A Morphological Study of Anatomical Variations in 96 Circles of Willis: an Autopsic Evaluation and Literature Review

Abstract

Aim and background: Because circle of Willis provides the best collateral source of blood flow in arterial occlusive disorders, identifying anatomical variants that could be present at this level is especially essential in planning surgery for cerebral aneurysms. Given the fact that the frequency of these anatomical variations of circle of Willis has not yet been sufficiently evaluated in the Romanian population until presently, we have conducted a research in a regional health unit, where there are admitted patients with neurological and neurosurgical diseases living in the North-Eastern region of Romania, in order to identify morphological features of the constituent vessels of fresh circles of Willis at the moment of the autopsy of the deceased patients in the Emergency Clinical Hospital „Prof. dr. N. Oblu” Ia�?i. There has been noted the presence or absence, variations of shape, position or trajectory of each arterial segment. In the end, our results were compared with those from literature in order to identify some particular pattern of this anastomotic structure in the population of the North-Eastern region of Romania. Materials and Methods: The present research is a descriptive in-hospital observational study on the morphology of the circles of Willis of 96 patients who died of various medical causes in the Emergency Clinical Hospital “Prof. dr. N. Oblu” Ia�?i, in a period of 30 months, to whom an anatomo-clinical autopsy was performed in order to determine the cause of death. Results: From the total of 96 available human brains, 28 cases (29.17%) were classified as ”atypical” as they expressed anatomical variants of the constituent vessels. Among the 28 deceased patients with atypical CW, the M: F ratio was 1.15 and the average age of the entire group was 61.78 years. From the 28 atypical circles of Willis, 19 of them (67.86%) presented multiple anatomical variants, and only 9 cases (32.14%) had a single anatomical variant. Among multiple variants of the vessels of the circle of Willis, we identified the association of two (32.14%), three (25%), four (7.14%), or five (3.57%) anatomical variants of those seven constituent arteries. Eight types of variations of the constituent arteries of the circle of Willis were identified: absence of a vessel, partial fetal ACP, hypoplasia, duplication, fenestration, azygos, common trunk with another vessel at the origin, longer length with sinuous trajectory. Conclusion: Our results showed intermediate values between those reported in various studies performed on circles of Willis obtained at autopsies. These differences can be interpreted as possible peculiarities of the population in North-Eastern region of Romania. Unlike all other studies with which we compared the results obtained, in our research two thirds of cases with variations presented multiple anatomical variants, including five simultaneous variants.