A fetal circle of Willis is associated with a decreased deep white matter lesion load

Objective: To investigate the relationship between morphologic differences in the circle of Willis and the presence and location of white matter lesions (WMLs). Methods: Two hundred forty-three consecutive patients with clinical manifestations of atherosclerotic disease underwent MRI of the brain and MR angiography of the circle of Willis. Results: Subjects with a fetal configuration of the circle of Willis demonstrated a decreased load of small (p < 0.01) and medium (p < 0.01) deep WMLs compared with subjects with a nonfetal configuration of the posterior part of the circle of Willis. Conclusion: A fetal configuration of the posterior part of the circle of Willis may be an important protecting determinant in the etiology of white matter lesions.