Practical Anatomy of Willis' Circle: A Comparison with DSA Manifestations

Objective To discuss the relationship between the anterior cerebral artery, anterior communicating artery and the occurrence of aneurysm by comparing anatomic variations of the anterior part of Willis' circle with DSA findings. Materials and Methods Thirty-five specimens of adult cerebral vessels were collected, and the anatomic variations of Willis' circle were observed. Whole cerebral DSA was performed in 50 cases and the observation was focused on the Willis' circle and its variations. A series of 57 aneurysms at cerebral base was collected, of which the aneurysms were located at anterior and posterior communicated artery in 13 and 24, respectively.Results Of 35 specimens of adult cerebral vessels, dysplasia of right A 1 was seen in 2, multiple branches and abnormal course of A 1 in 3. Of 50 cerebral DSA, developing abnormality of A 1 was found in 20, absent of A 1 at one side in 9 and thinned A 1 in 11. Of 57 cases with aneurysms at cerebral base, thinned or absent A 1 was found in 18, of which aneurysm of anterior communicated artery existed in 13 and variation of the three branches of internal carotid artery in 7.Conclusion The variation of the anterior part of Willis' circle is extremely complex, it occurs more often on the right side than the left side and is closely related to the occurrence of aneurysm.