Brain Arteriovenous Malformation

What Causes Brain Arteriovenous Malformation?

The cause of brain AVMs is unknown. They seem to occur most often during fetal development, but scientists have not yet determined what causes the blood vessels to begin developing abnormally. Most cases occur in people with no family history of the condition, suggesting that even if there is a genetic cause, it happens randomly or because of some external environmental trigger. However, scientists do not yet know what those triggers might be.

Is Brain Arteriovenous Malformation Hereditary?

Many scientists believe that there is an inherited risk for the development of a brain AVM. However, no specific genetic mutation has yet been definitively associated with the condition. Some studies have suggested genes that may be linked to the conditions that give rise to AVMs. The candidate genes include those involved in blood vessel development and control of inflammation. More research is needed to confirm the connection between these genes and AVMs.

How Is Brain Arteriovenous Malformation Detected?

A ruptured AVM that causes bleeding in the brain is a potentially life-threatening condition that requires emergency medical attention. Seek medical help immediately if you or a loved one experience any of the symptoms of an AVM rupture, including:

• Sudden severe headache
• Nausea and vomiting
• Weakness or numbness
• Sudden vision impairment
• Sudden speech difficulty
• Sudden difficulty comprehending language
• Loss of consciousness

How Is Brain Arteriovenous Malformation Diagnosed?

Because they often exhibit no symptoms, brain AVMs often go undiagnosed unless they are detected during an imaging scan for another purpose or there is evidence of bleeding in the brain. If a doctor suspects an AVM may be present, the diagnostic process may include:

• Physical exams and assessment of the patient’s medical history
• Computerized tomography (CT) scan
• Cerebral arteriography, a test that uses an injected dye and X-ray imaging to examine blood flow in the brain
• Spinal tap (lumbar puncture) to look for evidence of bleeding in the cerebrospinal fluid (CSF)

PLEASE CONSULT A PHYSICIAN FOR MORE INFORMATION.

How Is Brain Arteriovenous Malformation Treated?

Brain AVMs are commonly treated directly through surgical procedures to remove or bypass the malformation. In cases where symptoms are minimal, medication may be used to treat the symptoms and prevent complications.

Common treatment procedures include:

• Surgical removal. In this procedure, the AVM is removed entirely. The surgery requires the removal of part of the skull, and it is most effective when the AVM is in an easily accessible part of the brain.
• Endovascular embolization. This procedure involves intentionally blocking off the AVM so blood cannot flow through it. The procedure is performed using a long, thin tube inserted through an artery in the leg, so it does not require opening the skull. Embolization usually is not entirely effective on its own, and it is typically used in combination with other procedures.
• Stereotactic radiosurgery (SRS). This procedure uses precisely targeted radiation to damage the blood vessels in the AVM. Over time, the damaged AVM eventually “clots off,” and blood does not flow through it. SRS does not require an incision, but it is most effective on small AVMs in hard-to-reach locations.

How Does Brain Arteriovenous Malformation Progress?

Brain AVMs do not always cause significant symptoms, but severe complications are possible because of sudden brain bleeding (hemorrhage) or long-term oxygen deprivation to brain cells.

Complications of a brain AVM can include:

• Hemorrhagic stroke
• Stroke-like symptoms (weakness, numbness, speech difficulties)
• Brain aneurysm (a bulge in the wall of a blood vessel that may rupture)
• Build-up of fluid in the brain (hydrocephalus) that can cause brain damage

How Is Brain Arteriovenous Malformation Prevented?

There is no known way to prevent an AVM from forming. However, people with a diagnosed AVM may be able to reduce the risk of rupture and brain bleeding by avoiding activities that can increase blood pressure (such as heavy lifting) and blood-thinning medications.

Brain Arteriovenous Malformation Caregiver Tips

• Be aware of the warning signs of a ruptured AVM. Immediate treatment is the key to your loved one’s survival. An excruciating, unexplained headache is a symptom of bleeding in the brain. When it occurs, seek emergency medical help immediately.
• If your loved one experiences a stroke, create a safe, comfortable environment for their rehabilitation. It’s normal for someone to be confused and frightened after a stroke. The more you can put them at ease, the better. Install assistive devices, including ramps, handrails, and shower seats, if your loved one has mobility problems.

