BACKGROUND: Differentiating between posterior ethmoid and sphenoid sinuses can be difficult endoscopically. Anatomic relationships should guide surgery, irrespective of the ability to verify them with image guidance. The authors sought to verify an anatomic landmark found to be useful during endoscopic sinus surgery: the ability to see the sphenoid floor with a 0-degree nasal endoscope. METHODS: The angle formed by a nasal endoscope placed at the sphenoid ostium and the mucosa of the sphenoid floor was measured in 93 consecutive sphenoid sinuses radiologically. Angles of view of 3 common endoscopes were directly measured and compared to the radiologic measurements. RESULTS: The angle to the most inferior aerated portion of the sphenoid sinus averaged 113.6 degrees with a range of 77 to 145 degrees. The angle of view of the 3 endoscopes was found to be 38.1 degrees, 46.7 degrees, and 44.4 degrees. With these angles of view, the most inferior aerated portion of 100% of the radiologically assessed sinuses could not be seen with these endoscopes. CONCLUSION: Inability to see the mucosa of the floor of the sphenoid sinus with a 0-degree nasal endoscope appears to be a reliable finding. Individual variations that may affect this finding such as hypoplasia or severe mucosal edema should be identified preoperatively on imaging. In their absence, the inability to see the floor of an entered sinus with a 0-degree nasal endoscope provides another reliable clue to the position of the sphenoid sinus during endoscopic sinus surgery.
BACKGROUND: Differentiating between posterior ethmoid and sphenoid sinuses can be difficult endoscopically. Anatomic relationships should guide surgery, irrespective of the ability to verify them with image guidance. The authors sought to verify an anatomic landmark found to be useful during endoscopic sinus surgery: the ability to see the sphenoid floor with a 0-degree nasal endoscope. METHODS: The angle formed by a nasal endoscope placed at the sphenoid ostium and the mucosa of the sphenoid floor was measured in 93 consecutive sphenoid sinuses radiologically. Angles of view of 3 common endoscopes were directly measured and compared to the radiologic measurements. RESULTS: The angle to the most inferior aerated portion of the sphenoid sinus averaged 113.6 degrees with a range of 77 to 145 degrees. The angle of view of the 3 endoscopes was found to be 38.1 degrees, 46.7 degrees, and 44.4 degrees. With these angles of view, the most inferior aerated portion of 100% of the radiologically assessed sinuses could not be seen with these endoscopes. CONCLUSION: Inability to see the mucosa of the floor of the sphenoid sinus with a 0-degree nasal endoscope appears to be a reliable finding. Individual variations that may affect this finding such as hypoplasia or severe mucosal edema should be identified preoperatively on imaging. In their absence, the inability to see the floor of an entered sinus with a 0-degree nasal endoscope provides another reliable clue to the position of the sphenoid sinus during endoscopic sinus surgery.