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Abstract：
Background: A relationship between the geometry and symmetry of Willis\' circle and intracranial aneurysms was reported for anterior communicating and posterior communicating (PCom) aneurysms. A similar association with the middle cerebral artery (MCA) aneurysms instead appeared weaker. Methods: We reviewed 432 patients from six Italian centers with unilateral MCA aneurysms, analyzing the relationship between the caliber and symmetry of Willis\' circle and the presence of ruptured and unruptured presentation. CT-angiograms were evaluated to assess Willis\' circle geometrical characteristics and the MCA aneurysm side, dimension and rupture status. Results: The hypoplasia of the first segment of the anterior cerebral artery (A1) was in approximately one-quarter of patients and PCom hypoplasia was in almost 40%. About 9% had a fetal PCom ipsilaterally to the aneurysm. By comparing the aneurysmal and healthy sides, only the PCom hypoplasia appeared significantly higher in the affected side. Finally, the caliber of the internal carotid artery (ICA) and the first segment of MCA (M1) caliber were significantly greater in patients with unruptured aneurysms, and PCom hypoplasia appeared related to the incidence of an ipsilateral MCA aneurysm and its risk of rupture. Conclusions: Although according to these findings asymmetries of Willis\' circle are shown to be a risk factor for MCA aneurysm formation and rupture, the indifferent association with ipsilateral or contralateral hypoplasia remains a datum of difficult hemodynamic interpretation, thereby raising the concern that this association may be more casual than causal.
摘要：
背景：据报道，前交通和后交通（PCom）动脉瘤的威利斯环的几何形状和对称性与颅内动脉瘤之间的关系。相反，与大脑中动脉（MCA）动脉瘤的类似关联似乎较弱。方法：我们回顾了来自六个意大利中心的432例单侧MCA动脉瘤患者，分析威利斯圆的口径和对称性与破裂和未破裂表现的存在之间的关系。评估CT血管造影照片以评估Willis\'圆的几何特征和MCA动脉瘤侧，尺寸和破裂状态。结果：大脑前动脉（A1）第一段的发育不全约占患者的四分之一，而PCom发育不全几乎占40％。约有9％的胎儿在动脉瘤同侧有PCom。通过比较动脉瘤和健康侧，只有PCom发育不全在患侧出现明显升高。最后,未破裂动脉瘤患者的颈内动脉（ICA）口径和MCA（M1）第一段口径明显更大，PCom发育不全与同侧MCA动脉瘤的发生率及其破裂风险有关。结论：尽管根据这些发现，Willis环的不对称性被证明是MCA动脉瘤形成和破裂的危险因素，与同侧或对侧发育不全无关的关联仍然是难以解释血流动力学的数据，从而引起了人们的担忧，即这种联系可能比因果关系更随意。
