Gamma knife radiosurgery for pituitary tumours

Stereotactic radiosurgery with the gamma knife delivers focused radiation f rom a cobalt-60 source in a single session to a pituitary tumour with minim al radiation to the adjacent normal brain tissue. Currently, gamma knife ra diosurgery is predominantly used to treat failed pituitary surgery, althoug h it has a role as a primary treatment for patients unwilling or unsuitable , for medical reasons, to undergo trans-sphenoidal surgery. The major risk from gamma knife radiosurgery is radiation damage to the visual pathways, b ut this can be avoided by limiting the radiation dose to the optic chiasm t o under 10 Gy. In contrast, the neuronal and vascular structures running in the cavernous sinus are much less radiosensitive, allowing an ablative dos e to be administered to rumours showing lateral invasion and impinging on c ranial nerves Ill, IV, V and VI. Gamma knife radiosurgery appears to produc e remission in secretory tumours faster than fractionated radiotherapy. Fur thermore, the potential longterm risk of developing a second extra-pituitar y brain tumour, as well as the neuropsychiatric effects associated with con ventional radiation administration, seems less likely to occur with this fo rm of treatment.