Background: Posttraumatic olfactory dysfunction is a clinical challenge due to refractory characteristics and limited therapeutic options. Olfactory training has been proved to be effective for olfactory dysfunction with varied etiologies. We pooled existing studies to evaluate the effects of olfactory training in patients with posttraumatic olfactory dysfunction.Methods: A systematic literature review using PubMed, Embase, Cochrane Library, and Web of Science was conducted to identify studies assessing olfactory change in patients with posttraumatic olfactory dysfunction after olfactory training.Results: Of the initial 812 abstracts reviewed, 13 full‐text articles were included. Clinically significant results after olfactory training were defined as an improvement of threshold, discrimination, and identification (TDI) score ≥6 or University of Pennsylvania Smell Identification Test (UPSIT) score ≥4. Six studies were included in the meta‐analysis, 36.31% (95% confidence interval [CI], 0.28 to 0.45) of posttraumatic patients would achieve clinically significant results after olfactory training with a mean increase of TDI score of 4.61.Conclusion: Olfactory training might be a promising modality for the treatment of posttraumatic olfactory dysfunction. More high‐quality studies with controls are needed to clarify the effect of olfactory training on total olfactory performance and subcomponents of olfaction.

Purpose of Review: Olfactory dysfunction dramatically impairs quality of life with a prevalence of 20% in the general adult population. Psychophysical olfactory testing has been widely used to evaluate the ability to smell due to its validated utility and feasibility in clinic. This review summarizes the current literature regarding psychophysical olfactory testing and the clinical relevance of the olfactory testing with different components. Furthermore, the review highlights the diagnosis and treatment value of olfactory subtests in patients with olfactory dysfunction.Recent Findings: With the accumulation of studies of psychophysical olfactory testing in olfactory disorders, the clinical relevance of olfactory testing with different components is expanding. Different olfactory domains present with distinct olfactory processing and cortical activity. Psychophysical assessment of olfaction with three domains reveals different levels of olfactory processing and might assist with analyzing the pathophysiologic mechanism of the various olfactory disorders. Furthermore, olfactory thresholds provided the largest amount of non-redundant information to the olfactory diagnosis. Sinonasal olfactory dysfunction and non-sinonasal-related olfactory dysfunction are emerging classifications of smell disorders with certain characteristics of olfactory impairment and different responses to the therapy including steroids, sinus surgery, and olfactory training.Summary: These recent advancements should promote the understanding of psychophysical olfactory testing, the association between individual subcomponents and neurophysiological processes, and pave the way for precision assessment and treatment of the olfactory dysfunction.

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a heterogeneous disease that can be classified as eosinophilic or noneosinophilic. Nasal polyps can exhibit different types of mucosal inflammation and responses to treatment. Imbalanced ratios of T-helper 17(Th17) and regulatory T (Treg) cells may contribute to the pathogenesis of nasal polyps. This study assessed the frequency of Th17 and Treg cells and related cytokines in patients with nasal polyps and tested for associations with mucosal remodeling. Surgical samples from 12 controls and 33 CRSwNP patients were analyzed histopathologically. The frequency of Th17 and Treg cells in peripheral blood mononuclear cells (PBMCs) and tissues were determined using flow cytometry. Th17 and Treg cells-related cytokines in plasma were measured by Cytometric Bead Array (CBA) multiplex assays and enzyme-linked immunosorbent assays (ELISAs). Eosinophilic CRSwNP (ECRSwNP) patients exhibited robust eosinophilia, whereas non-ECRSwNP patients were characterized by neutrophilia. Compared with non-ECRSwNP, an increased Th17/Treg ratio in ECRSwNP was associated with a less increased frequency of Th17 cells and a more striking reduction of Treg cells. An altered Th17/Treg cell ratio was positively correlated with eosinophilic and neutrophilic infiltration, submucosal basement membrane thickness, and the degree of subepithelial collagen deposition. Compared with non-ECRSwNP, ECRSwNP had higher levels of IL-17A and IL-4, and lower levels of IL-10 and TGF-β1, whereas non-ECRSwNP showed higher levels of IFN-γ and IL-6. Th17/Treg cell imbalance in nasal polyps (both in tissues and PBMCs) with distinct cytokine profile may contribute to different inflammatory patterns (eosinophilic versus neutrophilic inflammation) and corresponding features of mucosal remodeling. Effective strategies can be designed to target a Th17/Treg imbalance to restore immune homeostasis in nasal polyps.

Background: Acute exacerbations (AE) in chronic rhinosinusitis (CRS) have been increasingly recognized as an important clinical issue. The purpose of this study is to summarize the current definitions and evaluation parameters of AE and then identify and quantify the clinical and immunopathologic characteristics of AE in CRS. Methods: A systematic review of the literature was performed on PubMed, Scopus, and Cochrane databases from January 1990 through August 2020 to identify studies relating to AE in CRS. Exclusion criteria included non-English and non-human studies, and case reports. Results: The definitions of AE in CRS among all the studies were based on a description of short-term worsening sinonasal symptoms. Patient-reported sinus infection and exacerbation related medical treatment during the preceding 3 months to 1 year were used to evaluate the frequency of AE in CRS. The average decline in 22-item Sino-Nasal Outcome Test (SNOT-22) score during an exacerbation was 7.83 points relative to baseline. Comorbid asthma, SNOT-22 scores ≥24, allergic rhinitis, eosinophil count ≥150/μL and autoimmune disease were positively associated with an exacerbation-prone CRS phenotype. AE in chronic rhinosinusitis with nasal polyps (CRSwNP) was associated with increased expression of mucus cytokines including myeloperoxidase (percentage increase [PI] = 101%), IL-5 (PI = 125%), and IL-6 (PI = 162%) and could be predicted by the increasing mucus cystatin and periostin. Conclusion: The definition of AE in CRS is largely driven by patient-reported symptoms and is associated with several risk factors. Quantitative changes in mucus cytokines associated with AE in CRSwNP and may be used to predict events. The development of a consistent definition of AE in CRS is critical to help define disease control and treatment efficacy.