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Year : 2020  |  Volume : 63  |  Issue : 4  |  Page : 651-653
Distal anterior cerebral artery aneurysm with bilateral fetal posterior cerebral arteries and trifurcation of anterior cerebral artery

1 Department of Neuropathology, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India
2 Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India

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Date of Submission31-Dec-2019
Date of Decision18-Apr-2020
Date of Acceptance21-Apr-2020
Date of Web Publication28-Oct-2020


Developmental vascular anomalies of brain are non-modifiable risk factors for the development of aneurysms and are prone for rupture. We report one such association in a 44–year-old gentleman who succumbed to subarachnoid hemorrhage (SAH) secondary to ruptured distal anterior cerebral artery aneurysm associated with vascular anomalies in the anterior and posterior circulation that included trifurcation of anterior cerebral artery and bilateral fetal posterior cerebral arteries. We identified multiple anomalies in circle of Willis that could have contributed to the formation of aneurysm and early rupture. Knowledge of these variations is essential to plan early and optimum management with close follow-up.

Keywords: Aneurysm, developmental vascular anomalies, fetal posterior cerebral arteries, subarachnoid hemorrhage, trifurcation

How to cite this article:
Sivakoti S, Chavali P, Nandeesh B N, Konar SK, Mahadevan A. Distal anterior cerebral artery aneurysm with bilateral fetal posterior cerebral arteries and trifurcation of anterior cerebral artery. Indian J Pathol Microbiol 2020;63:651-3

How to cite this URL:
Sivakoti S, Chavali P, Nandeesh B N, Konar SK, Mahadevan A. Distal anterior cerebral artery aneurysm with bilateral fetal posterior cerebral arteries and trifurcation of anterior cerebral artery. Indian J Pathol Microbiol [serial online] 2020 [cited 2021 May 16];63:651-3. Available from: https://www.ijpmonline.org/text.asp?2020/63/4/651/299294

   Introduction Top

Aneurysms are the most common vascular abnormalities. But not all aneurysms cause complications. The formation and progression of aneurysm is multifactorial. Multiple anomalies are not uncommon and account for 28% in intracerebral aneurysms, higher in posterior circulation and combined anterior and posterior part of circulation.[1] The present case is an example of an aneurysm associated with multiple developmental anomalies and acquired risk factors, which resulted in the development and complication at an early age.

   Case Presentation Top

A 44-year-old man presented to the neurosurgical emergency with a severe “thunderclap” type of headache associated with projectile vomiting and seizures. A CT scan of brain revealed subarachnoid hemorrhage (SAH) probably secondary to left distal anterior cerebral artery (ACA) aneurysm [Figure 1]a and [Figure 1]b. CT angiogram confirmed a saccular aneurysm at the branch point of A2 segment of left ACA [Figure 1]c and [Figure 1]d. He deteriorated rapidly and succumbed to death within 24 h of presentation.
Figure 1: (a) CT (Plain, Axial) shows thick basal subarachnoid hemorrhage with left side thin fronto-temporo-parietal subdural hematoma. (b) CT (Contrast, Axial) shows an aneurysm arising from the A2 segment of Anterior cerebral artery. (c) CT Angiogram (Coronal Recon.) shows a saccular aneurysm arising from A2 segment. (d) CT Angiogram (Sagittal Recon.) shows aneurysm directed anterosuperior at the branch point

