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Seventy-three patients have been treated with Gamma Knife radiosurgery (GKR) for pituitary adenomas. 12 had undergone surgery prior to GKR. Three had had previous radiation therapy. The prescription dose administered to the tumor margin ranged from 9 to 35 Gy. 65 patients were followed up for an average of 29 months. A slight expansion of tumor volume occurred in 3 cases. Otherwise, the tumor volume remained unchanged or decreased in the remainder. Endocrine changes were present in all except 3 cases. GKR was followed by a speedy decrease in raised serum hormone levels in the case of both growth hormone (GH)and adrenocortico-tropic hormone (ACTH). In 3 patients there was some visual deterioration associated with a slight increase in tumor volume. In 2 cases, the tumors were removed surgically. Some preliminary conclusions may be drawn. The dose required to correct an endocrinopathy may be higher than that required for control of tumor growth. The recommended prescription dose for endocrine-active adenomas may be more than 30 Gy. While clinical improvement may be noted in patients with raised serum prolactin levels (PRL), normalization of the endocrinopathy may be less readily achieved than in the case of raised GH and ACTH levels. Gamma Knife radiosurgery as a primary treatment of pituitary adenomas can be safe and effective.

From September 1994 to June 1995, eight patients with intractable parkinsonism underwent gamma thalamotomy in our hospital. All of these patients were male, with an average age of 59.3 years. The duration of the disease from initial diagnosis was 2-10 years (mean 6.8 years). All had failed or had serious side effects with antiparkinsonian medicine. Seven cases had tremor-dominant symptoms, while the other had mainly rigidity. Six cases had bilateral symptoms. Computed tomography or magnetic resonance imaging (MRI) was undertaken prior to treatment in all cases to exclude focal brain lesions. Stereotactic MRI was taken with the Leksell frame in place and both T1- and T2-weighted images were obtained. The targets were located in the area of Vim/Voa/Vop based on the Schaltenbrand atlas. In seven cases, two plugged 4-mm-collimator shots were used. The maximum dose was 160 Gy in six cases and 180 Gy in one case. In another case, a single 4-mm-collimator shot was used, and a maximum dose of 160 Gy was delivered to the target center. The border of the internal capsule was outside the 20-30% isodose line. We intended the 50% isodose line to have an oval-shaped region with the use of two shots and should correspond to the shape of Vim. Follow-up data were available for six patients (mean: 4.5 months, range: 2-9 months). Tremor disappeared in three cases and improved in the other three. In one of these six cases, the tremor disappeared just 3 days after gamma thalamotomy. Rigidity improved in four of these six cases. In only one patient, treated with a maximum dose of 180 Gy, was there any contralateral limb weakness, which developed 3 months after treatment and has been recovering gradually. Follow-up MRI T2-weighted images in this case showed that the diameter of the lesion was larger than intended and there was a region of diffuse edema in the thalamus and upper brain stem. No other complications occurred in this series.