Tuesday, May 11, 2010
A new Mayo Clinic study has found that Gamma Knife stereotactic radiosurgery is a safe and effective option for selected children with arteriovenous malformations. This study was presented at the American Association of Neurological Surgeons Annual Meeting in Philadelphia last week.
An intracranial arteriovenous malformation is an abnormal tangle of blood vessels in the brain. Normally, oxygen-rich blood enters the brain through arteries, which branch into smaller arterioles and subsequently to capillaries, the smallest blood vessels. Oxygen is removed from blood in the capillaries and used by the brain, and then blood passes into small venules and into larger veins that drain the blood from the brain to the heart and lungs. In an arteriovenous malformation, the blood passes directly from arteries to veins via the abnormal vessels, and the brain is not allowed to absorb oxygen from the blood, which can result in stroke-like symptoms, seizures or other symptoms. Arteriovenous malformations appear to be congenital (present at birth). About 0.14 percent of the population has an arteriovenous malformation.
"Blood flow through an arteriovenous malformation puts pressure on the abnormal vessels within the malformation which can rupture and cause bleeding within the brain," says Bruce Pollock, M.D., a Mayo Clinic neurosurgeon and study author. "Using stereotactic radiosurgery, focused radiation is directed to the arteriovenous malformation causing the vessels to slowly block off over several years and the majority of patients are protected from the risk of intracranial bleeding."
Dr. Pollock and a team of Mayo Clinic researchers collected data from 48 patients, ages 18 or under, who had Gamma Knife stereotactic radiosurgery for an arteriovenous malformation between 1990 and 2007 and had more than 12 months of follow-up data. Twenty-seven patients (57 percent) had a previous brain hemorrhage, and 15 of the arteriovenous malformations were in deep locations. The team found that 52 percent (25 patients) had obliteration of the malformation after their initial radiosurgery. Repeat radiosurgery was performed in 12 patients, five of whom had obliteration, for a total obliteration rate of 63 percent. Three patients had radiation-related deficits after initial or repeat radiosurgery, but no patients had arteriovenous malformation bleeding, neuro-cognitive decline or radiation-induced tumor after radiosurgery.
"Our 20-year experience with arteriovenous malformation radiosurgery has shown that the risks commonly associated with radiation exposure in children or adolescents are extremely low," says Dr. Pollock. "We believe that Gamma Knife stereotactic radiosurgery is a safe treatment option for many children with arteriovenous malformations."
The Mayo Clinic research team also included Michael Link, M.D., and Paula Schomberg, M.D.
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