up MRA, conducted once a year, showed no remarkable change for 11 years [Figure 3]b, but showed spontaneous disappearance of the aneurysm 13 years after the initial diagnosis [Figure 3]c. Further radiographic follow-up is planned.
Figure 3: (a) Magnetic resonance imaging at first examination showing a small unruptured aneurysm (arrow) arising from the bifurcation of the middle cerebral artery. (b) Magnetic resonance imaging performed 11 years after the initial diagnosis showing unremarkable change of the aneurysm size. (c) Magnetic resonance imaging performed 13 years after the initial diagnosis showing complete disappearance of the aneurysm

Click here to view



  Discussion Top


Spontaneous radiographic disappearance of intracranial aneurysms has been reported to occur under special conditions including postsubarachnoid hemorrhage aneurysms,[7] giant/fusiform aneurysms,[8] dissecting aneurysms,[9] mycotic aneurysms,[10] neoplastic aneurysms,[11] traumatic aneurysms,[12] aneurysms associated with moyamoya disease[13] or arteriovenous malformation,[14] aneurysms associated with the parent artery occlusion,[8] and aneurysms associated with surgical interventions.[15] Intimal repair around the aneurysm can occur in a small number of cases,[10],[11],[13],[14] but the major etiology of this phenomenon is thought to be spontaneous intra-aneurysmal thrombosis. It is common in giant intracranial aneurysms, occurring in approximately 50% of cases.[16] The natural history of intracranial aneurysms is a dynamic process thought to be governed by a delicate balance between thrombogenesis and thrombolysis. The exact mechanism behind the intra-aneurysmal thrombosis is unknown, but the turbulent blood flow within an aneurysm is a well-known fact, which can account for complete or partial thrombosis of the aneurysm, together with endothelial injury. Despite the fact that spontaneous thrombosis is more frequently associated with giant rather than nongiant aneurysms,[3] the latter comprise the majority of cerebral ischemia cases related to unruptured aneurysms.[17] Therefore, spontaneous thrombosis occurring in a small unruptured aneurysm may be tightly related with a radiologic disappearance.

Spontaneous radiologic disappearance or reduction in size of a small unruptured saccular aneurysm was reported to be rare. To the best of our knowledge, only five cases[4],[5],[6] including ours have been reported previously [Table 1]. The average age at initial diagnosis was 62.6 years and all aneurysms were located in the anterior cerebral circulation. The average size of the aneurysms was 3.8 mm in diameter. All cases showed a spontaneous disappearance or reduction in size on MRA or CT angiography without any intervention; the mean interval between the initial diagnosis and the radiographic disappearance was 7.0 years. The first case (case 1) of those presented is the initial case to show spontaneous radiographic disappearance and is also followed by spontaneous reappearance of a small unruptured saccular aneurysm.
Table 1: Summary of cases showing spontaneous disappearance of a small unruptured aneurysm

Click here to view


In current clinical practice, most patients with small unruptured saccular aneurysms are managed conservatively. However, as in our first case, even radiologically occult aneurysms have a risk of recanalization and of possible future rupture. Therefore, this observation should be kept in mind, and strict and vigilant radiographic follow-up is essential, even in patients with small unruptured saccular aneurysms.


  Conclusion Top


We report two cases of small unruptured saccular aneurysms showing spontaneous disappearance on MRA; one showed a spontaneous disappearance also followed by spontaneous reappearance on MRA. Therefore, even radiologically disappeared small unruptured aneurysms still have a risk of recanalization and of possible future rupture. Strict follow-up including serial imaging examinations is required.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Acknowledgments

The authors thank Dr. Alexander Zaboronok, Department of Neurosurgery, and Thomas Mayers of the Medical English Communications Center of the Faculty of Medicine, University of Tsukuba, for manuscript revision.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
de Aguiar GB, Pagotto MV, Conti ML, Veiga JC. Spontaneous thrombosis of giant intracranial aneurysm and posterior cerebral artery followed by also spontaneous recanalization. Surg Neurol Int 2016;7:15.  Back to cited text no. 1
    
2.
Atkinson JL, Lane JI, Colbassani HJ, Llewellyn DM. Spontaneous thrombosis of posterior cerebral artery aneurysm with angiographic reappearance. Case report. J Neurosurg 1993;79:434-7.  Back to cited text no. 2
    
