Facial Nerve Rehabilitation following Vestibular Schwannoma Removal: A Comparison between the Translabyrinthine and the Retrosigmoid Approach

Introduction. Vestibular schwannoma (VS) surgery frequently entails the risk of Facial Nerve (FN) dysfunction as a postoperative complication. The study aims to evaluate FN outcomes after VS surgery, specifically investigating whether the choice of surgical approach – Translabyrinthine (TL) or Retrosigmoid (RS) – may influence the severity of postoperative facial paralysis, while accounting for selected preoperative and intraoperative parameters. A secondary endpoint is to examine the quality of FN recovery during follow-up, highlighting the influence of surgical techniques; notably, this study is the first to utilize the Sunnybrook (SB) grading system for the evaluation of FN outcomes in the setting of VS surgery. Methods. This retrospective study included patients with a diagnosis of VS who underwent primary surgical treatment using the RS or TL approach between January 2018 and May 2024. Patients experiencing postoperative FN palsy were enrolled in the FN Outpatient Clinic (FNOC) at the Department of Otolaryngology-Head and Neck Surgery of the University Hospital of Modena for multidisciplinary follow-up scheduled every 3 months and rehabilitation lasting up to 24 months. Data were gathered from speech therapy and otolaryngology medical records, with particular attention to preoperative symptoms, radiological tumor characteristics, intraoperative findings, and postoperative complications, especially the FN outcomes assessed by the House-Brackmann (HB) and the SB grading scales. Results. A total of 108 patients who underwent VS surgery were included, with 55 (50.9%) treated using the RS approach and 53 (49.1%) using the TL technique. Tumor characteristics varied slightly between groups, with larger mean sizes observed in the RS group (24 mm vs. 20 mm). In the RS group, the Koos grade III was the most common (n=28, 25.9%), followed by the grade IV (n=20, 18.5%), while TL cases showed higher representation in Grade II (n=21, 19.4%). At discharge, postoperative FN paralysis was assessed using the HB grading system, showing a predominance of a Grade V (n=18, 16.7%) in the RS group and a Grade IV (n=13, 12%) in the TL group. At the first speech therapist assessment, SB scores averaged 28 and 36 points in the RS and TL groups, respectively. To address the second endpoint, only 12-month follow-up data were analysed, reducing the cohort to 85 patients – 46 RS (54.1%) and 39 TL (45.9%) – due to the 21.3% of patients discontinuing the therapeutic-rehabilitative program before 12 months. The SB grading system showed overlapping mean scores at 12 months (72 in RS, 73 in TL). When assessing whether the rate of FN recovery differed based on the surgical approach used, the trends were comparable between the groups. Botulinum toxin injections were used in 3 patients during rehabilitation. Among 10 patients showing unchanged scores compared to the previous follow-up visit, 2 patients in each group required hypoglossal-facial nerve anastomosis at 12 months. Conclusion. FN paralysis is one of the main factors affecting the quality of life in patients undergoing VS resection. Understanding whether the type of surgical approach can influence this functional outcome may also be useful in the treatment decision-making process. The study’s findings suggest that both RS and TL approaches yield comparable postoperative FN outcomes and similar long-term recovery at 12 months, though RS patients showed more severe initial paralysis and TL patients slightly better early SB scores.