Abstract: Objective To explore the procedure of computed tomography(CT)and evaluate its clinical value in evaluating the height of the ethmoidal sinus skull base before endoscopic sinus surgery. Methods A total of 100 patients with coronal CT scans of the sinuses(200 sides)were selected in our hospital for measurement of the distance between the mid-point of the sieves and the mid-line of the orbital level of the anterior ethmoid artery. The sinuses were classified using the Keros classification, and the correlation between the Keros classification and the height of the ethmoid sinus base was determined using the Pearson correlation coefficient. Results The distance between the top of the ethmoidal artery from the anterior ethmoid artery to the midline of the orbital level was the height of the base of the ethmoid sinus. According to the height of the ethmoidal sinus skull base, 44%(88/200)were type Ⅰ(more than 7 mm, high skull base), 41%(82/200)were type Ⅱ(4-7 mm, middle skull base), and 15%(30/200)were type Ⅲ(less than 4 mm, low skull base). According to the Keros classification, type Ⅰ accounted for 37%(74/200), type Ⅱ for 52%(104/200), and type Ⅲ for 11%(22/200)of the sinuses; the Pearson correlation coefficient between Keros classification and ethmoidal sinus skull base height was 0.384(P<0.001), which indicated a weak correlation. Conclusion The height of the ethmoidal sinus skull base is significantly different. Pre-operative CT imaging evaluation can effectively identify low skull base variations to help avoid skull base injury, and thus reduce the complications of endoscopic surgery.

Key words: Sinusitis, Ethmoid sinus, Complication, Skull base, Endoscopic surgery, Paranasal sinuses