Prognostic Analysis Of Surgical Resection In Large And Medium-sized Vetibular Schwannoma

Objectives To evaluate the relationship between surgical approach,the extent of resection in large and medium-sized vestibular schwannoma and posterative facial nerve and cochlear nerve function,and to provide clinical evidence for the improvement of clinical surgical treatment.Methods A single center retrospective of 312 cases with CPA tumors treated by the Department of Neurosurgery,Tian Medical University General Hospital from June 2013 to May 2016.A total of 76 Koos grade 3 and 4 patients were included through inclusion and exclusion criterias.We collected the data.Preoperative assessment included multimodality image fusion,hearing examination and physical examination.Preoperative MRI data was integrated into the 3D-Slicer software to complete the facial nerve fiber bundle tracing imaging to initially determine the positional relationship between the tumor and the facial nerve.Preoperative hearing was assessed and physical examination focused on the facial and lower cranial nerve function.Surgical approach,the extent of resection and cranial nerve preservation were recorded,neurosurgeron verified whether the spatial position of the facial nerve was consistent with the preoperation imaging during operations.Postoperative follow-up included the facial nerve function and hearing.According to the HB classification of facial nerve function,72 patients with intact facial nerve anatomy were divided into two groups(Group A:HB Ⅰ～Ⅱ;Group B:HB Ⅲ～Ⅵ)to evaluate the facial nerve function and analysis the influencing factors.The effective residual hearing standard:the speech perception threshold ≤ 50dB,and the language resolution is ≥ 50%.According to whether hearing was preserved after operation,patients were divided into two groups(Group C:hearing was not preserved;GroupD:hearing was preserved)to analysis the factors on postoperative hearing preservation.SPSS 23.0 software was used for statistical analysis.P<0.05 was considered statistically significant.Results Facial nerve reconstruction:68 cases of facial nerve can be reconstructed by DTI technology,including type 1 in 34 cases,type 2 in 22 cases,12 cases in type 3.17.1%had effective hearing and 14.5%had facial dysfunction preoperatively.All the operations were performed with retrosigmoid approach and tumors were resected totally.Actual position of the facial nerve during operations:type 1 in 36 cases,type 2 in 25 cases,15 cases in type 3,type 4 in one case.Preoperative reconstruction of the facial nerves were consistent with the actual displacement of the facial nerve.Facial nerve anatomic preservation was 94.7%,postoperative 1 year facial nerve function HB grade Ⅰ～Ⅱ in 53 cases.Univariate analysis of age,sex,tumor side,and preoperative hearing loss in both groups were not statistically significant(P>0.05);and tumor diameter,cysts,facial nerve displacement were statistically significant(all P<0.05).The diameter of group A was significantly smaller than that of group B,and the proportion of cystic tumor was significantly lower than group B.The ratio of group A was gradually decreased from type 1 to type 3.Multivariate logistic regression analysis showed that tumor size,cystsand facial nerve displacement were highly predictive factors for facial outcome(r=0.499 P<0.05).Hearing was preserved in 30.8%.Univariate analysis of the age,sex,tumor side,in both groups were not statistically significant(P>0.05);and tumor diameter was statistically significant(P<0.05).Conclusions Good preservation of facial nerve function and hearing can be achieved in the complete resection through retrosigmoid approach in large and medium-sized vestibular schwannomas(Koos grades 3 and 4).Tumor size,cysts and facial nerve displacement are important factors influencing facial nerve function.Tumor size is an important factor influencing hearing postoperatively.In addition,Multidisciplinary collaboration plays a key role in improving the effect of surgical treatment in large and medium-sized vestibular schwannomas.Microsurgical operation technique is the fundamental guarantee for good prognosis.Preoperative imaging assessment techniques,especially the DTI-based small fiber bundle reconstruction technique,play an important role for the preoperative evaluation of the spatial position relationship between the facial nerve and the tumor,design surgical plan,and the preservation of cranial nerve anatomy and function.This single-center,retrospective study provides important clinical evidence for improving the surgical outcome of large-and mid-range vestibular schwannomas.