TUMOR RESPONSE AND MORPHOLOGICAL-CHANGES OF ACOUSTIC NEURINOMAS AFTERRADIOSURGERY

Twenty-seven of the 1560 patients treated by radiosurgery during the p eriod 1984-1993 had acoustic neurinomas. Four cases were excluded from this study because they had a follow-up of less than 2 years. There w ere 24 neurinomas treated in 23 patients as one patient had a bilatera l rumour. Seven patients underwent radiosurgery for a recurrent tumour (already operated on once or twice), while it was the first treatment for 16 patients. The tumour volume ranged from 1.99 cm(3) to 18.30 cm (3), and the patient follow-up was from 2 to 8 years. To determine the target on CT/NMR for linear accelerator stereotactic irradiation, the Greitz-Bergstrom non-invasive head fixation device was used. It was a gain adopted for subsequent serial imaging, and for repeat radiosurger y when necessary. The total peripheral tumour dose ranged from 12 to 4 5 Gy. In 9 patients there was a reduction in tumour volume varying fro m 39 to 100%, while 14 of the neurinomas appeared stable after an aver age follow-up of 3 years. In one patient there was an increase in size of the tumour. Variable morphological changes were present in 66% of the neurinomas treated. Radiosurgery is indicated as an alternative to microsurgery for inoperable patients and for those who refuse surgery , for recurrent tumours, and as a post-operative complementary treatme nt for partially removed tumours. A gradual approach to radiosurgery, depending on tumour response, allows a greater efficacy with minimal r isk. In the present series no complications were observed. Hearing was preserved at almost the same level as that prior to radiosurgery in a ll patients.