Risk factors of facial nerve dysfunction after sporadic vestibular schwannoma resection - A narrative review with illustrative cases

Amidst progressive improvement of microsurgical techniques, facial nerve (FN) dysfunction is one of the most common complications after vestibular schwannoma (VS) resection. The current study discusses the risk factors associated with FN dysfunction, preservation of FN, and the patient's quality of life (QoL). In addition, the use of exoscope and FN outcomes was discussed. We searched PubMed and Scopus using the search terms vestibular schwannoma, acoustic neuroma, risk factors, facial nerve dysfunction, and microsurgery. Linkage or association studies available in full text were analyzed regarding risk factors of FN dysfunction after sporadic VS resection. We categorized risk factors for FN dysfunction into three groups: non-tumoral, tumoral, and surgical. Tumoral factors were identified as the most significant predictors of FN dysfunction, including large tumor size, tumor extension, FN adhesion, the presence of cystic lesions, and advanced tumor stage. Data regarding non-tumoral factors, such as age and sex, showed heterogeneity and inconsistency. While the middle cranial fossa (MCF) approach may lead to increased FN injury, it was not deemed a significant predictor of FN dysfunction. Furthermore, employing intraoperative monitoring of the FN was linked with improved FN outcomes. Our review indicates that mounting evidence supports the association of cystic lesions, large tumors, and tumor adhesion to the FN as critical predictors of adverse FN outcomes. When these risk factors necessitate partial resection, radiological follow-up is imperative to monitor for tumor recurrence and to determine the necessity of further surgical intervention.