Abstract
Objective Computed tomography (CT) is a powerful tool for delineating the anatomy of the anterior
skull base. The goal of this study is to further characterize the relevant anatomical
features of this area, along with other parameters important for endoscopic sinus
surgery.
Design Retrospective case review.
Setting Tertiary care hospital.
Participants Thirty patients who had CT scans of the paranasal sinuses.
Main Outcome Measures The following features were assessed using image analysis software: olfactory fossa
depth, the length and angle of the lateral lamella, fovea ethmoidalis length and shape,
ethmoid roof height and slope, and the position and course of the anterior ethmoid
artery. Statistical analysis was performed assessing for differences in the above
parameters.
Results The mean olfactory fossa depth of the anterior and posterior skull base was 3.4 ± 1.1
and 2.4 ± 0.9 mm, respectively (p < 0.05). The mean lateral lamella length was 3.6 ± 0.9 mm, which did not demonstrate
significant variability. The angle of the lateral lamella varied significantly by
skull base position, measuring 63.1 ± 17.8 degrees anteriorly, and 39.1 ± 17.9 degrees
posteriorly (p < 0.05). In scans classified as a Keros type I, 25.3% had lateral lamellae longer
than 4 mm. Furthermore, 43.7% had lateral lamellae with angles less than 45 degrees.
Moving anteriorly, the posterior skull base sloped downward in 46.7% of patients.
Conclusion Thorough preoperative assessment of CT scans is crucial to understanding the inherent
variability of skull base anatomy. Even “safe” anatomy can still contain features
such as long and acutely angled lateral lamella, which may predispose patients to
iatrogenic injury.
Keywords
olfactory fossa - safety - keros - anterior skull base anatomy - sinus surgery
