Indikationen für Gamma-Knife- Behandlungen

Abstract

The first radiosurgical tool ever to be developed and used clinically is the gamma knife. The gamma knife has been invented by the neurosurgeon Lars Leksell for the treatment of intracranial neurosurgical conditions. The prototype was first used in Stockholm in 1968. Today, the gamma knife is used for the treatment of intracranial benign and malignant tumours, the treatment of cerebral vascular malformations and functional neurosurgery. Until now, more than 300000 patients have been treated with the gamma knife worldwide. Over the last ten years, the use of gamma knife radiosurgery has grown exponentially. Because of its unparalleled precision, the great experience with more than 1200 publications, the minimal inconvenience to the patient and the excellent results especially in complicated and inoperable brain tumours, gamma knife treatment is the gold standard of radiosurgery today. In benign brain tumours. such as meningioma, acoustic neuroma or pituitary adenoma, long-term local tumour control is achieved in more than 90% following gamma knife treatment. In patients with skull base- and posterior fossa-meningioma, neurological function of cranial nerves may often be restored with gamma knife treatment, if the patient is referred in time. In impending neurological deficits as may occur in anterior clinoid process meningioma, a timely gamma knife treatment may prevent the impending optic nerve deficit altogether. In patients with acoustic neurinoma, gamma knife treatment allows for an effective tumour control without surgical risks, such as facial nerve palsy, postoperative infection, cerebrospinal fluid leak, etc. Therefore, gamma knife treatment is today the preferred treatment over surgery in patients with Samii Grade I-III acoustic neuromas. In patients with pituitary adenoma, normalisation of endocrine overproduction may be achieved besides local tumour control. In malignant brain tumours such as metastasis, local tumour control is achieved in more than 80%. Even so-called radioresistant tumours such as metastases of malignant melanomas or renal cell carcinomas respond with excellent local tumour control rates of more than 90% following gamma knife treatment. In patients with brain metastasis, gamma knife treatment is a noninvasive way to maintain a high Karnofsky performance score throughout the course of the disease even in the presence of multiple brain metastases. In our experience in Zurich, patients with cerebral metastasis who have been treated with the gamma knife do not die from their cerebral disease but from the systemic progression of the tumour. In cerebral vascular malformations, obliteration rates at two years following gamma knife treatment typically range from 66 to 80%. In functional neurosurgery, gamma knife treatment is now mostly used for the treatment of trigeminal neuralgia. Success rates are around 80% with a delay for pain relief of several months. Gamma knife treatment is also used as a noninvasive way to achieve thalamotomy in patients with movement disorders. Another means of radiosurgery is the treatment with a linear accelerator. Often such treatments are performed without a stereotactic head frame, the various machines and software may differ considerably from one another and so may the treatment protocols and the experience of the team. Because of all those factors, reproducability and comparability of clinical results following linear accelerator treatments remain somewhat questionable.