Stereotactic radiosurgery XIV: The role of the haemosiderin 'ring' in the development of adverse reactions following radiosurgery for intracranial cavernous malformations: a sustainable hypothesis.

There are strong data supporting the clinical efficacy of ionizing radiation therapy in the treatment of extracranial cavernous angiomas; no unusual complications occur. There is no a priori reason to anticipate a high rate of complications following radiosurgery for brain cavernous angiomas and yet equivalent dose prescriptions (site, size and target volume) to those used for AVM are associated with a considerably higher complication rate. The observed sub-acute reactions sometimes recover with steroid therapy. Previous authors have not sought to define the aetiological basis of this observation. Haemosiderin staining of the fringe of normal brain tissue surrounding the cavernoma is a unique feature of these brain lesions and the potential radiosensitizing properties of this iron based substance, for which there is a considerable experimental and clinical observational basis for radiosensitization, are reviewed. These provide good support for the concept that this characteristic feature of brain cavernomas accounts for the higher post radiation reaction/complication rate. Treatment considerations, stemming from these observations, are suggested.