Analysis Of Risk Factors Affecting Facial Nerve Function After Operation Of Acoustic Neuroma

Background: Acoustic neuroma,the intracranial benign tumor,is originated from vestibular nerve schwann cells in internal auditory canal(IAC).The function paralysis of facial nerve and hearing loss are the main complications after acoustic neuroma surgery,which are the important factors that affect patients with postopera-tive quality of life,so that the predictive factors of the function of postoperative facial nerve are the vital point of the research now.Methods: A retrospective analysis was performed on the clinical data of 73 patients with acoustic neuroma who underwent surgical treatment by retrosigmoid approach in neurosurgery department of the second affiliated hospital of nanchang university from January 2018 to January 2020.Then SPSS 25 software was used to make a statistical analysis based on the clinical information to explore the risk factors affecting facial nerve function.Results: In this subject,there were 34 males and 39 females with a median age of 51.3 years and a median course of 35.9 months.In our study,we observed 58 patients(79.5%)after surgery who had good FN(facial nerve)function(House-Brackman,H-B class I-II)and 15(20.5%)patients with damaged FN function(House-Brackman,H-B class III-VI).Univariate analysis showed that preoperative grade of hearing loss,Koos grade,hypertension,tumor maximum diameter,tumor volume,adhesion of facial nerve to tumors and ataxia were related to the prognosis of facial nerve.Multivariate logistic regression model showed the tumor maximum diameter as being an independent predictor of an unfavorable initial FN outcome(odds ratio OR=0.076,P=0.007),as well as tumor volume(OR=1.324,P=0.002).The facial nerve adhesion(OR=58.548,P=0.004)and the preoperative grade of hearing loss(OR=5.6,P=0.029)were associated to the prognosis of FN outcome.However,other preoperative clinical symptoms,such as internal auditory canal morphology,gasification of mastoid gas chamber,cystic character of the tumor,tumor site,anatomic preservation of the cochlear nerve,surgical resection range,and posterior wall abrasion of internal auditory canal were not associated with postoperative the prognosis of FN outcome.According to CT,anatomical structure and RSA surgical method,the safe length of the posterior wall of the inner auditory canal was about 0.85 cm,and the length of the anterior and posterior diameter was about 1.16 cm.The safety angle was about 46.5 degrees.Finally,the anatomical retention rate of facial nerve was up to 93.2%.Conclusion: After resection of vestibular schwannoma,patients with large tumors,severe preoperative hearing loss,and strong adhesion of facial nerve to the tumors are more likely to suffer from facial impairment.Meanwhile,preoperative simulation of RSA quantifying the size and safety angle of the back wall of internal auditory canal can provide effective guidance for the surgeon,which could increase the anatomical retention rate of facial nerve.