Intracranial Arteriovenous Malformation (AVM) Embolization

What is an intracranial AVM?

An intracranial AVM is a tangled collection of blood vessels in which there is an abnormal communication between the artery and vein. Intracranial AVM’s are a congenital malformation (present at birth) that may not present symptoms until adulthood. If left untreated, an AVM may rupture, causing release of blood from the vessel into the brain which may result in a serious stroke or death.

Treatment usually involves surgical removal of the AVM. However, because of the complex web of blood vessels that may be involved, there may be significant blood loss during surgery. Therefore, the neurosurgeon may consult with the Interventional Radiologist to determine if a pre-surgical AVM embolization may reduce the risk of blood loss during surgery.

What is an intracranial AVM embolization?

An AVM embolization is an interventional radiology procedure in which the blood vessels supplying the lesion are occluded (blocked off) using various types of embolic materials. These materials include small coils, polyvinyl alcohol particles, or n-butyl cyanoacrylate, which is a type of adhesive.

How is the embolization procedure performed?

Prior to your procedure you will be asked to undergo the following tests or procedures to evaluate your condition and determine the location and anatomy of the AVM:

History and Physical Examination
Blood tests
Neurological Examination
Imaging (CT, MRI)
Cerebral Angiography

A cerebral angiogram is an x-ray procedure that demonstrates the blood vessels in the brain. Contrast media (a liquid dye that may be seen on x-rays) is injected into a vein or artery, and x-ray pictures are then taken in rapid succession. The series of pictures reveals the size and shape of veins or arteries and vessel abnormalities.

Prior to the angiography procedure, you will either be put to sleep with general anesthesia or you will be given medications through your intravenous line to make you feel drowsy and relaxed. The Interventional Radiologist will determine which approach is best for you based on his/her clinical judgment. The Interventional Radiologist will also inject a local anesthetic in your groin area where the catheter will be inserted. He/she will then make a small puncture in your groin to access the femoral artery in your leg. A thin tube called a catheter is then introduced through the artery and advanced to the affected artery in your brain under x-ray guidance.

Once the catheter is properly positioned in the AVM, the Interventional Radiologist will select the appropriate embolic material to occlude, or block off, the vessels supplying the AVM. The embolic materials used may vary. The most common materials include polyvinyl alcohol (PVA) particles, n-Butyl cyanoacrylate, and coils. PVA looks like finely ground, white grains of sand. These particles become wedged in the blood vessels when injected through the catheters. n-Butyl Cyanoacrylate, or n-BCA, is a kind of ‘glue’ that is injected through the catheter at the location of the abnormal vessels. Upon contact with blood, the material solidifies so that the flow of blood to the malformed vessels is blocked. The coils are stainless steel coils coated with fibers to facilitate blood clotting.

Once the AVM is satisfactorily embolized, the catheter is removed and the Interventional Radiologist will apply pressure at the groin site for about 20 minutes to prevent bleeding.

After the procedure you will be monitored over night in a recovery room or in the intensive care unit. If there are no untoward events, you will be discharged approximately two days after the procedure. Or, if the embolization was performed as a pre-surgical procedure, you may undergo surgery for removal of the AVM.