An arteriovenous malformation (AVM) is a congenital disorder (present from birth) characterized by a complex, tangled web of arteries and veins in which there is a short circuit and high pressure due to arterial blood flowing rapidly in the veins. An AVM may occur in the brain, brainstem or spinal cord. The most common symptoms of an AVM include hemorrhaging (bleeding), seizures, headaches and neurological problems such as paralysis or loss of speech, memory or vision. AVMs that bleed can lead to serious neurological problems and sometimes death. Still, some people have AVMs that never cause problems.
Why do AVMs form?
It’s not clear why AVMs form, but researchers believe that these tangles of vessels are present from birth. Several rare genetic diseases are associated with AVMs.
How are brain AVMs detected?
The size, shape and location of brain AVMs can be detected using imaging tests such as:
Many AVMs are discovered only after they bleed or cause symptoms, because people with AVMs often have no symptoms. Like unruptured aneurysms, many AVMs can be detected incidentally during imaging for traumatic head injury, vision problems or headaches.
Is an AVM a serious health risk?
An AVM can cause hemorrhaging (bleeding) both into the brain and around the brain, seizures, headaches and neurological problems such as paralysis or loss of speech, memory or vision. AVMs that bleed can lead to serious neurological problems and sometimes death.
Treatment options for AVMs
Treating AVM as soon as possible is the best way to avoid serious complications. AVMs sometimes require a combination of treatments, including surgery, embolization and radiation.
Surgery: Surgical resection is performed to remove the tangled blood vessels. The surgeon uses a procedure called a craniotomy to reach the brain, during which a small opening is created in the skull. Once the surgeon has access to the AVM, the abnormal arteries and veins are removed. This redirects blood flow to normal vessels, preventing the AVM from leaking or bursting.
Embolization: Embolization involves inserting a type of glue into the AVM through a very thin tube called a catheter. This blocks blood flow into the AVM, which may help limit blood loss during surgery, as well as slow blood flow which may reduce the chance of bleeding if open surgery is not performed immediately afterwards.
Radiosurgery: During radiation treatment, beams of highly energized photons (light particles) are directed at the AVM using a tool called a Gamma Knife. Over time, this causes the AVM to shrink and scar, closing down abnormal blood vessels, so that blood no longer flows through them, reducing the risk of bleeding, and also perhaps making the AVM easier to treat using open surgical techniques.
Dural fistulae, dural AVMs and dural shunts (DAVS) all refer to a rare type of disease in which there is an abnormal short circuit between arteries and veins in the dura (leathery covering) over the brain and spine. While the cause of these diseases remains poorly understood, the way the disease causes problems for a patient has become clearer, mostly relating to the increasing pressure in the veins of the dura and over the brain itself.
Dural shunts can cause several problems, including bleeding or ischemic strokes resulting from congested veins, or decreased or even ceased functioning of the brain or spinal cord from general venous congestion.
How are brain DAVS detected?
The presence of a DAVS can be detected using imaging tests such as:
However, because of the complex nature of the disease, catheter angiography is a must. Most patients only come to know that they have a DAVS once they have had symptoms relating to its presence.
Are brain DAVS a serious health risk?
Dural shunts are complex in their effects, ranging from almost no risk to being seriously life threatening. Therefore, not all need to be treated aggressively. Some dural shunts have characteristics that make them more likely to rupture and cause strokes – at rates even higher than those of brain aneurysms. For this reason, dural shunts need to be thoroughly evaluated. Dural shunts with aggressive characteristics have a pattern of blood flow that puts a tremendous amount of flow into fragile, small veins on the surface of the brain, which can burst or create so much congestion that the brain no longer gets the blood flow it needs.
Treatment options for DAVS
Vascular disorders of the spine
Vascular disorders of the spine are a rare type of disease in which there is an abnormal short-circuit between arteries and veins occurring either in or around the spinal cord. They may either be similar to AVMs, which cause bleeding problems, or to DAVS, which cause congestion that can back up blood flow and lead to the spinal cord ceasing to function.
How are vascular disorders of the spine detected?
An MRI of the spine is a good way to look for these diseases, but a catheter angiogram is a must in order to fully understand the shape of the disease. Most patients only come to know they have a spinal vascular disorder once they have symptoms relating to its presence.
Treatment options for vascular disorders of the spine
Surgery: Surgical treatment can be performed to remove the abnormal connections. The surgeon uses a procedure called a laminectomy to reach the spine, during which a small opening is created in the bony covering (through the lamina) of the spinal cord. Once the surgeon has access to the shunt, the abnormal arteries and veins can be closed off.
Embolization: Embolization involves inserting glue into the location where the short circuit occurs through a very thin tube called a catheter. This blocks blood flow into the shunting point, eliminating the abnormal blood flow.
Surgery: Surgical treatment can be performed to remove the abnormal connections. The surgeon uses a procedure called a craniotomy to reach the brain, during which a small opening is created in the skull. Once the surgeon has access to the shunt, the abnormal arteries and veins can be closed off.
Embolization: Embolization involves inserting either coils or glue into the location where the short circuit occurs through a very thin tube called a catheter. This blocks blood flow into the shunting point, reducing the blood flow into the fragile veins.
