Arteriovenous malformations (AVMs) are faults in the blood vessels that are believed to be formed during fetal development i.e. before birth. In this condition the normal blood circulation in the body is disrupted due to the abnormal network between the arteries and veins, resulting in diversion of the blood from the capillaries that supply blood to the organs. An AVM can occur anywhere on the body; however those in the brain or spine especially can have widespread effects on the body.
An AVM in the brain may not show any symptoms, until it has ruptured resulting in brain hemorrhage (bleeding in the brain).
In cases where there is no brain hemorrhage, signs and symptoms of a brain AVM may include:
• Headache or pain in one area of the head
• Numbness or muscle weakness in one part of the body
• Vision loss
• Difficulty in speaking
• Severe unsteadiness
Symptoms usually emerge between 10 to 40 years of age, although they can appear at any age. Over time brain AVMs can incur damage to the brain tissue due to inadequate blood supply, the effects of which slowly build up leading to symptoms in early adulthood. However as you approach middle age, they usually remain stable and are less likely to cause symptoms.
When to seek medical attention?
Seek medical attention immediately if you notice any signs or symptoms of a brain AVM, such as headaches or seizures or other symptoms. A brain hemorrhage is the most common symptom that is life-threatening and requires emergency medical attention.
There is no particular cause of a brain AVM but research has revealed that most brain AVMs develop during fetal development. In a normal body, the heart supplies oxygen-rich blood to your brain through arteries. The blood flow in the arteries gets slowed down by passing through a series of smaller network of blood vessels and finally ending with the smallest blood vessels known as capillaries. The capillaries slowly provide oxygen rich blood to the brain tissue. After providing the tissue with the required nutrients and oxygen, the blood then passes into small blood vessels and then into larger veins thereby taking the blood back from the brain to the heart to get more oxygen.
In an AVM, the arteries and veins lack this supporting network of smaller blood vessels and capillaries. Instead, the blood flows quickly and directly from the arteries to veins, bypassing the surrounding tissues.
A brain AVMs can be diagnosed with the following tests:
Cerebral arteriography or cerebral angiography is the most specific test that reveals the location and characteristics of the blood vessel pattern, which is important while planning treatment.
Computerized tomography (CT) scans
A CT scan is an imaging technique that is particularly useful as a quick initial diagnostic tool for brain hemorrhage.
Magnetic resonance imaging (MRI)
MRI through the use of powerful magnets and radio waves creates images of your brain. A MRI is finer than a CT scan that can show more detailed changes in brain tissue associated with an AVM. It provides information regarding the exact location of the AVM and any associated bleeding in that area.
TREATMENT FOR AVM
The treatment of AVM depends on the symptoms, the type of AVM and its size and location.
Even if there are no symptoms, a person with an AVM should keep away from activities that will increase blood pressure and avoid blood thinners like warfarin. He should get regular checkups done with a neurologist or neurosurgeon.
If an AVM has led to brain hemorrhage and/or is in an area of the brain that can be easily operated on, then surgery may be recommended.
In this procedure, the surgeon inserts a catheter (a long thin tube) into a leg artery and guides it through blood vessels to your brain using X-ray imaging or fluoroscopy. Here the arteries of the AVM can be blocked by using liquid tissue adhesives, micro-coils, particles, and other materials. A less invasive procedure than traditional surgery, endovascular embolization may be performed alone or is commonly used prior to other surgical treatments. This makes the procedure safer by decreasing the size of AVM or the chances of bleeding.
If an AVM is located in an area that is difficult to operate by regular surgery, then it may be treated with stereotactic radiosurgery. Firstly, a cerebral angiogram is done to locate the AVM, and then focused high energy beam is concentrated on the brain AVM to cause direct damage to the vessels. This will produce a scar and allow the AVM to “clot off.”