An arteriovenous malformation (AVM) is a rare condition in which there is an abnormal connection between arteries and veins, bypassing the normal capillary system. The abnormal vessels can rupture and suffer from bleeding, as well as oxygen deprivation in the surrounding tissues. While AVMs can occur anywhere in the body, the brain and spinal cord are most commonly affected.
The exact causes of AVMs are not clear, but they are usually present at birth and may result from the formation of irregular connections between arteries and veins during fetal growth. There are few genetic conditions that increase one's risk of developing an AVM, such as hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome. They are rarely inherited.
According to the location, size, and type of the abnormal vessels, AVMs have different symptoms. Some people with AVMs may not have any symptoms and may not be aware of their condition until it causes a complication, such as bleeding or stroke.
Headache
Seizures
Muscle weakness or paralysis
Numbness or tingling
Dizziness
Vision or hearing problems
Difficulty speaking or understanding language
Loss of consciousness
Problems with movement, balance, memory, thinking, or behavior
Children and teens with AVMs may have trouble with learning or development. One type of AVM called a vein of Galen defect causes symptoms that appear at or shortly after birth, such as:
Enlargement of the head due to fluid buildup in the brain (hydrocephalus)
Swollen veins on the scalp
Seizures
Heart failure
Poor growth
In order to diagnose AVMs, imaging tests are performed to confirm the presence and location of the abnormal vessels, as well as to assess blood flow and bleeding risk. Some imaging tests include:
Computed tomography (CT) scan: This test uses X-rays to create cross-sectional images of the blood vessels and the brain or other organs.
Magnetic resonance imaging (MRI): This test uses a magnetic field and radio waves to create detailed images of the blood vessels and the brain or other organs.
Cerebral angiography: This test uses a dye that is injected through a catheter into the blood vessels to visualize them on X-rays or other imaging devices.
Magnetic resonance angiography (MRA): This test uses a magnetic field and radio waves to create images of the blood vessels and the blood flow.
Transcranial Doppler ultrasound: This test uses high-frequency sound waves to measure the speed and direction of the blood flow in the large and medium-sized vessels.
In addition to the patient's age, health, and preferences, the treatment of AVMs depends on the location, size, type, and symptoms of the abnormal vessels. Some of the possible treatment options include reducing the risk of complications, preventing bleeding, and improving the quality of life.
Medication: This may include pain relievers, anti-seizure drugs, or drugs that lower blood pressure or prevent blood clots.
Surgery: This involves removing the AVM through an opening in the skull (craniotomy) or through a small incision in the skin (endovascular surgery). It is possible to perform surgery with a microscope, laser, or a device that applies electrical currents or heat to seal off vessels (radiofrequency ablation).
Embolization: This involves injecting a substance (such as glue, coils, or particles) through a catheter into the AVM to block the blood flow and reduce the size or eliminate the AVM.
AVMs are damaged by high-energy rays (such as X-rays or gamma rays) and shrink or close over time as a result of radiation therapy. Radiation therapy can be delivered by a machine outside the body (external beam radiation) or by a device inside or near the AVM (stereotactic radiosurgery or brachytherapy).
There is no known way to prevent AVMs, as they are usually present at birth and have no clear causes. However, some steps that may help reduce the risk of complications or improve the outcome of treatment include:
Seeking medical attention if any symptoms of AVMs occur, such as headache, seizure, or neurological problems.
Following the advice of the healthcare provider regarding the best treatment option and the possible risks and benefits.
Taking the prescribed medication as directed and reporting any side effects or changes in symptoms.
Avoiding activities that may increase the blood pressure or the risk of bleeding, such as smoking, drinking alcohol, using illicit drugs, or taking blood thinners.
Having regular check-ups and follow-up imaging tests to monitor the condition and the effectiveness of treatment.
