There are a large number of options for the structure of the Willis system, some of them are considered as anomalies – aplasia, trifurcation, hypoplasia, the absence of certain arterial elements, etc. Depending on the type of vascular branching, the doctor determines its clinical significance and prognosis. The structural variants of the Willis circle are studied by invasive and non-invasive diagnostic methods (angiography, CT angiography, MR angiography, MRI, transcranial dopplerography).
Diagnostic measures are carried out in the presence of specific complaints of the patient, in other cases they are discovered by chance. Norma (the classic structure of the Willis circle) is found only in 35-50% of people. This created the basis to consider the specific structure of the vascular system of the brain as an individual feature of each person.
From this article you will learn: what are the options for the development of the Willis circle, what it is, what arteries are included in its composition. What diseases can be caused by a congenital or acquired pathology of the Willis circle.
The Willis circle (abbreviated VK) is a system of anastomoses (connections between vessels) of blood vessels located at the base of the brain. It provides an important connection between the systems of the internal carotid arteries and the vertebrobasilar basin.
The VK includes several arteries, which, connecting together, form a circle.
Some of these developmental options can lead to an increased risk of dangerous brain diseases such as aneurysm or stroke.
Nevertheless, for most people, various options for the structure of VK are a physiological norm, that is, they do not cause any symptoms or consequences.
Since complications of the incorrect development of the Willis circle arise in the brain, neurosurgeons and neurologists are involved in them.
The brain is, without exaggeration, the most important organ in the human body. Therefore, it is not surprising that its blood supply is one of the priority goals of the cardiovascular system. The brain receives blood from two sources – from the system of the internal carotid artery and from the vertebrobasilar basin.
In order to avoid catastrophic consequences when one of the large vessels is blocked, anastomoses exist between these two blood supply systems that form the Willis circle at the base of the brain.
VK consists of three pairs of main arteries:
- Anterior cerebral arteries (PMA) – depart from the internal carotid arteries.
- Internal carotid arteries (ICA) – the VK part includes their terminal part, before the passage of the middle cerebral arteries (SMA).
- The posterior cerebral arteries (ZMA) are the terminal branches of the basilar artery (BA), which is formed due to the fusion of the vertebral arteries (PA).
To complete the circle, there are also two connecting blood vessels:
- The front connecting artery (PSA) – connects two PMA.
- The posterior connective arteries (ZCA) are branches from the ICA that connect them to the ZMA.
There is a clear definition of the regulatory structure of this body. These are anastomoses that are collected in a ring and have the shape of a circle. This structure of this body is less than half the people. In other people, Willis circle anastomoses are formed with abnormalities in the branching of various vessels.
Anomaly of the arterial ring does not lead to common diseases of the organ, although a deficiency in the blood supply to organs periodically manifests itself in such diseases:
- Migraine headaches with a willis circle;
- Arterial encephalopathy – organ vessels are affected;
- Deviation in the blood supply to the head in an acute form, which is a dangerously complicated form – a stroke.
Variants of the structure and formation of the Willis circle types:
- Type of formation – trifurcation;
- The type of organ structure is aplasia;
- Type of hypoplasia;
- An anomaly in the structure in the complete absence of vascular branches and elements.
To study the anatomy of VK are used:
- Non-invasive diagnostic procedures;
- Invasive diagnostic research tests.
To ensure its metabolism, the brain must be provided with high-intensity blood supply, the main source of which is the Willis Circle.
Let’s see what it is, how it functions, what options for its development exist, how diagnostics and treatment of pathologies are carried out, if they are detected.
The brain has a complex structure of the vascular system.
The main component of the arterial network is the Willis circle (abbreviated VK), due to which reliable blood supply to this organ is carried out.
In fact, the Willis (or arterial) circle is an anastomosis (connection) of blood vessels in the form of an oval, located at the base of the brain.
Arterial blood enters the VC through the following main vessels:
- The right and left internal carotid arteries – form the anterior cerebral vessels in both hemispheres, connected by a vascular bridge.
- Vertebral arteries – after fusion create an unpaired basilar vessel, from which two posterior cerebral arteries depart. The posterior cerebral arteries are connected, in turn, with the internal carotid arteries – a closed system is obtained.
Features of the anatomy of VK are usually called options.
The classic version of the arterial circle is closed, has a symmetrical shape, which is formed by the following arteries:
- PMA – anterior cerebral.
- ZMA – posterior cerebral.
- PSA – front connecting.
- ZSA – back connecting.
- ICA – internal carotid (supraclavicular part).
The Willis circle is a compensatory mechanism for hemodynamic disorders due to the human anatomical structure.
Its purpose is to protect the brain from interruptions in blood supply in case of blood flow disturbance in any area.
Suppose, on one side of the brain, there is a risk of impaired blood delivery associated with congenital vascular maldevelopment or compression of the vessel, obstruction, etc.
Given the compensatory features of VK, located at the base of the brain, it is difficult to underestimate its role in the blood circulation. Its value increases significantly at the onset of occlusive changes (closure of the lumen) in the vessels. In this case, the further prognosis, the extent of neuronal damage, and the rate of symptom manifestation depend on the quality of the arterial ring.
A correctly formed classic circle is easier to cope with the delivery of blood to injured areas than a circle with destruction or the complete absence of vessels (or branches).
The anatomical structure of the Willis circle has various patterns of vessel structure. The formation of the vessels of the circle occurs in the womb.
The most common types of development options:
- Rear ICA trifurcation – splitting of the carotid artery into three branches. It is observed most often, up to 30% of all possible anomalies. The condition is not dangerous if there is no narrowing (occlusion) of the vessels, which can manifest itself in the form of a lack of blood flow to certain sections of the GM.
