What makes up circle of willis

The circle of Willis is a junction of several important arteries at the bottom part of the brain. It helps blood flow from both the front and back sections of the brain. The circle of Willis gets its name from the physician Thomas Willis, who described this part of the anatomy in It may play a passive role in protecting a person from some health issues, such as stroke.

However, it has an association with intracranial aneurysms. Keep reading to learn more about the circle of Willis, including its function and associated diseases. The circle of Willis is an important junction of arteries at the base of the brain. The structure encircles the middle area of the brain, including the stalk of the pituitary gland and other important structures.

Two arteries, called the carotid arteries, supply blood to the brain. They run along either side of the neck and lead directly to the circle of Willis. Each carotid artery branches into an internal and external carotid artery. The internal carotid artery then branches into the cerebral arteries. This structure allows all of the blood from the two internal carotid arteries to pass through the circle of Willis.

The circle of Willis is critical, as it is the meeting point of many important arteries supplying blood to the brain. The circle of Willis plays an important role, as it allows for proper blood flow from the arteries to both the front and back hemispheres of the brain.

The arteries that stem off from the circle of Willis supply much of the blood to the brain. The circle of Willis also serves as a sort of safety mechanism when it comes to blood flow. If a blockage or narrowing slows or prevents the blood flow in a connected artery, the change in pressure can cause blood to flow forward or backward in the circle of Willis to compensate. This mechanism could also help blood flow from one side of the brain to the other in a situation in which the arteries on one side have reduced blood flow.

In an emergency, such as a stroke, this may reduce the damage or aftereffects of the event. Importantly, the circle of Willis does not actively carry out the function. Instead, the natural shape of the circle and the way that pressure acts in the area simply allow for bidirectional blood flow when necessary.

Structural differences in the circle of Willis are common. The classic, complete anatomy of a circle of Willis is, in fact, only apparent in a minority of cases. It is more common to see one of a few variations in the structure of the circle of Willis. An incomplete circle of Willis can take a few different forms. Unable to process the form. Check for errors and try again.

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Edit article. View revision history Report problem with Article. Citation, DOI and article data. Gaillard, F. Circle of Willis. Reference article, Radiopaedia. Vascular , Central Nervous System. URL of Article. On this page:. In general, infections are not common in the blood vessels of the brain. This is due to the effect of the blood-brain barrier, a protective feature of the lining of the blood vessels of the brain.

However, while uncommon, an infection can spread within the circle of Willis. An infection can produce fevers, decreased alertness, loss of consciousness, and may trigger a stroke. Severe head trauma can stretch or tear any artery in the circle of Willis. If the arteries bleed, the built-in redundancy is not particularly effective because blood in the brain causes irritation and damage. Loss of blood from a damaged artery is likely to affect blood flow in other arteries in the circle of Willis as well.

When one of the arteries in the arm, the subclavian artery , becomes very narrowed, the basilar or vertebral arteries which normally send blood to the PCAs actually reverse their direction of blood flow in a direction described as retrograde backward flow. This problem may result in decreased blood supply to some areas of the brain that are supplied by arteries of the circle of Willis and may result in dizziness, vision changes, hearing changes, difficulty walking ataxia , and difficulty speaking dysarthria.

Treatment of subclavian steal syndrome varies and ranges from conservative observation if there are minimal symptoms or if surgery poses a health risk to an interventional procedure aimed at repairing the stenosis narrowing of the subclavian artery. If you have a defect in one or more of the blood vessels that comprise the circle of Willis, the decision process regarding your treatment can be quite complex. For example, if you have an aneurysm, your medical team may decide to watch it over time rather than putting you through the risk of surgery.

On the other hand, your medical team may decide that you need to have a reparative procedure if your aneurysm has a high risk of rupturing. There are several types of procedures that can repair a defect in the circle of Willis.

Because the structure is located so deep in the brain, it is not easily accessible. Sometimes, minimally invasive procedures, such as endovascular techniques are used. In that case, your healthcare providers will not make an incision directly in the brain or access the brain through the skull, but instead, reach the blood vessels by threading a wire or a catheter tube through another blood vessel in a more accessible region.

Keep in mind that even minimally invasive procedures can result in serious complications, which may require an emergency invasive technique. Recovery after any illness affecting the circle of Willis often takes time. These conditions can cause substantial brain damage, necessitating therapy to help you regain lost neurological function.

Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Completion of the circle of Willis varies by gender, age, and indication for computed tomography Angiography.

World Neurosurg. Circle of Willis variations in migraine patients with ischemic stroke. Brain Behav. Rosner J, Lui F. Neuroanatomy, circle of Willis. StatPearls Publishing. National Institute of Neurological Disorders and Stroke. Cerebral aneurysms fact sheet. Updated August 13, Brain infections. Diagn Interv Imaging. A forgotten vascular disease with important clinical implications—subclavian steal syndrome.

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