Pathophysiology of Olfactory Disorders and Potential Treatment Strategies

Structures and functions of the normal and injured human olfactory epithelium

The olfactory epithelium (OE) is directly exposed to environmental agents entering the nasal cavity, leaving OSNs prone to injury and degeneration. The causes of olfactory dysfunction are diverse and include head trauma, neurodegenerative diseases, and aging, but the main causes are chronic rhinosinusitis (CRS) and viral infections. In CRS and viral infections, reduced airflow due to local inflammation, inflammatory cytokine production, release of degranulated proteins from eosinophils, and cell injury lead to decreased olfactory function. It is well known that injury-induced loss of mature OSNs in the adult OE causes massive regeneration of new OSNs within a few months through the proliferation and differentiation of progenitor basal cells that are subsequently incorporated into olfactory neural circuits. Although normal olfactory function returns after injury in most cases, prolonged olfactory impairment and lack of improvement in olfactory function in some cases poses a major clinical problem. Persistent inflammation or severe injury in the OE results in morphological changes in the OE and respiratory epithelium and decreases the number of mature OSNs, resulting in irreversible loss of olfactory function. In this review, we discuss the histological structure and distribution of the human OE, and the pathogenesis of olfactory dysfunction associated with CRS and viral infection.

Clinical characteristics of local allergic rhinitis sensitized to house dust mites in Asia

PURPOSE

Local allergic rhinitis (LAR) is characterized by a localized nasal allergic response without evidence of systemic atopy. LAR is an underdiagnosed entity and is a diagnostic and therapeutic challenge for clinicians. This study aimed to investigate the prevalence and clinical characteristics of patients with LAR to house dust mites (LAR-HDM) in Korea.

METHODS

We performed a retrospective chart review of 336 adult patients with rhinitis symptoms who visited the Rhinologic Clinic at Korea University Guro Hospital from October 2019 to April 2021. Using results of the skin prick test, serologic test, and nasal provocation test, patients were classified as allergic rhinitis (AR) to HDM (AR-HDM), AR to other allergens, non-allergic rhinitis (NAR), or LAR-HDM. We excluded patients with AR to other allergens and compared the clinical characteristics of the remaining three groups. Patient demographic data were reviewed, and patients' nasal symptoms, olfactory function, serum total IgE, and severity of accompanying rhinosinusitis were evaluated.

RESULTS

In total, 336 patients were examined. AR-HDM was diagnosed in 138 (41.1%) patients, AR to other allergens in 36 (10.7%) patients, NAR in 21 (42.0%) patients, and LAR-HDM in 21 (6.3%) patients. The mean age of patients with LAR-HDM was significantly higher than that of patients with AR-HDM. There were no significant differences in sex, smoking history, asthma, and family history of allergic diseases between the groups. Compared to NAR patients, there were significantly more patients with LAR-HDM who had persistent nasal symptoms. The frequency of nasal itching and sneezing was significantly higher in the LAR-HDM group than in the NAR group. The olfactory function score in the LAR-HDM group was significantly worse than that in the AR-HDM group, and the Lund-Mackay score was significantly higher in the LAR-HDM group than in the other groups.

CONCLUSION

Clinical history and nasal symptoms are very similar in LAR-HDM and AR-HDM. Clinicians should take more care to differentiate them. LAR-HDM should also be considered in patients with persistent and severe nasal symptoms without systemic atopy.

Surgical and medical management of chronic rhinosinusitis in pediatric cystic fibrosis patients: Impact on olfactory symptoms

BACKGROUND AND PURPOSE

Olfactory dysfunction (OD) commonly occurs in patients with sinonasal dysfunction, but the prevalence and severity of olfactory issues in adolescents with cystic fibrosis (AwCF) is unclear. OD may contribute to dietary deficiencies and exacerbate nutritional challenges. We sought to review literature on the effectiveness of medical and surgical management of sinonasal symptoms in AwCF and the associated impact on olfactory function.

METHODS

We performed a systematic literature search of PubMed, Embase, Web of Science, and Ebsco CINAHL from 1980 to 2022 per PRISMA-ScR protocols to conduct a scoping review in an effort to compile data on study design, patient demographics, clinical characteristics and outcomes, along with risk of bias.

RESULTS

Of 368 abstracts, 3 articles exclusively evaluated AwCF for a total of 34 patients. Two studies evaluated endoscopic sinus surgery (ESS) and dornase alfa. An additional 6 articles were included for mixed pediatric and adult CF populations totaling 313 patients. Interventions included ESS, elexacaftor-tezacaftor-ivacaftor (ETI), ivacaftor, saline, dornase alfa, hyaluronic acid, and hyaluronic acid-tobramycin combination. Outcome measures included subjective assessment of OD using non-validated (4/9) and validated (4/9) surveys, and psychophysical (1/9) smell testing. Studies evaluating ESS, FESS, dornase alfa, ivacaftor, and both hypertonic and isotonic saline reported statistically significant improvement in OD, whereas ETI failed to improve OD despite improvement in other quality of life measures.

CONCLUSIONS

There is limited data regarding the impact of medical and surgical interventions on olfaction for AwCF. Assessment of olfaction was often limited to subjective and qualitative self-report. We suggest that tracking of olfactory outcomes with psychophysical testing is critical in this population with dietary challenges and weight management issues.

COVID-19 associated anosmia in pediatric patients: subject publications review

OBJECTIVE

Aim: To review the publications subject to the problem of COVID-19 associated anosmia incidence in pediatric patients as well as its pathogenesis, diagnostics, treatment and recovery. The peculiarity of pediatric COVID-19 anosmia is due to children accounting for very low percentage of COVID-19 patients (comparing to one in adults), mostly with milder course of the disease. Awareness of anosmia and its proper diagnostics is crucial in children and adolescents, considering it can be the only manifestation in COVID-19 positive pediatric patients.

PATIENTS AND METHODS

Materials and Methods: In order to achieve this goal a meta-analysis of information from databases followed by statistical processing and generalisation of the obtained data was carried out.

