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Home :: Stroke :: Stroke Treatment Options : AVM/AVF
AVM / AVF
AVM stands for Arterio Venous Malformation. It is a tangle of abnormal and poorly formed blood vessels with abnormal connectivity between them.  An AVF stands for Arterio Venous Fistula, also a combination of vessels with abnormal connections. Although the “plumbing” is slightly different in these two abnormalities, we shall discuss both under the same heading.

In a normal blood circulation to the brain, the main arteries course towards the region that they supply and divide into smaller and smaller branches. These small branches, called capillaries are of very small diameter about 1/5th the diameter of human hair. Since there are several of these capillaries, the blood flow in them becomes slow and of low pressure. Hence the high pressure blood flowing in the arteries reduced or looses its pressure when dividing into capillaries and forming veins.

Bleed due to repture of AVMIn AVMs the connections arise directly between arteries and veins, with no capillaries between them. This causes the blood from the arteries to flow through the abnormal vessels of the AVM, to flow at high pressure, quickly and directly to the veins. In fact, it never slows down enough to supply the brain with the oxygen it’s carrying.

AVM/AVF can cause many different problems, but the two most common are: 1) Rupture, resulting in a hemorrhagic stroke, and 2) Seizures.

Cause of AVM:
There are no established risk factors for AVM formation, growth or rupture. They are usually regarded as “congenital” or “developmental vascular anomalies”, i.e., one is born with them and they typically increase in size as the brain enlarges. With exception of few syndromic variants, they are considered as non hereditary and family members are not at increased risk.

Symptoms:
AVMs mostly present with rupture leading to brain hemorrhage (sudden onset headache, vomiting, seizure, loss of consciousness, progressive coma or sudden death). The annual risk of hemorrhage for a newly diagnosed AVM which has not bled is around 2 to 4 % per year. So the risk multiplies with each passing year and risk of bleeding over one’s life time may be very high especially if the AVM is discovered in a young person. The risk of rebleed is higher within the first year of bleeding and then the risk decreases to around 3 to 4 % per year.

Other possible symptoms of an AVM are seizures, headache, and other neurological symptoms like weakness or paralysis of one side of the body, numbness, tingling, problem with vision, hearing, balance, memory disturbances or personality changes.

Diagnosis:
The gold standard for the diagnosis and planning of management of AVM is Digital Subtraction Angiography (DSA). An AVM can also be diagnosed on CT scan and MRI, supplemented by CT/MR angiography.

Treatment options:
There are various treatment options available for the treatment of AVM and sometimes these modalities are combined to offer permanent cure of the AVM.

Embolization:
The Endovascular approach (Embolization) is the latest technique for treating AVMs. Embolization procedures are usually performed under general anesthesia (GA). A small needle hole is made in the groin artery through which a small catheter (plastic tube) is advanced from the groin into the brain vessels and then into the AVM. An embolic material is injected into the abnormal vessels which form the AVM to block the AVM off. Once this bunch of abnormal vessels is blocked, blood starts flowing through the normal route only, supplying the brain. Since AVMs do not grow back, the cure is immediate and permanent if the entire AVM is blocked.
Embolization
There is a small risk to this procedure and the chances of completely curing the AVM using this technique depends on the size of the AVM. It is at times combined with other treatments such as radiation or surgery.

Surgery:
This is the oldest method for treating AVMs. A small portion of the skull is opened to expose the brain and the AVM is surgically removed in an operating room under general anesthesia. Like embolization, the cure is immediate and permanent if the AVM is removed completely. The risks of surgery are considered to be high for AVMs that are located in deep parts of the brain with very important functions.

Radiotherapy:
This treatment is also known as Radio-surgery or Stereotactic Radiotherapy. A narrow beam of radiation is focused on the AVM such that a high dose is concentrated on the area of interest with a much lower dose delivered to the rest of the brain. This radiation causes the AVM to shrivel up and close off over a period of 2-3 years in up to 80% of patients. The risk of bleeding is slightly higher during this period and is generally not the first choice of treatment in AVMs which have bled. 
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