Neurotoxicity of Radiosurgery

Radiosurgery is a technique to deliver (in most cases) a single fraction of ionizing radiation, usually in the range of 10 to 25 Gy, to a precisely localized intracranial volume of pathological tissue. The radiobiological principles that govern the practice of single-fraction radiosurgery differ from those of conventional fractionated external beam radiation therapy. Rather, the results are primarily a consequence of either vascular effects or antiproliferative effects. The neurotoxicity of radiosurgery can be described according to its time course (immediate, acute, or chronic) and severity (mild, moderate, severe, life-threatening, or fatal( based on existing definitions established by the Radiation Therapy Oncology Group. Current indications for radiosurgery include arteriovenous malformations, acoustic neuromas, brain metastases, high-grade and other gliomas, meningiomas, and pituitary adenomas. The efficacy of radiosurgery and the time course and severity of radiosurgical neurotoxicity are dependent both on the nature of the lesion being treated and the normal tissue milieu which the lesion resides. This article describes the spectrum of neurotoxicity reported in the medical literature pertaining to the current variety of space-occupying lesions, benign tumors, and malignant neoplasms for which radiosurgery currently is being used.