Rationale: To evaluate the functional results of Gamma Knife surgery of vestibular schwannomas relying on a large and prospective series of consecutive cases.
Material and method: The first 1000 patients with cerebello-pontine angle schwannomas were consecutively treated by Gamma Knife in Marseille Timone University Hospital between July 1992 and March 2001. Patients without NF2 and or clinico-radiological arguments in favor of a facial origin accounted for a population of 927 patients (414 males, for 513 females) including 843 treated in first intention. In this series the Koos classification was: stage I 77 patients, stage II 520 patients, stage III 287 patients and stage IV 42 patients. The average Volume was 12.7mm3. Haring was usefull (Gardner and Robertson) before radiosurgery in 47% of the patients (subnormal in 20.3%).
Results: Tumor control at last follow-up was 97%. Globally, a clinical trigeminal injury was observed in 0.6% of the patients and a facial palsy in 1.3%. There was clearly a decrease of the incidence of neuropathies with time; no facial palsy being reported among the last 258 patients. The rate of functional hearing preservation (Gardner) for patients initially in class I was 77.8% (47.6% for class II) at 3 Years. This rate of functional preservation reached 95% among patients with tinnitus as a first symptom.
Conclusion: Today, strong evidence surports the superiority of Gamma Knife surgery in term of functional perservation and equal efficacy compared with microsurgical removal. Consequently, radiosurgery must be preferred as a first intention choice for young patients with few symptoms presenting with a small to middle size vestibular schwannomas (Koos I-III).