Anatomic basis for labyrinthine preservation during posterior fossa acoustic tumor surgery

Earlier diagnosis of acoustic tumors promises to increase our opportunity to identify patients with serviceable hearing. Critical to a posterior fossa transmeatal approach for acoustic tumor resection is preservation of the underlying labyrinth. Although the labyrinth has been recognized as a limiting factor in exposure of tumor in the internal auditory canal, few reports have detailed the microscopic surgical anatomy posterior to the internal auditory canal. An anatomic study was undertaken to determine consistent relationships between critical structures within the temporal bone relevant to hearing preservation surgery. The results of this study indicate that, whereas topographic landmarks are helpful for orientation, the more consistent relationship of the labyrinth to the vestibular aqueduct and singular canal allows a more accurate localization of the underlying labyrinth. Although the vestibule frequently prevents direct visualization of the transverse crest, a dissection based upon the microsurgical anatomy will maximize visualization of the lateral fundus while preserving the integrity of the labyrinth.