Hemorrhage risk of cerebral arteriovenous malformations before and after Gamma Knife radiosurgery

Keywords: arteriovenous malformation, radiosurgery, gamma knife, stroke, aneurysm

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     Arteriovenous malformations can cause hemorrhage before or after treatment.
To evaluate the hemorrhage rates of cerebral arteriovenous malformations (AVM) and the risk factors of hemorrhage before and after Gamma Knife radiosurgery (GKS).
     The annual hemorrhage rate was calculated as the number of hemorrhages divided by the patient years at risk. Characteristics of patients and AVM related to hemorrhagic or non-hemorrhagic presentation were evaluated by logistic regression. Risk factors predicting AVM hemorrhage during the period from the diagnosis to GKS of AVM and following radiosurgery were evaluated using Cox regression hazards model.
     The annual hemorrhage rate before GKS was 2.0% assuming patients were at risk for hemorrhage since their birth. The hemorrhage rate calculated between the diagnosis and GKS of AVM was 6.6% and reduced to 2.5% following GKS. Although small and deep nidi and those with deep and single draining veins tended to present themselves with hemorrhage, only nidi with single draining veins and those ruptured before were more likely to bleed once the AVM had been diagnosed. These factors no longer predisposed the nidus to a rupture following radiosurgery and the only predicting factor for hemorrhage was a low radiosurgical prescription dose to the margin of nidus.
     This was a retrospective study.
      Following radiosurgery, none of the patient or nidus related risk factors remain relevant to the occurrence of hemorrhage. The nidus treated with a high radiosurgical dose is less likely to bleed.
     The AVM hemorrhage rate seems to reduce after GKS.


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