CONCLUSION

Conclusions: Publications on COVID-19 anosmia in children and adolescents are less numerous than those concerning adult patients, so it is important to use every single trustworthy one. Anosmia/ageusia may be the only symptom, early identifier and the strongest predictor of COVID-19 infection in pediatric patients. Prospects for further scientific researches. Further researches regarding differential diagnostics of COVID-19 and other infections, including seasonal influenza, manifesting with both olfactory and taste dysfunction as well as anosmia diagnostics in children and adolescents with autistic spectrum and different types of mental disorders are possible.

Olfactory Dysfunction in Children: A Scoping Review

OBJECTIVE

Olfactory disorders are well-studied in the adult population, however, there is a paucity of literature characterizing olfactory dysfunction in pediatric patients. The purpose of this scoping review was to identify known causes of olfactory loss in pediatric populations, clarify the extent of use and validity of smell tests, and summarize current therapies for olfactory loss.

DATA SOURCES

PubMed, Ovid MEDLINE, and Web of Science.

REVIEW METHODS

Databases were systematically searched in September 2020. Two independent reviewers conducted the title and abstract screen, followed by review of full-texts for inclusion based on preset inclusion and exclusion criteria. Extracted data included study type, age/age-range of participants, gender, radiological evidence of olfactory dysfunction, types and results of smell tests used, etiology of olfactory loss, and therapies employed for olfactory loss.

RESULTS

A total of 103 articles (n = 1654) were eligible for final data extraction. The University of Pennsylvania Smell Identification Test was used most frequently for smell testing (21% of studies). In total, 45 causes of olfactory dysfunction have been elucidated by this study: 22 congenital and 23 acquired. Few therapies were described, and all were specific to the etiology of olfactory loss.

CONCLUSION

Olfactory dysfunction has a wide range of etiologies in the pediatric population, and clinicians should have a diagnostic algorithm for how to identify a cause should they encounter it in practice. If no etiology can be identified, education around safety should be provided to both the patient and their caregivers.

Validity and Reliability of the Malay Questionnaire for Olfactory Disorders

Background

Olfactory disorders (OD) are an umbrella term for a diverse group of smell problems. Numerous tests and questionnaires have been formulated to identify and test the severity of smell impairment, which is not readily available or translated for the Malaysian population. This study aimed to translate the Questionnaire for Olfactory Disorders (QOD) and validate and test the reliability of the Malay Questionnaire for Olfactory Disorders (mQOD).

Methods

This cross-sectional study was conducted in two tertiary centres. A forward and backward translation was conducted for the QOD. The translated questionnaire was distributed to subjects with self-reported smell disorders on days 1 and 7. Internal consistency was analysed using Cronbach's alpha and test-retest reliability was tested with an intraclass correlation coefficient. Confirmatory factor analysis was performed to test construct validity.

Results

A total of 375 participants were recruited, 52 dropped out and 323 completed the questionnaire a second time. The Cronbach's alpha coefficient was 0.537 for parosmia (P), 0.892 for life quality (LQ), 0.637 for sincerity (S) and 0.865 for visual analogue score (VAS). The intraclass correlation coefficient (ICC) for domain scores was > 0.9, while the ICC for all items was good to excellent. A three-factor model for mQOD showed an acceptable fit with indices chi-square value (CMIN)/degree of freedom (DF) = 3.332, Tucker-Lewis fit index (TLI) = 0.923, comparative fit index (CFI) = 0.939, root mean square error of approximation (RMSEA) = 0.079 and standardised root mean square residual (SRMR) = 0.0574.

Conclusion

The mQOD is a valid and reliable tool for assessing OD in patients.

Clinical and Imaging Evaluation of COVID-19-Related Olfactory Dysfunction

BACKGROUND

Olfactory dysfunction has been reported in 47.85% of COVID patients. It can be broadly categorized into conductive or sensorineural olfactory loss. Conductive loss occurs due to impaired nasal air flow, while sensorineural loss implies dysfunction of the olfactory epithelium or central olfactory pathways.

OBJECTIVES

The aim of this study was to analyze the clinical and imaging findings in patients with COVID-related olfactory dysfunction. Additionally, the study aimed to investigate the possible mechanisms of COVID-related olfactory dysfunction.

METHODS

The study included 110 patients with post-COVID-19 olfactory dysfunction, and a control group of 50 COVID-negative subjects with normal olfactory function. Endoscopic nasal examination was performed for all participants with special focus on the olfactory cleft. Smell testing was performed for all participants by using a smell diskettes test. Olfactory pathway magnetic resonance imaging (MRI) was done to assess the condition of the olfactory cleft and the dimensions and volume of the olfactory bulb.

RESULTS

Olfactory dysfunction was not associated with nasal symptoms in 51.8% of patients. MRI showed significantly increased olfactory bulb dimensions and volume competed to controls. Additionally, it revealed olfactory cleft edema in 57.3% of patients. On the other hand, radiological evidence of sinusitis was detected in only 15.5% of patients.

CONCLUSION

The average olfactory bulb volumes were significantly higher in the patients' group compared to the control group, indicating significant edema and swelling in the olfactory bulb in patients with COVID-related olfactory dysfunction. Furthermore, in most patients, no sinonasal symptoms such as nasal congestion or rhinorrhea were reported, and similarly, no radiological evidence of sinusitis was detected. Consequently, the most probable mechanism of COVID-related olfactory dysfunction is sensorineural loss through virus spread and damage to the olfactory epithelium and pathways.

Anosmia: Brighton Collaboration case definition and guidelines for data collection, analysis, and presentation of immunization safety data

This is a Brighton Collaboration case definition of anosmia to be used in the evaluation of adverse events following immunization, and for epidemiologic studies for the assessment of background incidence or hypothesis testing. The case definition was developed by a group of experts convened by the Coalition for Epidemic Preparedness Innovations (CEPI) in the context of active development of SARS-CoV-2 vaccines. The case definition format of the Brighton Collaboration was followed to develop a consensus definition and defined levels of certainty, after an exhaustive review of the literature and expert consultation. The document underwent peer review by the Brighton Collaboration Network and by two expert reviewers prior to submission.

