The risk of hemorrhage after radiosurgery for arteriovenous malformations.

Two hundred and one patients with arteriovenous malformations (AVMs) treated radiosurgically between May 1988 and February 1995 are analyzed in this study. Twelve patients sustained a posttreatment hemorrhage during this period. Pretreatment factors associated with increased hemorrhage risk were identified in 11 of these patients and included arterial aneurysms, venous aneurysms, venous outflow obstruction, periventricular location, prior embolization, and prior surgical treatment. A detailed statistical analysis, using both Poisson regression and parametric survival regression techniques, was undertaken to determine whether radiosurgery had any effect on the risk of hemorrhage, when compared to the natural history of the disease, in those patients in whom a complete angiographic cure was not achieved. No evidence was found to support a statistically significant departure from the natural hemorrhage rate at any time period after radiosurgical treatment. Significant risk factors for hemorrhage appeared to correlate with increasing AVM volume.