Brain arteriovenous malformations

  • The Cerebrovascular Surgery and Interventions Center treats arteriovenous malformations of the brain and other cerebrovascular conditions. Arteriovenous malformations (AVMs) are errors in blood vessel development in which tangles of arteries and veins connect abnormally. They can occur in the brain or elsewhere in the body. Brain AVMs are usually present at birth.

     

    Read more on AVMs in other parts of the body.

     

     

    Brain AVMs often cause no symptoms at all and are discovered during imaging for other reasons. More commonly, though, we see children with AVMs that have caused bleeding in the brain, seizures and other neurological problems. Symptoms may vary depending on the location of the AVM and can include:

     

    • seizures
    • persistent headaches
    • weakness or paralysis on one side of the body
    • problems with speaking
    • loss of coordination
    • numbness, tingling or pain

    How we care for brain AVMs at Boston Children's Hospital

    In treating brain AVMs, we seek to minimize the child’s long-term neurologic risks. In addition to treating the AVM itself, our specialists in neurology, physical/occupational therapy and speech/language therapy address any neurological symptoms that the AVM may have caused.

    Before treating a brain AVM, we carefully image it and the surrounding vessels and brain tissue using a variety of noninvasive techniques, each giving different kinds of information. When the AVM is accessible, and there is little danger of interfering with vital brain functions, we attempt to remove it surgically. If the AVM is complex, especially if it involves deep, hard-to-reach vessels, we may recommend endovascular embolization before operating. When the AVM’s location in the brain makes direct surgery too risky, and the AVM is small, we may recommend radiosurgery.

    The Cerebrovascular Surgery and Interventions Center has pioneered the practice of performing an additional angiogram after treatment, before waking the child from anesthesia, to verify that the entire AVM has been removed. This is important, because even a small portion of an AVM left in the brain can pose a risk of bleeding.

    Read more by clicking the Tests and Treatments tabs above.



  • Brain arteriovenous malformations (AVMs) are tangles of arteries and veins in the brain that are abnormally connected, usually from birth, leading to a variety of neurological symptoms. In rare cases, they are associated with conditions that run in families.

    In normal blood circulation, oxygen-rich blood from the heart travels at high pressure and speed through arteries that branch into smaller and smaller vessels, ending in capillaries. In the capillaries, blood flow slows down and loses pressure, allowing the body to take the oxygen it needs. The depleted blood then moves into the veins and returns to the heart and lungs to pick up more oxygen.

    In brain AVMs, the pattern is abnormal. Blood travels directly from the arteries to the veins through a tangle of abnormally formed, small, very irregular vessels. This direct connection, bypassing the capillaries, prevents the blood from slowing down, losing pressure and releasing its load of oxygen. This can cause several problems:

    • Brain tissue near the AVM can become dysfunctional and sometimes even undergo stroke due to a lack of oxygen.
    • Blood flow and fluid balance throughout the brain become abnormal.
    • The area where arteries and veins connect, known as the nidus, contains blood under high pressure—normally found only in arteries. The pressure can cause the arteries leading to the AVM to become enlarged and even develop aneurysms, while veins leading away may either enlarge and balloon out or become narrowed (stenosis). These abnormal vessels—leading to the AVM, within the AVM and leading away from the AVM—all can become weak and susceptible to rupture.
    • The tangle of AVM vessels itself can put pressure on nearby structures or block the normal flow of cerebrospinal fluid through and around the brain.
    • If the AVM is large, or if it blocks the flow of cerebrospinal fluid, hydrocephalus can develop.
    • Rarely, in newborns with a very large brain AVM, the flow may be so high that the baby experiences heart failure, as the heart struggles to pump enough blood both to supply the body and to flow through the AVM.
  • Before proceeding to treatment, the care team will first conduct a variety of specific neurologic tests to assess the child’s brain function. Sometimes we recommend genetic testing if we suspect an inherited disorder. 

    To help in choosing the best treatment, we carefully image the AVM and surrounding brain using noninvasive techniques, such as:

     

    Magnetic resonance imaging (MRI) uses a strong magnetic field, radio waves and advanced computer processing to produce 2- and 3-dimensional images of the head, neck and brain. MRI is noninvasive and is critical in helping to evaluate AVMs that may not be assessed adequately with other techniques.