Olfactory Regeneration with Nasally Administered Murine Adipose-Derived Stem Cells in Olfactory Epithelium Damaged Mice

In this study, we aimed to determine whether nasally administered murine adipose-derived stem cells (ADSCs) could support olfactory regeneration in vivo. Olfactory epithelium damage was induced in 8-week-old C57BL/6J male mice by intraperitoneal injection of methimazole. Seven days later, OriCell adipose-derived mesenchymal stem cells obtained from green fluorescent protein (GFP) transgenic C57BL/6 mice were nasally administered to the left nostril of these mice, and their innate odor aversion behavior to butyric acid was assessed. Mice showed significant recovery of odor aversion behavior, along with improved olfactory marker protein (OMP) expression on both sides of the upper-middle part of the nasal septal epithelium assessed by immunohistochemical staining 14 d after the treatment with ADSCs compared with vehicle control animals. Nerve growth factor (NGF) was detected in the ADSC culture supernatant, NGF was increased in the nasal epithelium of mice, and GFP-positive cells were observed on the surface of the left side nasal epithelium 24 h after left side nasal administration of ADSCs. The results of this study suggest that the regeneration of olfactory epithelium can be stimulated by nasally administered ADSCs secreting neurotrophic factors, thereby promoting the recovery of odor aversion behavior in vivo.

Autoimmunity, COVID-19 Omicron Variant, and Olfactory Dysfunction: A Literature Review

Smelling is a critical sense utilized daily. Consequently, smelling impairment or anosmia may lead to a reduction in life quality. Systemic diseases and particular autoimmune conditions can impair olfactory function; among others are Systemic Lupus Erythematosus, Sjögren Syndrome, and Rheumatoid Arthritis. Interactions between the olfactory process and the immune systems cause this phenomenon. Alongside autoimmune conditions, in the recent COVID-19 pandemic, anosmia was also described as a prevalent infection symptom. Nevertheless, the occurrence of anosmia is significantly less common in Omicron-infected patients. Several theories have been proposed to explain this phenomenon. One possibility is that the Omicron variant preferentially enters host cells via endocytosis, rather than plasma cell membrane fusion. This endosomal pathway is less dependent on the activation of Transmembrane serine protease 2 (TMPRSS2), expressed at the olfactory epithelium. As a result, the Omicron variant may have reduced efficiency in penetrating the olfactory epithelium, leading to a lower prevalence of anosmia. Furthermore, olfactory changes are known to be associated with inflammatory conditions. The Omicron variant elicits a less robust autoimmune and inflammatory response, believed to reduce the probability of anosmia. This review elaborates on the commonalities and differences in autoimmune and COVID-19 omicron-associated anosmia.

Pathogenesis and progression of anosmia and dysgeusia during the COVID-19 pandemic

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is the causative agent of COVID-19 which was detected in late 2019 in Wuhan, China. As of September 2022, there have been over 612 million confirmed cases of COVID-19 with over 6.5 million associated deaths. In many cases, anosmia and dysgeusia have been identified as primary symptoms of COVID-19 infection in patients. While the loss of smell (anosmia) and loss of taste (dysgeusia) due to COVID-19 infection is transient in most patients, many report that these symptoms persist following recovery. Understanding the pathogenesis of these symptoms is paramount to early treatment of the infection. We conducted a literature review of Google Scholar and PubMed to find and analyze studies discussing anosmia and dysgeusia in the context of COVID-19 to understand the progression and management of these symptoms. The mechanism for dysgeusia is largely unknown; however, pathogenesis of anosmia includes inflammation and cytokine release resulting from the infection that alters neuronal signaling, thus inducing the loss of smell that patients experience. Anosmia may be managed and potentially resolved sooner with a combination therapy of olfactory training and budesonide irrigation of the nasal cavity. It is important to note that the variants of SARS-CoV-2 are genetically distinguished from the original virion due to a mutation in their spike proteins, giving them a different symptom profile regarding anosmia and dysgeusia. This variability in symptomatology is an area of study that needs to be further explored.

Olfactory training assists in olfactory recovery after sinonasal surgery

Objectives

Olfactory dysfunction is a common complaint in patients with chronic rhinosinusitis (CRS). The study aimed to evaluate the effectiveness of olfactory training (OT) in patients with CRS after sinonasal surgery.

Methods

We enrolled 111 patients with CRS who underwent sinonasal surgery. Prior to surgery and 3 months after starting OT, the participants were assessed by both an olfactory function test and endoscopy. The Korean version of the Sniffin' Stick II (KVSS-II) was used to perform the olfactory function test. Over the course of 3 months, five odorants were used in OT (rose, lemon, cinnamon, orange, and peach).

Results

Over a 12-week duration, 37% of the participants in the OT group showed clinically relevant increase in olfactory function. The OT group had significantly higher olfactory outcomes for the total KVSS-II and identification scores than the non-OT group between the initial and follow-up assessments. The initial score influenced the degree of olfactory improvement after OT.

Conclusions

Patients with OT exhibited significantly higher total KVSS-II scores compared with non-OT patients following sinonasal surgery; in particular, the odor identification score was different between the two groups. The results of this study demonstrated that a 12-week period of repeated short-term exposure to various odors could be useful in enhancing olfactory activity in patients who underwent sinonasal surgery for the improvement of sensory-neural olfactory impairment.

Level of evidence

2c.

Molecular mechanisms involved in anosmia induced by SARS-CoV-2, with a focus on the transmembrane serine protease TMPRSS2

Since 2020, SARS-CoV-2 has caused a pandemic virus that has posed many challenges worldwide. Infection with this virus can result in a number of symptoms, one of which is anosmia. Olfactory dysfunction can be a temporary or long-term viral complication caused by a disorder of the olfactory neuroepithelium. Processes such as inflammation, apoptosis, and neuronal damage are involved in the development of SARS-CoV-2-induced anosmia. One of the receptors that play a key role in the entry of SARS-CoV-2 into the host cell is the transmembrane serine protease TMPRSS2, which facilitates this process by cleaving the viral S protein. The gene encoding TMPRSS2 is located on chromosome 21. It contains 15 exons and has many genetic variations, some of which increase the risk of disease. Delta strains have been shown to be more dependent on TMPRSS2 for cell entry than Omicron strains. Blockade of this receptor by serine protease inhibitors such as camostat and nafamostat can be helpful for treating SARS-CoV-2 symptoms, including anosmia. Proper understanding of the different functional aspects of this serine protease can help to overcome the therapeutic challenges of SARS-CoV-2 symptoms, including anosmia. In this review, we describe the cellular and molecular events involved in anosmia induced by SARS-CoV-2 with a focus on the function of the TMPRSS2 receptor.

