A few different changes are possible here, including fenestration and duplication.įenestration occurs when a single vessel divides into two channels and then becomes one channel again later.ĭuplication means that there are two distinct arteries where there is usually one. For instance, a change in the anterior communicating artery may keep the circle of Willis from being complete. The most common structural difference was the absence of a posterior communicating artery connecting to the circle of Willis. A smaller study in the Journal of Morphological Sciences found that at least one variation was present in the circle of Willis in 54% of cases. A study in PLOS ONE notes that about 70% of people may have an incomplete circle of Willis.Īn incomplete circle of Willis can take a few different forms. It is more common to see one of a few variations in the structure of the circle of Willis. The classic, complete anatomy of a circle of Willis is, in fact, only apparent in a minority of cases. Structural differences in the circle of Willis are common. The internal carotid arteries branch off from here into smaller arteries, which deliver much of the brain’s blood supply. The circle of Willis is critical, as it is the meeting point of many important arteries supplying blood to the brain. left and right posterior communicating arteries.left and right posterior cerebral arteries.
left and right anterior cerebral arteries.
Two arteries, called the carotid arteries, supply blood to the brain. The structure encircles the middle area of the brain, including the stalk of the pituitary gland and other important structures. The circle of Willis is an important junction of arteries at the base of the brain.
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