Asymmetry of the ethmoid roof: analysis using coronal computed tomography.

OBJECTIVES/HYPOTHESIS: To determine the incidence and degree of asymmetry in the height and contour of the ethmoid roof. STUDY DESIGN: Retrospective review of direct coronal paranasal sinus computed tomography (CT) scans. METHODS: Retrospective review of 200 consecutive direct coronal sinus CT scans done at New York University Medical Center from July 25, 2000 to October 11, 2000. The height and contour of the fovea ethmoidalis were examined for symmetry between the right and left sides. When an asymmetry in the height of the fovea ethmoidalis existed, this difference was quantified. RESULTS: In 19 scans (9.5%), there was an asymmetry between the height of the fovea ethmoidalis on the right and left sides. Of these 19, 12 (63.2%) were lower on the right side, whereas 7 (36.8%) were lower on the left. Ninety-six patients (48.0%) demonstrated a contour asymmetry with "flattening" of the ethmoid roof on one side, 46 on the right and 50 on the left. One patient demonstrated both height and contour asymmetry. The fovea ethmoidalis on the remaining 86 scans (43.0%) was symmetric. CONCLUSIONS: In a patient population with sinus and nasal symptoms, the height and contour of the right and left fovea ethmoidalis were symmetric in less than 50% of individuals. The asymmetry was most often the result of a difference in contour with flattening of the fovea on one side. This underscores the importance of careful preoperative and intraoperative review of paranasal sinus CT scans in patients undergoing endoscopic sinus surgery.