- Hypoplasia (or underdevelopment) of one or two CSA, PSA, or PMA segment – occurs when the diameter or parameters of the vessels decrease, it manifests itself in the form of a decrease in blood flow and brain nutrition. If there are no violations in other departments, then compensation will take place fully, without the appearance of symptoms.
- ZLA aplasia – absence or extremely weak development of the connective artery. More often observed in the back of the ring. Diagnosed with either full or incomplete open circle. People with this anomaly are automatically at risk of developing serious vascular pathologies.
- Aplasia of the anterior region (PSA) is the most unfavorable, there is no possibility of compensating blood supply to the vessels from the opposite side, since the carotid arteries are disconnected.
- The absence of PSA or ZSA – more often diagnosed in the posterior section of the VC, there is a loss of interaction between the branches of the carotid arteries and, as a result, loss of compensatory functions. That is, if necessary, supply from the left to the right is impossible.
- Merge of two arteries into one trunk (vessel) – deviation can provoke the development of ischemic diseases.
Some people may experience a combination of different options for the development of VC.
Congenital abnormalities can gradually create difficulty in blood supply or signs of decompensation with an excessive load on the arteries.
The consequences can be catastrophic at all – the development of aneurysm, hemorrhagic or ischemic strokes.
Even in young people, there may be a periodic appearance of migraine attacks.
In the older age category, aneurysms provoked by acquired pathologies (atherosclerosis, vasculitis infections, syphilis) are more likely to occur.
With the formation of aneurysm, there is a danger of rupture of the vessel and, as a result, hemorrhage in the brain.
Clinical syndromes caused by aneurysms of the arterial ring:
- pseudotumorous – nerve tissues and medulla are compressed;
- hemorrhagic extracerebral basal – after rupture of a vessel with subarachnoid hemorrhage;
- discirculatory – with slow growth or with the development of an exfoliating form of aneurysm.
Anomalies of branching options and deformation of the form (broken circle) weaken or lead to loss of compensation in complex cases (hypertensive crisis, thrombophlebitis, spasm, etc.).
The open Willis circle, unlike other GM arteries, is not balanced by the pressure of the brain tissue.
This may cause the following symptoms:
- often dizzy;
- with a sharp turn of the body there are unpleasant sensations;
- severe headache, which does not help painkillers;
- migraine attacks, accompanied by nausea, sometimes vomiting, photo and phonophobia.
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- What is the Willis circle – functions, anatomy and structural anomalies
- What is the function
- What is the function
- The structure of the Willis circle
- What is the function
- Willis Circle
- Possible pathologies
- Diagnostic methods
- Vertebrobasilar system
- Options for the development of the Willis Circle
- How are deviations detected?
- How to treat
- Overview of all development options for the Willis Circle, what does this mean in practice
- MRI and CT
- What is the function
- Willis circle: how it works, norm and anomalies (open, decreased blood flow), diagnosis, treatment
What is the Willis circle – functions, anatomy and structural anomalies
The vascular system of the brain has a complex structure.
One of its key components is the Willis circle, which is a closed complex of arteries, consisting of the posterior and anterior connective and other vessels that provide blood flow at the base of the brain.
Thanks to this system, the correct distribution of blood is carried out in case of a malfunction of the carotid arteries, therefore, any pathology in the development of the complex can lead to negative consequences.
This vascular system is a mechanism for protecting the brain, compensating for its impaired blood circulation in case of damage to certain arteries. With the development of obstruction, compression or rupture of blood vessels, congenital anomalies of the branches of the arterial bed are diagnosed.
Normally, even with abnormally developed arteries of the Willis circle, a person does not feel any features due to the full operation of other arteries.
The main task of the Willis circle is to ensure blood supply to certain areas of the brain. This function of the system is especially important for blood flow disorders in the vessels of the neck, which threatens oxygen starvation of the brain and causes various diseases.
Ensuring the health of the ring is achieved due to the fact that the carotid arteries are connected not only to each other, but also to each other with the arteries of the spine. This scheme provides the brain with the necessary nutrients.
The arterial circle of the big brain is located in the subarachnoid region, surrounding visual chiasm and middle brain formations with its elements. The classic Willis circle consists of:
- anterior connective artery (PSA);
- initial departments of anterior cerebral arteries (PMA);
- posterior cerebral arteries (ZMA);
- supraclinical part of the internal carotid artery (ICA);
- posterior connective arteries (ZCA).
All these vessels form a shape like a heptagon. At the same time, ICA transfer blood from the common carotid arteries to the brain and PMA, the communication between which is provided by the anterior connecting artery. ZMA originate from the main, which is formed by combining vertebral vessels. The posterior connective artery, whether ICA or ZMA, receives nutrition from the basilar or internal carotid.
So, a ring is formed that provides a connection between two arterial flows, different parts of which are capable of taking on the function of blood supply to those areas of the brain that lack nutrients due to the narrowing or blockage of other elements of the brain network.
The carotid and anterior cerebral arteries are distinguished by the maximum structural constancy, while ZMA and connecting branches are characterized by developmental variability and individual branching features.
There are a large number of options for the structure of the Willis system, some of them are considered as anomalies – this is aplasia, trifurcation, hypoplasia, the absence of certain arterial elements, etc.
Depending on the type of vascular branching, the doctor determines its clinical significance and prognosis.
The structural variants of the Willis circle are studied by invasive and non-invasive diagnostic methods (angiography, CT angiography, MR angiography, MRI, transcranial dopplerography).
This created the basis to consider the specific structure of the vascular system of the brain as an individual feature of each person.
Nevertheless, some variants of the Willis circle are recognized as abnormal, for example, doubling of vessels or their absence, but such deviations are rare and often do not require treatment, since they do not cause pathological processes.
Anatomy provides for the complex structure of internal systems, which ensures optimal functioning of the body. Nevertheless, due to certain, not always explainable factors, deviations in the development of organs / systems, including the Willis circle, are observed.
