The term “frontoethmoidal” refers to a region or structure that involves both the frontal sinus and the ethmoid sinus. The frontal sinus is located in the frontal bone, specifically in the forehead region, while the ethmoid sinus is a group of air cells within the ethmoid bone between the eyes. When used together, “frontoethmoidal” typically describes an anatomical area or condition that involves both the frontal and ethmoid sinuses.