Optimum Height From the Roof of the Choana for Seeking the Sphenoid Ostium

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Abstract
Objective: The purpose of this study was to investigate the optimum height that the sphenoid sinus ostium can be probed safely from the roof of choana in a large group of patients. Methods: The study was performed retrospectively. The 200 sphenoid ostia of the 100 patients whose thin-section computed tomography (CT) including the sphenoid sinus region, made for various reasons, were included in the study. The height of the sphenoid ostium and the skull base from the choana roof were measured on sagittal images of CT. Also, by calculating the ratio of first measurement to the second one, the location of the sphenoid ostium at the anterior wall of sphenoid sinus was determined proportionally. Results: The mean height of the sphenoid ostium from the choana roof was 10.9 (SD, 2.3) mm (range, 5.7-21.5 mm), and the mean height of skull base along the anterior wall of sphenoid sinus from the choana roof was 21.3 (SD, 3.2) mm (range, 13.3-30.6 mm). The ratio of the first measurement to the second measurement was 0.5 (SD, 0.08) (range, 0.29-0.77). Conclusions: In conclusion, under endoscopic view, the sphenoid sinus ostium can be safely probed between 13.3 mm (the minimum skull base height) and 5.7 mm (the minimum sphenoid sinus ostium height) distance upward from the choana, but determining the height of the sphenoid sinus ostium preoperatively on CTs for each patient separately will increase the chance of success in probing the sphenoid sinus.