As a rule, abnormal variants of its development are manifested in the asymmetry of the arterial branches or in the absence of some sites. Often the vessels that make up the vicious circle have different diameters, sometimes their localization is different.
Some deviations lead to the pathological consequences described below.
This phenomenon is a protrusion of the artery outward, while the Willis circle is often the localization of the pathology. In young patients, aneurysm, as a rule, is the result of an abnormal structure of the vascular system of the brain. In adults, aneurysms are often caused by one of the following problems:
- infectious vasculitis;
- syphilitic endarteritis.
Deviation is often asymptomatic until a rupture of the aneurysm occurs, which leads to cerebral hemorrhage. Symptoms of this phenomenon:
- intense headaches;
- vomiting, nausea;
- acute reaction to bright light;
- coma (if therapeutic measures were not taken in a timely manner).
A consequence of this malformation of the Willis circle is a decrease in blood vessel parameters. In the absence of blood flow disorders in other brain basins, hypoplasia is asymptomatic. This disease can be detected by MRI. The causes of congenital anomalies lie in intrauterine growth disorders caused by:
- transferred during pregnancy by some infectious pathologies;
- falls, bruises of the abdomen during gestation;
- the use of pregnant poisonous, teratogenic, toxic substances, including alcohol, drugs of a certain type, drugs;
- burdened by a hereditary history.
A condition in which the Willis circle is open due to the absence of a connecting vessel is called aplasia of the posterior connecting arteries of the brain. An anomaly can be observed in the anterior region, but less frequently. If the artery is present, but is poorly developed, the incompletely closed Willis circle is diagnosed.
Aplasia of the anterior connecting vessel does not allow blood supply to the affected area of the brain through the delivery of blood from another vasculature due to fragmentation of the arteries.
With an unformed CSA, there is no connection between the posterior and anterior zones of the Willis circle, and the anastomoses do not work.
The anomaly is characterized by the splitting of the vessel into 3 elements. This pathology is observed in about a third of cases and is not dangerous until there are no signs of occlusive changes.
There is anterior and posterior trifurcation, which form during embryonic development. Sometimes the anomaly is complicated, resulting in aneurysms, atherosclerosis, hypertension, migraine may appear, but this rarely happens.
As a rule, no neurological symptoms are detected, therefore trifurcation does not require special treatment.
The brain provides all the most important physiological functions and mental activity of a person. Brain neurons need a significant influx of nutrients and oxygen, the source of which is blood.
If blood flow is disturbed, part of the nerve cells may die, which is fraught with serious consequences. Therefore, nature has invented a mechanism for compensating for the lack of blood in one of the two vascular pools of the brain.
This is the Willis circle connecting carotid and vertebral pools.
What is this anatomical formation? What are the dangerous anomalies of its development? How do they change the blood supply to the brain? Patients are interested in the answers to these questions, since many of them have problems with blood vessels.
What is the function
The cerebral blood supply scheme is reduced to a developed vascular network, originating from two main sources. These are carotid and vertebral pools. It is the arteries of the Willis circle that provide their connection and mutual compensation for blood flow disorders in one of them.
Also, due to this anatomical formation, circulatory disorders in one pool in a certain half of the brain are eliminated due to the flow of blood from the other half. Therefore, the clinic of insufficient blood supply to the brain may be absent.
The common carotid artery is divided into internal and external branches. The right and left internal carotid arteries should provide blood supply to its half of the brain. They create anterior cerebral arteries in both hemispheres, between which there is a connecting vascular bridge. So the front section of the arterial circle is formed.
Two vertebral arteries merge into a single basilar vessel. Then this cerebral artery is divided into two posterior cerebral arteries, which are part of the posterior semi-arterial vascular ring.
The carotid and vertebral pools are connected using the posterior connecting branches.
Thus, the normal anatomy of the arterial ring implies the participation in its formation of the following arteries originating from different pools:
- front and rear cerebral:
- internal carotid;
- front and back connecting.
The ring of arteries occupies the base of the brain, being in front of the Varolian bridge, along which the main artery passes. Inside the ring are the intersection of the optic nerves, the structure of the midbrain.
According to medical statistics, only 35–45% of people have the classic arterial circle as described in anatomical atlases.
What does this mean for the rest of the population? Obviously, even the anomalous structure of the Willis circle does not always lead to brain disasters.
But a person with structural features may complain of periodic headaches, often of a migraine nature, and dizziness.
Also, noise in the head, memory impairment, attention and a decrease in the emotional background can be disturbing. Sometimes the abnormal arrangement of blood vessels manifests itself suddenly as an ischemic or hemorrhagic cerebral stroke. The protective role of the vascular ring is obvious in the following pathological circumstances:
- organic (stroke, aneurysm, atherosclerosis);
- functional (vascular spasms, dystonia, hypertensive crisis).
In this case, the vessels of the opposite side take on the function of blood supply, transferring blood along the collaterals – the connecting vessels.
Diagnostic measures are carried out in the presence of specific complaints of the patient, in other cases they are discovered by chance. Norma (the classic structure of the Willis circle) is found only in 35-50% of people.
The consequences and prognosis of such a deviation are unfavorable from the point of view of the impossibility of decompensation of blood flow disorders.
What is the function
The structure of the Willis circle
What is the function
When there is a problem with the supply of nutrients to the brain, the Willis circle is included. It helps to pump blood from other departments. In this case, its pathology can have negative health consequences.
Unlike other cerebral arteries, pressure differences are not observed in the parts of the circle. This is due to the lack of pressure balancing of the brain tissue. This can lead to the following negative consequences:
- Frequent dizziness.
- Unpleasant sensations with a sharp change in the position of the head.
- Severe headaches that can not always be stopped even with painkillers.
