Preservation of hearing in vestibular schwannomas treated by radiosurgery using Leksell Gamma Knife: preliminary report of a prospective Belgian clinical study.

Introduction: Radiosurgery is an alternative to the microsurgical resection of vestibular schwannoma (VS). Since its introduction, radiosurgery has been used in more than 8000 patients with VS worldwide and the long term tumor control rates are reported to be 86 to 100%. The aim of this study is to report our experience with Leksell Gamma Knife (LGK) radiosurgery in the management of VS and to evaluate the serviceable hearing preservation rate after one-year follow-up.

Material and methods: Between January 2000 and October 2002, 95 patients with unilateral VS underwent LGK radiosurgery at the University Erasmus Hospital of Brussels with the first worldwide installed LGK C. All patients in our series underwent evaluation with high resolution neurodiagnostic imaging including computed tomography and MRI, and clinical evaluation as well as audiological tests that included tonal and vocal audiometries. The Gardner Robertson (GR) classification is used to report the results of this study. We identified 48 patients treated for VS with LGK, tested and retested with vocal and tonal audiometries by the same team, and followed for a minimum of one year. There were 38 patients with previously untreated VS (9 grade I, 9 grade II, 20 grade III according to Koos) and 10 patients with postoperative evolutive residual tumor.

Results: Before LGK, 24 patients had serviceable (17 GR class I and 7 GR class II) hearing; 16 (67%) of these patients had preservation of serviceable hearing (Pure tone average < 50 db and Speech discrimination > 50%) at the one-year audiological follow-up. It was observed that 9 of the 17 GR class I patients (52.9%) maintained their level of audition and 14 of these (82.3%) preserved serviceable hearing. No deterioration of hearing occurred in the 7 patients with preradiosurgery radiosurgery nonserviceable hearing (GR class III) at the one-year follow-up. One patient improved from GR class V to III after LGK. No patient developed trigeminal neuropathy and only one patient who had preradiosurgery facial nerve dysfunction experienced deterioration at one-year follow-up.

Conclusions: In view of the high tumor control rate and excellent long-term cranial nerve preservation rates, LGK radiosurgery should now be considered as an excellent alternative strategy to microsurgery for the management of VS grade I to III as well as in cases of residual tumor after microsurgery. Compared to results obtained in centers with long-term experience, our data suggest that LGK radiosurgery is an efficient reproducible therapeutic approach that offers high rate of hearing preservation. This justifies the choice of radiosurgery as the first treatment option in VS.