Cerebral Arteriovenous Malformation Haemorrhagic

A cerebral arteriovenous malformation is an abnormal tangle of blood vessels in the brain that can rupture and cause life-threatening bleeding, affecting people of all ages but most commonly diagnosed in those between 20 and 50 years old.

Table of contents

• What is a cerebral arteriovenous malformation?
• Symptoms and warning signs
• When bleeding occurs
• Causes and risk factors
• How AVMs are diagnosed
• Treatment options
• Recovery and outlook

What is a cerebral arteriovenous malformation?

A cerebral arteriovenous malformation (AVM) is an abnormal tangle of blood vessels in the brain that creates irregular connections between arteries and veins. Normally, arteries carry oxygen-rich blood from the heart to the brain, while veins carry oxygen-depleted blood back to the lungs and heart. Between these two types of vessels, tiny blood vessels called capillaries slow down blood flow and allow oxygen and nutrients to reach surrounding tissues^[1].

In a brain AVM, this normal process is disrupted. Blood passes directly from arteries to veins through the abnormal tangle of vessels, bypassing the capillary system entirely. This creates high-flow arterial blood connecting directly to veins that are not designed to handle such high pressure. The abnormal tangle of blood vessels looks like a bird’s nest and is called the nidus^[3].

Brain AVMs are rare, affecting about 1 in 100,000 people. They are present in less than 1% of the population overall^[2][5]. Most people are born with these malformations, although in some cases AVMs can form later in life^[1][5]. Men and women are equally likely to have an AVM^[5].

• Brain
• Arteries
• Veins
• Spinal cord

Symptoms and warning signs

About half of people with brain AVMs experience no symptoms until the malformation ruptures and bleeds. Many AVMs are discovered accidentally during brain imaging performed for other reasons^[1][5]. In about 15% of people with AVMs, no significant symptoms occur at all^[3].

When symptoms do appear, they can vary depending on the size and location of the AVM. Common symptoms include:

• Headaches that can vary in frequency, duration, and intensity, sometimes becoming as severe as migraines. The headache pain may be felt on one or both sides of the head^[2]
• Seizures, which can be the first symptom in 25% of cases. These seizures may involve convulsions, loss of control over movement, or changes in consciousness^[2][5]
• Muscle weakness or paralysis in one part of the body^[2]
• Numbness or tingling sensations in certain areas^[3]
• Vision problems, particularly if the AVM is located near the optic nerve or in the back portion of the brain where images are processed^[2]
• Dizziness and problems with balance^[3]
• Difficulty with movement, speech, memory, or thinking^[3]

About 40% of patients with brain AVMs experience headaches as a symptom, with a higher occurrence in female patients. The average age of patients who experience seizures as their first symptom is 25 years^[5].

When bleeding occurs

The most serious complication of a brain AVM is bleeding into the brain, known as a hemorrhage. This is the most common first symptom caused by an AVM, occurring in about 70% of symptomatic patients. In about 50% of people with a brain AVM, a brain bleed is their initial symptom^[3][5].

When an AVM ruptures and bleeds, symptoms typically appear suddenly and can include:

• Sudden onset of severe headache^[5]
• Confusion or disturbed sleep^[4]
• Weakness in an area of the body^[5]
• Nausea and vomiting^[5]
• Neck stiffness or sensitivity to sound and light^[5]
• In severe cases, progression to coma^[5]

Bleeding from an AVM is associated with a 10% to 30% risk of death. There is also a 10% to 20% chance of disability following a hemorrhage^[5][9]. Once an AVM bleeds, the risk of re-bleeding increases significantly. The re-bleed rate rises from the usual 2% to 4% per year to 6% to 18% per year for at least a year following the initial hemorrhage^[7].

The best available data suggests that unruptured AVMs have a 1% to 3% per year risk of bleeding once discovered^[5].

Causes and risk factors

The exact cause of cerebral AVMs is not fully understood. Most people who have them are born with them, suggesting they develop during fetal development^[1][3]. Growing evidence suggests there may be a genetic component, though AVMs rarely run in families^[3][4].

Brain AVMs are most commonly diagnosed in people between the ages of 20 and 40, though they can be found in children and older adults as well. The most common age for brain AVMs to be diagnosed is in the 30s to 40s. The risk of symptoms is highest between ages 30 and 50^[3][5].

Certain factors can increase the risk of bleeding from an AVM, including:

• Prior hemorrhage from the AVM^[7]
• Smaller AVM size^[10]
• Deep venous drainage patterns^[10]
• High arterial feeding pressures^[10]
• Current or planned pregnancy^[4]
• Presence of weak areas in the blood vessels, such as aneurysms (balloon-like bulges in blood vessel walls)^[7]

In just under half of patients who experience bleeding from an AVM, a specific source of the hemorrhage can be identified. This is most commonly an intranidal false aneurysm (a weakened area within the tangle of abnormal vessels). Other potential bleeding sources include flow-related aneurysms and associated aneurysms^[7].

How AVMs are diagnosed

When an AVM causes bleeding, it is typically first detected on a computed tomography (CT) scan, which uses X-rays to create detailed cross-sectional images of the brain^[5][6]. A CT scan can show nearly all parts of the body and is commonly used to diagnose disease or injury^[6].