Intranasal application of adeno-associated viruses: a systematic review

Adeno-associated viruses (AAVs) represent some of the most commonly employed vectors for targeted gene delivery and their extensive study has resulted in the approval of multiple gene therapies to treat human diseases. The intranasal route of vector application in gene therapy offers several advantages over traditional ways of administration. In addition to targeting local tissue like the olfactory epithelium, it provides minimally invasive access to various organ systems, including the central nervous system and the respiratory tract. Through a systematic literature review, a total of 53 articles that investigated the intranasal application of AAVs were identified, included, and summarized in this manuscript. Within these studies, AAV-based gene therapy was mainly investigated for its application in various infectious, pulmonary, or neurologic and/or psychiatric diseases. This review gives a comprehensive overview of the current technological state of the art regarding the intranasal application of AAVs for gene transfer and discusses remaining hurdles, which still have to be resolved before this approach can effectively be implemented in the routine clinical setting.

Mechanistic Understanding of the Olfactory Neuroepithelium Involvement Leading to Short-Term Anosmia in COVID-19 Using the Adverse Outcome Pathway Framework

Loss of the sense of smell (anosmia) has been included as a COVID-19 symptom by the World Health Organization. The majority of patients recover the sense of smell within a few weeks postinfection (short-term anosmia), while others report persistent anosmia. Several studies have investigated the mechanisms leading to anosmia in COVID-19; however, the evidence is scattered, and the mechanisms remain poorly understood. Based on a comprehensive review of the literature, we aim here to evaluate the current knowledge and uncertainties regarding the mechanisms leading to short-term anosmia following SARS-CoV-2 infection. We applied an adverse outcome pathway (AOP) framework, well established in toxicology, to propose a sequence of measurable key events (KEs) leading to short-term anosmia in COVID-19. Those KEs are (1) SARS-CoV-2 Spike proteins binding to ACE-2 expressed by the sustentacular (SUS) cells in the olfactory epithelium (OE); (2) viral entry into SUS cells; (3) viral replication in the SUS cells; (4) SUS cell death; (5) damage to the olfactory sensory neurons and the olfactory epithelium (OE). This AOP-aligned approach allows for the identification of gaps where more research should be conducted and where therapeutic intervention could act. Finally, this AOP gives a frame to explain several disease features and can be linked to specific factors that lead to interindividual differences in response to SARS-CoV-2 infection.

ARTICLE REVIEW: THE USE OF AROMATHERAPY FOR ANOSMIA PATIENTS DURING THE COVID-19 PANDEMIC

This study was conducted to determine the benefits of aromatherapy for anosmia people after exposure to COVID-19. Aromatherapy was often used for health therapy so it has the potential for the treatment of anosmia. This study is necessary to be done because there are a lot of anosmia sufferers and there is no effective way to treat it. The study of post-COVID-19 anosmia continues to evolve and more needs to be researched. This study was conducted by reviewing several literature studies originating from international and national journals, theses, and dissertations with a year limit of the last 10 years. From some literature it is known that aromatherapy can reduce the risk caused by anosmia. Aromatherapy can enter through the body's circulatory system and olfactory system through fragrances, It will affect the condition, memory, and psyche of a person. Although not very effective, further research on the benefits of aromatherapy for people with anosmia is necessary.

Post-COVID-19 olfactory dysfunction: carbamazepine as a treatment option in a series of cases

Olfactory dysfunction is reported frequently in patients with coronavirus disease 2019. However, an effective treatment for this dysfunction is unknown. The present study evaluated carbamazepine as a treatment option for olfactory dysfunction based on its use in cases of neuralgia, especially of the V cranial nerve. The study included 10 patients with coronavirus disease with olfactory complaints who were part of a cohort of 172 coronavirus disease patients monitored for late neurological manifestations. Carbamazepine was administered for 11 weeks. The adverse effects reported were drowsiness (9/10) and dizziness (2/10); 9 of the 10 patients reported improved olfactory function after carbamazepine treatment. While the role of carbamazepine in the control of post-coronavirus disease olfactory dysfunction could not be confirmed in this study, the satisfactory response observed in most patients in this series suggests that further studies are warranted.

Omega-3 supplementation in postviral olfactory dysfunction: a pilot study

BACKGROUND

This study aimed to examine whether omega-3 supplementation would support olfactory recovery among postviral olfactory dysfunction patients.

METHODOLOGY

Patients with postviral olfactory dysfunction were included in this non-blinded, prospective pilot study. Structured medical history was taken from the patients, including the following: age, sex, history of COVID-19 infection, and duration of symptoms. Patients were randomly assigned to receive olfactory training only (control group) versus olfactory training with omega-3 supplementation (treatment group). All patients exposed themselves twice a day to four odours (phenyl ethyl alcohol [rose], eucalyptol [eucalyptus], citronellal [lemon], and eugenol [cloves]). Olfactory function was measured before and after training using "Sniffin' Sticks", comprised of tests for odour threshold, discrimination, and identification. The average interval between olfactory tests was 3 months.

RESULTS

Fifty-eight patients were included in the study, 25 men and 33 women. Generally, an improvement in olfactory scores was observed. Compared to the control group, the improvement in odour thresholds was more pronounced in the omega-3 group. Age, sex, and duration of symptoms had no effect on olfactory scores among both control and treatment groups.

CONCLUSION

Overall, the present results indicate that omega-3 supplementation may be an option for adjunct therapy with olfactory training in patients with postviral olfactory dysfunction.

