Abstract
Objective: Document measurements of the bony operculum of the petrous ridge as it relates to surgical anatomy of the temporal bone and thereby establish a new surgical landmark for the middle fossa craniotomy approach to the internal auditory canal.
Method: We analyzed 25 cadaveric temporal bones. Precise measurements were taken to identify the relationship of the bony operculum of the petrous ridge to: foramen spinosum, foramen of the greater superficial petrosal nerve, arcuate eminence, porus acousticus, and inner table of the calvarium.
Results: The following measurements of the operculum in relation to well established surgical landmarks of the floor of the middle cranial fossa were identified: operculum to foramen spinosum, 26.3mm [24.6-28.0]; operculum to foramen of greater superficial petrosal nerve, 16.8mm [14.0-19.7]; operculum to arcuate eminence, 17.3mm [15.1-19.4]; operculum to superior border of porus acousticus, 5.3mm [3.5-7.1]; distance from inner table of calvarium to operculum, 37.0mm [33.5-40.5]; width of the operculum, 13.5mm [11.3-15.7].
Conclusion: This consistently present bony ridge can be used reliably to help safely identify the IAC when approached via middle fossa craniotomy, as it indicates the appropriate vertical plane of dissection.
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