Facial nerve elongation as predictive factors of facial nerve outcome after the vestibular schwannoma resection

Background: To analyze risk factors affecting the long-term facial nerve functional outcomes in patients receiving vestibular schwannoma surgery. Method: A total of 89 cases receiving vestibular schwannoma surgery via retrosigmoid sinus approach were analyzed retrospectively. The facial nerve functional outcomes of all enrolled patients were evaluated 6 months after the operation according to House-Brackmann grading scale. The relationships between facial nerve injury and its potential risk factors were analyzed. Results: : Postoperative facial nerve injury was found in 53 patients (59.6%) 6 months after the operation. The results of univariate logistic regression analysis indicated that the tumor volume, the maximum tumor diameter, the facial nerve elongation, the enlargement of internal auditory canal (IAC), the IAC size on the affected side, and the facial nerve adhesion to tumor were significantly correlated with the occurrence of facial nerve injury. The multivariate logistic regression analysis revealed that the facial nerve elongation, the facial nerve adhesion to tumor, the tumor volume, and the enlargement of IAC were the independent risk factors of facial nerve injury 6 months after vestibular schwannoma surgery. The ROC curve showed that the cut-off points of the facial nerve elongation, tumor volume and enlargement of IAC were 2.925cm,10.965 cm³ and 1.818 respectively. When the cut-off points were exceeded, the possibility of facial nerve injury would largely increase. Conclusion: With the growth of the facial nerve elongation, the tumor volume, the facial nerve adhesion to tumor, and the enlargement of IAC, the possibility of facial nerve injury after the vestibular schwannoma surgery would accordingly increase.