Neuroimmunoendocrine Link Between Chronic Kidney Disease and Olfactory Deficits

Chronic kidney disease (CKD) is a multifactorial pathology that progressively leads to the deterioration of metabolic functions and results from deficient glomerular filtration and electrolyte imbalance. Its economic impact on public health is challenging. Mexico has a high prevalence of CKD that is strongly associated with some of the most common metabolic disorders like diabetes and hypertension. The gradual loss of kidney functions provokes an inflammatory state and endocrine alterations affecting several systems. High serum levels of prolactin have been associated with CKD progression, inflammation, and olfactory function. Also, the nutritional status is altered due to impaired renal function. The decrease in calorie and protein intake is often accompanied by malnutrition, which can be severe at advanced stages of the disease. Nutrition and olfactory functioning are closely interconnected, and CKD patients often complain of olfactory deficits, which ultimately can lead to deficient food intake. CKD patients present a wide range of deficits in olfaction like odor discrimination, identification, and detection threshold. The chronic inflammatory status in CKD damages the olfactory epithelium leading to deficiencies in the chemical detection of odor molecules. Additionally, the decline in cognitive functioning impairs the capacity of odor differentiation. It is not clear whether peritoneal dialysis and hemodialysis improve the olfactory deficits, but renal transplants have a strong positive effect. In the present review, we discuss whether the olfactory deficiencies caused by CKD are the result of the induced inflammatory state, the hyperprolactinemia, or a combination of both.

Effect of Lavender (Lavandula angustifolia L.) syrup on olfactory dysfunction in COVID-19 infection: A pilot controlled clinical trial

OBJECTIVE

The effect of lavender syrup on COVID-19-induced olfactory dysfunction (OD) has been assessed in this study.

MATERIALS AND METHODS

This pilot clinical trial was conducted in Gonbad-E-Kavoos (Golestan province, Iran). Twenty-three outpatients with COVID-19 and OD in lavender group took 9 ml of lavender syrup/bid for 3 weeks along with the standard COVID-19 treatments and 20 patients in control group took only standard COVID-19 treatments. The severity of OD was assessed by the visual analogue scale (VAS). Data analysis was performed by Friedman and Mann-Whitney tests using SPSS software.

RESULTS

The mean± standard deviation of age was 36.6±9.1, and 42.6±10.4 years (p=0.05), and the duration of symptoms was 7.4±3.5, and 7.5±3.4 days (p=0.98) in the lavender and control group, respectively. The VAS score for OD decreased from 6.8±3.04 to 0.26±0.86 in the lavender group and from 5.3±3.4 to 1±2.61 in the control group. Although, VAS for OD was significantly decreased in both groups (p<0.001), the amount of VAS decrease was 6.6±2.9 scores in the lavender group, and 4.3±4 in the control group (p=0.03). No side effects were observed in the lavender group.

CONCLUSION

The present study showed that lavender syrup is an effective treatment for COVID-19-induced OD. It is suggested to conduct further studies with larger sample size.

First-episode olfactory hallucination in a patient with anxiety disorder: A case report

BACKGROUND

Olfactory hallucination refers to olfactory perception in the absence of chemical stimuli. Although it has been associated with many neurological and psychotic disorders, it has rarely been reported as the first and only symptom in patients with anxiety disorder, and its treatment remains inadequate.

CASE SUMMARY

A 66-year-old woman who had been experiencing gradually worsening olfactory hallucinations for almost 4 years was diagnosed with generalized anxiety disorder. Olfactory hallucination disappeared after treatment with anti-anxiety drugs.

CONCLUSION

Olfactory hallucination can be the first and only symptom in patients with anxiety disorder and may be effectively treated with anti-anxiety medication. In fact, it can precede the diagnosis of anxiety disorder by several years.

Comparison of Olfactory Cleft Width and Volumes in Patients with COVID-19 Anosmia and COVID-19 Cases Without Anosmia

Introduction

The aim of this study was to assess the relationship between olfactory cleft width/volume and COVID-19-related anosmia.

Methods

This study consisted of PCR-proven COVID-19 patients. Cases with COVID-19-related anosmia constituted Group 1 and cases without any olfactory dysfunction (OD) throughout COVID-19 infection or after recovery constituted Group 2. A total of 50 patients were included in the study, comprising 24 cases in Group 1 and 26 cases in Group 2. Group 1 patients underwent a 4-item-odor identification test during active symptoms and a Sniffin' Sticks test after reconversion of PCR results to negative. All patients in Group 2 also underwent the Sniffin' Stick test to document normosmia. All cases had paranasal sinus CT performed. Olfactory cleft widths and olfactory volumes were measured. The differences in width and volume between groups and the correlation with odor test scores (threshold-discrimination-identification [TDI]) were calculated. In addition, regression analyzes analysis was performed for cleft widths, volumes, and TDI scores according to age.

Results

Olfactory cleft widths and olfactory volumes were significantly higher in Group 1 than those in Group 2 (p = 0.001; p < 0.01). There was a significant negative correlation between total TDI scores and olfactory cleft widths and total olfactory volumes (r = −0.665; r = −0.731, respectively). Patients younger than 40 years of age had significantly higher right olfactory cleft width, left olfactory cleft width, and olfactory cleft volume than those in patients older than 40 years of age (p = 0.004, p = 0.005, p = 0.003; p < 0,01, respectively). However, patients younger than 40 years of age had a significantly lower total TDI score and in all other values individually (t-d-i) than those in patients older than 40 years of age (p = 0.004; p < 0.01).

Conclusion

Patients with COVID-19-related OD had larger olfactory cleft width and volumes than those without OD in this study. Total TDI score was found to be inversely correlated with cleft width and volume.

The Circadian Clock, the Brain, and COVID-19: The Cases of Olfaction and the Timing of Sleep

Daily rhythms of behavior and neurophysiology are integral to the circadian clocks of all animals. Examples of circadian clock regulation in the human brain include daily rhythms in sleep-wake, cognitive function, olfactory sensitivity, and risk for ischemic stroke, all of which overlap with symptoms displayed by many COVID-19 patients. Motivated by the relatively unexplored, yet pervasive, overlap between circadian functions and COVID-19 neurological symptoms, this perspective piece uses daily variations in the sense of smell and the timing of sleep and wakefulness as illustrative examples. We propose that time-stamping clinical data and testing may expand and refine diagnosis and treatment of COVID-19.

