Arteriovenous Malformation (AVM)- Brain 

Introduction
Cerebral arteriovenous malformation (AVM) is a rare condition that occurs in the brain of less than 1% of all people.  An AVM is an abnormal tangle of blood vessels that develops between the arteries and veins.  AVMs are fragile structures and prone to swelling and bleeding.  Ruptured AVMs are life-threatening and require immediate emergency medical treatment.  AVMs can be treated with medications, surgery, embolization, and radiosurgery.

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Anatomy
Your brain is the control center of your body.  Your brain controls the way you think, behave, and feel.  It communicates with the nerves in your body for functions you can control, such as moving your arms and legs.  Your brain also controls the life-sustaining functions that you cannot control.  This includes your heartbeat, body temperature, blood pressure, and body metabolism.
 
The cells in your brain need oxygen to function and survive.  Oxygen is carried to your brain by red blood cells.  Your red blood cells travel to your brain in tubes called arteries.  The internal carotid and the vertebral arteries carry blood to your brain. 
 
The internal carotid and the vertebral arteries branch off to transport blood to areas throughout your brain.  The branches of the internal carotid artery supply blood to the front and top areas of your brain.  These branches include the anterior cerebral, anterior communicating, middle cerebral, and posterior communicating arteries. 
 
The vertebral artery branches into the anterior spinal artery and supplies blood to your brain and spinal cord.  The junction of your two vertebral arteries forms your basilar artery.  Your basilar artery branches into the cerebellar and posterior cerebellar arteries that supply blood to the lower and back areas of your brain.  The arterial branches form a circular formation in the center of your brain called the Circle of Willis. 

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Causes
The exact cause of AVM is unknown.  AVM is a condition that some people are born with.  It appears that AVMs occur as a result of a rupture or blood clot in a developing baby during pregnancy. Researchers do not believe that AVMs are an inherited condition, unless they are associated with specific inherited conditions, such as Von Hippel-Lindau Disease or hereditary hemorrhagic telangiesctasia.
 
AVMs are abnormalities in the connections between the arteries and veins in the brain.  The affected areas lack capillaries and instead have a tangle of abnormal blood vessels that connect the arteries and veins.  The abnormal blood vessels are called a nidus.
 
A nidus is very fragile and prone to bleeding.  Bleeding can be fatal or cause a stroke.  The nidus may swell and compress surrounding brain tissues, resulting in functional impairments.

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Symptoms
An AVM may not cause symptoms until it swells or bleeds.  Bleeding most frequently occurs between the ages of 15 and 20 years old, but may also occur later in life.  AVMs can cause headaches and seizures.  In some women with AVM, pregnancy can cause abrupt symptoms.
 
You should immediately have someone take you to the emergency room of a hospital or call for an ambulance, usually by dialing 911, if you have a severe headache, vomiting, vision changes, seizures, weakness or numbness, or other symptoms of a ruptured AVM.  When an AVM ruptures and bleeds, it may cause similar symptoms to a stroke.  Symptoms may include sleepiness, confusion, irritability, and changes in thinking skills, such as memory.  You may have difficulty speaking and your sense of smell may seem different.  You may experience eyelid drooping, dizziness, and a buzzing noise in your ears.

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Diagnosis
A doctor can begin to diagnose an AVM after completing a medical history, physical examination, neurological examination, and tests.  Computed tomography (CT) scans and magnetic imaging resonance (MRI) scans are used to create pictures of the brain’s structures.  A magnetic resonance angiography (MRA) is used to record the flow of blood throughout the brain.  Superselective angiography provides the most detailed images of the blood vessels in an AVM.  It uses a special dye at the site of the AVM to enhance the images.

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Treatment
Treatments for AVMs are very individualized.  Medications may be used to relieve the symptoms of AVMs, including anti-seizure medications.  Depending on the location in the brain, some AVMs may be treated with surgery, endovascular embolization, or radiosurgery.
 
Surgery may be used to remove AVMs that are located in a superficial area of the brain.  AVMs that are located deep inside the brain are not usually treated with conventional surgery because it could potentially harm healthy brain tissue.  Endovascular embolization may be used with surgery or radiosurgery.  Embolization involves inserting a clotting agent in the AVM with a catheter.  Embolization plugs the AVM and helps to correct the abnormal blood flow.
 
Radiosurgery is a less invasive treatment for AVM.  Radiation is used to destroy the abnormal blood vessels in an AVM.  Stereotactic Radiosurgery (SRS) and Stereotactic Radiotherapy (SRT) are both methods of delivering radiation therapy to AVMs. SRS involves a single radiation treatment.  SRT uses a series of treatments over time.  Both methods spare healthy tissues as much as possible because the radiation precisely targets the AVM.  The procedures are painless and usually performed on an outpatient basis.
 
Image-Guided Radiation Therapy (IGRT) is a type of external beam radiation therapy for AVM that adjusts for the size and shape of the AVM throughout treatment.  IGRT uses advanced imaging technology to visualize the AVM before each treatment.  Based on the daily images, the radiation is configured before each treatment.  In turn, the radiation is more precise, effective, and results in fewer side effects.  Its versatility helps to spare as much healthy tissue as possible, while delivering a precise high-dose radiation treatment.
 
The experience of AVM and AVM treatments can be an emotional process for people with AVMs and their loved ones.  It is important that you receive support from a positive source.  Some people find comfort in their family, friends, counselors, co-workers, and faith.  AVM, brain injury, or stroke support groups are another good option.  They can be a source of information and support from people who understand what you are experiencing.  Ask your doctor for support group locations in your area.

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Prevention
A ruptured AVM is a medical emergency.  If you experience the symptoms of an AVM, you should immediately have someone take you to the emergency room of a hospital or call an ambulance.  It is vital to receive emergency medical treatment to prevent death and preserve brain function.

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Am I at Risk
AVM in the brain is a rare condition that occurs in less than 1% of all people.  You may have a greater risk for AVM if you have Von Hippel-Lendau Disease or hereditary hemorrhagic telangiesctasia.  Some people with a cerebral AVM also have a cerebral aneurysm.  Pregnancy increases the risk of AVM rupture because of increased blood volume and blood pressure.  AVMs that have bled once have a high risk of bleeding again within a year from the first incident.

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Complications
In some cases, AVM-related brain bleeding may lead to permanent impairments or death.  People with AVM may develop seizures and require anti-seizure medications for the rest of their lives.

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Advancements
Researchers are studying ways to predict the risk of AVM bleeding, including the role of high blood pressure.  Researchers are trying to determine better non-invasive imaging techniques and radiosurgery methods.

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This information is intended for educational and informational purposes only. It should not be used in place of an individual consultation or examination or replace the advice of your health care professional and should not be relied upon to determine diagnosis or course of treatment.

The iHealthSpot patient education library was written collaboratively by the iHealthSpot editorial team which includes Senior Medical Authors Dr. Mary Car-Blanchard, OTD/OTR/L and Valerie K. Clark, and the following editorial advisors: Steve Meadows, MD, Ernie F. Soto, DDS, Ronald J. Glatzer, MD, Jonathan Rosenberg, MD, Christopher M. Nolte, MD, David Applebaum, MD, Jonathan M. Tarrash, MD, and Paula Soto, RN/BSN. This content complies with the HONcode standard for trustworthy health information. The library commenced development on September 1, 2005 with the latest update/addition on April 13th, 2016. For information on iHealthSpot’s other services including medical website design, visit www.iHealthSpot.com.