- Migraine attacks, which are accompanied by photophobia, nausea, reaction to sounds.
One of the most dangerous pathologies is considered aneurysm. It appears due to thinning and increased elasticity of the artery wall. Moreover, this process is completely asymptomatic. Any effect on the head area leads to instant rupture of the aneurysm. If timely measures are not taken, a person will simply die.
The classic Willis circle is formed by:
- The initial departments of the anterior cerebral arteries (PMA);
- Anterior Connective Artery (PSA);
- Back cerebral arteries (ZMA);
- Back connecting arteries (ZCA);
- The supraclavicular part of the internal carotid artery (ICA).
The listed vessels form a semblance of a heptagon. ICA bring blood to the brain from the common carotid and, on the basis of the brain, give PMA, which communicate with each other through PSA. The posterior cerebral arteries begin from the main, formed by the union of two vertebrates. There is a connection between the ICA and ZMA – the posterior connecting vessels, depending on the diameter, receiving food from either the internal carotid system or the basilar artery.
Thus, a ring is formed that connects two arterial flows – from the basin of the internal carotid and basilar arteries, different parts of which can take on the function of providing nutrition to those parts of the brain that lack blood when clogging or narrowing other components of the brain network.
The Willis circle is located in the subarachnoid space of the base of the brain, surrounding visual chiasm and the formation of the midbrain with its constituent elements, behind the Varoliev bridge, on the surface of which there is a basilar artery.
The anterior cerebral and carotid arteries are distinguished by the greatest constancy in the structure; the posterior cerebral and connective branches are very variable in their anatomy and branching features. However, changes from the front of the Willis circle are of greater clinical significance due to more pronounced symptoms and a worse prognosis.
The anterior cerebral artery, as a rule, is well formed and normally its lumen reaches one and a half to two and a half millimeters. PSA of the same size and about a centimeter long. The clearance of the left internal carotid artery is normally greater than the right by 0,5-1 mm. The middle cerebral artery also has some asymmetry in size: on the left it is thicker than on the right.
Given the functional significance of the arterial network of the base of the brain, it becomes clear why these arteries are so important. It is not only about serious diseases like stroke or aneurysm. The Willis circle helps provide the brain with blood as much as possible with functional disorders (spasm), some variants of the structure of arteries, when the vascular ring still remains closed, but the diameter of individual vessels does not allow delivering the necessary amount of blood.
The role of the Willis circle increases dramatically with complete occlusion of any of the arteries. Then the prognosis, the rate of increase in symptoms, and the volume of the lesion of the nerve tissue will depend on how this ring is formed and how much it is able to redirect blood to those parts of the brain that are undernourished.
Among the most common abnormalities of the arteries of the brain indicate: aplasia, hypoplasia of individual branches, trifurcation, fusion of two arteries into one trunk and some other varieties. Some people have a combination of different vascular abnormalities.
The most common development option for the Willis circle is considered to be posterior ICA trifurcation, which accounts for almost a fifth of all arterial ring anomalies. With this type of structure, three cerebral arteries begin immediately from the ICA – the anterior, middle and posterior, and the ZMA will be a continuation of the posterior connecting branch.
A similar structure is characteristic of the circulatory system of the fetal brain at a period of 16 weeks of pregnancy, but later the size of the vessels change, the posterior connective decreases, and the remaining branches increase significantly. If such a transformation of blood vessels does not occur, then subsequently the child is born with posterior trifurcation.
Another frequent variant of the structure of the Willis circle is considered to be aplasia of the ARA, which occurs under various adverse external conditions and genetic abnormalities during embryogenesis. In the absence of this artery, the Willis circle does not close on the side where it does not exist, that is, there is no relationship between the system of the internal carotid artery and the basilar basin.
The absence of PSA is also diagnosed, but much less often than the back. With this type of structure of the arterial ring there is no relationship between the branches of the carotid arteries, therefore it is impossible to “transfer” blood from the vessels of the left half to the right if necessary.
Aplasia of the anterior connecting artery does not give a chance to carry out blood flow in the affected part of the brain by delivering blood from the opposite vasculature, since the carotid arteries are disconnected. With an unformed SAA, there is no relationship between the anterior and posterior parts of the Willis circle; anastomoses do not function. This type of branching of the arterial system seems unfavorable in terms of possible decompensation of blood flow disorders.
Rare forms of the structure of the Willis circle include:
- The median artery of the corpus callosum;
- The union of the anterior cerebral arteries into one common trunk or their parietal course, when they are in close contact with each other;
- Anterior trifurcation of the internal carotid artery (two anterior cerebral arteries depart from one carotid at once);
- Split, double anterior connecting artery;
- Bilateral absence of ZCA;
- Trifurcation of the carotid arteries from two sides.
Anomalies of vascular branching and the open circle of the Willis circle make it incapable of playing the role of anastomosis in critical situations – with hypertensive crisis, thrombosis, spasm, atherosclerosis. In addition, some types of branching suggest large areas of necrosis of the nervous tissue with circulatory failure.
The open circle of Willis is considered a serious anomaly predisposing to various kinds of cerebrovascular disorders. The openness of the anterior part of the arterial ring arising from PSA aplasia or anterior carotid artery trifurcation, and the Willis circle due to anomalies of the posterior part of the vascular bed – aplasia of the posterior connective, basilar artery, posterior ICA trifurcation are distinguished.
If the connecting branches are completely absent, they speak of the complete openness of the Willis circle, and when the arteries are preserved, but stenosed, hypoplastic, then the openness is considered incomplete.