Severe Acute Respiratory Syndrome Coronavirus 2 Infects and Damages the Mature and Immature Olfactory Sensory Neurons of Hamsters

Background

Coronavirus Disease 2019 (COVID-19) is primarily an acute respiratory tract infection. Distinctively, a substantial proportion of COVID-19 patients develop olfactory dysfunction of uncertain underlying mechanism which can be severe and prolonged. The roles of inflammatory obstruction of the olfactory clefts leading to conductive impairment, inflammatory cytokines affecting olfactory neuronal function, destruction of olfactory neurons or their supporting cells, and direct invasion of olfactory bulbs, in causing olfactory dysfunction are uncertain.

Methods

In this study, we investigated the location for the pathogenesis of SARS-CoV-2 from the olfactory epithelium (OE) of the nasopharynx to the olfactory bulb of golden Syrian hamsters.

Results

After intranasal inoculation with SARS-CoV-2, inflammatory cell infiltration and proinflammatory cytokine/chemokine responses were detected in the nasal turbinate tissues which peaked between 2 to 4 days post-infection with the highest viral load detected at day 2 post-infection. Besides the nasopharyngeal pseudo-columnar ciliated respiratory epithelial cells, SARS-CoV-2 viral antigens were also detected in the more superficial mature olfactory sensory neurons labeled by olfactory marker protein (OMP), the less mature olfactory neurons labelled by Tuj1 at more basal position, and the sustentacular cells which provide metabolic and physical support for the olfactory neurons, resulting in apoptosis and severe destruction of the OE. During the whole course of infection, SARS-CoV-2 viral antigens were not detected in the olfactory bulb.

Conclusions

Besides acute inflammation at OE, infection of mature and immature olfactory neurons, and the supporting sustentacular cells by SARS-CoV-2 may contribute to the unique olfactory dysfunction of COVID-19 which is not reported with SARS-CoV.

COVID-19-related smell and taste disorders: A guide for nurses

ABSTRACT

Olfactory impairment is recognized as a hallmark of COVID-19. This article highlights dysfunction of smell and taste associated with COVID-19 and discusses implications for nursing practice.

Long Term Olfactory Outcomes Following Frontal Sinus Surgery in Chronic Rhinosinusitis

OBJECTIVES/HYPOTHESIS

No studies have evaluated the impact of the types of frontal sinus surgery (FSS) on objective olfaction scores. This study evaluated olfactory function and quality of life (QOL) in chronic rhinosinusitis (CRS) patients before and after total ethmoidectomy with frontal sinusotomy (FS).

STUDY DESIGN

Prospective cohort study.

METHODS

A prospective study of adult CRS patients undergoing FSS (Draf 2 or Draf 3 procedures) was conducted at a tertiary care center. Primary outcomes included brief smell identification test (BSIT) and sinonasal outcome test-22 (SNOT-22), which were assessed during preoperative evaluation, 6 to 9 weeks postoperatively, and 12 to 24 weeks postoperatively. Normosmia was defined as BSIT ≥9. Statistical significance was determined using the Wilcoxon signed-rank test with α = .05.

RESULTS

Thirty-eight patients followed up 12 to 24 weeks after FSS. The differences between baseline and long-term outcomes for BSIT (6.11 vs. 8.24, P = .00034) and SNOT-22 (55.49 vs. 24.32, P < .00001) scores were found to be statistically significant. Although both subgroups had clinically significant olfactory improvements, only the Draf 2 cohort experienced a statistically significant improvement in olfaction at long-term follow-up. There was no statistically significant change in data from 6 to 9 weeks to 12 to 24 weeks postoperatively.

CONCLUSIONS

Patients undergoing total ethmoidectomy with FS demonstrated statistically significant increases in olfaction and QOL at long-term postoperative follow-up. This study demonstrated that FS does not negatively impact the olfactory improvement seen in sinus surgery. The lack of statistically significant changes in these olfactory metrics from short to long-term follow-up suggests that there is no additional negative effect of FSS in the long term.

LEVEL OF EVIDENCE

3 Laryngoscope, 2021.

The clinical course and diagnostic relevance of olfactory loss in a SARS-CoV-2 infection

Background: The acute onset of olfactory and/or gustatory dysfunction is a frequent complaint during the COVID-19 pandemic. It is predominantly reported by subjects with asymptomatic to mild disease severity during the early stage of the infection. The high prevalence of anosmia/dysosmia and/or ageusia/dysgeusia in this current era implements a strong correlation with a SARSCoV-2 infection and these symptoms could therefore be seen as important prodromes. The purpose of this study was to outline the occurrence, epidemiology and clinical course of olfactory and/or gustatory disorders in (suspected) COVID-19 cases and to analyse the diagnostic significance of these neurosensory dysfunctions. Methods: An online questionnaire was carried out which addressed 500 participants with new onset olfactory and/or gustatory impairment during the COVID-19 pandemic. Results: Acute olfactory and gustatory loss was reported by 487 (97.4%) and 464 (92.8%), respectively. A significant higher prevalence of neurosensory complaints was reported by women and people of younger age. The most prevalent concurrent symptoms were fatigue, headaches, nasal congestion, dry cough, rhinorrhoea and sneezing. The recovery rate after 8 weeks was 41.9% for olfactory impairment and 53.7% for gustatory impairment. Among the 93 subjects tested, 82 (88.2%) tested positive for SARSCoV-2. Conclusion: Olfactory and/or gustatory disorders are prevalent clinical findings during the COVID-19 pandemic. Neurosensory impairments, isolated or in association with other mild complaints, need to be addressed as potential symptoms of a SARS-CoV-2 infection and should be implemented as clinical markers.

