Volume: 43 Issue: 3
Year: 2023, Page: 831-834, Doi: https://doi.org/10.51248/.v43i3.2557
Introduction and Aim: The Circle of Willis (CoW) is an arterial hexagon in the interpeduncular fossa formed by the basilar and internal carotid arteries. It permits anastomotic circulation between that two-arterial system. Variations in the pattern and the calibre of the arteries that make up the CoW were common. Few noted variations include hypoplasia or aplasia of either one or both posterior or anterior communicating arteries, aplasia, or fenestrations of the anterior communicating artery. Considering the surgical importance of this arterial circle, as it allows equalization of blood flow between the two sides of the brain, this observational study was done to identify the variations in the formation pattern and the gross morphometry of CoW.
Materials and Methods: Thirty radiological images of patients undergoing neurovascular imaging for various reasons in the Department of Radiology and patients were obtained for the study.
Results: Among the 30 studied CT and MR angiographic images, 21 (73.3%) of the circles exhibit the usual pattern of CoW formation, and the remaining 9 (27.7%) showed variations. Among the 30 radiological images, 25 (83.33%) were complete circles, 4 (13.33%) were incomplete in the posterior part and 1 (3.33%) was incomplete in the anterior part of the CoW.
Conclusion: Understanding the typical formation of CoW and its variations is essential in the surgical correction of a few intracranial emergencies like hemorrhage, infarction, aneurysms, and other neurovascular surgeries of the brain.
Keywords: Circle of Willis; Communicating vessels; Hemorrhage; Hypoplastic
1. O'Connor, J.P. Thomas Willis and the background to Cerebri Anatome. J R Soc Med. 2003; 96(3):139-143.
2. Windle, B.C., Bertram, C.A. On the arteries forming the circle of Willis. J Anat Physiol. 1887; 22:289-293.
3. Prince, E.A., Ahn, S.H. Basic vascular neuroanatomy of the brain and spine: what the general interventional radiologist needs to know. Semin Intervent Radiol. 2013; 30(3):234-239.
4. Menshawi, K., Mohr, J.P., Gutierrez. J. A Functional perspective on the embryology and anatomy of the cerebral blood supply. J Stroke. 2015; 17(2):144-158.
5. Krishnaswamy, A., Klein, J.P., Kapadia, S.R. Clinical cerebrovascular anatomy. Catheter Cardiovasc Interv. 2010; 75(4):530-539.
6. Robben, D., Türetken, E., Sunaert, S., Thijs, V., Wilms, G., Fua, P., et al., Simultaneous segmentation, and anatomical labelling of the cerebral vasculature. Med Image Anal. 2016; 32:201-215.
7. Hartkamp, K., Grond, V.J., Hillen, B. Circle of Willis: Morphologic variation on three-dimensional time-of-flight MR angiograms. Radiol.1998; 207:103-111.
8. Eftekhar, B., Dadmehr, M., Ansari, S., Ghodsi, M., Nazparvar, B., Ketabchi, E. Are the distributions of variations of circle of Willis different in different populations? - Results of an anatomical study and review of literature. BMC Neurol. 2006; 6:22.
9. Bergman, R.A., Afifi, A.K., Miyaucchi, R. Compendium of human anatomic variations text atlas and world literature. Baltimore Urban and Schwarenberg; 1988: 66-68.
10. Prasanna, L. C., Andrade, L. S., Ravichandra, P., Hosapatna, M. An insight into the circle of Willis, its variation in the formation and component vessels in the adult human cadavers. Ethiopian Medical Journal. 58; 2:145-150.
11. Fawcett, E., Blachford, J.V. The circle of Willis: An examination of 700 specimens. J Anat and Physiol. 1905; 40:63-70.
12. Maaly, M.A., Ismail, A.A. Three-dimensional magnetic resonance angiography of the circle of willis: Anatomical variations in general Egyptian population. Egyptian Journal of Radiology and Nuclear Medicine. 2011; 42:405-412.
13. Kamath, S. Observations on the length and diameter of vessel forming the circle of Willis. J Anat. 1981;133: 419-423.
14. Orlandini, G.E., Ruggiero, C.S., Orlandini, Z., Gulisano, M. Blood vessel size of circulus arteriosus cerebri (circle of Willis): Statistical research on 100 human subjects. Act Anat. 1985; 123:72-76.
15. Hillen, B. The variability of the circulus arteriosus (Willis II): Order or anarchy. Acta Ant .1987;129:74-80.
16. Van-Overbeeke, J.J., Hillen, B., Tulleken, C.A. A comparative study of the circle of Willis in fetal and adult life. The configuration of posterior bifurcation of the posterior communicating artery. J Anat. 1991; 176:45-54.
17. Windle, B.C., Bertram, C.A. On the arteries forming the circle of Willis. J Anat Physiol. 1887; 22:289-293.
18. Vare, A.M., Bansal, P.C. Arterial pattern at the base of the human brain. J Anat Soc India. 1970; 19 (3):71-79.
19. Luzsa, G. X- ray Anatomy of the vascular system. Butterworth; 1974: 131-141.
20. Osborn, A. Diagnostic Cerebral Angiography. 2nd ed. Lippincott. Williams and Wilkins. New York 1999; 105-111.
21. Riggs, H.E. Retraction from Rana P V S. Dr. Thomas Willis and his ‘Circle’ in the brain. Nepal Journal of Neuroscience 2005; 2:77-79.
22. Stephen, P.L., John. Cerebral angiography; the anterior cerebral disease. In: Henry J M Barnett, Mohr JP, Bennett M
Stein, editors. Stroke. Pathophysiology, Diagnosis and Management. 2nd ed. Churchill Livingstone. New York 1991; 217-299.
23. Macchi, C., Catini, C., Federico, C. Magnetic resonance angiographic evaluation of circulus arteriosus cerebri (circle of Willis): a morphologic study in 100 human healthy subjects. Ital J Anat Embryol. 1996; 101(2): 115-123.
24. Kane, A.G., Dillon, W.P., Barkovich, A.J., Norman, D., Dowd, C.F., Kane, T.T. Reduced calibre of the internal carotid artery: A normal finding with ipsilateral absence or hypoplasia of the A1 segment. Am J Neuroradiol. 1996;17(7): 1295-1301.
25. Schomer, D.F., Marks, M.P. The anatomy of the posterior communicating artery as a risk factor for ischemic cerebral infarction. New Eng J Med.1994;330 (22): 1565-1570.
26. Pradhan, P., Baral, K., Dan, U., Prasad, R. Morphological study of circle of Willis–A short review. J Anat Soc Ind. 2009; 58(1):35-39.
27. Wu, H.M., Chuang, Y.M. The clinical relevance of the fetal variant of the circle of Willis and its influence on the cerebral collateral circulation. Acta Neurol Taiwan. 2011;20(4):232-242
Praveena Ravichandran, Kumar MR Bhat, Mamatha Hosapatna, Prasanna L.C. Radiological observations of the branches of circle of willis for surgical perception. Biomedicine: 2023; 43(3): 831-834