Clinical signs of anomalies of vascular branching of the Willis circle occur when the blood flow through the collaterals becomes insufficient due to various reasons. For example, fatty plaques formed in the arteries, a thrombus appeared or an embolus migrated from the left half of the heart, and the aneurysm ruptured. A healthy person does not feel non-classical branching of blood vessels, since his brain does not feel the need for bypasses of the blood flow.
the development of stroke / disorders associated with insufficient blood supply to the brain area
Symptoms of obstructed blood flow can be very different. If we are not talking about a stroke, then patients complain of dizziness, headaches, decreased intellectual abilities, memory, and attention. Psychological issues are also frequent – often anomalous branching of vessels is accompanied by neurosis, panic attacks, emotional lability of its owners.
A characteristic manifestation of the non-classical development of the Willis circle is considered migraine. A lot of observations have been devoted to the question of the relationship between the structure of the arteries of the brain and migraine, which indicate that the majority of patients with migraine have some kind of abnormality. Especially often with migraine, deviations in the structure of the posterior arterial system are diagnosed.
Reduced blood flow through the vessels of the arterial ring of the brain can provoke periodic headaches and disorders like discirculatory encephalopathy – apathy or irritability, decreased performance, fatigue, etc. Typically, this conclusion can be found in the results of MR angiography and it speaks of hypoplasia of those or other vessels.
Human anatomy provides for the complex structure of internal systems, which ensures the full functioning of the body. Unfortunately, often for certain reasons, developmental abnormalities are observed. This also happens in the case of the Willis Circle. Its normal structure is observed in only half of people.
Most often, deviations from the classical version of development are manifested in the asymmetry of the outgoing branches or the absence of certain sections of the circle. Often there is a difference in the diameters of the vertebral arteries in the posterior and anterior parts. Research results show that violation of the symmetry of the circle sometimes causes frequent migraine attacks.
Among the most significant pathologies:
- Hypoplasia It is a malformation in which arteries have greatly reduced parameters. If there are no blood flow disturbances in other brain pools, then hypoplasia will be asymptomatic. Such a pathology can be detected during a comprehensive diagnosis of the state of the brain. It can be clearly seen in the images obtained by magnetic resonance imaging.
- Aneurysm. This is a protrusion of the artery wall to the outside. Deviation is asymptomatic until a rupture of the aneurysm occurs. This leads to cerebral hemorrhage. In this case, unbearable headaches, bouts of nausea and vomiting, acute reactions to bright light appear. If measures are not taken in time, a person may fall into a coma and die.
- Aplasia. This is a condition in which the Willis circle is not closed due to the absence of a connecting artery. It can be observed both in the anterior and in the posterior. If the artery is still present, but is extremely poorly developed, then an incomplete open circle is diagnosed. Pathology in the front of the circle is extremely rare, only in 4% of cases. Most often, the deviation is found behind. An open circle is examined using an MRI. The reason for this phenomenon is a halt in development at the stage of fetal formation.
- Trifurcation of the carotid artery. This is a splitting of the artery into three components. Such a deviation is observed in 28% of cases. It is not dangerous until occlusive changes in the arteries are observed. Distinguish between anterior and posterior trifurcation. This deviation is associated with a delay in the reduction of the connective arteries during embryonic development.
Pathologies that are extremely rare include Geibner’s artery, splitting of the anterior connecting artery, plexus-like form of the basilar artery and some others.
Treatment of anomalies in the developmental options of the Willis circle is not required. The vast majority of people do not even have an idea about their presence.
You need to treat diseases to which they can lead. Pathologies of the arterial circle belong to the field of neurology. Therefore, a neurologist appoints a course of therapy with drugs to normalize blood circulation.
The therapeutic course for pathologies of the Willis circle includes:
- Ingestion or as an intravenous injection of drugs to improve blood circulation (Cavinton, Pentoxifylline).
- The appointment of nootropics to improve brain metabolism (Fezam, Vinpotropil, Nootropil).
- The course of antioxidants (Mexidol, Cytoflavin).
- The course of metabolic drugs (Actovegin).
- Vitamin therapy, B vitamins are especially useful.
Aplasia of the anterior connecting vessel does not allow blood supply to the affected area of the brain through the delivery of blood from another vasculature due to fragmentation of the arteries. With an unformed CSA, there is no connection between the posterior and anterior zones of the Willis circle, and the anastomoses do not work. The consequences and prognosis of such a deviation are unfavorable from the point of view of the impossibility of decompensation of blood flow disorders.
The anomaly is characterized by the splitting of the vessel into 3 elements. This pathology is observed in about a third of cases and is not dangerous until there are no signs of occlusive changes. There is anterior and posterior trifurcation, which form during embryonic development. Sometimes the anomaly is complicated, resulting in aneurysms, atherosclerosis, hypertension, migraine may appear, but this rarely happens. As a rule, no neurological symptoms are detected, therefore trifurcation does not require special treatment.
Few people know what the Willis Circle is. This is a network of vessels and arteries that penetrates the brain and most often has the shape of a circle.
The structure of the Willis circle may vary among different people, so the norm is not always definitely defined.
Even if the structure or operation of the arteries of the Willis circle is impaired, this may not affect the human health for a long time.
In fact, these arteries play a supporting role, and therefore rarely lead to any serious pathologies.
The Wallisian circle is located at the base of the brain and is a network of arteries
The Willis circle is located at the base of the skull and is a network of anastomoses. Together, the arteries form a circle, hence the name. The Willis circle can be either closed or open. Neither of these phenomena can be called pathology, leading to serious diseases or impaired brain function.
The Willis circle, the treatment of pathologies of which is rarely required, has several structural options. All of them are considered the norm and do not require any additional examination. Neurologists or neurosurgeons are studying this system.
The classic Willis circle, corresponding to the norm, form 5 arteries, which are located in the brain polygon. If one of the vessels is absent, the system turns out to be open, but this does not mean that a person with a similar structure of the Willis circle will have to face any consequences.
Statistics show that the classic closed Willis circle is found only in 50% of people, other experts say that this percentage is even less.
