The gamma knife is a stereotactic radiosurgery device which allows well defined, deep seated brain tumors, or arteriovenous malformations having a diameter of less than 3 cm, to be treated in a single session under local anesthesia. This technique, which was first described over 40 years ago, has undergone major development in recent years and is the most commonly used method for radiosurgery worldwide. The principle relies on the over-lapping of narrow collimated beams from 201 cobalt-60 sources. The technique, which was introduced into Switzerland in September 1994, has rapidly gained recognition. 184 patients have been treated by 30 April 1997. An average follow-up period of 15 months is much too short for analysis of patients treated by radiosurgery. However, our series of benign tumors shows stabilization of volume in the first few months followed by a slow reduction of the tumor volume, in all but two cases. The gamma knife represents the treatment of choice for recurrent and unsuccessfully operated patients with endocrine active pituitary adenomas. With brain metastases, a rapid reduction in tumor volume is seen in the first few weeks in the majority of cases. The tumor volume may then remain stable or reduce further until complete disappearance. In the case of arteriovenous malformations complete obliteration of the nidus is not seen, on average, for 2-3 years. Individual patient follow-up studies illustrate these results. To date our results have shown zero morbidity and mortality. International statistics from 58,766 cases (as of December 1996) from 77 gamma knife centers demonstrate the value of this technique as a complement or, depending on the indication, an alternative to classical microsurgery.
Anesthesia, Local Arteriovenous Malformations