3.
Brownlee RD, Tranmer BI, Sevick RJ, Karmy G, Curry BJ. Spontaneous thrombosis of an unruptured anterior communicating artery aneurysm. An unusual cause of ischemic stroke. Stroke 1995;26:1945-9.  Back to cited text no. 3
    
4.
Choi CY, Han SR, Yee GT, Lee CH. Spontaneous regression of an unruptured and non-giant intracranial aneurysm. J Korean Neurosurg Soc 2012;52:243-5.  Back to cited text no. 4
    
5.
Yamada Y, Kinjo T, Ohki M, Kayama T. Spontaneous thrombosis of an unruptured internal carotid artery aneurysm: A case report. Surg Cereb Strok 2010;38:114-8.  Back to cited text no. 5
    
6.
Yokoya S, Hino A, Oka H. Rare spontaneous disappearance of intracranial aneurysm. World Neurosurg 2020;134:452-3.  Back to cited text no. 6
    
7.
Little AS, Garrett M, Germain R, Farhataziz N, Albuquerque FC, McDougall CG, et al. Evaluation of patients with spontaneous subarachnoid hemorrhage and negative angiography. Neurosurgery 2007;61:1139-50.  Back to cited text no. 7
    
8.
Kondo A, Yasuhara T, Sugiu K, Ohmoto T. Spontaneous thrombosis of a fusiform aneurysm arising from the distal posterior cerebral artery: Case report. No Shinkei Geka 2003;31:189-93.  Back to cited text no. 8
    
9.
Zhang YS, Wang S, Wang Y, Tian ZB, Liu J, Wang K, et al. Treatment for spontaneous intracranial dissecting aneurysms in childhood: A retrospective study of 26 cases. Front Neurol 2016;7:224.  Back to cited text no. 9
    
10.
Allen LM, Fowler AM, Walker C, Derdeyn CP, Nguyen BV, Hasso AN, et al. Retrospective review of cerebral mycotic aneurysms in 26 patients: Focus on treatment in strongly immunocompromised patients with a brief literature review. AJNR Am J Neuroradiol 2013;34:823-7.  Back to cited text no. 10
    
11.
Huang Y, Chen J, Wang J. Intracranial aneurysm disappeared after resection of a cardiac myxoma. Int J Clin Exp Med 2015;8:8214-7.  Back to cited text no. 11
    
12.
Morón F, Benndorf G, Akpek S, Dempsy R, Strother CM. Spontaneous thrombosis of a traumatic posterior cerebral artery aneurysm in a child. AJNR Am J Neuroradiol 2005;26:58-60.  Back to cited text no. 12
    
13.
Peltier J, Vinchon M, Soto-Ares G, Dhellemmes P. Disappearance of a middle cerebral artery aneurysm associated with Moyamoya syndrome after revascularization in a child: Case report. Childs Nerv Syst 2008;24:1483-7.  Back to cited text no. 13
    
14.
Hodozuka A, Sako K, Yonemasu Y, Suzuki N, Fujita T, Ohgami S. Spontaneous disappearance of aneurysm after total removal of accompanying intracranial arteriovenous malformation. Case report. Neurol Med Chir (Tokyo) 1991;31:966-71.  Back to cited text no. 14
    
15.
Pop R, Chibarro S, Manisor M, Proust F, Beaujeux R. Spontaneous thrombosis of a basilar tip aneurysm after ventriculoperitoneal shunting. BMJ Case Rep 2015;2015:bcr2015011841.  Back to cited text no. 15
    
16.
Whittle IR, Dorsch NW, Besser M. Spontaneous thrombosis in giant intracranial aneurysms. J Neurol Neurosurg Psychiatry 1982;45:1040-7.  Back to cited text no. 16
    
17.
Calviere L, Viguier A, Da Silva NA Jr., Cognard C, Larrue V. Unruptured intracranial aneurysm as a cause of cerebral ischemia. Clin Neurol Neurosurg 2011;113:28-33.  Back to cited text no. 17
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1]



 

Top
 
 
  Search
 
<
Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
Access Statistics
Email Alert *
Add to My List *
* Registration required (free)  

 
  In this article
   Abstract
  Introduction
  Case Reports
  Discussion
  Conclusion
   References
   Article Figures
   Article Tables

 Article Access Statistics
    Viewed158    
    Printed8    
    Emailed0    
    PDF Downloaded22    
    Comments [Add]    

Recommend this journal