Factors affecting final facial nerve outcome following vestibular schwannoma surgery

OBJECTIVE: To determine factors affecting facial nerve outcome of vestibular schwannoma surgery. METHODS: This retrospective cohort study comprised 652 patients. The outcome measure was House-Brackmann classification at two years post-operatively. Univariate and multivariate analyses were carried out to determine the factors affecting facial nerve outcome. The incidence rates of hemifacial spasm, metallic taste and crocodile tear syndrome were recorded. RESULTS: For tumours less than 1.5 cm, 95 per cent of outcomes were normal, 100 per cent were satisfactory (House-Brackmann grades I-III) and 0 per cent were unsatisfactory (grades IV-VI). For tumours 1.5-2.4 cm, 83 per cent of outcomes were normal, 99 per cent were satisfactory and 1 per cent were unsatisfactory. For tumours 2.5-3.4 cm, 68 per cent of outcomes were normal, 96 per cent were satisfactory and 4 per cent were unsatisfactory. For tumours 3.5-4.4 cm, 52 per cent of outcomes were normal, 80 per cent were satisfactory and 20 per cent were unsatisfactory. For tumours larger than 4.4 cm, 50 per cent of outcomes were normal, 72 per cent were satisfactory and 28 per cent were unsatisfactory. CONCLUSION: Tumour size and operation year were significant predictors of facial nerve outcome. The surgical learning curve was steepest for the first 50 patients.