Contents:
- Medical Video: Arteriovenous Malformations (AVMs) | Boston Children's Hospital
- Relationship to normal arteries and veins
- Relationship to abnormal arteries and veins
- What does a brain AVM look like?
- Who has the potential to experience brain AVM?
- What are the symptoms of AVM?
- How to diagnose AVM?
- How to handle AVM?
- What about the prognosis?
Medical Video: Arteriovenous Malformations (AVMs) | Boston Children's Hospital
Arterial malformation, or abbreviated AVM, is a group of abnormal blood vessels that are interconnected with one another. AVM can occur in different limbs, but brain AVM is the most problematic. Another term for AVM is arteriovenous fistula.
To understand the reasons why AVM is dangerous, it is first important to understand how normal blood vessels are related to one another.
Relationship to normal arteries and veins
There are two main types of blood vessels: arteries and veins. Arteries carry oxygen-rich blood from the heart and lungs to other parts such as muscles, bones and brain, while veins bring blood back to the heart and lungs to get oxygen back. As the arteries move deeper into the tissues of the body, they become smaller and smaller, until they reach the maximum narrowing point - this part is known as capillary. Blood flow slows down so that it can be transferred from the artery to the vein.
Thus, one of the important functions of capillaries is to relieve some of the pressure that is centered on the blood as it flows through the larger arteries into the tissue.
The vein comes out of the capillary and progressively enlarges when it comes out of the organ on its way back to the heart and lungs to add oxygen.
Relationship to abnormal arteries and veins
Brain AVMs come from arteries and veins that are connected without capillaries. This causes pressure on the arteries when moving directly into the vein within the range of the AVM. This rare blood flow produces parts that have high pressure and turbulence and cause the AVM to expand over time, and affect the function around brain tissue.
What does a brain AVM look like?
Brain AVMs vary in shape. Some are usually small and have not been seen for decades. Others form large and tortuous channels in the arteries, which pulsate strongly because they are connected directly to the vein. AVM can be found anywhere in the brain, including the cerebral cortex, white matter, and brain stem.
Who has the potential to experience brain AVM?
Brain AVMs affect about 0.1% of the population, some even start at birth, but rarely affect more than one member of the same family. They are equal in men and women. People generally begin to feel symptoms between the ages of 10 and 30 years, but rarely occur in those over 50 years.
What are the symptoms of AVM?
About half of patients know of AVM after experiencing subarachnoid bleeding. The other half is affected by seizures, headaches, and stroke symptoms such as hemiplegia or hemiparesis.
How to diagnose AVM?
Diagnosis of AVM is often carried out by radiologists with only CAT brain scans. However, most doctors feel more comfortable doing a diagnosis of AVM after doing an MRI examination. In cases when bleeding occurs, the AVM can be completely covered by intracerebral hemorrhage, requiring a cerebral angiogram to determine the final diagnosis.
How to handle AVM?
The most common types of treatment available include surgical resection, endovascular embolization, and stereotactic radiosurgery, all of which can be used alone or in combination. In general, this treatment aims to reduce the risk of bleeding, and prevent rebleeding.
The issue currently under intensive research is whether doctors should treat AVM before causing bleeding. Apparently, there were no studies that assessed the risk of bleeding when the AVM ruptured and sometimes the symptoms of AVM were not treated. Some people even believe that AVM found before bleeding has a lower risk than those found after bleeding. However, uncertainty causes many surgeons and patients to decide to undergo surgery, regardless of the risk that the action itself can cause permanent brain injury.
What about the prognosis?
The prognosis of AVM depends on several factors, starting with whether AVM is found before or after bleeding. More than 90% of those who experience bleeding can be saved after the event. In those with AVM found before bleeding, the prognosis is directly related to the size of the AVM, symptoms, closeness to the vital areas of the brain and, as mentioned above, whether or not treatment is done on the AVM.
