1998 年 48 巻 Special1 号 p. 51-57
In order to identify the best strategy for the treatment of acoustic schwannomas, we analyzed the role of tumor size and its relation to successful gamma knife radiosurgery. Seventy-seven patients who had had been followed up for more than 2 years after radiosurgery were analyzed from the view points of tumor control and functional outcome. They were divided into 2 groups; 55 cases had no prior surgery (group A), and 22 cases had undergone previous surgery (group B). Of the latter group, 7 cases with large tumors were treated by radiosurgery after intentional surgical resection to minimize functional damage. They were classified as the B-I sub-group, with the other 15 cases being referred to as the B-S sub-group. The actuarial reduction rate of all cases at 2, 3 and 4 years was 68%, 80% and 83%, respectively. There were 2 cases (2.6%) who needed surgical extirpation after radiosurgery. Large sized tumors were less controlled than small to medium sized tumors (p = 0.0008). Useful hearing was preserved in 88% of all cases and no patient suffered worse permanent facial dysfunction. Comparing the groups, the pre-radiosurgical hearing (Gardner & Robertson classification) of A to B-S or B-I was 2.5 to 4.7 (p = 0.063) or 3.3 (p =0.24), and facial functions (House & Brackmann grading) were 1.0 to 2.5 (p = 0.006) or 1.3 (p =0.13), respectively. Gamma knife radiosurgery may be a good choice in small to medium sized tumors, especially in patients with useful hearing. Combined therapy for large tumors with intentional partial removal followed by radiosurgery also appears to offer an excellent functional outcome.
