Anatomical Variations of the Willis Circle: A Risk Factor for Brain Lesions in Sickle Cell Patients

Abstract

: Background and objective : The brain lesions observed in sickle cell patients are often known to be due to vessels occlusions. But other factors could be associated with the genesis of these lesions. The objective of this study was to assess the association between the presence of anatomical variations in the Willis circle and that of brain lesions found on MRI in sickle cell patients. Methods : We conducted a bicentric cross-sectional study with retrolective analysis of images at the medical imaging departments of the HUDERF in Brussels (Belgium) and the Yaoundé General Hospital (Cameroon), over a period of 12 months from November 2020 to October 2021. We included 187 homozygous sickle cell patients with documented electrophoresis and brain MRI results. The MRI were carried out in T1, T2, T2*, FLAIR, Diffusion and 3D TOF sequences on Siemens ® 1.5 Tesla devices. The collected data were analyzed using SPSS ® software version 20.0 for Windows ® with a significant p<0.05. Results : The mean age of patients was 8.76 years with no significant difference between the sexes. Variations in the Willis circle were present in 20 cases (10.70%) with a predominance in the posterior hemicircle (6.96% versus 3.74% for the anterior hemicircle; p=0.04). The most common variation was type G corresponding to hypoplasia or absence of the anterior communicating artery in the anterior hemicircle, and hypoplasia or unilateral absence of a posterior communicating artery in the posterior hemicircle. At the parenchymal level, brain lesions were found in 11 cases (5.88%) including ischemic lesions (3.21%) and leukopathies (1.07%). In general, the existence of these lesions was significantly associated with the presence of the Willis circle variations (p=0.01). Conclusion and recommendation : The presence of anatomical variations of the Willis arterial circle in sickle cell patients is associated with the existence of brain lesions. We therefore conclude that anatomical variations of the Willis circle could be an unknown factor increasing the risk of brain damages and therefore morbidity in these patients. We recommend that a larger sample study be conducted to verify our findings.