    • MRI uses no x-rays or radiation exposure of any kind.
    • Sometimes a contrast dye is injected through an IV during scanning to get a better image.
    • The child must lie still inside an MRI scanner—a large, tube-shaped magnet—sometimes requiring her to be sedated.
    • In response to the magnetic field and the radio waves of the scanner, water molecules in the body give off tiny pulses of energy. A computer constructs detailed images out of these pulses, showing the head, neck and brain anatomy. Read more.

    CT angiography (CTA) uses the technology of a conventional CT scan, along with an injected special dye (known as contrast) to generate images of the blood vessels of the upper chest, neck and brain.

    • CTA generates images somewhat similar to those seen with cerebral catheter angiography, but since the dye is injected into a vein through a standard IV, rather than into an artery, CTA is less invasive.
    • During the test, the child must lie still on a table that slides slowly through a donut-shaped device. A computer constructs 3D images of the blood vessels from the CTA images.
    • Young children may need sedation to keep them still.

    Magnetic resonance angiography (MRA) is a group of MRI-based imaging techniques used to evaluate blood vessels in the brain, head and neck. Unlike CT angiography, many MRA scans do not rely on contrast injected into the veins to generate images of the vessels, although contrast injections are sometimes used. Like conventional MRI, MRA avoids the use of x-rays.

    Cerebral angiography, sometimes called cerebral arteriography or catheter angiography, can often provide additional valuable information about an AVM. It produces highly detailed images of the arteries and veins, using live x-rays.

    • The neuroradiologist or neurointerventionalist inserts a small needle into the femoral artery in the groin. Then, the specialist introduces a soft, thin wire that guides a catheter up to the arteries leading to the region containing the AVM.
    • A special dye, injected through the catheter, allows the radiologist to more clearly see the malformation or damage, as well as the pattern of arteries and veins surrounding it. The catheter also can be used to deliver treatments directly from within the vessels.
    • Cerebral angiography can take from 30 minutes to several hours, and in almost all children, it is performed under general anesthesia. After the angiogram, patients lie flat for four hours in the recovery room; during this time, with their parents close by, they can sleep, watch TV or use a handheld device.
    • We ask patients not to do vigorous exercise for several days after the procedure, although they can return to school as soon as they are ready to do so. Read more about angiograms.

    The treatment team will provide advance instructions on how to prepare for these tests.

  • The choice of treatment for brain arteriovenous malformations (AVMs) is very individual and will depend on the AVM’s complexity, how easy it is to reach surgically and whether removing it would run the risk of interfering with vital brain functions.

    In addition to treating the brain AVM itself, Boston Children’s Hospital addresses any neurological symptoms it may have caused, referring patients to physical therapists, occupational therapists or speech and language therapists as needed and providing close support to help children and families cope with any resulting disability.

     

    Surgery

    At Boston Children’s Hospital, the usual approach to AVMs is to attempt surgical removal if feasible and safe.

     

    If your child is having surgery for an AVM, plan to spend about four hours in the pre-operative clinic to meet with nurses, the anesthesiologist and the neurointerventionalist. You will receive instructions ahead of time on how to prepare.

     

    • Children can bring a favorite toy or blanket into the procedure room, and parents can stay close by, in the family waiting area, while procedures are being performed. Parents are welcome to stay with their children in the recovery room, the ICU and the hospital floor rooms afterward.
    • If the AVM is complex, especially if it is supplied by deep, hard-to-reach vessels, we may recommend endovascular embolization (see below) as a separate step before operating.
    • After the operation, we perform an additional angiogram before waking the child from anesthesia, to verify that the entire AVM has been removed. This is important, because even a small portion of the AVM left in the brain can pose a risk of bleeding.

     

    Endovascular embolization

    Endovascular embolization is a minimally invasive, catheter-based technique that seeks to close off as much blood flow as possible to the AVM. By itself, embolization is rarely curative for AVM, but it can make surgery easier and safer, decreasing blood loss and providing a clean field for the surgeon’s operation.

