Accessory Ethmoidal Foramina: An Anatomical Study

Purpose: To examine the distances between the anterior lacrimal crest and the anterior, posterior, and accessory ethmoidal foramina and the optic canal in adult cadavers. Methods: Fifty-four orbits from 27 Japanese cadavers (17 male and 10 female; average age at death, 79.7 years; range, 61–96 years) had previously been fixed in 10% buffered formalin before use. The shallowest and deepest ethmoidal foramina were defined as the anterior and posterior ethmoidal foramina, respectively, and all intermediate foramina were defined as accessory foramina. The distances from the anterior lacrimal crest to the accessory, anterior, and posterior ethmoidal foramina and to the optic canal were examined. Results: Accessory ethmoidal foramina were detected in 18 orbits (33.3%) from 11 cadavers; one accessory foramen (middle ethmoidal foramen) was identified in 17 orbits and 2 foramina (additional deep middle ethmoidal foramen) in one orbit. The middle and deep middle ethmoidal foramina were located 29.8 mm and 32.0 mm posterior to the anterior lacrimal crest, respectively. There were no significant side- or gender-related differences in distances from the anterior lacrimal crest to the middle ethmoidal foramen (p > 0.05, Mann-Whitney U test). The mean distances from the anterior lacrimal crest to the anterior and posterior ethmoidal foramina and the optic canal were 19.6 mm, 33.5 mm, and 41.9 mm, respectively. Conclusions: The authors demonstrated the locations of the accessory ethmoidal foramina in adult cadavers. These observations may help to ensure the safe and precise performance of medial orbital wall surgeries.