Management of Internal Auditory Canal for Acoustic Neuromas Surgery by Retro Sigmoid Approach

Study Design: Many acoustic neuromas reach the lateral end of internal auditory canal (IAC). In this case, total removal of the tumor supposes to drill widely the IAC or to use endoscopic procedure. When hearing will be probably lost after surgery (large tumor, grade IV, poor audition before surgery, cochlear nerve injured during dissection in pontocerebellar angle), drilling of petrous bone is only limited superiorly by superior petrous sinus, and temporal dura, inferiorly by the jugular bulb and anteriorly by the facial nerve. When audition can be saved (small tumor grades I and II, good hearing, easy dissection in PC angle) one-stop drilling to preserve inner ear structures. Drilling is then limited by functional structures: superiorly and inferiorly by the same limits, anteriorly by the posterior semicircular canal and the vestibular cavity. Then endoscopic angled view (30 degrees) is useful in this case to preserve these structures. Methods: We report our experience about 200 consecutive patients and then detail our procedures. Results and Conclusion: If these microscopic and endoscopic procedures permit to remove safely the whole tumor in the IAC rarely a useful audition is preserved.