Does endoscopic sinus surgery improve olfaction in nasal polyposis?

BACKGROUND Olfactory dysfunction in chronic rhinosinusitis (CRS) is among the most prominent manifestations of CRS and contributes to CRS diagnostic criteria. This is particularly true in CRS with nasal polyps (CRSwNP). The detailed mechanism of olfactory dysfunction in CRSwNP is unclear. Leading theories include mechanical obstruction of the airflow to the olfactory neuroepithelium, chronic inflammatory injury to the neuroepithelium, or a combination of both. Impaired olfaction not only leads to major safety concerns but also significantly impacts quality of life (QOL). Thus, it is an important element in several CRS health-related QOL measures. Endoscopic sinus surgery (ESS) is an effective treatment for medically refractory CRSwNP. The goals of surgery include the removal of polyps obstructing the nasal cavity and sinuses, as well as the creation of patent sinus drainage pathways. These wide sinusotomies facilitate the application of topical postoperative medical treatments designed to minimize disease progression and treat infection. Thus, it is possible that surgery also will improve olfaction. However, evidence supporting olfactory improvement after ESS is conflicting, with estimates of improvements ranging from 25% to 100%. This review seeks to evaluate the best available evidence, focusing on the change in objective olfactory outcomes in CRSwNP after surgical intervention. LITERATURE REVIEW Multiple prospective studies have evaluated the effects of ESS on olfaction in CRSwNP patients. This review focuses on the use of quantifiable olfactory measures to evaluate the effect of ESS on olfaction and assesses the sustainability of the outcome. Specifically, we have chosen a recent high-quality systematic review and individual studies (not included in the systematic review) that provide the best evidence on which to base clinical practice patterns. Based on the data presented in 31 studies, Kohli et al. showed in a systematic review that CRSwNP patients experienced significant olfactory improvement after ESS on objective and subjective scales. Specifically, they examined the studies that looked at olfaction outcomes in CRSwNP patients and compared them to a heterogenous group of CRS patients that included CRS without nasal polyps (CRSsNP) and CRSwNP patients. Overall, polyp patients tended to have greater improvement in olfaction after surgery. Objective olfactory measures included both the 40item Smell Identification Test (SIT-40) and Sniffin’ Sticks (Burghart, Wedel, Germany). CRSwNP patients, as compared to a heterogenous CRS cohort, have a greater improvement (higher score indicates better smell) in both measures. The SIT-40 mean difference was 7.87 for the CRSwNP group versus 3.49 for the comparison group (P 5.006). The Sniffin’ Sticks (Burghart) threshold, discrimination, and identification mean difference was 12.81 6 5.87 for the CRSwNP group versus 28.84 6 7.98 for the comparison group (P< 0.0001). The olfaction improvements in CRSwNP patients were found to be above the minimal clinically significant threshold for both the SIT-40 and Sniffin’ sticks (Burghart) tests ( 4 and 5.5, respectively). Similarly, in seven studies (437 patients) the subjective measures of olfaction using the visual analog score (VAS) showed greater reduction (improvement in olfaction) among CRSwNP patients (7.92 6 1.89 to 3.38 6 2.21; P<.0001). It is important to note that CRSwNP patients generally started with a lower baseline olfaction and postoperatively did not achieve the same level of olfactory function as the heterogenous group. Overall, heterogenous CRS patients with baseline dysosmia experienced greater improvements compared to normosmic patients. However, all CRS (including those From the Department of Otolaryngology–Head and Neck Surgery, University of Miami–Miller School of Medicine (A.A., C.G.L., R.R.C.), Miami, Florida, U.S.A.