High-resolution computed tomography analysis of the medial infratemporal fossa: A pilot study

Background: The medial aspect of the infratemporal fossa (ITF) can be accessed endoscopically. Two important landmarks to help guide dissection in this area have previously been identified: the anterior border of the foramen ovale (AFO) and the "bony bridge" (BB), a consistent bridge of bone between the foramen ovale and spinosum. We conducted a pilot study using high-resolution computed tomography (HRCT) to measure the distances to these structures. Methods: Thirty measurements were acquired from 15 adult patients undergoing HRCT scans of the sinuses. The position of the anterior nasal spine (ANS), AFO, and BB on the 3 orthogonal planes were identified by 3 observers. Euclidian distances between each of these structures were calculated. A cadaveric dissection was performed and images were acquired to provide an endoscopic view. Results: Fifteen HRCT scans of the sinuses (8 females) were analyzed. The mean distances from the ANS to the AFO and BB were 78.5 ± 5.9 mm and 83.2 ± 6.0 mm, respectively. For males alone, these distances were 80.3 ± 4.3 mm and 85.3 ± 4.8 mm, respectively, and in females 77.0 ± 6.5 mm and 81.4 ± 6.7 mm, respectively. Conclusion: Average distance from the ANS to the AFO and BB was 78.5 mm and 83.2 mm, respectively. These measurements can be used by endoscopic skull base surgeons to guide dissection in the ITF.