Computed tomography anatomy of the anterior ethmoid canal.

The roof of the anterior ethmoid swings up anteriorly from its more or less horizontal course at the point where the anterior ethmoid canal (AEC) is situated. The AEC is an important structure in endoscopic sinus surgery since its injury results in bleeding into the nasal cavity and may result in intraorbital bleeding. We therefore investigated the location of this canal and the anatomic characteristics of the area surrounding the canal using coronal computed tomography (CT) of the paranasal sinuses. One hundred sides of 50 paranasal coronal CT images in patients with sinusitis were analyzed to assess the location of the AEC, the shape of the superolateral wall of the ethmoid sinus anterior and posterior to the AEC, and pneumatization of the roof of the anterior ethmoid sinus. The AEC is situated in the second quarter of the roof of the ethmoid sinus. The superolateral wall anterior to the AEC demonstrated an acute angle in 99% of sides, while the superolateral wall posterior to the AEC showed an obtuse angle in 87% of sides. The ethmoid cell anterior to the AEC pneumatized posteriorly over the AEC in 26% of sides. We conclude that coronal CT confirmation of the anatomic characteristics of the AEC, and the area surrounding the canal, is invaluable for preoperative planning for endoscopic sinus surgery.