Age-dependent differences of the anterior skull base.

OBJECTIVE

Imaging of the anterior skull base and paranasal sinuses is essential before surgery of the nose and paranasal sinuses. It is important to know individual anatomical variations to define a "dangerous ethmoid" to prevent complications such as considerable bleeding or injury to the brain. This study aimed to analyze the relevant parameters with special regard to age-dependent differences.

METHODS

This was a retrospective, single center study of 865 patients. Data from cone beam computed tomography (CBCT) of 116 patients less than 18 years of age and 749 adult patients were analyzed. Keros type, the course of the anterior ethmoid artery, the course of the uncinate process and the angle between the lateral lamella and the cribriform of the olfactory fossa were evaluated.

RESULTS

Different frequencies of the course of the uncinate process between young and adult persons could be shown: onset at the lamina papyracea 67% vs. 64%; onset at the skull base, 22% vs. 26%; and onset at the middle turbinate, 11% vs. 10%. Differences in the course of the anterior ethmoid artery could be evaluated in the same way: course at the skull base, 49% vs. 44%; free course with a distance to the skull base of less than 3mm, 11% vs. 19%; and free course with a distance to the skull base more than 3mm, 40% vs. 37%. Significant differences could be found in the frequencies of the height of the olfactory fossa: Keros type I, 28% vs. 16%; Keros type II, 51% vs. 60%; and Keros type III, 21% vs. 24%. The angle between the lateral lamella and the cribriform plate showed significant differences dependent on the course of the anterior ethmoid artery (skull base=123° vs. distance<3mm=117° vs. distance>3mm=110°) and dependent on the height of the olfactory fossa (Keros type I=135° vs. Keros type II=117° vs. Keros type III=104°). Analysis of the angle as a factor of age and Keros type showed a significant difference in Keros type I (125° vs. 132°) and Keros type II (105° vs. 110°).

CONCLUSION

Cone beam computed tomography (CBCT) of the anterior skull base allows the assessment of individual anatomical-radiological risk profiles and the identification of a "dangerous ethmoid". Significant age-dependent differences in the frequencies of anatomic landmarks and the angles of the ethmoid roof could be evaluated and led to significantly different risk profiles between children and adults.