Ask the Experts - What Is the Risk of Hemorrhage for Unruptured AVMs...
Ask the Experts - What Is the Risk of Hemorrhage for Unruptured AVMs...
What is the risk of hemorrhage for unruptured arteriovenous malformations (AVMs) found incidentally on MRI? Does this risk differ according to the age of the patient? Does the risk change depending on the size of the AVM? What is the risk for rehemmorhage of an AVM that has already ruptured in the above categories?
Stephen Deputy, MD
No prospective studies have been undertaken to look at the natural history of a cerebral AVM. According to several retrospective studies, however, the yearly risk of hemorrhage for unruptured AVMs is between 2% and 4%. The risk of rebleeding after an initial hemorrhage is reported to be 6% to 17.9% during the first year and is the same as for unruptured lesions in subsequent years (2% to 4% per year).
Likewise, there are no decisive data concerning differences in the risk of hemorrhage depending on the size of the AVM or the patient's age. Some reports indicate that the smaller the size of an unruptured AVM is significantly related to a higher risk of first hemorrhage, but other reports have not found that association. Although evidence exists that smaller AVMs are more prone to bleed, this finding is subject to question because the smaller AVMs are less likely to produce symptoms, such as seizures or neurologic deficits, that signal their presence before they bleed. According to some, the risk of rebleeding may increase with advancing age. But other clinical studies have found that the risk of bleeding or rebleeding may be higher in the pediatric population than in adults.
What is the risk of hemorrhage for unruptured arteriovenous malformations (AVMs) found incidentally on MRI? Does this risk differ according to the age of the patient? Does the risk change depending on the size of the AVM? What is the risk for rehemmorhage of an AVM that has already ruptured in the above categories?
Stephen Deputy, MD
No prospective studies have been undertaken to look at the natural history of a cerebral AVM. According to several retrospective studies, however, the yearly risk of hemorrhage for unruptured AVMs is between 2% and 4%. The risk of rebleeding after an initial hemorrhage is reported to be 6% to 17.9% during the first year and is the same as for unruptured lesions in subsequent years (2% to 4% per year).
Likewise, there are no decisive data concerning differences in the risk of hemorrhage depending on the size of the AVM or the patient's age. Some reports indicate that the smaller the size of an unruptured AVM is significantly related to a higher risk of first hemorrhage, but other reports have not found that association. Although evidence exists that smaller AVMs are more prone to bleed, this finding is subject to question because the smaller AVMs are less likely to produce symptoms, such as seizures or neurologic deficits, that signal their presence before they bleed. According to some, the risk of rebleeding may increase with advancing age. But other clinical studies have found that the risk of bleeding or rebleeding may be higher in the pediatric population than in adults.
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