Arteriovenous malformation animal model for radiosurgery: the rete mirabile.

PURPOSE To study the effects of single-dose radiation on the porcine rete mirabile, a tangle of microvessels that mimics human arteriovenous malformations of the brain.

METHODS Eight retia mirabilia received a single dose of radiation under stereotactic location with digital angiography and CT. The following doses were applied: 20, 30, 40, 50, 60, 70, 80, and 90 Gy. The animals were followed up for a period of 7 months. Findings at neurologic examination, serial angiography, and histopathologic examination were analyzed.

RESULTS Progressive occlusion as observed by angiography corresponded to the histopathologic finding of intimal hyperplasia; that is, marked thickening of the vessel wall, progressing to occlusion of the vascular lumen, and associated thrombosis. A direct dose response was noted for these changes. Neurologic findings were related to the dose distribution and to histologic findings in structures adjacent to the rete mirabile.

CONCLUSION The rete mirabile is an excellent model by which to study the radiologic and histologic effects of single-dose radiation to the microvasculature of the central nervous system.