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VASCULAR MALFORMATIONS

Arteriovenous Malformation (AVM)

These are congenital lesions, present at the time of birth, that consist of a tangle of abnormal blood vessels. Blood reaches an AVM through feeding arteries, and then swirls through the tangle of vessels that comprise the nidus or core of the AVM. The blood then leaves through enlarged veins, without ever supplying nutrients to the immediately surrounding normal brain tissue.

An AVM rarely causes symptoms before adulthood. Sudden bleeding or hemorrhage is the greatest threat from an AVM, even one that has never caused symptoms before. Therefore treatment is considered whenever an AVM is identified. Stroke like symptoms may develop; as if blood flow is "stolen" by the AVM, rather than supplying the surrounding brain. The AVM may also cause seizures due to irritation of the surrounding brain tissue.

Once an AVM is found, because of symptoms or by coincidence, the management options should be considered. Sometimes it may be reasonable to simply observe, and not perform any intervention. However, because of the potential risk of serious bleeding from an untreated AVM, this may not be the safest choice. Treatment options include microsurgical resection, GKS, and endovascular embolization. The goal of these treatments is to obliterate or remove the AVM, such that future bleeding cannot occur. Successful treatment may also reverse the irritation to surrounding brain tissue.

GKS for AVM is based upon localizing images of MRI and cerebral angiography. AVM's less than 3 cm in diameter are treated with a single GKS procedure. The effects are a gradual thickening of the AVM vessel walls, eventually leading to complete obliteration of the AVM over the course of 2 to 3 years, for most patients.


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