Medical Editor: William C. Shiel, Jr., MD, FACP, FACR
South Dakota Senator Tim Johnson underwent surgery on Wednesday, December 13, 2006 for bleeding in the brain caused by a rare but often fatal condition known as an arteriovenous malformation (AVM) of the brain.
An arteriovenous malformation is a congenital disorder (meaning that it is present at birth) of the blood vessels in the brain, brainstem, or spinal cord characterized by a complex, tangled web of abnormal arteries and veins connected by one or more fistulas (abnormal communications).
About 300,000 Americans are estimated to have an AVM, and most people with an AVM do not develop symptoms. However, about 12% of those affected will develop significant symptoms from an AVM. Most commonly, symptoms include hemorrhaging (bleeding), seizures, headaches, and neurological problems such as paralysis or loss of speech, memory, or vision. Hemorrhage is the most serious complication of AVMs. While most hemorrhages associated with AVMs are small, massive hemorrhages that led to death have also occurred. It is estimated that between 2 and 4% of all AVMs will hemorrhage each year.
When symptoms from an AVM occur, they most often develop in early adulthood (before the age of 40). However, older persons may experience a seizure or an episode of bleeding related to an AVM. AVMs occur equally in persons of both sexes and all races.
AVMs can be seen on imaging studies such as CT scan and MRI scans, but a special procedure known as angiography (delineation of the arteries and veins through injection of a contrast substance followed by imaging studies) is needed to fully characterize the AVM before treatment is attempted.
Surgery is the best-known and longest-standing treatment for AVM. Surgery for an AVM involves identifying the margins of the malformation, ligating (tying off) or clipping the feeder arterial vessels, obliterating the draining veins, and removing or obliterating the nidus (the nest) of the AVM. The prognosis (outcome) of the treatment depends upon many factors, including the location and extent of the AVM, the underlying health status of the patient, and the effectiveness of the surgical procedure.
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