Surgical exposure of the internal auditory canal by the middle cranial fossa approach for acoustic neurinoma is much more difficult than by the trans labyrinthine approach, because there are so few surgical landmarks in the middle cranial fossa to approach to the internal auditory canal.
We developed a new method to identify the internal auditory canal easily and accurately by the following teckniques: 1) tracing bilateral internal auditory canal and external auditory canal from high-rsolution CT in several slice levels and a tumor from enhanced MRI and the fluoroscopic image was composed. 2) determination of the drilling line on the middle cranial fossa which showed the relationship of the external auditory canal and internal auditory canal.
As the result, among 6 tumor excisions operated on with this new method, the internal auditory canal was easily reached without causing damage to the inner ear structure.
