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To evaluate the results of Gamma Knife radiosurgery treating vestibular schwannomas (VS) secondary to type 2 neurofibromatosis (NF2) we reviewed our clinical experience. Among the VS that have been treated between July 1992 and January 2002, we could analyze retrospectively the data of 50 VS from 37 patients. Fourteen patients had the mild phenotype while 23 were affected by the severe form. Before radiosurgery, one or two microsurgery attempts had been undertaken in 16 VS. Tumor Volume ranged from 120 to 14405 mm3 (mean: 3468 mm3) at the time of treatment; 12 tumors were Koos stade 4. Median clinical and radiological follow-up was 62 Months and ranged from 27 to 123 Months. The 5-Year and 10-Year actuarial survival rates without failure justifying tumor removal were 90 and 85% respectively. The 5-Year actuarial survival rate without hearing decreasing was 36% when selecting the cases of useful hearing (Gardner I & II) at the time of treatment. Severe phenotype (p=0.05) and dose (>12 Gy) delivered at the tumor margin (p=0.032) were correlated to hearing deterioration at univariated analysis. Permanent facial neuropathy occurred in 2%. Even though the level of tumor control and hearing preservation is not the same as for sporadic VS, these results show that Gamma Knife radiosurgery is a valuable alternative treatment for VS in NF2 patients. Future orientation of early proactive radiosurgical treatment of intracanalicular VS will probably improve these results.

Significant morbidity is expected after microsurgery for recurrent or growing residual vestibular schwannoma (VS). In order to avoid this procedure, radiosurgery appeared as an interesting alternative. The purpose of this study is to analyze the results of Gamma Knife radiosurgery in this indication. Between July 1992 and January 2002, 60 patients (including 12 NF2 patients) underwent radiosurgical treatment after one or more attempts of surgical resection (including 27 growing remnant VS and 19 recurrent VS) and could be followed with enough informations, out of 103 patients (10% of the VS population treated during the same period). Mean interval between surgical removal and radiosurgery was 71.5 Months (1.8-127.8 Months). Technical difficulties during the procedure were observed in the 12 cases, mainly due to problems in identifying the target. Median follow-up was 51.6 Months. Four out of 58 patients (7%, confidence interval: 1.9-16.7) were diagnosed as failure. Statistical study failed to find significant parameters influencing failure. Facial and trigeminal nerves were not impaired while one case of severe bulbopontine radio-induced injury leading to a lower cranial nerve deficit was observed. These results show that, in spite of additional difficulties to treat these patients with radiosurgery, this treatment is efficient with acceptable morbidity and can avoid another microsurgical procedure. The strategy of planned combined micro-and radiosurgical treatment of large VS deserves additional investigations to be validated.