Arteriovenous fistulas

Arteriovenous fistulas of the brain and spinal cord vessels are pathological connections between an artery and a vein through which blood flows, bypassing the capillary network. There are several causes of arteriovenous fistulas. Some of them are congenital and are associated with mutations in the genes responsible for normal vessel growth. They can occur in certain hereditary diseases, such as Rendu-Osler-Weber disease. Acquired fistulas are formed by trauma to adjacent arteries and veins (for example, with a bullet or knife wound, trauma, surgery, puncture biopsy of an organ). In some cases, arteriovenous malformation is diagnosed. A fistula usually forms immediately or within a few hours after a vascular injury. Sometimes a fistula is created artificially, for example, for hemodialysis, to avoid repeated puncture of the vessels during each procedure. 

Symptoms

Fistulas located in the brain cause a wide range of symptoms. Among them are headaches, pulsating noise in the ear, the frequency of which coincides with the pulse, visual impairment and eye movement, redness of the eyes. As hemorrhage develops, severe headaches, dizziness, nausea, and vomiting occur. Subsequently, the functions of the brain and cranial nerves may be impaired, which is manifested by paralysis, speech, gait, and memory disorders. Congenital arteriovenous fistulas usually manifest themselves with pronounced cosmetic defects (purple-colored adjacent skin and an unsightly appearance).

If a large arteriovenous fistula is not treated in time, then a large volume of blood under pressure from the artery enters the vein. The vein wall, in turn, is not as strong as the arteries, and under the influence of high-pressure blood flow, the vein expands, its wall is damaged, which in turn contributes to the development of varicose veins and their thrombosis. As a result of arteriovenous discharge of a large volume of blood, systemic arterial pressure decreases, the compensatory heart rate and cardiac output increase, which over time can lead to the development of heart failure.