Background: The aim of this study was to evaluate the benefit of patients with olfactory dysfunction from local (group A) or systemic (group B) administration of corticosteroids.
Methods: This unblinded study was conducted at a smell and taste outpatient clinic of an institutional referral center. Patients with olfactory loss after infections of the upper respiratory tract, patients with apparent sinonasal disease, and patients suffering from "idiopathic" smell loss were included. Effects of mometasone nasal spray, administered for 1-3 months, were studied in 37 patients. In addition, effects of oral prednisolone were analyzed in 55 patients who received decreasing doses over 21 days, starting with a dose of 40 mg. Olfactory function before and after treatment was measured.
Results: Although odor identification scores tended to increase (p = 0.05), mometasone nasal spray did not significantly improve olfactory function, when looking at the entire group of patients or when analyzing the three diagnostic categories separately. In contrast, after systemic administration of corticosteroids, improvement of olfactory function was seen over all diagnostic categories (p < 0.001). Interestingly, olfactory function also improved in patients diagnosed with olfactory loss after upper respiratory tract infection (p = 0.05) and in patients initially diagnosed with "idiopathic," olfactory dysfunction (p = 0.008).
Conclusion: In many patients, local application of corticosteroids appears to have little or no positive effect on olfactory dysfunction, especially when considering long-term changes. Duration of disease, the patient's age/sex, or the presence of parosmia does not appear to predict the response to therapy with corticosteroids.