Cerebral arteriovenous malformation (AVM) is a tangle of abnormal blood vessels connecting veins and arteries in your brain.
Arteries carry blood from the heart to other body parts, which get smaller until they turn into capillaries. Nutrients and oxygen exchange takes place in the capillaries. The blood then passes from capillaries to your heart through veins (Image A).
But in cerebral malformations, arteries directly connect to veins without capillaries in between, creating an area of high pressure. The veins cannot take this pressure and enlarge and bulge to accept extra blood (Image B).
AVMs can form anywhere in the body but is more common in the brain or spine. Even so, cerebral AVMs are rare and seen to affect less than 1% of the population.
AVMs in the brain are mainly silent and are picked up on scans for other health issues. However, when present, common symptoms are headaches and seizures.
Treating AVMs as soon as they are diagnosed lowers the risk of complications such as a stroke.
A cerebral AVM may not cause symptoms unless it ruptures. In almost half of the cases, brain hemorrhage is the first indication.
Some common symptoms include:
- Severe headache
- Numbness or weakness in one part of the body
- Difficulty speaking
- Vision loss
- Severe unsteadiness
If left unattended, AVMs can damage the brain tissue. These can affect any age group. There are multiple types of AVM’s and depending upon the type different age groups are affected.
Galen defect, a severe type of brain AVM can cause symptoms immediately after birth. As a major blood vessel is involved in this AVM, it causes accumulation of fluid in the brain and brain swelling. Common symptoms include seizures, visible veins on the scalp, congestive heart failure, and failure to thrive. In contrast Dural AV fistulas, another type of cerebral AVM usually affects people of middle to old age.
There are multiple treatment options for AVM, and their main goal is to prevent bleeding in the brain.
Your doctor will decide the ideal treatment option based on your health, age, and location of the AVM.
Medicines can be helpful to manage AVM symptoms such as headaches and seizures. However, surgery may be needed in the majority of cases. First step after an AVM is diagnosed on CT or MRI of the brain is to go a angiogram (DSA). This gives us information about the arteries/veins involved, type of AVM, actual size and if there are any danger signs which can predict the chances of bleeding inside the brain. Once this information is there following treatments can be planned.
Treatment options include:
- Conservative management: some AVM’s which are incidentally detected and having low risk features on angiogram can be followed up for months to years on imaging. Only symptomatic treatment if required can be given.
- Surgical removal: It is an ideal option if the AVM is very small and is at a location that is easily accessible surgically. Resection is usually done when the AVM can be removed with little risk of seizures or bleeding. As AVMs in the deeper brain parts have a higher risk of these complications, your doctor will recommend other options.
- Endovascular embolization: It is a minimally invasive procedure involving the insertion of a flexible, thin tube (catheter) through a cut in the groin to deliver obstructive materials like glue into AVM and close the abnormal connection. This form of therapy is highly involved and carry low risk of complications.
- Stereotactic radiosurgery: It uses a highly concentrated radiation beam that focuses on the site of AVM. The radiation beam damages the blood vessels and forms scar tissue, stopping the blood flow into the AVM. It is not a typical surgery as the procedure is cut-free. Radiosurgery is ideal for smaller, unruptured AVMs.
- Combined approach: some AVM’s are tricky due to multiple reasons and no one form of therapy can cure them. In these cases combined approach like embolization followed by surgery or radiosurgery is carried out.