    Embolization is performed under general anesthesia by a neurointerventionalist with the help of specialized anesthesiologists, nurses and technologists and x-ray guidance. Parents will receive instructions on how to prepare ahead of time.

     

    • The neurointerventionalist inserts a catheter (a thin, flexible tube) into an artery in the groin through a tiny incision, then advances it up the aorta (the main artery in the middle of the body) and guides it to the AVM. The catheter injects a specially designed medical glue, filling as much of the nidus (the area where veins and arteries connect) as possible.
    • In some cases, embolization and surgical removal can be performed on the same day, but in most cases, the child will have embolization first, stay overnight in the ICU, and then have surgery the following morning.
    • Most children have no pain or other symptoms with embolization. Though there are some serious risks, complications are rare.
    • Embolization requires exposing patients to ionizing radiation (x-rays). Because children are more sensitive to radiation exposure than adults, we have adjusted our equipment and procedures to deliver the lowest possible dose.

     

    Stereotactic radiosurgery

    When traditional surgery is too risky because the brain AVM is hard to reach or is in an “eloquent” area of the brain (with vital functions such as language), our team may recommend radiosurgery. Most often used to treat hard-to-reach brain tumors, stereotactic radiosurgery involves no incisions. Instead, the radiosurgeon aims a beam of high-energy radiation at the AVM.

     

    • The tightly focused radiation—generated by a linear accelerator, a proton beam or a gamma knife—is precisely guided by 3D images and computer calculations. As a result, nearby tissues are minimally affected.
    • After treatment, the abnormal blood vessels gradually wither and close down.
    • Stereotactic radiosurgery generally takes 30 minutes to two hours. Children can often go home the same day or after an overnight stay. 

     

    Preparation and follow-up for AVM treatment

    If your child is scheduled to come to Boston Children’s, you will receive specific information on how to prepare. Because these procedures involve general anesthesia, we usually ask patients to refrain from eating, drinking and sometimes from taking medicines for a certain period of time.

     

    After treatment, most children leave the hospital within a few days. Sometimes, if the situation warrants, we will admit the child to the ICU for several days of observation. Children then return for a follow-up office visit within a few weeks of discharge.

     

    We also perform a follow-up angiogram one year after surgery to verify that there is no residual or recurrent AVM. If this angiogram is “clean,” we then follow patients with MRI scans, at first annually, and then less frequently. Follow up may be in part through video teleconference for patients who live outside the Boston area.

  • The Cerebrovascular Surgery and Interventions Center conducts ongoing research to improve diagnostic and therapeutic approaches to brain AVMs and other forms of cerebrovascular disease (CVD). Our clinical research is complemented by basic science discoveries in the Vascular Biology Program.


    Your child’s brain model is ready

    Turning to 3D printing technology, the Center has begun creating plastic models that faithfully reproduce the brain anatomy of patients with CVD. These models, using data from the child’s brain scans, help our surgeons and neurointerventionalists plan and “walk through” procedures ahead of time.

     

     

     

     

     

     

    CVD biomarkers

    Neurosurgeon Edward Smith, MD, is beginning to identify telltale proteins in the urine of patients with brain AVMs and other cerebrovascular disorders. These “biomarkers” may help in diagnosing and monitoring AVMs, reducing families’ need to travel to Boston Children’s for follow-up imaging studies. Dr. Smith has already validated the utility of urine biomarkers of several kinds of brain tumors. Read more.

    Refining catheter procedures

    A variety of novel techniques developed and trialed here have allowed safe use of catheters and endovascular devices in infants’ tiny vessels. We also successfully adopted Onyx, an improved material used in catheter embolization procedures in adults, to treat cerebral and spinal AVMs and other CVD conditions in children. We have an unparalleled safety record in treating children with this condition.

     

     

    Reducing brain hemorrhage

    Advances in understanding the risk for brain hemorrhage in children with AVMs have helped us select the best treatment options.

     

    CVD Dynamic Database

    Our comprehensive patient database, representing the largest experience with pediatric CVD disease in the world, provides rich source material for ongoing studies, innovation and quality improvement. The database allows us to track long-term outcomes of children with brain AVMs, compare the results of different procedures and evaluate newly adopted interventions.

    See some of our published papers on brain AVMs.

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