Facial Nerve Palsy Recovery After Vestibular Schwannoma Surgery: Temporal Patterns and Early Predictors of Functional Outcome

Abstract

Background and Objectives: Facial nerve palsy (FNP) remains a clinically relevant complication after vestibular schwannoma (VS) resection. Recovery trajectories vary according to the severity of neural injury and early postoperative facial function. This study aimed to characterize the temporal pattern of facial nerve recovery during the first postoperative year and to explore factors associated with favorable long-term function. Materials and Methods: We retrospectively analyzed 51 adult patients who developed FNP after VS surgery between 2020 and 2023. Facial nerve function was assessed using the House–Brackmann (HB) grading system and the Sunnybrook Facial Grading System (SBFGS) at discharge and at 1, 3, 6, and 12 months postoperatively. Longitudinal changes were analyzed using non-parametric repeated-measures methods with effect-size estimation. Favorable 12-month facial nerve function was defined as HB grade I–II. Given the limited number of unfavorable outcomes, associations with 12-month recovery were explored using parsimonious Firth-penalized logistic regression models. Results: At discharge, 45.1% of patients had HB II, 29.4% HB III–IV, and 25.5% HB V–VI. Facial function improved significantly during follow-up. Median SBFGS total score increased from 58.0 at discharge to 99.0 at 12 months (Friedman χ2 = 118.78, df = 4, p < 0.001; Kendall’s W = 0.58), while HB grade also improved significantly (χ2 = 107.48, df = 4, p < 0.001; W = 0.53). At 12 months, 37/51 patients (72.5%) achieved HB I–II and none remained in the HB V–VI category. Synkinesis, defined as an SBFGS synkinesis subscore > 0, was observed in 10/51 patients (19.6%) at 6 months and 19/51 (37.3%) at 12 months. HB grade and SBFGS score at discharge were strongly inversely correlated (Spearman ρ = −0.943, p < 0.001) and were therefore evaluated in separate models. After adjustment for age and tumor size, each one-grade increase in discharge HB was associated with lower odds of favorable 12-month function (OR 0.30, 95% CI 0.11–0.58; p < 0.001), whereas each 10-point increase in discharge SBFGS was associated with higher odds of favorable function (OR 1.90, 95% CI 1.32–3.53; p < 0.001). Conclusions: Facial nerve function showed substantial longitudinal improvement during the first year after VS surgery. Early postoperative facial function was independently associated with 12-month outcome in exploratory penalized regression analyses. Recovery may continue over several months, supporting prolonged functional surveillance, while the independent contribution of rehabilitation and the effect of nerve grafting require evaluation in larger prospective cohorts.