Abstract
The circle of Willis supplies blood to the brain and other pivotal structures, and has considerable importance in clinical teaching and practice. Studies have described angiographic anatomical variations in the circle of Willis in populations diverse in age, gender, race, and geographical region using different research methodologies, including study designs and diagnostic modalities. This comprehensive review compares and contrasts the findings of these studies in terms of prevalence, comorbidities, and clinical applications of anatomical variations across these different studies. Moreover, an embryological and physiological basis of these variations has been discussed in this review.
PubMed, Medline, and Google Scholar were searched for full-text scientific papers in English published from 1980 to 2018 about anatomical variations in the circle of Willis on CT and MRI angiograms. Most articles concluded that there was a relationship between some anatomical variations and age, gender, race, and comorbidities. Some anatomical variations in the circle of Willis are related to age, gender, race, and comorbidities. Future studies focusing on the detectability of small blood vessels using magnetic resonance imaging and computed tomography are warranted.