Surgical Anatomy for the Infracochlear Approach to the Petrous Apex

Lee, Ho Ki; Lee, Won Sang; Kim, Hee Nam; Kim, Won Sok; Kim, Jie Soo

Abstract

BACKGROUND: Infracochlear approach indroduced by Ghorayeb et al. in 1988, was performed to reach the petrous apex with the canal wall-down procedure. Giddings et al. described the transcanal infracochlear approach preserving the posterior wall of the external auditory canal for treatment of the cholesterol granuloma in the petrous apex in 1991.
OBJECTIVES
Surgical anatomy for the infracochlear approach to the petrous apex was reviewed in order to understand clinical applicability of this approach.
MATERIALS AND METHODS
This study was performed using 20 human cadaveric temporal bones by the microscopic dissection. Measurements were obtained between different structures to find reliable angles and distances to guide working in the petrous apex region.
RESULTS
The petrous apex was entered through the fenestra between the cochlea, carotid, and jugular bulb. The mean area of the fenestrae was 11.7+/-5.5mm2. The distance from the vertical segment of the facial nerve to the petrous apex was 25.3+/-2.4mm. The angle of the approach to the petrous apex was 37.3+/-5.1degrees to the axis of the internal auditory canal.
CONCLUSION
The infracochlear approach could be used to obtain the route for a drainage procedure or a biopsy at the petrous apex without damaging hearing organs and major vessels. The canal-down procedure was needed to assess the petrous apex successfully.