Preoperative sagittal CT evaluation of the frontal recess

Endoscopic surgical approaches for chronic frontal sinusitis require the reestablishment of adequate frontal sinus ventilation and drainage for relief of symptoms. After the resection of anterior ethmoid mucosal disease and cellular structure, the anterior to posterior depth of the nasofrontal beak to the base of skull at the insertion of the ethmoidal bulla (frontal sinus ostium) often represents a critical margin for functional success. However, little information concerning this dimension is available. Depending on intraoperative surgical judgment of this distance, extended endoscopic surgical procedures involving additional bone resection may be indicated. These approaches may be hazardous due to the proximity of the cranial cavity and orbit. In addition, secondary stenosis can result from the subsequent inflammatory response. Improved CT imaging, high resolution sagittal reformatting, and computer workstations provide the ability to obtain direct preoperative measurements of the frontal recess. We used a paramedian sagittal section and recorded the maximal anterior to posterior depth from the nasofrontal beak to the base of skull at the insertion of the ethmoidal bulla in 20 patients, 31 sides, undergoing primary endoscopic frontoethmoidectomy. In addition, we found a positive correlation between this distance and agger nasi air cell size measured in the same 31 sides.