Facial nerve recovery trajectories and predictors after vestibular schwannoma surgery: a single-centre cohort study of 213 patients

BACKGROUND: After tumour control, facial nerve preservation is a primary objective in vestibular schwannoma surgery. Predicting long-term recovery remains challenging, and the prognostic value of the Koos grade is unclear. OBJECTIVE: The primary outcome was facial palsy at 12 months (partial or severe). Secondary outcomes included Day 1 function, recovery trajectory, intraoperative signal status, Koos grade, complications and difference in surgical approaches. METHODS: Retrospective cohort study at Sahlgrenska University Hospital (2006-2024). Two reviewers independently extracted clinical data and assigned blinded Koos grades. Predictors were assessed using multivariable logistic regression. RESULTS: Of 293 surgically treated patients, 213 with complete follow-up formed the study cohort (retrosigmoid 121, translabyrinthine 92). Sixty-four (30.0%) had any palsy at 12 months: 50 (23.5%) partial and 14 (6.6%) severe. Day 1 facial function dominated all models: severe palsy at Day 1 carried an adjusted odds ratio (OR) of 222.08 (95% CI 26.45-1864.44; Firth-corrected OR 128, 21-762), while partial function had an OR of 8.83 (3.93-19.83). Female sex was independently associated with palsy (OR 2.87, p = 0.013); surgical approach was not (OR 0.77, p = 0.550). Koos grade showed no association (OR 1.19, p = 0.730). Among patients with normal Day 1 function, 90% remained palsy free at 1 year; among those with severe palsy, only 4.5% recovered. CONCLUSIONS: A single bedside examination on post-operative Day 1 predicts long-term facial nerve outcome more powerfully than any variable tested, including Koos grade; comparison of surgical approaches remained inconclusive owing to era confounding. Three recovery trajectories provide a framework for tailored post-operative management.