Background: Ethmoid arteries, branches of the ophthalmic artery, are crucial structures supplying ethmoid mucosa. Its locations are important during ethmoid sinus surgery. There has been no study in Thais before.
Objective: To determine the number and locations of ethmoid arteries in relation to important surrounding structures.
Material and Method: A prospective, descriptive study in 42 Thai cadaveric adult half-heads was conducted at departments of Otorhinolaryngology and Anatomy, Faculty of Medicine, Khon Kaen University, Thailand. Meticulous dissections were performed to identify number of ethmoid arteries branching from ophthalmic artery and site of entrance of the arteries into ethmoid sinus. Relationships of these arteries with anterior ethmoid crest, optic foramen, bulla lamella and middle third of basal lamella of middle turbinate were studied.
Outcomes: Types of ethmoid arteries, distances between ethmoid arteries and their relations to important surrounding structures: anterior lacrimal crest, optic foramen, superior aspects of bulla lamella, middle third of basal lamella of middle turbinate and the superior aspect of anterior wall of sphenoid sinus.
Results: All specimens had anterior and posterior ethmoid arteries. The prevalence of tertiary ethmoid artery was 36% (95%CI 22-52%). The mean distance between the anterior ethmoid artery and anterior lacrimal crest, anterior ethmoid artery and posterior ethmoid artery and the distance between posterior ethmoid artery and optic foramen were 24.3, 13.5 and 6.4 millimeters respectively. Most of the entry of anterior ethmoid artery into the ethmoid sinus was in the posterior half of the distance between the bulla lamella and middle third of basal lamella of middle turbinate, 85.7%.
Conclusion: This is the first study of location of ethmoid arteries in Thai adult cadavers. The information of the present study may be useful for sinus surgeon.

Keywords: Ethmoid artery, Anterior ethmoid artery, Posterior ethmoid artery, Tertiary artery, Sinus surgery