The Willis circle has several important features:
- There are about 12 options for the structure of the Willis Circle. Most of them lack any part of the artery, but this does not affect the patient’s condition. The most common is the option in which there is no posterior connective artery.
- Some variants of the structure of the Willis circle are still considered an anomaly. For example, the absence of 2 arteries at once, bifurcation of the vessel, arterial trifurcation (splitting simultaneously into 3 parts).
- Non-classical options for the structure of the circle are usually associated with its front part, they are much more common. But they do not lead to various complications, therefore they are not always diagnosed. With the back of the circle it’s the other way around.
The main task of the circle is to ensure blood supply. In the event that any vessel in the brain fails, the vessels of the Willis circle are used as spare.
This allows brain cells not to die when a vessel becomes clogged or hemorrhage in brain tissue.
This function is important not only in such serious conditions as a stroke, but also in spasms of cerebral vessels, when the blood supply to its tissues worsens.
The brain is considered one of the most complex organs of the human body. Many experts are sure that its functioning is individual, therefore, they are not always talking about the anomaly of the Willis circle. It is difficult to predict or predict the consequences. Sometimes even minor pathologies of the Willis circle lead to serious complications.
The consequences are very diverse: from developmental delay to migraines. It is difficult to diagnose a pathology, therefore, for a sufficiently long time, the disease can proceed without a clear diagnosis. One of the deviations is the classical structure of the circle, but the vessels of different diameters. This asymmetry leads to headaches.
The most common pathologies of the Willis circle are:
- Hypoplasia of the vessels. This pathology is associated with a reduced diameter of the vessels. Due to the small size of the artery, blood flows more slowly and in smaller quantities through them. In the absence of disturbance in other vessels of the brain, this pathology can go unnoticed for a long time. However, with abnormalities in the blood supply to the brain, the main function of the Willis circle will be disrupted – additional nutrition. Detecting hypoplasia is very easy with MRI.
- Aneurysm of the cerebral vessel. This can affect any vessel in the brain. Aneurysm is a protrusion and thinning of the wall of a vessel or artery. The patient does not feel any discomfort until the aneurysm bursts and causes hemorrhage, which is accompanied by severe headaches and nausea. This condition is life threatening and requires immediate medical attention.
- Aplasia of blood vessels. This is the absence of any part of the Willis circle. This anomaly develops in the womb. Determining how dangerous it is is difficult. The consequences depend on which part is missing, whether there are other violations, etc.
- Arterial trifurcation. Splitting of an artery into 3 branches is observed quite often. As a rule, this condition is not dangerous to human life and does not lead to any negative consequences.
Not all pathologies require treatment, sometimes it is enough to observe and adhere to the rules of prevention so as not to encounter complications.
Symptoms of pathologies can be different: headaches, dizziness, nausea, fear of bright light, decreased memory and attention, in children there may be a delay in intellectual development.
MRI allows you to assess the condition of blood vessels and arteries of the brain
Non-invasive methods such as CT and MRI are usually used to diagnose cerebrovascular disease. In most cases, the pathology is detected by chance during a comprehensive examination.
Less often, the patient goes to the doctor with symptoms that already exist, which manifest themselves in the form of chronic headaches and memory impairments.
The most common methods for diagnosing pathologies of the Willis circle are:
- MRI Magnetic resonance imaging is considered the most modern and informative method for examining the brain. Moreover, such a diagnosis can not be called cheap. The MRI method allows you to see all the vessels and arteries of the hemispheres, the movement of blood through them in dynamics. The patient can receive both pictures and a recording disc. MRI has several contraindications. In particular, this procedure cannot be carried out in the presence of metal objects in the body, since the tomograph is a large magnet.
- CT The method of computed tomography is similar to MRI, but this examination is carried out using x-ray radiation. For this reason, the CT method cannot be called completely safe. It is performed as necessary if MRI is not possible. For high-quality diagnosis, it is necessary to use a contrast agent containing iodine. In rare cases, it causes an allergic reaction.
- Angiography. The method of angiography is to obtain an image using x-rays. This method is older than MRI or CT. It allows you to assess the condition and patency of the vessels. This method has its drawbacks. In this case, it is necessary to introduce contrast directly into the test vessel or artery using a catheter or puncture. This can lead to some complications.
- Dopplerography. This diagnostic method is performed using ultrasound. Ultrasonic waves are absolutely safe for the body, so this examination has virtually no contraindications.
The vertebrobasilar system is formed from the vertebral arterial vessels and the main (basilar) artery, which is formed from the fusion of the vertebral vessels. The vertebral blood paths originate, like the carotid ones, in the chest cavity and through the bone channel of the cervical vertebrae reach the brain. Their connection occurs in the region of the posterior cranial fossa, where the main artery is formed.
The basilar bloodstream is responsible for supplying blood to the posterior parts of the brain. The most common diseases are thrombosis and aneurysms.
The appearance of thrombosis is caused by damage to blood vessels, which can be caused by a variety of factors, from trauma to atherosclerosis. Complications of thrombosis is embolism, as a result of which thromboembolism develops. The disease is accompanied by neurological symptoms that indicate the presence of lesions of the bridge.
Deposits of atherosclerotic plaques in the basilar artery can lead to its occlusion and, as a result, to ischemic stroke.
Options for the development of the Willis Circle
- hypoplasia of one or two zsa;
- hypoplasia or absence of a PMA segment;
- PSA hypoplasia;
- the absence of one of the ZCA.
Before the development of these diseases or their complications, a person does not even know that he has anomalies in the development of cerebral vessels.
Aneurysm is a protrusion of the vascular wall. Aneurysms of the vessels included in the VK are the most common aneurysms of the brain. Most often, they occur in the PSA, on the bifurcation (bifurcation site) of the ICA and in the ZCA, on the bifurcation of BA.
