Objectives: To assess the reduction of mucosal surface after total sphenoethmoidectomy.

Study design: Prospective study.

Methods: Twelve normal, consecutive computed tomography scans were used. Computed tomography measurements were made at two different levels: the cribriform plate, and the upper level of the maxillary antrum. The length of the lateral wall of the ethmoid sinus and the perimeter of each ethmoid cell were measured at each level and on each side. The whole perimeter of the ethmoid sinus was evaluated for each CT scan level. For each side and each level, the ratio between the ethmoid sinus perimeter and the lateral ethmoid wall length was calculated.

Results: The mean length of the lateral ethmoid sinus wall was 61.7±1.3 mm and 59.9±1.6 mm at the upper and lower parts of the ethmoid sinus, respectively. The mean ethmoid sinus perimeter was 263.2±11.5 mm and 250.4±11.1 mm at the upper and lower parts of the ethmoid sinus, respectively. No significant statistical difference was observed between measurements as a function of side (right or left) or level (upper or lower). The mean ratio between the ethmoid sinus perimeter and the lateral ethmoid wall length was 4.2.

Conclusion: After total sphenoethmoidectomy, the mucosal surface of the ethmoid sinuses is reduced by a factor of 4.2; about 76 per cent of the mucosa is removed during total sphenoethmoidectomy.