Evaluation of the Incidence of Other Cranial Neuropathies in Patients With Postviral Olfactory Loss

Importance

Postviral olfactory loss is a common cause of olfactory impairment, affecting both quality of life as well as overall patient mortality. It is currently unclear why some patients are able to recover fully after a loss while others experience permanent deficit. There is a lack of research on the possible association between postviral olfactory loss and other cranial neuropathies.

Objective

To evaluate the incidence of other cranial nerve deficits in patients with postviral olfactory loss and determine if there is an association with neurologic injury in this group. This study also sought to determine if other known risk factors were associated with postviral olfactory loss.

Design, Setting, and Participants

A case-control study was conducted at a tertiary care rhinology clinic from January 2015 to January 2018 to review the incidence of cranial neuropathies in 2 groups of patients, those with postviral olfactory loss and those with chronic rhinosinusitis without olfactory loss used as a control group.

Exposures

The Stanford Translational Research Integrated Database Environment (STRIDE) system was used for patient identification and data extraction. Patients with a history of olfactory loss or chronic rhinosinusitis as well as incidence of cranial neuropathies were identified by using International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) codes.

Main Outcomes and Measures

This study reviewed incidence of postviral or idiopathic cranial neuropathies in both patient groups, while also evaluating for any difference in demographic characteristics, comorbidities, or other patient-related factors.

Results

There were 91 patients in the postviral olfactory loss group and 100 patients in the control group, which were age and sex matched as closely as possible. Of the 91 patients with postviral olfactory loss, mean (SD) age was 56.8 (15.3), and 58 (64%) were women; for the control group, the mean (SD) age was 57.5 (15.6) years, and 63 (63%) were women. Racial breakdown was similar across cases and controls, with white individuals making up 59% to 65%; Asian individuals, 20% to 24%; black individuals, approximately 3%; Hispanic individuals, approximately 1%; and the remaining patients being of other race/ethnicity. The incidence of other cranial neuropathies in the postviral olfactory loss group was 11% compared with 2% within the control group (odds ratio, 6.1; 95% CI, 1.3-28.4). The study also found 2 cases of multiple cranial neuropathies within a single patient within the olfactory group. Family history of neurologic disease was associated with more than 2-fold greater odds of cranial nerve deficit (odds ratio, 3.05; 95% CI, 0.59-15.68).

Conclusions and Relevance

Postviral olfactory loss appears to be associated with a higher incidence of other cranial neuropathies. It is possible that there is an inherent vulnerability to nerve damage or decreased ability for nerve recovery in patients who experience this disease process.

An overview of smell and taste problems in paediatric COVID-19 patients

At the start of the COVID‐19 pandemic in March 2020, fever and respiratory symptoms were the indications for virus testing in our hospital. As data have continued to accumulate worldwide, gastrointestinal, neurological, cardiovascular, cutaneous and ocular symptoms have been reported for confirmed COVID‐19 cases. There have been few case reports on problems with taste and smell in paediatric COVID‐19. However, new symptoms can provide diagnostic and testing criteria for patients with no other clinical presentation, especially in older children.

The Importance of Considering Olfactory Dysfunction During the COVID-19 Pandemic and in Clinical Practice

The emergence of a worldwide pandemic due to coronavirus disease 2019 (COVID-19) and frequent reports of smell loss in COVID-19-infected patients have brought new attention to this very important sense. Data are emerging that smell impairment is a prominent symptom in COVID-19 and that this coronavirus behaves differently in causing olfactory dysfunction compared with other respiratory viruses. Anosmia and hyposmia, the complete and partial loss of smell, respectively, can result from many causes, most commonly from viral infections, sinonasal disease, and head trauma. Olfactory dysfunction negatively impacts quality of life, because sense of smell is important for flavor perception and the enjoyment of food. Olfaction is also important for the detection of warning smells, such as smoke, natural gas leaks, and spoiled food. Allergists and immunologists frequently encounter anosmia and hyposmia in patients with severe chronic rhinosinusitis with nasal polyps, and will likely see more infection-induced olfactory dysfunction in the era of COVID-19. Therefore, now more than ever, it is crucial that we understand this impairment, how to evaluate and how to measure it. In this review, we offer a clinically relevant primer for the allergist and immunologist on olfactory dysfunction subtypes, exploring the pathophysiology, appropriate clinical assessment, objective smell testing, and management of this condition. We will also focus on the emerging literature on COVID-19 olfactory dysfunction, its unique features, and its important implications for this pandemic.

A comprehensive update of ICET-A Network on COVID-19 in thalassemias: what we know and where we stand

A review of the literature on COVID-19 pandemic in patients with thalassemias is presented. Globally, the prevalence of COVID-19 among  β-thalassemia patients seems to be lower than in general population; associated co-morbidities aggravated the severity of  COVID- 19, leading to a poorer prognosis, irrespective of age. A multicenter registry will enhance the understanding of COVID-19 in these patients and will lead to more evidence-based management recommendations.

Anosmia and Ageusia: Not an Uncommon Presentation of COVID-19 Infection in Children and Adolescents

Since the emergence of a cluster of viral pneumonia cases in Wuhan, Hubei Province, People's Republic of China, at the end of December 2019, caused by severe acute respiratory syndrome coronavirus (SARS-CoV-2), a novel coronavirus also known as "coronavirus disease 2019 (COVID-19)," as of 7 April 2020, more than 1,214,466 cases of COVID-19 have been reported in more than 200 countries and territories, resulting in more than 67,767 deaths. The disease was recognized by World Health Organization (WHO) as a pandemic on 11 March 2020. Published reports of adult patients with COVID-19 infection described symptoms including fever, cough, fatigue, sputum production, headache, dyspnea and diarrhea. Children usually showed milder respiratory symptoms or were asymptomatic, while loss of taste or sensation of smell were seldom reported. In this paper, we report three cases of pediatric patients with COVID-19 infection who presented with anosmia and/or ageusia.

Effect of Omega-3 Supplementation in Patients With Smell Dysfunction Following Endoscopic Sellar and Parasellar Tumor Resection: A Multicenter Prospective Randomized Controlled Trial

BACKGROUND

Endoscopic endonasal approaches pose the potential risk of olfactory loss. Loss of olfaction and potentially taste can be permanent and greatly affect patients' quality of life. Treatments for olfactory loss have had limited success. Omega-3 supplementation may be a therapeutic option with its effect on wound healing and nerve regeneration.

