- Department of Neurosurgery, Firoozgar Hospital, Tehran University of Medical Sciences, Tehran, Iran
- Department of Neurosurgery, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran
Department of Neurosurgery, Sina Hospital, Tehran University of Medical Sciences, Tehran, Iran
DOI:10.4103/2152-7806.112185Copyright: © 2013 Hashemi SMR This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
How to cite this article: Ramak Hashemi SM, Mahmoodi R, Amirjamshidi A. Variations in the Anatomy of the Willis’ circle: A 3-year cross-sectional study from Iran (2006-2009). Are the distributions of variations of circle of Willis different in different populations? Result of an anatomical study and review of literature. Surg Neurol Int 17-May-2013;4:65
How to cite this URL: Ramak Hashemi SM, Mahmoodi R, Amirjamshidi A. Variations in the Anatomy of the Willis’ circle: A 3-year cross-sectional study from Iran (2006-2009). Are the distributions of variations of circle of Willis different in different populations? Result of an anatomical study and review of literature. Surg Neurol Int 17-May-2013;4:65. Available from: http://sni.wpengine.com/surgicalint_articles/variations-in-the-anatomy-of-the-willis-circle-a-3-year-cross-sectional-study-from-iran-2006-2009-are-the-distributions-of-variations-of-circle-of-willis-different-in-different-population/
Background:It is not well known whether the distributions of variations of circle of Willis (CW) are different in different populations. Previous studies have indicated: (a) The variations of the structure of the CW in different populations and ethnic and (b) some correlation between those congenital anatomical variations and possible cerebrovascular diseases. The frequency of such anatomical variations has not been evaluated sufficiently in the Iranian population. The aim of this study is to find the variations of the anatomy of the vessels in the CW in sample population of Iranian people and compare it with other available studies in the literature, providing a new grouping for variations.
Methods:Samples were obtained from 200 autopsies in different ages, all retrieved in the department of Forensic Medicine, Tehran university of Medical Sciences after achieving permission from the Department of Ethics and Medico-legal Sciences. The CW was examined directly, using magnification, at the base of the brain. The cerebral vessels were observed for their configuration and their calibers were measured directly. Variations were noted and grouped into different categories.
Results:Out of the 200 specimens examined, 69 (34.5%) were compatible with the typical anatomy of the CW. In the remaining 65.5% of the specimens, there were variations in the CW. Hypoplasia of the posterior communicating arteries was the most common variation in our study. One of the autopsies showed the presence of an aneurysm (0.5%).
Conclusion:The anatomical variations found in our study were not significantly different from those reported in the literature. Based on the available data; (a) there is no evidence that the distribution of the variations of the anatomy of the CW is different in various societies and (b) the prevalence of the congenital aneurysmal changes in this region is not low in the Iranian population.
Keywords: Aneurysm, autopsy, circle of Willis, variation
It has been shown that about 50% of the population carries a kind of variation in their circle of Willis (CW) congenitally.[
This is a cross-sectional study, regarding the data collected from evaluating the CW directly in fresh cadaveric specimens autopsied during a 3-year period. The variants of age and sex varied in the specimens incidentally and consequently. Brains were obtained from fresh cadavers autopsied using standard techniques while all the brains having evidences of pathologies or traumatic brain injury were excluded. Finally, 200 specimens were evaluated. The vessels were observed for caliber and typical configuration and the variations were identified and grouped into seven different categories. The diameter of the vessels less than 1 mm was defined as hypoplasia. The normal vascular pattern was defined as Type A. Type B was coined as hypoplasia of the anterior communicating artery (A com hypoplasia), Type C, as A1 hypoplasia, Type D, as unilateral aplasia of the posterior communicating artery (P com aplasia), Type E, as bilateral P com aplasia, Type F, as unilateral P com hypoplasia Type I as MCA hypoplasia, Type G bilateral P com hypoplasia, Type H other rare variations [
The analysis of the data showed; 169 (84.5%) were male and 31 (15.5%) were female. The age range varied between 16 and 71 years (mean 41.2 (SD 14.41)). There was no significant difference between anatomic variation considering gender of the specimens (P < 0.001). Among these 200 cases, 69 (34.5%) had normal anatomical pattern (Type A), 28 (14%) had A com hypoplasia (Type B), 9 (4.5%) had MCA hypoplasia (Type I), 6 (3%) showed P com aplasia (Type D), and 2 cases (1%) had bilateral P com aplasia (Type G). Hypoplasia of P com was unilateral in 37 (17.5%) and bilateral in 48 cases (24%). Persistent fetal circulation defined as aplasia of the first segment of posterior communicating arteries (PCA) (Type H), was seen in one case (0.5%). In some cases there were two concomitant variations. Hypoplasia of A com and unilateral hypoplasia of P com was seen concurrently in 14 cases (7%). Concomitant bilateral P com hypoplasia and A com hypoplasia was seen in four cases (2%). Hypoplasia of the first segment of ACA and hypoplasia of P com happened together in five cases (2.5%). A com aneurysm of CW was seen in one case (0.5%) [
Comparing the results of our study and similar reports in the literature. Those reported from the Iranian population are similar regarding the more common occurrence of aplasia of the P com arteries versus those reported from Morroccan and French races. The numbers are not sufficient for a reasonable statistical analysis of the results neither in each series nor as in the cumulated form of the data
The purpose of this cadaveric study was to identify the congenital variations of the anatomy of CW in a rather small (200 cases) sample of population taken from fresh cadavers in the Department of Forensic Medicine to estimate the prevalence of the anatomic variations (as hypoplasia and aplasia) in each segment. This is the second study reported from the Iranian population in the literature and is the largest one after the Eftekhar et al.[
There is controversy among the authors about the definition of hypoplasia. Some consider hypoplasia when diameter of a vessel is less than 1.5 mm.[
The cadavers included, were those who died of natural causes or accidents and autopsies have been done regardless the gender of the specimens. The gender of the specimens have not been mentioned in some other studies as in ours[
Even though the goal of our cadaveric study was not to determine the actuarial incidence of congenital aneurysm in the Iranian population, but this number (0.5%) is near to the similar studies.[
The findings of this article are important for those with closely related research interest. The results of evaluation of CW 200 fresh cadavers were compared with similar studies in the literature. There were no significant difference in the detected variations regarding the Iranian population and other studies except for the aplasia of the P com segments.
