Arteriovenous Malformations and Epilepsy
What is an Arteriovenous Malformation AVM?
Blood vessels carry blood throughout our bodies. Our heart pumps blood into the aorta which then divides into several smaller arteries that supply blood to the organs. The arteries further divide into smaller and smaller segments and finally end up as capillaries.
It is through these capillaries that oxygen and nutrients diffuse into the organs from blood. CO2 and waste materials diffuse out of the organs into the blood as well. The capillaries then form veins that carry the blood back to the heart.
The presence of capillaries ensures that the pressure of flow is lessened as blood enters the veins. Veins are thin-walled, and a large amount of pressure can cause them to rupture.
An AVM is an abnormal, direct connection between arteries and veins without the capillaries. As a result, the high pressure is transmitted directly to the veins. This can cause the veins to balloon and eventually rupture and bleed if left untreated.
AVMs can occur in various places throughout the body including the brain. If an AVM in the brain ruptures and bleeds, the blood can irritate the brain tissue leading to various symptoms including seizures.
Why Do We Get AVMs?
The abnormal connection between arteries and veins is due to mutations in the genes that code for the blood vessels formation. Why these mutations occur, however, is still largely unknown.
Medical researchers have also found out that AVMs alone are not hereditary, but they may be involved with rare inheritable conditions like hereditary hemorrhagic telangiectasia.
Fortunately, AVMs though dangerous, are very rare and occur in about 10 people out of 100,000.
What are the AVM Symptoms?
Generally, AVMs grow slowly and insidiously for years with no symptoms. Your doctor may find it when you are getting scanned for something else, what the medical profession calls an incidental finding.
Some may have symptoms like headaches, but this is extremely rare.
If the AVM ruptures, the resultant bleeding can cause a stroke with typical symptoms like severe, unbearable headache, speech problems, and sudden weakness in your limbs, depending on the location in your brain where the AVM was.
As mentioned before, the leaking blood can irritate the brain tissue and cause abnormal electrical discharge which leads to epilepsy. Epilepsy is seen in about a third of the cases with AVM.
How do we Diagnose an AVM?
As you may have guessed we need a CT scan or an MRI scan to diagnose an AVM. Your doctor will do a special kind of CT called contrast CT angiogram (CTA) where a small amount of dye is injected into your bloodstream to better visualize the AVM.
Once the AVM is localized, your doctor will do a formal angiogram. This is like the contrast CTA – your doctor injects the dye into arteries supplying your brain to identify the arteries and veins making up the AVM and the feeding artery of the AVM.
The angiogram is necessary to decide on treatment.
How do we Treat AVM?
The good news is that even if they do find an AVM the risk of it rupturing and bleeding is low (2-3% a year). Furthermore, this risk reduces with age. Pregnancy also does not increase the risk of AVM rupture.
While there are many new innovative yet safe methods to treat AVMs it is not a one-shoe-fits-all type of treatment. There is a lot of art in this type of treatment. Each case must be very carefully assessed – where is the AVM? How big is it? Etc. – and the treatment is tailored to the individual.
If the AVM is not ruptured, then depending on the risk of rupture we can offer options like radiosurgery, injecting scarring material, or open resection.
If the AVM has ruptured and bled then it likely needs surgical treatment – doctors will try to reduce the bleeding by blocking the feeding arteries through a process called embolization. Then they will remove the abnormal mass of blood vessels.
We can treat seizures with anti-seizure medication. However, if the patient does not have seizures we do not give antiseizure medication in advance.
Always consult your doctor before opting for any treatment of AVM. It is mostly a team approach to get it treated successfully.