The Relation of the Anterior Ethmoidal Foramen to the Cranial Base.

ABSTRACT

PURPOSE: To perform a radiological analysis of the relation of the anterior ethmoidal foramen (AEF) to the cranial base and olfactory fossa (OF). METHODS: Retrospective analysis of computed tomography coronal scans of 35 orbits of 35 patients with Graves orbitopathy. Following a standard multiplanar reconstruction of the orbit, the authors measured the vertical and the horizontal distances of the AEF to the cranial base and to the lateral border of the OF, respectively. The height of the OF was measured at the level of the AEF and at the position of Keros classification. The presence of supraorbital ethmoid cells (SOEC) was also recorded. RESULTS: The vertical distance of the AEF to the cranial base ranged from 0.1 to 7.3 mm with a mean = 2.5 mm (SD = 2.17). In 47.5% of the orbits the foramen was adjacent (<1 mm) to the cranial base. The horizontal distance of the AEF to the lateral border of the OF ranged from 2.3 to 9.5 mm (mean = 5.4 mm, SD = 1.98). The presence of an SOEC (n = 12) increased significantly both the distance from the AEF to the cranial base and to the lateral border of the OF. The height of the OF at the level of AEF is not correlated with the depth of the OF at the level of Keros classification. CONCLUSIONS: In the absence of supraorbital pneumatization, the AEF location is a dangerous landmark for the upper limit of the transconjunctival medial wall decompression.