STEREOTAXIC RADIOSURGERY OF ARTERIOVENOUS-MALFORMATIONS - PATHOLOGICAL-CHANGES IN RESECTED TISSUE

Both stereotactic radiosurgery and microsurgery are treatment modaliti es for arteriovenous malformations (AVM), and more recently, multimoda lity treatment using these approaches has been utilized. We surgically resected AVMs from 33 patients (ages 7 - 64 years old, mean age 30.4) 1 - 11 years after radiosurgery. AVM volumes were 0.8 - 117 cm(3) (me an 21.6 cm(3)), and doses ranged from 4.6 - 45 GyE (mean 21.2 GyE). AV Ms resected were submitted for pathologic review. Each AVM was evaluat ed for the following radiation changes, and the number of AVMs demonst rating these changes were noted: endothelial proliferation (27), hyali ne (18) and calcium (10) in AVM vessel walls, partial (9) or complete (24) thrombosis of some AVM vessels, and necrosis of vessels (15) and adjacent brain tissue (11). A semiquantitative scale (mild, moderate, severe) incorporating the aforementioned changes present in each case classified the extent of radiation-induced change. There was a signifi cant correlation (r = 0.624, p < 0.01) between extent of radiation cha nge and dose of radiation received. There was no absolute radiation do se threshold below which radiation-induced changes were absent. Howeve r, all but one patient receiving greater than 20 GyE developed moderat e to severe radiation vascular changes and the 3 patients treated with greater than 30 GyE all had severe radiation-induced changes. Radiati on changes in AVMs following stereotactic radiosurgery appear to be do se-related. The correlation of dose to extent of radiation change may allow the determination of the optimal dose of radiation to treat AVMs .