Brain Arteriovenous Malformation Brain Science

Brain AVMs form in the junction between arteries and veins. Arteries carry oxygen-rich blood from the heart, and veins carry blood back to the heart after the blood’s oxygen supply has been depleted by the body’s cells. In a normally developed vascular system, arteries and veins are linked by a network of tiny blood vessels called capillaries. As blood passes through the capillaries, it slows down, and oxygen can easily pass through the vessels’ thin walls and into the surrounding brain cells. Blood pressure, which is high in arteries, also drops as the blood spreads through the web of capillaries.  Veins typically handle lower pressures than arteries.

In an AVM, arteries connect directly to veins with no capillaries in between. As a result, high-pressure blood flow from the arteries continues directly into the veins, raising the risk of rupture. The fast, high-pressure blood flow also makes it more difficult for the surrounding brain cells to get oxygen, potentially causing long-term damage to the cells.

Brain Arteriovenous Malformation Research

Title: Treatment of Brain AVMs (TOBAS) Study (TOBAS)

Stage: Recruiting

Principal investigator: Jean Raymond, MD  

CHUM-Montreal

Montreal, Quebec

The objectives of this study and registry are to offer the best management possible for patients with brain arteriovenous malformations (AVMs) (ruptured or unruptured) in terms of long-term outcomes, despite the presence of uncertainty. Management may include interventional therapy (with endovascular procedures, neurosurgery, or radiotherapy, alone or in combination) or conservative management.

The trial has been designed to test the following: a) whether medical management or interventional therapy will reduce the risk of death or debilitating stroke (due to hemorrhage or infarction) by an absolute magnitude of about 15% (over ten years) for unruptured AVMs (from 30% to 15%); b) to test if endovascular treatment can improve the safety and efficacy of surgery or radiation therapy by at least 10% (80% to 90%).

As for the nested trial on the role of embolization in the treatment of brain AVMs by other means: the pre-surgical or pre-radiosurgery embolization of cerebral AVMs can decrease the number of treatment failures from 20% to 10%. In addition, embolization of cerebral AVMs can be accomplished with an acceptable risk, defined as permanent disabling neurological complications of 8%.

Title: A Randomized Trial of Unruptured Brain AVMs (ARUBA)

Stage: Completed

Principal investigator: J.P. Mohr, MS, MD   

Columbia University

New York, NY

Brain arteriovenous malformations (BAVMs) are an infrequent but important cause of stroke, particularly in a young population. Current invasive treatment strategies are varied and include endovascular procedures, neurosurgery, and radiotherapy. All of these treatments are administered on the assumption that they can be achieved at acceptably minor complication rates, decrease the risk of subsequent hemorrhage, and lead to better long-term outcomes.

Recent data from the literature comparing initial presentation and outcome for patients with ruptured and unruptured BAVMs have raised the possibility that such elective invasive treatment for unruptured BAVMs may yield worse outcomes than managing patients symptomatically with therapy. 

Unfortunately, no controlled clinical trials have yet been undertaken for the management of unruptured BAVMs to address these concerns. Therefore, the goal of this randomized controlled trial is to determine if the long-term outcomes of patients who receive medical management for symptoms (e.g., headache, seizures) associated with an unruptured BAVM are superior to those who receive medical management and invasive therapy to eradicate the BAVM.

Participants will be randomly assigned to receive either symptomatic medical management alone or such management with invasive therapies (any combination of surgery, endovascular embolization, or radiotherapy). Functional assessment will be carried out at the time of randomization, pre-intervention, and 48-hour post-intervention, and for all participants at one month and at six-month intervals throughout the follow-up period, which will be a minimum of 5 years.

Title: Intraoperative Laser Speckle Contrast Imaging of Cerebral Blood Flow

Stage: Recruiting

Contact: Kristina Adrean  

Dell Seton Medical Center

Austin, TX

The purpose of this research study is to evaluate the ability of laser speckle contrast imaging to visualize blood flow in real-time during neurosurgery. Real-time blood flow visualization during surgery could help neurosurgeons better understand the consequences of vascular occlusion events during surgery, recognize potential adverse complications, and thus prompt timely intervention to reduce the risk of stroke. The current standard for visualizing cerebral blood flow during surgery is indocyanine green angiography (ICGA), which involves administering a bolus of fluorescent dye intravenously and imaging the wash-in of the dye to determine which vessels are perfused. Unfortunately, ICGA can only be used a few times during surgery due to the need to inject a fluorescent dye and provides only an instantaneous view of perfusion rather than a continuous view. Laser speckle contrast imaging does not require any dyes or tissue contact and has the potential to provide complementary information to ICGA. In this study, we plan to collect blood flow images with laser speckle contrast imaging and to compare the images with ICGA that is performed as part of routine care during neurovascular surgical procedures such as aneurysm clipping.