Occurrence and influencing factors of morphological variations of circle of Willis in healthy individuals living in Tibet plateau region for an extended period

SHANG Zouxiao; LI Shihai; TANG Yi; XUE Hua; LIU Shudong; YANG Dengyu

doi:10.3969/j.issn.1002-266X.2025.02.001

Abstract：Objective To observe the occurrence of morphological variations of the cerebral arterial ring(circle of Willis)in healthy people who have long resided in the Tibetan plateau region,and to analyze the factors affecting the com-pleteness of the circle of Willis.Methods Totally 334 cases of healthy people living in the Tibetan plateau region were selected,214 cases of Han nationality and 120 cases of Tibetan.Cranial magnetic resonance and magnetic resonance angiog-raphy were used to assess the circle of Willis morphology and completeness.Data on sex,age,ethnicity,body mass index(BMI),altitude of residence,duration of residence in the plateau region,history of smoking,and history of drinking were collected from the study subjects to analyze the factors affecting the completeness of the circle of Willis.Results Among 334 study subjects,85 cases of circle of Willis were complete,210 cases were partially complete and 39 cases were incom-plete,and the completeness rate of circle of Willis was 24.9%.There were 288 cases of complete anterior circulation and 92 cases of complete posterior circulation of circle of Willis.The rate of complete anterior circulation was higher in the Tibetan population than in the Han population(P<0.05).There were 249 cases of circle of Willis morphologic variations(partially complete+incomplete)(74.6%),46 cases of anterior circulation variations(13.8%,of which 29 were E-type variations),and 242 cases of posterior circulation variations(72.5%,of which 61 were E-type and 73 were G-type).The circle of Willis completeness rate was higher in Tibetan population than in Han population,and the circle of Willis com-pleteness rate was higher in females than in males(all P<0.05).The circle of Willis completeness rate was not related to age,BMI,smoking,alcohol consumption,altitude of residence,or duration of residence in plateau area(all P>0.05).Ethnicity,gender,and smoking influences were further incorporated into Logistic regression analysis,and the Logistic re-gression analysis showed that ethnicity was an independent influencing factor for the completeness of the circle of Willis,and Tibetan ethnicity was a protective factor for the circle of Willis completeness(OR=0.594,95%CI:0.357-0.997).Conclusion The incidence of morphological variants of the circle of Willis was relatively high in healthy populations liv-ing in Tibet plateau region for an extended period,with a predominance of posterior circulation morphological variants;eth-nicity was an independent influencing factor for the circle of Willis completeness,and the rate of circle of Willis complete-ness was higher in the Tibetan population than in the Han population.