GAMMA-KNIFE RADIOSURGERY FOR CEREBRAL ARTERIOVENOUS-MALFORMATIONS - AN AUTOPSY REPORT FOCUSING ON IRRADIATION-INDUCED CHANGES OBSERVED IN NIDUS-UNRELATED ARTERIES

BACKGROUND In radiosurgical treatment for an arteriovenous malformatio n (AVM), the effects of irradiation on the intranidal and perinidal an gioarchitectures have seldom been analyzed histologically, An autopsy case is reported, studying an AVM treated by gamma knife radiosurgery. Postmortem studies following AVM-unrelated death were performed after a 2-year angiography had demonstrated complete nidus obliteration. Ir radiation-induced changes were also observed in surrounding nidus-unre lated arteries and the choroid plexus, both of which were within the i rradiation target. METHODS Microscopic studies were performed using a coronal section of the brain including the center of the AVM, on which the percent isodose volume gradient, corrected with a magnification r ate, was superimposed. RESULTS This study disclosed that intimal hyper trophy can occur in a normal, AVM-unrelated pial artery due to irradia tion of 10 Gy or more and that more remarkable intimal hypertrophy wit h fragmentation of the elastic laminae, or even complete occlusion, ca n occur in these arteries with 25 Gy. Similarly, irradiation-induced d egeneration was present in the choroid plexus, which had been exposed to doses varying from 10 Gy to 25 Gy. CONCLUSIONS A normal surrounding blood vessel may also be affected by high-dose, single-fraction irrad iation though the abnormal vessels have been reported to be move susce ptible.