Gamma knife radiosurgery for cerebral arteriovenous malformations: an autopsy report focusing on irradiation-induced changes observed in nidus-unrelated arteries.

ABSTRACT

BACKGROUND: In radiosurgical treatment for an arteriovenous malformation (AVM), the effects of irradiation on the intranidal and perinidal angioarchitectures 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. Irradiation-induced changes were also observed in surrounding nidus-unrelated arteries and the choroid plexus, both of which were within the irradiation 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 rate, was superimposed. RESULTS: This study disclosed that intimal hypertrophy can occur in a normal, AVM-unrelated pial artery due to irradiation of 10 Gy or more and that more remarkable intimal hypertrophy with fragmentation of the elastic laminae, or even complete occlusion, can occur in these arteries with 25 Gy. Similarly, irradiation-induced degeneration 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 irradiation though the abnormal vessels have been reported to be more susceptible.