Sense of smell in chronic rhinosinusitis: A multicentric study on 811 patients

Olfactory Dysfunction and Alzheimer's Disease: A Review

 Alzheimer's disease is the most common cause of dementia, and it is one of the leading causes of death globally. Identification and validation of biomarkers that herald the onset and progression of Alzheimer's disease is of paramount importance for early reliable diagnosis and effective pharmacological therapy commencement. A substantial body of evidence has emerged demonstrating that olfactory dysfunction is a preclinical symptom of neurodegenerative diseases including Alzheimer's disease. While a correlation between olfactory dysfunction and Alzheimer's disease onset and progression in humans exists, the mechanism underlying this relationship remains unknown. The aim of this article is to review the current state of knowledge regarding the range of potential factors that may contribute to the development of Alzheimer's disease-related olfactory dysfunction. This review predominantly focuses on genetic mutations associated with Alzheimer's disease including amyloid-β protein precursor, presenilin 1 and 2, and apolipoprotein E mutations, that may (in varying ways) drive the cellular events that lead to and sustain olfactory dysfunction.

Olfactory Loss in Rhinosinusitis: Mechanisms of Loss and Recovery

Chronic rhinosinusitis (CRS) is a highly prevalent disease and up to 83% of CRS patients suffer from olfactory dysfunction (OD). Because OD is specifically seen in those CRS patients that present with a type 2 eosinophilic inflammation, it is believed that type 2 inflammatory mediators at the level of the olfactory epithelium are involved in the development of this olfactory loss. However, due to the difficulties in obtaining tissue from the olfactory epithelium, little is known about the true mechanisms of inflammatory OD. Thanks to the COVID-19 pandemic, interest in olfaction has been growing rapidly and several studies have been focusing on disease mechanisms of OD in inflammatory conditions. In this paper, we summarize the most recent data exploring the pathophysiological mechanisms underlying OD in CRS. We also review what is known about the potential capacity of olfactory recovery of the currently available treatments in those patients.

Type 2 and Non-type 2 Inflammation in the Upper Airways: Cellular and Molecular Alterations in Olfactory Neuroepithelium Cell Populations

PURPOSE OF REVIEW

Neurogenesis occurring in the olfactory epithelium is critical to continuously replace olfactory neurons to maintain olfactory function, but is impaired during chronic type 2 and non-type 2 inflammation of the upper airways. In this review, we describe the neurobiology of olfaction and the olfactory alterations in chronic rhinosinusitis with nasal polyps (type 2 inflammation) and post-viral acute rhinosinusitis (non-type 2 inflammation), highlighting the role of immune response attenuating olfactory neurogenesis as a possibly mechanism for the loss of smell in these diseases.

RECENT FINDINGS

Several studies have provided relevant insights into the role of basal stem cells as direct participants in the progression of chronic inflammation identifying a functional switch away from a neuro-regenerative phenotype to one contributing to immune defense, a process that induces a deficient replacement of olfactory neurons. The interaction between olfactory stem cells and immune system might critically underlie ongoing loss of smell in type 2 and non-type 2 inflammatory upper airway diseases. In this review, we describe the neurobiology of olfaction and the olfactory alterations in type 2 and non-type 2 inflammatory upper airway diseases, highlighting the role of immune response attenuating olfactory neurogenesis, as a possibly mechanism for the lack of loss of smell recovery.

Clinical utility of and correlation between Sniffin' Sticks and TIB smell identification test (TIBSIT) among Hong Kong Chinese with or without chronic rhinosinusitis

Introduction

Olfactory dysfunction (OD) is common among patients with chronic rhinosinusitis (CRS). Validated and culturally specific tests, such as the "Sniffin' Sticks" test (SST) and the TIB Smell Identification Test (TIBSIT), are crucial for the diagnosis and monitoring of OD. However, they have not been utilised in Hong Kong Chinese and their correlations are unknown.

Methods

Twelve CRS patients and twenty healthy volunteers were prospectively recruited from a joint allergy-otorhinolaryngology clinic in Hong Kong and performed both SST and TIBSIT. Demographics, baseline characteristics and all test results were compared and analysed.

