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Hearing outcome after gamma knife radiosurgery for vestibular schwannoma: a prospective Belgian clinical study. Introduction: Leksel Gamma Knife® (LGK) radiosurgery is a safe and efficient therapeutic approach for vestibular schwannoma (VS) with low side effects. The goal of radiosurgery is not necessarily to cause significant tumour necrosis or to obtain a complete radiographic response, but to halt the tumour’s growth permanently through its biological elimination. The 2 major aims of radiosurgery for VS are long-term tumour control and functional hearing preservation. The purpose of this study is to report our experience with LGK radiosurgery in the management of VS and to evaluate the hearing preservation rate after a minimum one-year follow-up.
Material and methods: Between January 2000 and January 2011, 415 patients with unilateral VS underwent LGK radiosurgery at the University Erasmus Hospital of Brussels. There were 349 patients with previously untreated VS (86 grade I, 96 grade II, 141 grade III, 9 grade IVa, 17 unknown grades, according to Koos) and 66 patients with post-operative residual tumour. All patients in our series underwent evaluation with high resolution neurodiagnostic imaging including computed tomography and magnetic resonance imaging, and clinical evaluation as well as audiological tests that included tonal and speech audiometries. The Gardner Robertson (GR) classification is used to report the results of this study. We identified 276 patients treated for VS with LGK, tested and retested with speech and tonal audiometries by the same team, and followed for a minimum of one year.
Results: Before LGK, 144 patients had serviceable (85 GR class I and 59 GR class II) hearing; 95 (65.97%) of these patients had preservation of serviceable hearing (Pure tone average ≤ 50 db and Speech discrimination ≥ 50%) at minimum one-year audiological follow-up. It was observed that 44 of the 85 GR class I patients (51.76%) maintained their level of audition and 66 of these (74.64%) preserved serviceable hearing. In the 34 patients with preradiosurgery nonserviceable hearing (GR class III-IV) 25 of these patients (73.52%) maintained their hearing. The tumour was stable or declining in size in 90.44% of cases.
Conclusion: LGK radiosurgery provides excellent tumour control in vestibular schwannomas and has low toxicity even after long-term follow-up.