Facial Nerve Preservation in Hannover IV Vestibular Schwannomas. What Factors Can Predict Facial Outcome?

OBJECTIVE: This article aims to analyze the multiple clinical, imaging, and perioperative factors that may contribute with postoperative facial nerve (FN) function in a series of Hannover IV Vestibular Schwannomas (VS) operated by a single surgeon at a third-level center in Argentina. MATERIALS AND METHODS: Retrospective, single-center, analytical study of a cohort of 133 Hannover IV VS operated by the senior author between 2008 and 2023. RESULTS: Mean follow-up was 14 months (12, 33). Gross total resection (GTR) was achieved in 55% and near total resection (NTR) in 23%. FN function was optimal (HB I and II) in 46% of patients immediately after surgery, which improved up to 66% during follow-up. Multivariate analysis revealed that factors linked to poorer early facial outcomes included preoperative gait instability, larger tumor size, and postoperative hemorrhagic complications. Regarding late facial status, factors associated with poorer outcomes included the facial grade at diagnosis and postoperatively, second surgery, and complications such as meningitis. CONCLUSIONS: Surgery for Hannover IV VS remains a surgical challenge, even in experienced hands. There are individual factors that might contribute to FN results like revision surgery, size, ventral-superior FN displacement, and complications. A detailed analysis of the MRI, FN monitoring and a precise FN dissection could be crucial for a satisfactory result.