The Management Of Internal Auditory Canal In Acoustic Neuroma Surgery

Objective:To evaluate the significance of properly drilling theposterosuperior wall of internal auditory canal in acoustic neuroma surgery.Methods:135cases patients with acoustic neuroma who underwentoperation from January,2007to September2012September in depart-mentof neurosurgery, the First Affiliated Hospital of Chongqing MedicalUniversity were retrospectively analyzed. Suboccipital retrosigmoidapproach was used for all the patients. All our patients were operated viaretrosigmoid approach in lateral park beach position. All our patientsunderwent intraoperative nerve monitoring. High speed steel cutting drillwas used to remove the posterior wall of internal auditory canal duringoperation. At the beginning, high speed steel cutting drill was used to drill.After the posterosuperior wall of internal auditory canal was partly drilledopen, high speed diamond drill was used to finely strip. Posterior wall ofinternal auditory canal was drilled as the main part. The superior wall ofinternal auditory canal shall be regarded as an important part when highjugular bulb is present. Results: Almost all our patients are suffering from hearing lose beforeoperation, we can just focus on the rate of total resection of the tumor and therate of anatomical and anatomical preservation of the facial nerve. Amongthe135patients with acoustic neuroma(from T3a–T4b),125patients (92.6%) were treated with total resection,8patients were treated with subtotalresection (5.9%), and2patients were treated with partial resection (1.5%).The facial nerve was anatomically preserved for126cases of patients(93.3%). The facial nerve was functionally preserved for82cases of patients(60.7%) after the patients left hospital (according to theHouse-Brackmann(HB) facial nerve grading system): gradeⅠ-Ⅱ,14cases(10.4%) and grade Ⅲ,68(50.4%)). Leakage of cerebrospinal fluid occurredin5cases of135patients. Among them,4patients were recovered afterexpectant treatment and1case was recovered after surgical repair.1case of135patients was dead. When the gasification of mastoid and petrous apexare very well, we could not drill the posterosuperior wall of internalauditory canal to prevent the CSF fistula after operation,neuroendoscope-assisted microneurosurgery is useful at this moment.Conclusions: Since acoustic neuroma in the internal auditory canal cannot be observed by microscope, the posterosuperior wall has to be drilledopen to get real total resection of the tumor in order to reduce the risk ofrecurrence. In our experience, appropriate management oftheposterosuperior wall of internal auditory canal is very important for totalresection of the tumor and preservation of the facial nerve.