Facial nerve function and influencing factors after excision of Koos grade 3 and 4 vestibular schwannomas

Abstract

Objective To investigate the factors influencing facial nerve function after excision of Koos grade 3 and 4 vestibular schwannomas. Methods A retrospective analysis was conducted on 72 cases of Koos grade 3 and 4 vestibular schwannomas admitted to Department of Neurosurgery at General Hospital of Tianjin Medical University General from June 2013 to May 2016, which were followed up for 12-48 months. According to the House-Brackmann classification of facial nerve function assessed at 1 year after operation, the patients were divided into two groups (Group A: H-B Ⅰ-Ⅱ, Group B: H-B Ⅲ-Ⅵ) to evaluate the facial nerve function and analyzing the influencing factors. Results A total of 53 patients belonged to Group A and 19 cases were in Group B at 1 year after operation. The tumor size(OR=2.538, 95%CI: 1.231-5.231, P=0.012), cysts(OR=6.209, 95%CI: 1.635-23.582, P=0.007) and facial nerve displacement(type vs. type 1: OR=6.103, 95%CI: 1.218-30.586, P=0.028) were significantly different (all P<0.05) between the two groups. Multivariate logistic regression analysis showed that tumor size, cysts and facial nerve displacement were highly predictive factors for postoperative facial function (r=0.499, P<0.05). Facial nerve function was better in cases with small tumors, non-cystic tumors and anterior facial nerve displa-cement (type 1). Conclusions Tumor size, cysts and facial nerve displacement are important factors that influence postoperative facial nerve function in cases of Koos grade 3 and 4 (large and medium-sized) vestibular schawannomas. Accurate preoperative assessment is beneficial to the protection and recovery of facial nerve function. Key words: Neuroma, acoustic; Facial nerve; Microsurgery; Root cause analysis; Koos grading system