Surgical Anatomy of the Anterior Ethmoidal Canal in Ethmoid Roof

Objectives/Hypothesis This study was undertaken to examine three main relationships. First, the distance and angle from the anterior ethmoidal canal to the limen nasi and the sill were measured. Second, the location of the anterior ethmoidal canal was examined in relation to the lamellas and the skull base. Third, the existence of bony defects in the canal and the course of the canal through the anterior cranial fossa were studied. Study Design This study employed both sagittal computed tomography and cadaver dissection. Methods Seventy sagittally divided heads from randomly chosen Korean adult cadavers were used. Sagittal computed tomography was performed on all specimens. Then they were meticulously dissected under a surgical microscope. Results The mean distance and angle between the limen nasi and the anterior ethmoidal canal were 49.0 mm and 54.5°, respectively. The anterior ethmoidal canal was located between the second and third lamella in 61 of 70 cases. In 60 of 70 cases it was attached to the base of the skull, and in the remaining 10 cases it ran 2 to 3 mm below the skull base. When viewed from the superior side, the course of the anterior ethmoidal canal formed a diagonal line from the lateral to the medial side. Partial bony defects of the anterior ethmoidal canal were observed in eight cases, and complete bony defects in none. Conclusion This study provides surgeons with a better understanding of the anatomy of the anterior ethmoidal canal.