Low-dose radiosurgery for large vestibular schwannomas: long-term results of functional preservation.

Object: The author conducted a study to assess the long-term results obtained in patients who underwent GKS for large vestibular schwannomas (> 3 cm in diameter). Facial and cochlear nerve functions were evaluated.

Methods: Twenty consecutive large tumors in 18 patients (including two cases of neurofibromatosus Type 2 [NF2]) were followed for more than 6 years. There were eight tumors that were more than 4 cm in maximum diameter. Microsurgery had already been performed prior to GKS in 11 patients (nine recurrent and two residual tumors). Four patients (including one with NF2) died during the follow-up period of other diseases or by accident. Fourteen of 15 tumors were stable or decreased in size. Microsurgery was performed in one patient 2 years after radiosurgery. Facial nerve function was preserved in all patients and hearing preserved in four of five patients with cochlear nerve function prior to radiosurgery. No adverse effects of radiosurgery have been observed to date.

Conclusions: Gamma knife surgery seems to have a place in the low-dose treatment of selected large vestibular schwannoma in patients with a reasonable chance of retaining facial function and pretreatment hearing level. Patients with severe brainstem compression should first be undergo microsurgery.