Hearing preservation in retrosigmoid approach of small vestibular schwannomas: prognostic value of the degree of internal auditory canal filling.

OBJECTIVES: To assess the contribution of preoperative radiologic appearance of vestibular schwannoma (VS) on the magnetic resonance imaging in constructive interference in steady-state sequences and demonstrate if the degree of the internal auditory canal (IAC) filling is correlated with hearing and facial preservation. PATIENTS: A group of 278 patients who underwent VS surgery in a tertiary referral center. INTERVENTION: Retrosigmoid approach surgery. MAIN OUTCOME MEASURES: Patients were classified in 4 groups according to the percentage of IAC filling on the preoperative magnetic resonance imaging as Group IAC 1(IAC empty or filled <25% and with free fundus), Group IAC 2 (IAC filled from 25% to 50% with free fundus), Group IAC 3 (IAC filled from 50% to 75% with free fundus), and Group IAC 4 (complete filling of the IAC without fundus obliteration). RESULTS: A good correlation was observed between the IAC classification and the rate of hearing and facial preservation. The global rate of postoperative facial palsy was 10.4%. The global rate of hearing preservation in 213 patients with preoperative hearing class A and B was 40.8%. Regression analysis showed that the degree of lateral extension of the VS in the IAC was a strong predictor of hearing preservation ( p < 0.04). CONCLUSION: The retrosigmoid approach yields good facial outcomes in selected patients with possible hearing preservation. In case of patient with small tumor and IAC empty or filled less than 75% and with free fundus, surgery is the treatment of choice for patients with serviceable hearing and the desire to retain it.