New method of identifying the internal auditory canal as seen from the middle cranial fossa approach.

OBJECTIVES: The middle cranial fossa approach allows one to remove acoustic tumors and preserve the facial nerve and hearing. However, there are no consistent landmarks on the surface of the temporal bone to identify the internal auditory canal. This study was designed to identify the internal auditory canal by use of external and internal references as seen during the middle cranial fossa approach.

METHODS: We dissected 32 temporal bones using the middle cranial fossa approach and measured the distances from the posterior origin of the zygomatic arch to an imaginary coronal line between the foramen spinosum and the foramen ovale. We measured the angle between the lines drawn from the posterior origin of the zygomatic root to the foramen spinosum and from the foramen spinosum to the porus of the internal auditory canal.

RESULTS: The distances were 14.7 mm and 22.9 mm, respectively, and the angle was roughly 90 degrees.

CONCLUSIONS: In this study, we found external and internal landmarks that help to locate the internal auditory canal.