Results

Patients with CRS demonstrated significantly lower test scores than healthy controls (all p < 0.001). Significant and strong correlations were observed between all composite and subtest scores, particularly between the composite SST and TIBSIT scores (ρ = 0.789, p < 0.001). Multivariate analysis demonstrated that the presence of CRS and increasing age were significantly associated with OD.

Conclusion

Both SST and TIBSIT are useful olfactory tests and are strongly correlated among Hong Kong Chinese. We advocate that either test can be used for measuring OD among CRS patients.

Real-Life Effects of Omalizumab on Chronic Rhinosinusitis with Nasal Polyposis

Chronic rhinosinusitis with nasal polyposis (CRSwNP) is an inflammatory disease of the nasal and sinus mucosa. This inflammatory process is supported by a multitude of cytokines, including IL-4, IL-5, and IL-13 produced by Th2 cells, as well as by IgE produced by B lymphocytes in response to a stimulus. Omalizumab is an anti-IgE monoclonal antibody with well-recognized roles in allergic asthma and chronic spontaneous urticaria. The aim of this study was to evaluate the clinical efficacy of omalizumab in a cohort of 13 patients suffering from chronic rhinosinusitis with CRSwNP. The inclusion criteria considered were as follows: 18 years of age, with a diagnosis of chronic rhinosinusitis with severe nasal polyposis expressed by an NPS greater than or equal to 5 and/or a SNOT-22 greater than or equal to 50. In addition, in the enrolled patients, the classic treatment with corticosteroids had to have been suspended due to recurrence after surgery or lack of response. Our results highlighted that omalizumab treatment for 16 weeks improved the parameters analyzed: SNOT-22, NPS, NRS, and NCS. The clinical efficacy of omalizumab was further strengthened by a significant improvement in respiratory function as well as reductions in the nasal polyps' size and in the associated symptoms.

Chronic Rhinosinusitis with Nasal Polyps: A Survey on Routine Management and Evaluation of Disease Control in Practice

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a disease with a significant impact on quality of life. The overall goal of CRSwNP management, as with other chronic conditions, is to achieve "disease control", and for that reason, a definition of control of disease is pivotal in deciding the best treatment strategy. Although many staging systems have already been developed to evaluate the disease, disease control is not yet to be standardized, and a specific tool that is consistently applied and accepted by all practitioners is still missing in daily clinical practice. To gain an overview of the implementation and limitations of existing guidelines and to shed light on real-life definitions of control and disease severity, we conducted a nationwide survey of otorhinolaryngologists routinely treating CRSwNP to identify unmet clinical needs in Italy. The results showed homogeneous responses regarding the knowledge contained in international guidelines while highlighting the difficulty of their implementation in day-to-day practice. Respondents called attention to the importance of clinical symptoms, giving more weight to the patient's perspective. Among the symptoms to be considered, respondents emphasized nasal obstruction, followed by loss of sense of smell and rhinorrhea. Others also believe that the physician's perspective should be considered, and the inclusion of endoscopy as a measure of control was warranted by many. The need for a specific tool that is able to unequivocally ascertain disease control is increasingly pivotal in this new era of biologics for treating CRSwNP.

Olfactory dysfunction in chronic rhinosinusitis: insights into the underlying mechanisms and treatments

INTRODUCTION

Olfactory dysfunction (OD) is a typical symptom of chronic rhinosinusitis (CRS), which adversely affects the patient's quality of life and results in mood depression. Studies investigating the impairment of olfactory epithelium (OE) have indicated that inflammation-induced cell damage and dysfunction in OE plays a vital role in the development of OD. Consequently, glucocorticoids and biologics are beneficial in the management of OD in CRS patients. However, the mechanisms underlying OE impairment in CRS patients have not been fully elucidated.

AREAS COVERED

This review focuses on mechanisms underlying inflammation-induced cell impairment in OE of CRS patients. Additionally, the methods used for detection of olfaction and both currently available and potentially new clinical treatments for OD are reviewed.

EXPERT OPINION

Chronic inflammation in OE impairs not only olfactory sensory neurons but also non-neuronal cells that are responsible for regeneration and support for neurons. The current treatment for OD in CRS is mainly aimed at attenuating and preventing inflammation. Strategies for use of combinations of these therapies may achieve greater efficacy in restoration of the damaged OE and consequently better management of OD.