Volumetric computed tomography analysis of the olfactory cleft in patients with chronic rhinosinusitis

Background: Commonly used computed tomography (CT) staging systems for chronic rhinosinusitis (CRS) focus on the sinuses and do not quantify disease in the olfactory cleft. The goal of the current study was to determine whether precise measurements of olfactory cleft opacification better correlate with olfaction in patients with CRS. Methods: Olfaction was assessed using the 40-item Smell Identification Test (SIT-40) before and after sinus surgery in adult patients. Olfactory cleft opacification was quantified precisely using three-dimensional (3D), computerized volumetric analysis, as well as via semiquantitative Likert scale estimations at predetermined anatomic sites. Sinus opacification was also quantified using the Lund-Mackay staging system. Results: The overall cohort (n = 199) included 89 (44.7%) patients with CRS with nasal polyposis (CRSwNP) and 110 (55.3%) with CRS without nasal polyposis (CRSsNP). The olfactory cleft opacified volume correlated with objective olfaction as determined by the SIT-40 (Spearman's rank correlation coefficient [R_s] = -0.461; p < 0.001). The correlation was significantly stronger in the CRSwNP subgroup (R_s = -0.573; p < 0.001), whereas no appreciable correlation was found in the CRSsNP group (R_s = -0.141; p = 0.141). Correlations between sinus-specific Lund-Mackay CT scoring and SIT-40 scores were weaker in the CRSwNP (R_s = -0.377; p < 0.001) subgroup but stronger in the CRSsNP (R_s = -0.225; p = 0.018) group when compared to olfactory cleft correlations. Greater intraclass correlations (ICCs) were found between quantitative volumetric measures of olfactory cleft opacification (ICC = 0.844; p < 0.001) as compared with semiquantitative Likert grading (ICC = 0.627; p < 0.001). Conclusion: Quantitative measures of olfactory cleft opacification correlate with objective olfaction, with the strongest correlations seen in patients with nasal polyps.