Delayed biologic reactions to stereotactic charged-particle radiosurgery in the human brain

Over 350 patients have been treated for inoperable intracranial arteriovenous malformations with charged-particle radiosurgery. Focussed accelerated helium ion beams derived from charged-particle cyclotrons are stereotactically directed into the brain to obliterate abnormal shunts. Treated patients demonstrate delayed changes in brain anatomy and function that occur months to years after radiosurgery. The underlying mechanisms of the brain's delayed reaction to charged-particle radiosurgery involve complex perturbations in cerebrovascular and metabolic function. This report describes the wide range of delayed reactions that may occur in the brain after radiosurgery, including hemodynamic changes, blood-brain barrier disruption and vasogenic edema, metabolic suppression, and parenchymal necrosis. These delayed reactions to injury in the brain involve potential target cells that include cerebral endothelial cells, oligodendroglia and astrocytes.