An arteriovenous malformation (AVM) in the brain is a relatively rare condition – occurring in less that 1 percent of the population. It can, however, be neurologically morbid in young adults ages 15 to 20, who are at the greatest risk for hemorrhage and least likely to exhibit symptoms. About 2 to 4 percent of all AVMs each year hemorrhage.
An AVM’s tangled mass of blood vessels, which forms in utero, produces multiple direct connections between arteries and veins without the normal, intervening capillaries. Symptoms often are not present until later in life or until after the AVM ruptures.
A small number of congenital syndromes, such as Sturge-Weber, Rendu-Osler-Weber, ataxia telangiectasia, and Wyburn-Mason, are associated with AVMs. Once formed, extrinsic factors, such as arterial shunting, growth factors and intracranial hemorrhage, may alter the size and shape of an AVM.
The most common types of AVMs are:
- Arteriovenous (AV) fistula – direct connections between arteries and veins that can occur in a variety of locations, resulting in symptoms caused by increased pressure in the venous side of the circulation
- Cavernous Malformation – the second most common cerebral vascular malformation, although often found incidentally, occurring anywhere throughout the central nervous system and resulting in headaches, bleeding or seizures
- True Arteriovenous Malformation (AVM) – high-flow cerebrovascular lesions occurring on the proximal intracranial vessels in various locations and ranging in size from microscopic to more than 10 cm in diameter
- Developmental Venous Anomalies – benign abnormal developmental anomalies of the cerebral venous system that rarely hemorrhage and, therefore, are not treated by surgery or radiosurgery
- Capillary Telangiectasia – benign focal collections of dilated capillaries with normal intervening brain structures that are mostly found in the posterior fossa, particularly the pons, and do not require treatment
The challenge of diagnosing an asymptomatic condition
Only about 12 percent of patients with AVM present with symptoms. Most frequently the AVM is discovered when a patient receives imaging for another condition. Symptoms may include:
- Sudden and severe headaches or seizures
- Seizures
- Muscle weakness or paralysis
- Numbness and tingling
- Problems with vision, language use, coordination or memory
Some symptoms, while rare, may result from the “steal effect,” where a very large AVM with high blood flow steals blood from other areas of the brain and causes decreased function in that area.
A thorough diagnostic workup may include:
- Cerebral angiogram
- Computed tomography (CT) angiogram
- Cranial MRI with functional imaging to determine the precise location and proximity to brain areas that control critical functions
- Electroencephalogram (EEG)
- Magnetic resonance angiography (MRA)
- Magnetic resonance veniogram
The AVM treatment arsenal
Neurosurgeons evaluate the size, location and involved blood vessels, as well as a patient’s age and medical history and co-morbidities, in order to develop the most appropriate treatment plan. Preferred treatments include:
- Microsurgery
- Selective vessel AVM embolization
- Radiosurgery
Microsurgery is used to close the blood vessels, remove the AVM and eliminate the risk of future bleeding. A vascular surgeon often performs microsurgery in conjunction with staged, catheter-based embolization by an interventional neuroradiologist.
Stereotactic radiosurgery can be used in lieu of surgery for AVMs that are located deep within the brain or are too close to critical brain regions. Radiosurgery is particularly effective with small AVMs. We are fortunate to have the two most sophisticated technologies for the treatment of AVMs at the Swedish Radiosurgery Center. With both radiosurgery platforms under one roof – CyberKnife® and Gamma Knife® – we are able to select the most appropriate treatment that will provide the best possible outcomes. Regardless of the technology, the precise delivery of high-dose radiation directly to the AVM causes the blood flow to slowly close off over time, until the AVM is obliterated and the bleeding stops completely.
Expertise and experience drive outcomes
The neurosurgeons and interventional neuroradiologists at the Swedish Cerebrovascular Center are regional resources for the treatment of AVMs of all types. With their expertise and experience with diagnosing and treating AVMs, along with the expertise of the nursing staff in the dedicated ICU and on the nursing floors, and the specially designed neurosurgical operating rooms and endovascular suites, the Swedish Neuroscience Institute is a resource you can count on for quality care.
For more information about arteriovenous malformations, please visit www.swedish.org/cerebrovascular or call the Swedish Cerebrovascular Center at 206-320-3470.
