Arteriovenous malformation (AVM)

2021-08-03 10:49 PM

An arteriovenous malformation (AVM) is an abnormal connection between arteries and veins that interrupts the normal flow of blood between them. 

Arteriovenous Malformation

Arteriovenous Malformation

Define

An arteriovenous malformation (AVM) is an abnormal connection between arteries and veins that interrupts the normal flow of blood between them. Congenital AVM can develop anywhere in the body but occur most often in the brain or spine. A cerebral arteriovenous fistula can occur in any part of the brain. The cause is not clear.

You may not know you have an AVM until you have symptoms, such as headaches or moving impairments. In severe cases, the rupture of a blood vessel causes bleeding in the brain (hemorrhage). Once a cerebral arteriovenous catheterization is diagnosed, successful treatment is often possible.

Symptoms

An AVM usually has no signs or symptoms until the arteriovenous catheter ruptures, leading to bleeding in the brain (hemorrhage).

Signs and symptoms of a cerebral arteriovenous fistula include:

Epileptic.

The murmur can be heard with a stethoscope from the skull.

Tinnitus.

Headache.

Weakness or numbness.

When bleeding into the brain occurs, signs and symptoms may be similar to a stroke and may include:

Sudden headache.

Weakness or numbness.

Loss of vision.

Hard to say.

Inability to understand others.

Unsteady standing if heavy.

Arteriovenous catheter bleeding is life-threatening and requires urgent medical attention.

Symptoms can begin at any age but are more likely to experience symptoms before the age of 50. A cerebral arteriovenous fistula can damage brain tissue over time. The effects slowly increase, sometimes causing symptoms in early adulthood. However, by middle age, cerebral arteriovenous shunts tend to be stable and less likely to cause symptoms.

For women, pregnancy can initiate symptoms or get worse because blood flow increases and blood volume increases during pregnancy.

If you notice any signs or symptoms of a cerebral arteriovenous fistula, get medical help right away.

Causes

A cerebral arteriovenous fistula is an abnormal connection between arteries and veins in the brain. Doctors believe that cerebral arteriovenous shunts develop during fetal development. Why this happens for some babies and others not is unknown.

Normally, the heart pumps oxygen-rich blood to the brain through arteries, which branch into smaller arterioles and then to capillaries, the smallest blood vessels. Oxygen is removed from the blood in the capillaries and used for the brain. The oxygen-depleted blood then enters a small vein and then into a larger vein, returning it to the heart and lungs for more oxygen.

If there is a cerebral arteriovenous fistula, blood flows directly from the artery to the vein through the abnormal vessels. This disrupts the normal flow of blood through the brain.

Risk factors

Anyone can be born with a cerebral arteriovenous fistula, but cerebral arteriovenous shunting is more common in boys than girls.

Symptoms of a cerebral AVM are more likely to occur before age 50. Brain tissue can damage over time. The effects build up slowly, sometimes causing symptoms in early adulthood. However, by middle age, cerebral arteriovenous shunts tend to be stable and less likely to cause symptoms.

For women, pregnancy can begin or get worse because of symptoms of increased blood flow and blood volume during pregnancy.

Complications

Complications of cerebral arteriovenous catheterization include:

Bleeding in the brain (hemorrhage). The walls of the affected arteries and veins may become thin or weak. Arteriovenous catheterization puts pressure on the walls because there are no available capillaries to slow blood flow, which can cause bleeding. Very minor bleeding causes limited damage to surrounding tissues and does not present noticeable symptoms. However, larger bleeding can cause a stroke with brain damage.

Reduced oxygen to brain tissue. With a cerebral arteriovenous catheterization, blood does not pass through a network of capillaries but flows directly from the artery to the vein. The rapid blood flow through the altered path because it is not slowed down by the channels of the smaller blood vessels. The tissues around the brain cannot easily absorb oxygen from rapidly flowing blood. Without enough oxygen, brain tissues can weaken or die completely. This leads to stroke-like symptoms, such as difficulty speaking or standing unsteadily.

Blood vessels are thin and weak. A cerebral arteriovenous catheterization puts pressure on the thin and weak walls of the blood vessels. Causes blood vessel walls to swell, which can grow and become fragile.

Brain damage. The blood flow is faster and more abundant to supply blood to the cerebral arteriovenous fistula. As a result, the cerebral arteriovenous shunt enlarges, moving or compressing parts of the brain. This can prevent cerebrospinal fluid from flowing freely throughout the hemispheres of the brain. If fluid builds up, it can push up brain tissue - called hydrocephalus.

Tests and diagnostics

The diagnosis of a cerebral arteriovenous catheterization usually begins with a comprehensive medical examination by a doctor who specializes in the nervous system. Depending on the results, your doctor may order one or more tests. Imaging is usually done by someone who specializes in brain and nervous system imaging.

Three main tests are used to diagnose a cerebral arteriovenous fistula:

CT scan. Computed tomography (CT scan) takes pictures of the brain using X-rays. Dye is sometimes injected through a syringe into a vein so that the cerebral arteriovenous feeding arteries and the cerebral arteriovenous drain veins can be viewed in more detail. This is called a CTA scan.

MRI and MRA. Magnetic resonance imaging (MRI), which is shown to be more sensitive than CT in cerebral arteriovenous catheterization, creates images using a large magnet and radio waves. MRI also provides information about the exact location of the malformation, which is important for determining treatment options. Staining may also be injected to see better blood circulation in the brain. This is called an MRA.

Brain angiography. Cerebral angiography is the most detailed examination and the best way to diagnose a cerebral arteriovenous fistula. The test shows the location and characteristics of the feeding arteries and draining veins. A catheter is inserted into an artery in the groin. This tube is threaded up the brain to the blood vessels. Colorants are injected into the blood vessels of the brain and X-rays are taken.

Treatments and drugs

Optional treatment for cerebral arteriovenous catheterization involves several procedures and depends on the size and location of the abnormal blood vessels. Medications may also be used to treat related symptoms, such as headaches or seizures.

Surgical removal

Surgical treatment of small cerebral arteriovenous catheters is relatively safe and effective. Part of the skull is temporarily removed to gain access to this cerebral arteriovenous catheter. The neurosurgery, aided by a high-end microscope, takes a cerebral arteriovenous fistula with a special clip and carefully removes it from the surrounding brain tissue. Sometimes this is done with a laser. The skull bone is then placed back and the scalp is closed.

Osteotomy is usually performed when a cerebral arteriovenous catheter can be removed with acceptable risk to prevent bleeding or convulsions. Cerebral arteriovenous catheterization in deep brain regions carries a higher risk of complications. In these cases, other therapeutic approaches are considered.

Endovascular embolism

In this procedure, a catheter is inserted into a leg artery and threaded to a cerebral artery. The catheter is placed in one of the arteries feeding to the AVM, and tiny particles of a glue-like substance are injected to block and reduce blood flow into the AVM.

Endovascular embolization may be performed alone, before other treatments to reduce the size of the AVM, or surgery to reduce the risk of bleeding during the operation. Some large cerebral arteriovenous catheters, or endovascular embolization, can relieve symptoms such as stroke by redirecting blood back to normal brain tissue.

Radiation wave

This treatment uses precisely focused radiation to destroy the cerebral arteriovenous fistula. Radiation to the vessels is the cause of a cerebral arteriovenous catheterization so that the blood clot is slowly occluded in the months or years following treatment. This treatment works best for small cerebral arteriovenous catheters and for those without life-threatening bleeding.