Efficacy of olfactory training in patients with olfactory loss: a systematic review and meta-analysis

Maximizing Participation in Olfactory Training in a Sample with Post-COVID-19 Olfactory Loss

PURPOSE

This study aims to highlight the feasibility of an olfactory training program entirely monitored through online media in COVID-19 patients.

METHODS

Classic olfactory training was performed with a sample with olfactory loss due COVID-19 (n = 11). Participants were engaged on a weekly video call in order to improve adherence and collect information regarding the number of correct answers and the individuals' perception of olfactory function. The olfactory status after training was compared to two groups, one composed of participants who contracted COVID-19 but did not report olfactory loss (n = 11) and a sample composed of healthy participants (n = 11).

RESULTS

The experimental group showed improvements throughout the training period (TDI score on week 0 was 20.3 (5.6) and 24.6 (4.3) for week 12, and on week 24 was 25.4 (6.2) (F = 5.115, df = 2, 20, p = 0.016), and post hoc tests showed that participants significantly improved their TDI score in W12 compared to W0 (SMD = 0.869, p = 0.041) and in W24 compared to W0 (SMD = 0.859, p = 0.041). The experimental group showed lower scores when compared with both groups, and the no OT COVID-19 group showed lower scores than the healthy control group, even though they did not report olfactory alterations.

CONCLUSIONS

Findings suggest that the strategies applied to improve adherence were successful since 100% of the sample completed the training adherence, offering a valuable framework for future olfactory training studies.

Tissue Engineering and Regenerative Medicine in the Field of Otorhinolaryngology

BACKGROUND

Otorhinolaryngology is a medical specialty that focuses on the clinical study and treatments of diseases within head and neck regions, specifically including the ear, nose, and throat (ENT), but excluding eyes and brain. These anatomical structures play significant roles in a person's daily life, including eating, speaking as well as facial appearance and expression, thus greatly impacting one's overall satisfaction and quality of life. Consequently, injuries to these regions can significantly impact a person's well-being, leading to extensive research in the field of tissue engineering and regenerative medicine over many years.

METHODS

This chapter provides an overview of the anatomical characteristics of otorhinolaryngologic tissues and explores the tissue engineering and regenerative medicine research in otology (ear), rhinology (nose), facial bone, larynx, and trachea.

RESULTS AND CONCLUSION

The integration of tissue engineering and regenerative medicine in otorhinolaryngology holds the promise of broadening the therapeutic choices for a wide range of conditions, ultimately improving quality of a patient's life.

Can immersive olfactory training serve as an alternative treatment for patients with smell dysfunction?

Objectives

Olfactory training (OT) has emerged as a first-line therapeutic approach to the management of olfactory dysfunction. Conventional OT (COT) involves the systematic home-based exposure to four distinct odors. Previous research has demonstrated that immersive OT (IOT) involving full-body exposure to dozens of distinct odors could also improve overall olfactory function. This study compared IOT and COT in terms of efficacy.

Methods

A total of 60 patients were enrolled and assigned to three groups. The IOT group (n = 25) underwent immersive exposure to 64 odors once daily in a specialized theater. COT participants (n = 17) sniffed four typical odors in a set of four jars twice daily at home. A control group (n = 18) underwent passive observation. Olfactory function was assessed before and after training.

Results

Significant improvements in composite threshold-discrimination-identification (TDI) scores were observed after training in both the IOT (mean difference = 2.5 ± 1.1. p = .030) and COT (mean difference = 4.2 ± 1.3, p = .002) groups. No changes were observed in the control group. A significantly higher proportion of patients in the COT group (41%) presented improvements of clinical importance (TDI ≥5.5) compared to the controls (p = .018). The improvements attained in the IOT group (20%) were less pronounced (p = .38).

Conclusion

While IOT did not exhibit the same efficacy as COT in restoring olfactory function, it still demonstrated promising outcomes. Future efforts to advance olfactory recovery should focus on cross-modal integration.

Level of Evidence

Level 3.