For AVMs that have not caused bleeding, magnetic resonance imaging (MRI) is often performed. This test uses magnetic fields and radio waves to create high-resolution images of the brain tissue and surrounding structures^[5][6].

To determine the exact location, size, and anatomy of an AVM, blood vessels in the brain must be imaged through a test called angiography. There are several types of angiography:

• Cerebral angiography (also called cerebral arteriography) is the most detailed test and is considered the gold standard for diagnosing brain AVMs. A thin tube called a catheter is inserted into an artery, usually in the groin or wrist, and threaded to the brain using X-ray guidance. A special dye is injected into the blood vessels to make them visible on X-ray images. This reveals the location of feeding arteries and draining veins, which is critical for planning treatment^[5][6]
• CT angiography involves injecting dye through a tube into a vein during a CT scan, allowing the arteries feeding the AVM and the veins draining it to be viewed in greater detail^[6]
• MR angiography (MRA) uses magnetic resonance technology to visualize blood vessels and can be performed non-invasively^[5]

Cerebral catheter angiography is an invasive test with a very small risk of causing serious harm, most importantly a small risk of stroke. However, it provides additional information not available from other tests^[5].

Additional tests may include an electroencephalogram (EEG) to evaluate seizure activity^[4].

Treatment options

A bleeding AVM is a medical emergency. The immediate goal of treatment is to prevent further complications by controlling the bleeding and seizures, and if possible, removing the AVM^[4].

There are four main management options for people diagnosed with a brain AVM:

Medical management and observation

Some AVMs may be best treated by managing symptoms without attempting to remove the malformation. Medications are prescribed to manage symptoms such as seizures or headaches. Standard anticonvulsant therapy is generally sufficient to control seizures. Common medications include phenytoin, carbamazepine, valproic acid, or lamotrigine^[10].

This option may be chosen when attempts to treat the AVM with other methods may pose more risk of harm to the patient than the AVM itself. This approach is particularly considered for older patients or those with AVMs that have no high-risk features^[4][10].

Open brain surgery

Surgical removal of the AVM requires opening the skull in a procedure called a craniotomy. The abnormal connection between arteries and veins is physically removed from the brain. For surgery to be beneficial, the entire AVM must be removed, which results in a permanent cure^[5].

This procedure is typically used for AVMs located in areas that are accessible for surgical intervention. Surgery may be the first choice for certain types of AVMs or if other treatment methods cannot be performed^[5].

Endovascular treatment (embolization)

This minimally invasive procedure involves guiding a catheter through a small cut in the groin or arm into an artery. The catheter is moved through the blood vessels to reach the small vessels in the brain where the AVM is located. A glue-like substance is then injected into the abnormal vessels to stop blood flow through the AVM and reduce the risk of bleeding^[4].

Embolization can be performed alone or in combination with other treatments to reduce risks or prepare the AVM for surgical removal. It may be the first choice for some kinds of AVMs or when surgery cannot be performed^[4][5].

In cases where a specific weak point or bleeding source can be identified, partial targeted embolization has been used successfully in 90% of cases, with a 9% related technical complication rate that does not result in long-term harm^[7].

Stereotactic radiosurgery

This non-invasive procedure uses focused radiation aimed directly at the area of the AVM. The radiation causes scarring and shrinkage of the abnormal blood vessels, reducing the risk of bleeding over time^[4][5].

Stereotactic radiosurgery is particularly useful for small AVMs deep in the brain that are difficult to remove by surgery. It is also known as Gamma Knife surgery^[5].

Sometimes these treatments are used together. The choice of treatment depends on the type of AVM, its location, symptoms, and the individual’s general health^[2].

Recovery and outlook

Some people whose first symptom is excessive brain bleeding will die from the hemorrhage. Others may have permanent seizures and problems with brain and nervous system function^[4].

After treatment, patients typically experience a period of recovery. Immediately following surgery, a hospital stay of several days to a week is usually required for observation and monitoring for potential complications such as bleeding, infection, or neurological changes^[16].

Fatigue is one of the most common symptoms after treatment. It is normal to feel tired for several weeks or even months as the body heals. Swelling and discomfort at the treatment site are also common, especially after open surgical procedures^[16].

Follow-up appointments are scheduled to monitor recovery, typically including imaging tests such as MRIs or CT scans to ensure that the AVM has been fully treated and that no new problems have developed^[16].

Research on patients with untreated AVMs shows that the condition can have a significant negative impact on quality of life. In one study, anxiety and discomfort were the most prevalent factors affecting quality of life, especially in younger patients aged 18 to 34 years. Female patients showed greater dependence than men, though males had more significant impairment in their usual activities. Older patients were affected more significantly in their self-care and usual activities compared with younger people^[14].

After partial targeted embolization to treat specific bleeding sources, the mean follow-up period showed an annual hemorrhage rate of 0.7%, which is significantly lower than the expected re-bleeding rate in the first two years following an initial hemorrhage^[7].

AVMs that do not cause symptoms by the time people reach their late 40s or early 50s are more likely to remain stable and only rarely cause symptoms^[4].

Possible long-term complications may include brain damage, language difficulties, numbness of any part of the face or body, persistent headaches, seizures, and vision changes^[4].