[Stereotaxic radiosurgery]

Radiosurgery aims at the precise destruction of small, defined volumes of tissue by employing ionizing radiation energy. Its methodologies may be subdivided into closed-skull, external focussed beam radiosurgery, and interstitial radiosurgery (brachytherapy). Focussed beam stereotactic radiosurgery has been used successfully for over two decades to treat cerebral arteriovenous malformations. Complete obliteration ranges from 30% to 50% after one year. After two years, obliteration is observed in up to 90% of patients. Outcome, however, is influenced by patient selection. In the treatment of acoustic neurinomas, follow-up data of larger series show that radiosurgery performed under local anesthesia on an out-patient basis is competitive with microsurgery data. Using multiple isocenters and magnetic resonance localization, tumor growth control is achieved in more than 90% of patients with preservation of hearing in approximately 50%. Pituitary tumors with Cushing's syndrome, acromegaly, Nelson's syndrome, prolactinomas and non-secreting adenomas have been treated. Only a small subgroup of patients with low-grade gliomas are candidates for interstitial radiosurgery, namely those with circumscribed tumors with limited spread of tumor cells into the periphery. For this subgroup, which usually comprises not more than 25% of all low-grade gliomas, interstitial radiosurgery competes with surgical resection. Local, single high-dose treatment remains controversial for highly malignant infiltrative tumors, and a significant treatment benefit remains to be demonstrated. Radiosurgery can be used to effectively treat solitary brain metastases (< or = 3 cm diameters) with less invasiveness, and dissection of normal tissue; it may be performed with lower morbidity and with less expense in comparison with open surgery.