The identification of the internal auditory canal in the subtemporal-transpetrosal extradural approach

Objective To introduce a new method of identifying the internal auditory canal in the subtemporal-transpetrosal extradural approach.Methods Fixed in formalin,20 sides of 10 Chinese adult cadaveric heads were filled with red and blue silica gel.Following the subtemporal-transpetrosal extradural approach,the operation was performed.After the exposure of the extradural trajectory in the middle fossa,the petroclival region was seen after drilling the apex of the petrosal bone while preserving the internal auditory canal (IAC).The temporal origin of the zygomatic process (TOZP),greater superficial petrosal nerve (GSPN),arcuate eminence (AE),foramen spinosum (FS),and the anterior tip and posterior tip of the internal auditory meatus were identified.The angles formed by POZ,FS,and the anterior tip and posterior tip of internal auditory meatus were measured.Results The angle formed by TOZP,FS,and the anterior tip of internal auditory meatus was about 90,97.6 ± 11.4 (81.3-114.7).The angle formed by TOZP,FS,and the posterior tip of internal auditory meatus was 82.6° ± 10.82° (67.0°-105.0°).GSPN and AE formed an angle of 122.7° ± 7.6° (108.1°-137.5°).GSPN and the interior border of the IAC formed an angle of 46.6° ± 4.9° (35.0-55.2°).Conclusion With little variation and easiness of location,the temporal origin of the zygomatic process (TOZP) and the foramen spinosum (FS) can be used in the identification of the IAC.It offers a new method,especially in the subtemporal-transpetrosal extradural approach. Key words: Anatomy;  Internal auditory canal ;  Subtemporal ;  Extradural approach