OBJECTIVE

To evaluate the impact on olfaction in patients treated with omega-3 supplementation following endoscopic skull base tumor resection.

METHODS

In this multi-institutional, prospective, randomized controlled trial, 110 patients with sellar or parasellar tumors undergoing endoscopic resection were randomized to nasal saline irrigations or nasal saline irrigations plus omega-3 supplementation. The University of Pennsylvania Smell Identification Test (UPSIT) was administered preoperatively and at 6 wk, 3 mo, and 6 mo postoperatively.

RESULTS

Eighty-seven patients completed all 6 mo of follow-up (41 control arm, 46 omega-3 arm). At 6 wk postoperatively, 25% of patients in both groups experienced a clinically significant loss in olfaction. At 3 and 6 mo, patients receiving omega-3 demonstrated significantly less persistent olfactory loss compared to patients without supplementation (P = .02 and P = .01, respectively). After controlling for multiple confounding variables, omega-3 supplementation was found to be protective against olfactory loss (odds ratio [OR] 0.05, 95% CI 0.003-0.81, P = .03). Tumor functionality was a significant independent predictor for olfactory loss (OR 32.7, 95% CI 1.15-929.5, P = .04).

CONCLUSION

Omega-3 supplementation appears to be protective for the olfactory system during the healing period in patients who undergo endoscopic resection of sellar and parasellar masses.

Proinflammatory Cytokines in the Olfactory Mucosa Result in COVID-19 Induced Anosmia

Studies have found increased rates of dysosmia in patients with Novel Coronavirus disease 2019 (COVID-19). However, the mechanism that causes olfactory loss is unknown. The primary objective of this study was to explore local proinflammatory cytokine levels in the olfactory epithelium in patients with COVID-19. Biopsies of the olfactory epithelium were taken from patients with confirmed COVID-19 as well as uninfected controls. Levels of tumor necrosis factor α (TNF-α) and interleukin-1-beta (IL-1β) were assessed using ELISA and compared between groups. Average TNF-α levels were significantly increased in the olfactory epithelium of the COVID-19 group compared to the control group (P < 0.05). However, no differences in IL-1β were seen between groups. Elevated levels of the proinflammatory cytokine TNF-α were seen in the olfactory epithelium in patients with COVID-19. This suggests that direct inflammation of the olfactory epithelium could play a role in the acute olfactory loss described in many patients with COVID-19.

Anosmia in COVID-19: Mechanisms and Significance

The global pandemic of coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 remains a challenge for prevention due to asymptomatic or paucisymptomatic patients. Anecdotal and preliminary evidence from multiple institutions shows that these patients present with a sudden onset of anosmia without rhinitis. We aim to review the pathophysiology of anosmia related to viral upper respiratory infections and the prognostic implications. Current evidence suggests that SARS-CoV-2-related anosmia may be a new viral syndrome specific to COVID-19 and can be mediated by intranasal inoculation of SARS-CoV-2 into the olfactory neural circuitry. The clinical course of neuroinvasion of SARS-CoV-2 is yet unclear, however an extended follow up of these patients to assess for neurological sequelae including encephalitis, cerebrovascular accidents and long-term neurodegenerative risk may be indicated.

Olfactory dysfunction in the pathophysiological continuum of dementia

Sensory capacities like smell, taste, hearing, vision decline with aging, but increasing evidence show that sensory dysfunctions are one of the early signs diagnosing the conversion from physiological to pathological brain state. Smell loss represents the best characterized sense in clinical practice and is considered as one of the first preclinical signs of Alzheimer's and Parkinson's disease, occurring a decade or more before the onset of cognitive and motor symptoms. Despite the numerous scientific reports and the adoption in clinical practice, the etiology of sensory damage as prodromal of dementia remains largely unexplored and more studies are needed to resolve the mechanisms underlying sensory network dysfunction. Although both cognitive and sensory domains are progressively affected, loss of sensory experience in early stages plays a major role in reducing the autonomy of demented people in their daily tasks or even possibly contributing to their cognitive decline. Interestingly, the chemosensory circuitry is devoid of a blood brain barrier, representing a vulnerable port of entry for neurotoxic species that can spread to the brain. Furthermore, the exposure of the olfactory system to the external environment make it more susceptible to mechanical injury and trauma, which can cause degenerative neuroinflammation. In this review, we will summarize several findings about chemosensory impairment signing the conversion from healthy to pathological brain aging and we will try to connect those observations to the promising research linking environmental influences to sporadic dementia. The scientific body of knowledge will support the use of chemosensory diagnostics in the presymptomatic stages of AD and other biomarkers with the scope of finding treatment strategies before the onset of the disease.

Small-Scale Biological and Artificial Multidimensional Sensors for 3D Sensing

A vast majority of existing sub-millimeter-scale sensors have a planar, 2D geometry as a result of conventional top-down lithographic procedures. However, 2D sensors often suffer from restricted sensing capability, allowing only partial measurements of 3D quantities. Here, nano/microscale sensors with different geometric (1D, 2D, and 3D) configurations are reviewed to introduce their advantages and limitations when sensing changes in quantities in 3D space. This Review categorizes sensors based on their geometric configuration and sensing capabilities. Among the sensors reviewed here, the 3D configuration sensors defined on polyhedral structures are especially advantageous when sensing spatially distributed 3D quantities. The nano- and microscale vertex configuration forming polyhedral structures enable full 3D spatial sensing due to orthogonally aligned sensing elements. Particularly, the cubic configuration leveraged in 3D sensors offers an array of diverse applications in the field of biosensing for micro-organisms and proteins, optical metamaterials for invisibility cloaking, 3D imaging, and low-power remote sensing of position and angular momentum for use in microbots. Here, various 3D sensors are compared to assess the advantages of their geometry and its impact on sensing mechanisms. 3D biosensors in nature are also explored to provide vital clues for the development of novel 3D sensors.