Most brain aneurysms do not cause any symptoms until they rupture. However, with large protrusions, compression of adjacent tissues of the central nervous system may occur, which in some people leads to:
- double vision;
- dilated pupils;
- the occurrence of pain behind the eyeballs;
- Sudden onset of severe headache.
- Nausea and vomiting.
- Stiffness in the neck.
- Temporary loss of vision or consciousness.
Violation of the symmetry of blood flow through the arteries of the brain can contribute to the development of atherosclerotic lesions, which increases the risk of ischemic stroke. An open VC does not provide good collateral blood flow, so the size of the stroke can increase.
- A sudden onset of numbness or weakness in the muscles of one half of the body.
- Sudden impairment of consciousness, impaired speech or its understanding.
- Sudden visual impairment.
- Sudden disturbances in walking, dizziness, loss of balance and coordination.
- Sudden onset of headache.
How are deviations detected?
Most often, the pathologies of the development of the Willis circle are revealed during a comprehensive examination of a patient who complained of a headache. First of all, in such a situation, specialists check the presence of circulatory disorders of the brain.
The most accurate modern diagnostic method is MRI. The examination is carried out on a special magnetic resonance imager. Its principle of action is based on fixing reactions of body cells in response to exposure to a strong magnetic field.
Such an examination helps to get a complete picture of the structure of any internal organs, including the vascular system. MRI is considered completely safe, as it is a non-invasive examination and does not involve the use of radiation.
One of the most popular methods for examining the vascular system is angiography. This technique involves the introduction of a special contrasting substance into the patient’s blood. After it is evenly distributed over all arteries, an x-ray is taken. All pathologies are clearly visible on it.
Such an examination can be carried out using a conventional radiograph or under the control of computed tomography. Contrasting agent is completely harmless to humans. After a certain time, it is completely excreted from the body naturally.
Computed tomography is also used to determine the exact location and condition of the arteries. Such an examination is carried out using x-ray irradiation. And although the dose of the investment is extremely small, this diagnostic method cannot be called completely safe for health.
How to treat
If the examination revealed pathologies that are not life-threatening, for example, trifurcation, then no special treatment is required in this case. But it is worth remembering that the state of health can deteriorate sharply with the appearance of complications, for example, vascular thrombosis. Therefore, the patient is recommended measures aimed at the prevention of complications.
It is necessary to adhere to proper nutrition, exclude the use of excessively fatty foods, fried, smoked dishes. To refuse from bad habits. Try to eat as many fresh vegetables and fruits as possible. Lead an active lifestyle, walk more in the fresh air. All this favorably affects the health of the cardiovascular system as a whole.
If an aneurysm is diagnosed, urgent surgery is required. No other methods can deal with such a problem. The operation is performed under general anesthesia.
The surgeon makes a trepanation hole in the patient’s skull. After that, he spreads the tissues to get to the damaged artery. Using special tools, the doctor removes the aneurysm and bandages the vessel.
Then it remains only to restore the meninges and suture. Most often, after such an operation, medication is necessary, which is aimed at preventing possible complications.
There is a variant of the operation in which the aneurysm is not removed, therefore, there is no rupture of blood vessels. This procedure is performed under local anesthesia. The surgeon makes a small puncture in the vessel and inserts a special tool into it. With its help, a specialist fills the cavity of the aneurysm with a certain material in the form of microscopic spirals.
During the operation, the surgeon must act very carefully, since the slightest inaccuracy will lead to rupture of the aneurysm and hemorrhage. Three months after such treatment, a follow-up examination is mandatory.
The Willis Circle is a reserve system of blood supply to the brain. In the case of pathology, regular examinations are necessary to identify the likelihood of developing aneurysm.
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Overview of all development options for the Willis Circle, what does this mean in practice
% distribution of cases of aneurysms in the arteries of the brain
If an acute circulatory disorder occurs against the background of the abnormal structure of the arteries of the base of the brain, then the clinic will have obvious symptoms of a stroke – paresis and paralysis, speech impairment, pathological reflexes, impaired consciousness up to a coma.
Separately, it is worth mentioning aneurysms – the expansion of the vessels of the brain. According to statistics, it is in the arteries of the Willis circle that the largest number occurs. Arterial aneurysm of this area is fraught with rupture and massive subarachnoid hemorrhage with a stroke clinic, coma and gross neurological manifestations.
Aneurysm is an independent pathology, and not an option for individual branching of blood vessels, but it much more often accompanies the non-classical types of the Willis circle.
The development of ultrasound Dopplerography and magnetic resonance imaging techniques made it possible to make the study of the structure of the Willis circle a generally accessible and safe event. The main methods for diagnosing variants of the vascular system of the brain include:
- X-ray contrast angiography is one of the most informative methods, but has contraindications associated with the need for contrast (pathology of the liver, kidneys, allergy to contrast, etc.);
- Transcranial dopplerography – the procedure is safe, affordable, requires devices with a Doppler sensor, which are in many medical institutions;
- MR-angiography – performed on a magnetic tomography scanner, has contraindications, a significant drawback is the high cost.
Willis circle in the diagnostic image
Selective angiography of cerebral vessels refers to invasive procedures when a catheter is inserted into the femoral artery, advancing to the zone of cerebral arteries of interest. Upon reaching the required area, contrast medium is supplied. The method is used most often during surgical treatment (stenting, angioplasty).
Instead of selective angiography, CT angiography can be used when a contrast medium is injected intravenously, and then pictures of the head are taken in different projections and sections. Subsequently, you can recreate a three-dimensional image of the vascular structures of the brain.
Transcranial dopplerography allows you to determine the nature of blood flow in the vessels of the brain (reduced, absent), but it does not provide enough data on the anatomical structure of the arteries. An important advantage of it is the almost complete absence of contraindications and low cost.
