Risk for hemorrhage during the 2-year latency period following gamma kniferadiosurgery for arteriovenous malformations

Purpose: Radiosurgery does not immediately obliterate an arteriovenous malf ormation (AVM), and the risk for hemorrhage still persists until the AVM is occluded, There is controversy about whether this risk is altered after as compared to before radiosurgery. The aim of this paper is to study this to pic further and to suggest a model to predict the risk for posttreatment he morrhage, Methods and Materials: The incidence of hemorrhages within the first 24 mon ths following Gamma Knife radiosurgery was studied retrospectively among 15 93 AVM patients, and was related to patient, AVM, and treatment parameters. Results: Fifty-six patients experienced a hemorrhage in the latency period, representing an average annual incidence of 1.8%. The incidence of posttre atment hemorrhage was related to the patient's age, AVM volume, minimum dos e, and average dose delivered to the AVM nidus, Based on these observations , an equation was defined that could quantify the probability for a posttre atment hemorrhage to occur. Conclusion: A model that can predict the probability for a hemorrhage withi n the first 24 months after radiosurgery is presented. The risk is higher f or larger AVMs and for older patients, and it is lower when higher doses of radiation are used. (C) 2001 Elsevier Science Inc.