The Correlationship Between Internal Auditory Meatus Drilling And Surgical Outcome In Vestibular Schwannoma Microsurgery

Objective:The study was carried out to evaluate the effect determined by drilling off the posterior wall of internal auditory meatus(IAM), and analyze its clinical meaning regarding to the preservation of the facial nerve.Method:This retrospective study involved two groups of patients with vestibular schwannomas who underwent microsurgical treatment with or without elimination of the posterior of the IAM in the 1st hospital of Shanxi Medical University. The 26 cases of the undrilled group were treated during Oct. 2007 and Sept. 2010 while the 27 cases of the drilled group were enrolled from Oct. 2010 through Sept.2013. SPSS 13.0 were utilized to statistically analyze the correlationship between the surgical outcome, including the postoperative function of the facial nerve(House-Brackmenn Classification System) respectively at 3 days, 1 week, 6 months and 1 year, and the surgical modality. Further analyze would be made as to its meaning toward the FN preservation and operative effects.Results:Among the undrilled 26 cases, gross total resection was achieved in 16(61.5%) of the patients, and subtotal resection was achieved in 5 cases(19.2%). Good FN outcome(H-B grade from I to II) rate within the first 3 days were 84.61%; accordingly, good outcome rates of the 7 days, 6 months and 1 year post-operative were respectivedly 30.76%, 42.31% and 57.69%. As to the 27 drilled cases, 24(88.9%) cases received gross total resection and 2(7.4%) cases underwent subtotal removal. Partial removal was performed in 1(3.7%) of the 27 patients. Post-operative good outcome rates were 88.89% at the meantime, 40.74% after 1 week, 48.15% at the 6 months follow up and 85.19% after received the treatment for 1 year. Wilcoxon signed rank tests revealed the rate of the gross total removal among the two groups was statistically significant(P<0.05), and result of χ2 test showed that the FN good outcome rate after 1 year of the surgery was statistically significant(P<0.05), too.Conclusion:A familiar understanding of the anatomy of the IAM and good comprehension of the varieties of the FN around VSs and intra-operative neurophysiological monitoring as well as adequate drilling of the posterior wall of the IAM could increase the rate of the gross total removal and the FN preservation, so as to increase the post-operative life quality, this would be of great importance during the clinical practice.