Based on this observation we can infer that the prevalence of variation of CW in the different studied races and ethnics are rather similar and the results have not yet been of enough amount for a valid statistical analysis. Even though these variations can be the explanatory cause of differences in neurological deficits that might be created by same surgical vascular techniques used for different patients, but commutation of data are needed to be performed by different researchers in any community to fill up the defect in the literature.
Limitations and suggestions
The accuracy of the anatomical studies evaluating the intracranial vasculature is highly dependent on the technical preparation of the specimens. Given the high prevalence of variation of CW (% 65/5),[
The authors are thankful to the Department of Forensic Medicine for their kind contribution and support.
1. Battacharji SK, Hutchinson EC, McCall AJ. The circle of Willis, The incidence of developmental abnormalities in normal and infarcted brains. Brain. 1967. 90: 747-58
2. 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-
3. Fisher CM. The Circle of Willis: Anatomical variations. Vasc Dis. 1965. 2: 99-105
4. Hoksbergen AW, Fulesdi B, Legemate AD, Csiba I. Collateral configuration of the circle of Willis: Transcranial color-coded duplex ultrasonography and comparison with postmortem anatomy. Stroke. 2000. 31: 1346-51
5. Horikoshi T, Akiyama I, Yamagata Z, Sugita M, Nukui H. Magnetic resonance angiographic evidence of sex-linked variations in the Circle of Willis and the occurrence of cerebral aneurysms. J Neurosurg. 2002. 96: 697-703
6. Jeroen Hendrikse A, Fleur VR, Yolanda van der G, Willem PT, Mali M, Jeroen van der G. Distribution of cerebral blood flow in the Circle of Willis. Radiology. 2005. 235: 184-9
7. Kapoor K, Singh B, Dewan L. Variations in the configuration of the circle of Willis. Anat Sci Int. 2008. 83: 96-106
8. El Khamlichi A, Azouzi M, Bellakhdar F, Ouhcein A, Lahlaidi A. Anatomic configuration of circle of Willis in the adult studied by injection technics. Apropos of 100 brains. Neurochirurgie. 1985. 31: 287-93
9. Lazorthes G, Gouazé A, Jacques Santini J, Salamon G. Le Cercle Artériel du Cerveau (Circulus Arteriosus Cerebri). Surg Radiol Anat. 1979. 1: 241-57
10. Macchi C, Molino Lova R, Miniati B, Zito A, Catini C, Gulisano M. Collateral circulation in internal carotid artery occlusion. A study by duplex scan and magnetic resonance angiography. Minerva Cardioangiol. 2002. 50: 695-700
11. Meyer A, Hierons R. Observations on the history of the ‘Circle of Willis’. Med Hist. 1962. 6: 119-130
12. Miralles M, Dolz JL, Cotillas J, Aldoma J, Santiso MA, Gimenez A. The role of the Circle of Willis in carotid occlusion: Assessment with phase contrast MR angiography and transcranial duplex. Eur J Vasc Endovasc Surg. 1995. 10: 424-30
13. Rhoton AL. The supratentorial arteries. Neurosurgery. 2002. 51: S53-120
14. Riggs HE, Rupp C. Variation in form of Circle of Willis. The relation of the variations to collateral circulation: Anatomic analysis. Arch Neurol. 1963. 8: 8-14
15. Rodriguez-Hernandez A, Miric S, Lawton MT. Twig like middle cerebral arteries. Neurosurgery. 2012. 71: E522-
16. Schomer FD, Marks MP, Steinberg GK, Johnstone IM, Boothroyd DB, Ross MR. The anatomy of the posterior communicating artery as a risk factor for ischemic cerebral infarction. N Engl J Med. 1994. 330: 1565-70
17. Symonds C. The circle of Willis. Br Med J. 1955. 1: 119-24