Gamma knife treatment of acoustic neurinoma

The results of treatment of acoustic neurinomas using Gamma Knife radiosurgery (GKR) during a 6-year period in our center were reviewed. Since May 7, 1990, we treated 88 cases of acoustic neurinoma with GKR. During a 52-month mean follow-up period, MRI was obtained in 63 patients. Reduction in tumor size occurred in 34 (54%) cases, and another 27 (42.8%) tumors showed no change. The tumor control rate was thus 95%. Tumor size increased in 3 (4.8%) cases, but one case is still in early follow-up. Two cases were operated after GKR. Histological examination of the tumors removed at surgery 8 months after GKR were obtained. The examinations showed enlargement of nucleoli and cytoplasm and proliferation of endothelial cells due to delayed radiation changes. Post-GKR facial neuropathy was noted in 7 (8.8%) patients, of which 4 recovered during the follow-up period. The tumor volume, margin dose, number of isocenters and marginal isodose did not have any statistically significant relationship with the development of facial neuropathy. Transient trigeminal neuropathy were noted in 3 patients. Hearing was preserved in 2 of 3 hearing patients. In conclusion, our GKR results for acoustic neurinomas were very similar to the previously reported series, which makes GKR for acoustic tumors an excellent treatment modality for small- to medium-sized tumors with or without microsurgical tumor removal.