Arteriovenous malformations of the brain

Arteriovenous malformations (AVMs) of the brain are the abnormalities in the blood vessels of the brain. It is a very rare condition which affects less than 1% of the entire population. Over a period, these malformations can lead to damage of the brain tissue.

The vascular system originally comprises of arteries, veins and capillaries. Arteries carry pure blood from the heart to other organs of the body; veins carry impure blood away from these organs to the heart while capillaries connect the arteries and the veins. AVMs develop when this connection is not established due to the absence of capillaries, thereby, disrupting the vital process in the brain.

Symptoms

The signs and symptoms of AVMs are not evident until AVM gets ruptured followed by bleeding in the brain (hemorrhage). This is the first sign in nearly half of the patients with AVMs. The other signs and symptoms which may be developed in some people with AVMs include:

• Seizures
• Headache or pain in one part of the head
• Muscle weakness or numbness localized to a body part

Depending on the location of the AVMs, some of the more serious symptoms which may be experienced by some people include:

• Severe headache
• Paralysis
• Difficulty to speak
• Loss of vision
• Difficulty to understand conversations
• Unsteadiness

Symptoms are usually evident in people aged between 10 years to 40 years. Pregnant women have more severe symptoms associated with changes in blood pressure and blood volume.

Causes

The exact cause of AVMs is not known. AVMs are usually present at the time of birth and are believed to form during the fetal development. However, they may sometimes develop later in one’s life.

Due to the lack of capillaries, the blood from the arteries quickly enters the veins in the brain, bypassing the tissues which need oxygen. This leads to the damage of the brain tissue.

Risk factors

Males are more prone to develop AVMs and rarely a family history can increase the risk of developing this condition.

Complications

The following complications can occur due to AVMs in the brain:

• Thin and weak blood vessels
• Hemorrhages (bleeding in the brain)
• Decreased absorption of oxygen by the brain tissue
• Brain damage

Diagnosis

During the diagnosis of AVMs, the neurologist checks the signs and symptoms and performs a physical examination. For a detailed diagnosis and to rule out other possible causes with similar symptoms, the doctor may recommend the following tests:

• Cerebral angiography test is performed to get the exact location of the affected arteries and veins
• CT (computerized tomography) scan is done to get a detailed cross-sectional view of the brain
• MRI (magnetic resonance imaging) scan is performed to get a more detailed view when compared to a CT scan

Self care

Before the medical help is available some of the measures which the patient needs to take include:

• Avoid activities such as lifting heavy objects, which increase the blood pressure and further increase the strain on the AVMs.
• Avoid blood-thinning agents such as warfarin as they increase the risk of bleeding.

Treatment

Several treatment options are available for AVMs of the brain. Treatment aims at preventing hemorrhage and controlling seizures. Bleeding in the brain associated with AVMs is an emergency medical condition. Treatment depends on several factors such as health and age of the patient, location and size of the abnormal blood vessels.

Medications are prescribed to provide symptomatic relief. Surgery is the best treatment option for AVMs and may include the following approaches:

Resection is the surgical procedure which is performed to remove easily accessible AVMs by temporarily removing a part of the skull.

If the AVMs are located in the deeper regions of the brain, then they are involved with the risk of hemorrhages or seizures. In such cases the other surgical methods such as stereotactic radio surgery and endovascular embolization may be appropriate. Stereotactic radio surgery focuses on high energy radio waves at the site of AVMs which leads to the damage of such blood vessels. Endovascular embolization involves the insertion of a catheter (a flexible thin tube) into the AVMs to close these abnormal blood vessels.