An arteriovenous malformation model for stereotactic radiosurgery research

OBJECTIVE: To introduce the utilization of a swine arteriovenous malformation (AVM) model for stereotactic radiosurgery research and to describe the morphological changes in the vessels after radiation. METHODS: The model was created in six animals by creation of a right-sided carotid-jugular fistula. Pre- and postsurgical hemodynamic evaluation was performed. The left rete was radiated in four animals; two animals were not radiated. All animals were sacrificed 4 months after surgery, and the bilateral retia were obtained at autopsy. RESULTS: There were no procedure-related complications. A pressure gradient of 20 mmHg across the nidus was obtained after surgery. The peak velocity in the arterial feeder increased from 18.5 to 83 cm/s. Microscopic examination of the control animals showed intimal hyperplasia and disrupted internal elastic lamina, similar to human AVMs. The radiated retia showed more prominent intimal hyperplasia. This was confirmed by histometric studies showing greater luminal occlusion in radiated specimens. Adventitial fibrosis was prominent in the radiated retia and was absent in the control animals. Immunohistochemical studies showed proliferating smooth muscle cells in the intima. The adventitial fibrosis consisted of smooth muscle cells surrounded by collagen Type IV extracellular matrix. CONCLUSION: The nidus component and high-flow vasculopathy make this an attractive model for stereotactic radiosurgery research. Histology of the radiated models is similar to those described in radiated human AVMs. Further studies of the model are warranted to gain a better understanding of the cellular and molecular events in AVM vessels after stereotactic radiosurgery.