MR angiography is one of the most expensive, but at the same time, a rather informative way to diagnose the structure of the Willis circle. It is carried out in a magnetic tomograph and the contraindications to it are the same as for conventional MRI (high obesity, claustrophobia, the presence in the body of metal implants that conduct a magnetic field).
The MR picture shows the structure of the vessels of the Willis circle, the presence or absence of connections between them, aplasia or hypoplasia of arteries. When evaluating the result, a specialist can determine the diameter of each artery and the features of its branching.
As a rule, abnormalities of the arterial circle are detected unexpectedly. This usually occurs with a detailed examination for the presence of concomitant symptoms (constantly spinning or headache).
MRI and CT
MRI (magnetic resonance imaging) is one of the most accurate diagnostic methods. This is the safest way to obtain a detailed image, on which the structure of the vascular system of the brain is fixed.
The essence of the method is the use of a magnetic field and radio waves to fix the response of GM cells to their effects.
CT (computed tomography) – a method using x-ray irradiation. This study allows you to get more voluminous images that are captured at different angles. This method has contraindications.
This is the most common method used to assess circulatory disorders in the brain.
Cerebral angiography allows you to study any vessels in as much detail as possible, which makes it an indispensable procedure in the diagnosis of cardiovascular diseases.
The principle of its operation is similar to a conventional x-ray, with the only difference that the vessels in the x-ray image are not visible, so they need to be contrasted. For this, during angiography, a puncture of the vessel is performed, then a catheter is inserted into it, through which an X-ray contrast drug is injected, which will reflect the radiation.
Thanks to this, it is possible not only to obtain a snapshot of the test vessel, but even to reproduce its three-dimensional image.
Ultrasound dopplerography of cerebral vessels (USDG) is also one of the main diagnostic methods.
The principle of its work is the action of ultrasonic waves on the blood cells, reflected from them, the waves allow you to get a complete picture of the vessels and blood flow inside them.
With the help of ultrasound scan it is possible to get a comprehensive picture of the structure of blood vessels and arteries, the presence of pathologies and the speed of blood flow in them.
- CT angiography is a non-invasive (that is, without penetration into the body) X-ray examination, during which a contrast agent is injected into the bloodstream to visualize the blood vessels of the brain, and then computed tomography is performed.
- Magnetic resonance imaging is a non-invasive method that uses a magnetic field and radio frequency waves to obtain a detailed image of the vessels of the brain.
- Brain angiography is an invasive examination during which a special catheter is inserted into the artery of the brain. After that, contrast is introduced through the catheter and an x-ray is taken.
Today, the pathology of the cerebral vessels (GM) maintains a leading position among the causes of mortality and disability of the population not only in the post-Soviet space, but throughout the world. Therefore, it is necessary to represent their anatomical structure.
GM blood circulation is provided from the systems of the internal carotid and vertebrobasillar arteries. As a result of their connection, an arterial circle of the large brain is formed, also called Willisiev.
- 1. Anatomical structure
- 2. Importance and pathology of the Willis circle
The brain is nourished with blood by the internal carotid and vertebrobasillar vessels. The internal carotid artery (a.carotis interna) is a continuation of the common carotid, located outside the external carotid artery. They are usually two pieces (located respectively on the right and left).
In the neck, a.carotis interna does not. The vessel rises up to the base of the skull, and enters the carotid canal of the temporal bone. At the top of the temporal bone, it enters the cranial cavity through a ragged hole. A.
What is the function
Vascular abnormalities are formed during fetal development during embryogenesis disorders. This can lead to adverse external influences, diseases of the expectant mother, or genetic factors.
If there are no connecting branches at all, experts say that the Willis circle is completely open. If the vessels are formed, but their diameter is less than the anatomical norm, or they are underdeveloped, it is believed that the circle is not fully open.
The most common causes of openness are:
- The front of the ring is the absence of the anterior connecting artery, trifurcation of the anterior cerebral artery.
- The posterior part is the absence of the posterior connecting artery, basilar artery, posterior trifurcation of the internal carotid artery.
Anomalies in the structure of the arterial system of the Willis circle are felt only if necessary in bypass routes of blood flow. This can be with the formation of an atherosclerotic plaque, thrombus, severe spasm, rupture of the vessel.
Willis circle: how it works, norm and anomalies (open, decreased blood flow), diagnosis, treatment
Often, patients learn about the presence of violations in the structure of the vascular system of the brain only after the examination, which was sent by specialists in connection with health problems. They have a question, how to treat vascular abnormalities? First of all, it is necessary to prevent decompensation in the circulatory system, strive to maintain the level of blood flow at a physiological level, and not cause vascular overload.
To do this, carry out the following preventive measures:
- blood coagulation control;
- measurement of cholesterol;
- normalization of blood pressure;
- timely treatment of cardiovascular diseases and autonomic dystonia.
In the presence of migraine attacks, especially with visual impairment, it is mandatory to consult a doctor to clarify the diagnosis. Of the examinations, magnetic resonance angiography and transcranial dopplerography are the most informative.
If abnormalities in the structure of the arteries are detected, regular medical examinations should be regularly performed, visiting a physician, neurologist, cardiologist. It is necessary to provide course administration of vascular preparations (inside, intravenously drip), including Cavinton, Pentoxifylline. Mandatory is the intake of nootropics that improve the metabolism and blood supply to the nervous tissue (Nootropil, Fezam, Vinpotropil).
It is also important to take antioxidant (Mexidol, Cytoflavin) and metabolic (Actovegin) drugs several times a year. B vitamins are needed to maintain brain neuron functionality and immune defenses.
Patients with deviations in the structure of vascular collaterals should avoid nervous and physical overstrain, increase stress resistance, eat right, maintain a positive emotional tone.
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