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Autopsy findings

A partial autopsy was performed. On opening the skull, a thin film of SAH was observed covering bilateral frontal and fronto-parietal regions, predominantly on the right side. At the base of the brain, blood was seen filling the basal cisterns and the vessels of the anterior circulation was embedded within the hemorrhage. The circle of Willis was carefully dissected out from the hemorrhage and examined. The A1 segments of bilateral ACA was normal. Distal to the Anterior Communicating artery (ACom), three arteries were found to originate, one of them being thin (string-like) that appeared to be in continuity with the right A1 segment of ACA and the other two of relatively equal size appeared as branches of the left ACA. The left ACA with its two vascular branches appeared to supply most of the blood to the frontal cortices bilaterally. One of the left ACA branches showed a bilobed saccular aneurysm which was situated approximately 1.5 cm distance (distal) from the ACOM [Figure 2]. The aneurysm was measuring approximately 0.7–0.8 cm in diameter and the neck was incorporated at the origin of a branch. The two posterior communicating arteries (PCom) were seen continuing as PCAs and the calibers of bilateral PCom were thicker than the precommunicating PCA (P1 segment). There were no other aneurysms detected in the ACA or other vessels of the Circle of Willis. Grade 1 atherosclerotic changes were seen involving bilateral ICA, MCA, and PCA, and basilar artery also. The cause of death in this patient was due to rupture of aneurysm with massive SAH causing raised intracranial tension, central herniation, and brain stem compression accompanied by hemorrhage leading to death in this patient with multiple vascular anomalies of Circle of Willis.
Figure 2: Shows anomalies both in anterior and posterior circulation of brain and left distal ACA aneurysm. Thin arrow indicates (↘) trifurcation of A2 segment, arrow head indicate (◂) fetal PCA which is thicker than PCA (⋆) and thick arrow indicate (←) bilobed sacular aneurysm in left distal ACA

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   Discussion Top

The vascular system of the brain comprises of anterior and posterior circulation derived from internal carotid and vertebrobasilar system respectively, that anastomose at the base of the brain. Complete symmetrical anastomosis pattern is seen in 30–50% of general population.[2],[3] The various arterial anomalies that can occur, include variation in caliber of the vessel like hypoplasia and aplasia, and presence of accessory vessels like duplication, trifurcation, and fenestration. These are considered as developmental modification rather than genetically determined anomalies, resulting from maldevelopment in the early embryonic life and persistence in postnatal life.[4] They play an important role in cerebrovascular diseases, aneurysms, and migraine. Orakdogen et al. observed association of vascular variation with aneurysms in 57.8% of cases.[1] Anomalies are more frequently observed in aneurysms that rupture as compared to non-bleeding aneurysms and the frequency of associated anomalies is higher in the presence of multiple aneurysms.[5],[6] ACom and PCom aneurysm are seen associated with variants around circle of Willis suggesting the development of aneurysm due to hemodynamic stress.[7],[8],[9] The intracranial vessels possess thin internal elastic lamina, lower proportion of cells in media, lack of external elastic lamina, thinner adventitia, and lack of connective tissue support in subarachnoid space as compared to extracranial vessels, hence these vessels are more vulnerable for aneurysm formation.

There is a wide variation in the incidence of anatomical variation in circle of Willis. Some studies observed fetal origin of posterior cerebral artery (FPCA) as the most common normal variation of circle of Willis accounting for 28% among the general population. Bilateral persistence of fetal PCA accounts for 8%.[10] Orakdogen et al. studied variation in 128 aneurysmal cases, hypoplasia and aplasia were observed to be the most common variations.[1] Hypo/aplasia is frequently observed in the anterior circulation followed by posterior circulation. Duplications and triplication are predominantly seen in anterior part of cerebral circulation with anterior communicating artery being the most commonly involved vessel followed by anterior cerebral artery and persistence of midline corpus callosal branch of ACA.[3] Distal ACA are often associated with anomalies. Bihemispheric ACA is more common and trifurcation and azygous are comparatively less.[11] The incidence of trifurcation of anterior cerebral artery in general population is 2–13%.[12] This is a normal variation in the circle of Willis, and not considered a risk factor of aneurysm.

