An arteriovenous fistula is an abnormal short-circuit connection that occurs between an artery and a vein. It is not uncommon for AV fistulas to show up in the head region.
What is an arteriovenous fistula?
An arteriovenous fistula is an unnatural connection between a vein and an artery. It also goes by the names AV fistula or dural fistula. Normally, blood flow occurs from the arteries through the arterioles, capillaries, venules, and finally veins toward the heart. However, if an arteriovenous fistula is present, there is a direct flow of blood from the artery into the vein. AV fistulas are either congenital or develop during life. While congenital arteriovenous fistulas rarely present, acquired fistulas most commonly result from injury. Arteries and veins are affected, which are located close to each other. An arteriovenous fistula often occurs in the brain area. In this case, a durafistula forms in the region of the dura mater (hard meninges). This unnatural connection results in the occurrence of symptoms such as visual disturbances or tinnitus. Arteriovenous fistulas show up only rarely. Women over 40 are particularly affected by AV fistulas
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Causes
The causes of arteriovenous fistula formation vary. In addition to injuries to arteries and veins, thromboses (blood clots) in the sinuses, which are specialized blood vessels, are also possible in the head. Unlike the actual veins, these vessels turn out to be stiff. In addition, they are partially composed of the dura mater. If sinus vein thrombosis occurs, it results in the formation of abnormal blood vessels. This creates an unnatural connection between an artery and a vein. Injuries to veins and arteries often occur as a result of accidents, falls, or exposure to force that causes an acute opening between the artery and vein. In many cases, however, no specific cause for the development of an arteriovenous fistula can be determined at all. The short circuit between vein and artery poses a risk of bleeding. While an artery is so sturdily equipped that it can easily withstand higher blood pressure, this is not the case with the relatively thin-walled veins. The fistula between the artery and the vein leads to higher pressure on the vein, which can result in the accumulation of blood. If bulges form in the vein, the resistance of the vein wall also decreases, which in turn increases the risk of venous hemorrhage.
Symptoms, complaints, and signs
If an arteriovenous fistula develops, various symptoms may occur. The way these manifest themselves depends on the extent and location of the AV fistula. A dural fistula in the head is often associated with ringing in the ears (tinnitus). The affected person hears a pulse-like murmur. It occurs due to increased vascular blood flow. Another common symptom of arteriovenous fistula formation is visual disturbances. The reason for this is the accumulation of blood, which results in increased pressure in the veins. This in turn has a negative effect on vision. In addition, the conjunctiva may redden and swell at the orbit. If the increased pressure occurs in the cerebral veins, there is a risk of a dangerous stroke. Another feared complication is the occurrence of life-threatening hemorrhages, but this is rarely the case. The severity of the symptoms also depends on whether the fistula was caused by violence or indirectly. Traumatic fistulas, for example, are more likely to cause more intense symptoms. In some cases, the vessels of the spinal canal are also affected by the AV fistula. Then, in slow progression, sensory disturbances, weakness in the legs or difficulties in urination or defecation occur.
Diagnosis and course
To diagnose an AV fistula, the attending physician first looks at the patient’s medical history. A physical examination also takes place, during which he pays particular attention to neurologic abnormalities. In order to make a concrete diagnosis of an arteriovenous fistula, imaging procedures such as angiography or magnetic resonance imaging (MRI) are performed. The course of the disease in the case of an arteriovenous fistula depends on the start of therapy.If treatment is not performed in time, serious complications such as nervous deficits or bleeding may occur. However, the size of the AV fistula also plays a significant role.
Complications
Complications that can be caused by an untreated atriovenous fistula (AV fistula) depend mainly on the diameter of the affected artery and vein, which are directly connected, and on their position. Basically, complications can be caused by severe bleeding because the vein cannot withstand the arterial blood pressure and ruptures occur. Complications caused by untreated AV fistulas in the body are usually manageable and reversible. AV fistulas that have formed in the brain, on the other hand, can cause serious complications from hemorrhage that may be accompanied by irreversible nerve damage and neurologic deficits. Basically, bleeding through AV fistulas in the brain poses a danger to life, because vital centers may be hit by spatial stress of the “leaked” blood. AV fistulas in the head are also called durafistula after the hard meninges dura. In these cases, complications such as visual and auditory disturbances present themselves even if there is no bleeding (yet). If bleeding occurs in the brain – or in rare cases in the spinal cord – the affected nerves and ganglia are shut down, resulting in complications that are often comparable to those of a stroke. Complications that may be seen with durafistulas in the spinal cord include motor impairment of the legs, sensory deficits, and difficulty keeping stool and urine under control (incontinence).
