Facial Nerve Function Preservation And Hearing Preservation After Microsurgery In Large And Giant Vestibular Schwannomas Via Retrosigmoid Approach And Analysis Of Prognostic Factors

Object:To study the facial nerve fuctional preservation and possibility of heating preservation of large and giant acoustic neuroma after microsurgical resection via retrosigmoid approach.Analyse possible prognostic factors that may affect the postoperative facial nerve function and hearing preservation.Material and Method:166 acoustic neuromas microsurgically removed via restrosigmoid approach monitored by electromyographic and brainstem evoked potential recordings at the Neurosurgical Department, Xiangya hospital from January 2002 to April 2009 by the same surgeon (Professor Yuan Xianrui,MD&PhD) are studied retrospectively.The facial nerve function was studied in a total of 166 cases,of which 95 cases' follow-ups are more than 1 year.94 cases with complete documents of hearing function were analysed to find the possibility of hearing preservation and prognostic factors affect post-operative hearing preservation.Facial nerve function was classified by the House-Brackmann grading criteria at 24 hours,1 week,3 months,6 months,9 months and≥1 year after surgery.Hearing function was tested by pure tone audiometry(PTA) and speech discrimination score(SDS),and then classified according to American Academy of Otolaryngology-Head and Neck Surgery(AAO- HNS) criteria.At last we use multiple linear stepwise regression analysis with SPSS 13.0 statistical software in order to understand the relevant factors affecting postoperative facial nerve function and hearing function.Results:Of 166 cases,total resection in 160 cases,near total resection in 5 cases,and subtotal in 1 case,total resection rate is 96.4%. Facial function of 94 cases whose follow-up is up to 1 year are as follow: H-B:H-BⅠin 37 cases;H-BⅡin 45 cases;H-BⅢin 9 cases;H-BⅣin 4 cases,excellent House-Brackmann classification rate(H-BⅠ-Ⅱgrade) is 86.3%.Among the 94 cases with complete documents of hearing function,cochlear nerve was clear anatomically preserved in 16 cases, failed in 6 cases due to tumor invasion,and the rest are not sure because of absence of cochlear nerve monitoring.According to AAO-HNS criteria,there are 7 serviceable hearing preservation(grade A in 1 case, grade B in 6 cases) in the 94 cases followed-up,accounting for 7.4% (7/94),the rate of serviceable hearing preservation is 27.5(3/11) when excluding the NF-Ⅱcases and cases without preoperative serviceable hearing.Conclusion:1 With the facial nerve monitoring,retrosigmoid approach in microsurgical resection of large and giant acoustic neuroma is a safe and effective approach to preserve facial nerve anatomically and to retain good postoperative facial nerve function and hearing function;2 Postoperative facial nerve function of large and giant acoustic changes dynamically:facial nerve function achieves the best immediately after the operation,and then deteriorates the worst from 1 week to 3 month after the surgery,and improve gradually to the level of immediate postoperative from 6 month after the surgery to more than 1 year.The change is a course of quick deterioration and gradual improvement;3 Long-term facial nerve function is related with the operator's positively correlated with early postoperative facial nerve function(immediately after surgery) and tumor size;4 There is possibility of hearing preservation in large and giant acoustic neuromas after microsurgery via retrosigmoid approach and improvement occur in some cases.As a result, hearing preservation should be attempted in large and giant acoustic meuromas as far as possible;5 Positive correlation is found between postoperative hearing and pre-operative hearing.Negative correlation is found between postoperative hearing and whether NF-Ⅱor not.