Anomalies like bifurcation and fenestration are associated with risk of developing aneurysm at branching points, while circle of Willis anomalies like azygous and absent ACA, hypoplastic and aplastic A1 segment of ACA, trifurcated and bihemispheric A2 segment of ACA and fetal PCA are associated with increased incidence of rupture of an aneurysm.[12],[13]

Development of aneurysm is multifactorial. Knowledge about anatomical variation is important for appropriate planning and treatment. Anatomical variation causes hemodynamic stress on the distal areas of the wall and results in propagation of aneurysm. To our knowledge, the present case is the first case reported in literature with unusual combination of bilateral fetal PCA and trifurcation of ACA resulting in dominance of left anterior circulation vessels causing early progression of Distal ACA aneurysm and rupture. To conclude, not all anatomical variants in Circle of Willis are responsible for formation of aneurysm but can cause progression of aneurysm to early rupture. Association of multiple anatomical variation can reduce the mean age of incidence of aneurysmal rupture as seen in this case. The knowledge of vascular variation is helpful for the neurosurgeon to avoid complications during surgery.

Declaration of patient consent

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

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Orakdogen M, Emon ST, Somay H, Engin T, Hakan T. Vascular variations associated with intracranial aneurysms. Turk Neurosurg 2017;27:853-62.  Back to cited text no. 1
Kapoor K, Singh B, Dewan LI. Variations in the configuration of the circle of Willis. Anat Sci Int 2008;83:96-106.  Back to cited text no. 2
Iqbal S. A comprehensive study of the anatomical variations of the circle of Willis in adult human brains. J Clin Diagn Res 2013;7:2423-7.  Back to cited text no. 3
Malamateniou C, Adams ME, Srinivasan L, Allsop JM, Counsell SJ, Cowan FM, et al. The anatomic variations of the circle of Willis in preterm-at-term and term-born infants: An MR angiography study at 3T. Am J Neuroradiol 2009;30:1955-62.  Back to cited text no. 4
Stojanović N, Stefanović I, Ranđelović S, Mitić R, Bošnjaković P, Stojanov D. Presence of anatomical variations of the circle of Willis in patients undergoing surgical treatment for ruptured intracranial aneurysms. Vojnosanit Pregl 2009;66:711-7.  Back to cited text no. 5
Mazighi M, Porter PJ, Rodesch G, Alvarez H, Aghakhani N, Lasjaunias P. Vascular anomalies and the risk of multiple aneurysms development and bleeding. Interv Neuroradiol 2002;8:15-20.  Back to cited text no. 6
Gibo H, Carver CC, Rhoton AL Jr, Lenkey C, Mitchell RJ. Microsurgical anatomy of the middle cerebral artery. J Neurosurg 1981;54:151-69.  Back to cited text no. 7
Kayembe KN, Sasahara M, Hazama F. Cerebral aneurysms and variations in the circle of Willis. Stroke 1984;15:846-50.  Back to cited text no. 8
Krasny A, Nensa F, Sandalcioglu IE, Göricke SL, Wanke I, Gramsch C, et al. Association of aneurysms and variation of the A1 segment. J Neurointerv Surg 2014;6:178-83.  Back to cited text no. 9
Kamath S. Observations on the length and diameter of vessels forming the circle of Willis. J Anat 1981;133:419-23.  Back to cited text no. 10
Lehecka M, Dashti R, Lehto H, Kivisaari R, Niemela M, Hernesniemi J. Distal anterior cerebral artery aneurysms. Acta Neurochir Suppl 2010;107:15-26.  Back to cited text no. 11
Dimmick SJ, Faulder KC. Normal variants of the cerebral circulation at multidetector CT angiography. Radiographics 2009;29:1027-43.  Back to cited text no. 12
Lazzaro MA, Ouyang B, Chen M. The role of circle of Willis anomalies in cerebral aneurysm rupture. J Neurointerv Surg 2012;4:22-6.  Back to cited text no. 13

Correspondence Address:
B N Nandeesh
Department of Neuropathology, National institute of Mental Health and Neurosciences, Bengaluru
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_1021_19

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