When should you see a doctor?
An arteriovenous fistula does not necessarily need to be treated by a doctor. Medical advice is needed if the fistula has not healed after three to five days at the latest or if accompanying symptoms occur. If there is accompanying itching, weeping or pain, a doctor must clarify the cause and, if necessary, initiate treatment directly. If there is also severe physical discomfort or fever, it is best to consult an emergency physician. It is possible that the complaints are based on another illness that must be diagnosed in the hospital. If a reddish streak is observed in the area around the arteriovenous fistula, sepsis may be present – an ambulance must be alerted immediately. Patients at risk should always see a doctor if they have a fistula. The same applies to patients who have already suffered from arterial disease. Otherwise, an arteriovenous fistula must be clarified when there is uncertainty about the symptom and the first symptoms occur. In general, the earlier a fistula is clearly diagnosed, the better the treatment options.
Treatment and therapy
As part of therapy for arteriovenous fistula, attention is usually paid to avoiding bleeding. For this purpose, endovascular embolization is performed. In this method, the physician sticks the abnormal blood vessel with the help of a catheter. The fine catheter can be inserted into the body through the arteries. The fistula is then treated with a tissue adhesive or other materials. There is also the option of closing the affected vessel from the venous side with special platinum coils. In some cases, a stent, an internal vessel splint made of wire, is also used. In this way, the normal course of the vessel can be restored. In some patients, a combination of several of these methods is also used. If these procedures fail to close the arteriovenous fistula, surgery must be performed. In this procedure, the surgeon cuts the AV fistula. However, there are certain risks associated with surgical treatment of a dural fistula. These include the undesirable occlusion of a blood vessel.
Outlook and prognosis
Arteriovenous fistula has a good chance of healing if diagnosed early and subsequently treated. Fistula occurs more frequently in women older than 40 years. Often, there are preexisting conditions that worsen a prognostic outlook. Patients who refuse treatment or seek it too late can expect an acute condition. Hemorrhages may occur, triggering a stroke or heart attack.There is a risk of lifelong impairment or premature sudden death. If treatment takes place in time, there is a good prognosis for patients without other pre-existing conditions. A surgical procedure is performed, which is fully completed within a few hours. Afterwards, the patient needs some time to heal and can be discharged as symptom-free after a few weeks or months. Everyday life has to be adapted to the new conditions and control examinations should be attended. Nevertheless, the patient can go about his or her daily life under normal conditions. Provided that no further sequelae have occurred, no further treatment measures are required after the procedure. Alternatively, individual therapy approaches are offered to treat the consequences of the arteriovenous fistula. Functional disorders, such as decreased hearing or vision, are treated with appropriate devices. In the case of nerve damage, there is an increased risk that these can no longer be successfully corrected.
Prevention
Effective preventive measures against the development of arteriovenous fistula are not known.
Follow-up
There are usually no special measures and options for aftercare available to the person affected by this disease, so that in the first place an early examination and treatment by a physician must take place. The disease cannot be cured on its own, so that treatment by a physician must take place in any case. The earlier the disease is detected by a doctor, the better is usually the further course of this disease. In most cases, the life expectancy of the affected person is not reduced or otherwise limited. The treatment itself is performed by a minor surgical intervention, which usually proceeds without complications. After such an operation, the affected person should in any case rest and continue to take care of his body. Exertion or other stressful physical activities should be avoided. Above all, the affected part of the body should be protected. Regular examinations by a doctor are also necessary after the operation. Further measures of aftercare are not necessary. In many cases, other diseases can also indicate this fistula, so a doctor should be consulted at the first signs and symptoms.
What you can do yourself
An arteriovenous fistula (AV fistula) is a vascular connection between an artery and a vein. As a result, a short circuit occurs between the arterial and venous sides of the bloodstream, bypassing the capillary system. Usually the connections are formed by an injury with hemorrhage, which in rare cases can produce a stimulus to form the fistula. The symptoms that occur depend on the size of the fistula and the arterial and venous vessels involved, as well as their location. If the fistulas are smaller outside the brain and there are hardly any symptoms, there is no need for self-help measures or adaptation in everyday life. In many cases, however, the unwanted fistulas form in the brain in the area of the hard meninges (dura mater). The auditory and visual centers are often affected. For example, tinnitus and visual disturbances may develop. Because of the uncertain prognosis about the further course of the disease, what is needed in these cases is not so much an adjustment in everyday life or the application of self-help measures, but rather an exact diagnosis and a possible treatment that should prevent a progression of the disease and associated serious symptoms. In the head region, the main risk is hemorrhage, which occupies space and can cause mild to severe neurologic deficits.
