Impact of circle of Willis anatomic variations on anterior circulation aneurysm rupture

Introduction: The rupture risk assessments for intracranial aneurysms are generally based estructuraly on size, morphology and topography of the aneurysm. However, hemodynamics plays a fundamental role in aneurismal rupture. There is a definite correlation between the anomalies of circle of Willis and aneurysm formation, especially asymmetric proximal segments of anterior circulation. But, whether this association is related to intracranial aneurysm rupture, isn’t well known.

Objective: The aim of this study is to compare the anomaly of the proximal segments of the anterior circulation of the circle of Willis, are presents in patients with ruptured and unruptured intracerebral aneurysms.

Materials and Methods: A cross-sectional study was performed in adult patients with cerebral aneurysm diagnosed from July 2015 to February 2017. Brain vascular imaging was reviewed for aneurysm size, morphology and presence of anomaly of circle of Willis in the proximal segments of anterior circulation. Relevant medical history and demographics were obtained from the medical records.

Results: During this period 77 patients were diagnosed, of which 63 (81.8%) were women. There were 25 (32.46%) cases of ruptured aneurysm. Mean aneurysm size was 5.32 ± 2.98 mm. Circle of Willis anomaly was present in 30 (38.96%), of which 18 (75%) was in ruptured and 12 (23.07%) was unruptured aneurysms. Logistic regression analysis revealed a higher risk of aneurysm rupture when an anomaly of circle of Willis was present (significant p-value, OR 8.57 (CI 2.89 to 25.37)).

Conclusion: There was a significant higher association between the anomaly of circle of Willis and aneurysm ruptured in the proximal segments of anterior circulation. Circle of Willis anomalies may play an important role in hemodynamics alteration to relation to aneurysm rupture. The presence of a circle of Willis anomaly may be an important factor for selecting patients for preventive aneurysm treatment.