Effect of Olfactory Rehabilitation on the Recovery of Post-Coronavirus Disease Olfactory Dysfunction: A Randomized Controlled Trial

Introduction Persistent olfactory dysfunction was seen in many patients upon coronavirus disease 2019 (COVID-19) infection recovery. However, research on its management was very limited, especially among the Southeast Asian population. Objectives We aim to investigate the role of olfactory rehabilitation and topical corticosteroids among post-COVID-19 olfactory dysfunction patients in Malaysia, and at the same time to determine factors leading to olfactory recovery post-COVID-19 infection. Methods Adult Malaysians with persistent olfactory dysfunction one month post-COVID-19 recovery were recruited. Thirty-one patients were randomly assigned into three groups with 10 patients being given olfactory training (Group 1), another 10 being given mometasone furoate nasal spray/olfactory training (Group 2), and 11 patients being assigned to the control group (Group 3). All groups were followed up for an average duration of six months. Olfactory function was evaluated by Top International Biotech Smell Identification Test (TIBSIT) scores and Olfactory Disorder Questionnaire (eODQ) prior to randomization, at three and six months after recruitment. Results The baseline characteristics of patients were similar in all groups. Generally, patients of all three groups showed a statistically significant improvement in the TIBSIT scores after six months. The TIBSIT scores for Group 2 were statistically significantly higher than the control at three months but not at six months. As for Group 1, no statistically significant differences in TIBSIT scores at both three and six months were noted when compared to control. Statistically significant improvements were seen in the eODQ scores in all three groups. Conclusion No superiority of intervention for post-COVID-19 olfactory dysfunction was seen compared to control.

Recovery rates and long-term olfactory dysfunction following COVID-19 infection

Objectives

Olfactory dysfunction is one of the most recognized symptoms of COVID-19, significantly impacting quality of life, particularly in cases where recovery is prolonged. This review aims to explore patterns of olfactory recovery post-COVID-19 infection, with particular focus on delayed recovery.

Data Sources

Published literature in the English language, including senior author's own work, online and social media platforms, and patients' anecdotal reports.

Method

A comprehensive review of the literature was undertaken by the authors with guidance from the senior author with expertise in the field of olfaction.

Results

Based on self-report, an estimated 95% of patients recover their olfactory function within 6 months post-COVID-19 infection. However, psychophysical testing detects higher rates of persistent olfactory dysfunction. Recovery has been found to continue for at least 2 years postinfection; negative prognostic indicators include severe olfactory loss in the acute phase, female sex, and older age. Variability in quantitative and qualitative disturbance in prolonged cases likely reflects both peripheral and central pathophysiological mechanisms. Limitations of many of the reviewed studies reflect lack of psychophysical testing and baseline olfactory assessment.

Conclusions

Post-COVID-19 olfactory dysfunction remains a significant health and psychosocial burden. Emerging evidence is improving awareness and knowledge among clinicians to better support patients through their olfactory rehabilitation, with hope of recovery after several months or years. Further research is needed to better understand the underlying pathogenesis of delayed recovery, identify at risk individuals earlier in the disease course, and develop therapeutic targets.

The efficacy of olfactory training in improving olfactory function: a meta-analysis

PURPOSE

Study the efficacy of olfactory training in smell recovery.

METHODS

An extensive search was performed through different databases in order to find articles analyzing the efficacy of olfactory training as a treatment for olfactory dysfunction. Methodological quality of primary studies within the final sample was assessed following PRISMA guidelines. Standardized mean differences in pre-post olfactory training groups, and also in experimental-control and pre-follow up if possible, were computed by Hedges' g effect size statistic. Each effect size was weighted by its inverse variance.

RESULTS

Final sample was composed of 36 articles (45 pre-post effect sizes). Contrasts were performed separately for odor identification, odor discrimination, odor threshold and general olfactory function. Moderate to large and heterogeneous effect was obtained for olfactory function (g = 0.755, k = 45, SE = 0.093, CI 95% = [0.572, 0.937]), different moderators had a significant effects, such as, training duration, age and anosmia diagnosis.

CONCLUSION

Olfactory training was found to have a positive and significant effect on rehabilitating the olfactory function.

Comparison of the incidence of smell and taste disorders between influenza and COVID-19

OBJECTIVE

Smell and taste disorders among patients with COVID-19 has become increasingly reported in the literature, however the prevalence varies. Post-infectious respiratory dysfunction has also been linked to influenza. In this study, we aimed to compare the rates of smell and taste disorders between COVID-19 and Influenza in unvaccinated patients.

STUDY DESIGN

Retrospective cohort study.

SETTING

TriNetX research network.

METHODS

Two queries were made on 7/1/2023 to include Influenza without a diagnosis of COVID-19 and a COVID-19 without a diagnosis of Influenza. The queries included patients from January 1 to December 31, 2022 from 102 Healthcare Organizations. The resultant population of patients with ICD-10 codes for COVID-19 and Influenza were matched using demographic characteristics to evaluate the risk of smell disorders.

RESULTS

The overall 3-month incidence of smell and taste disorders was 0.73 % in the COVID-19 population and 0.1 % in the influenza population. The 3-month matched risk ratios were 11.1 [95 % CI (8.8,13.8)]; p < 0.001) times higher for disorders of the smell and taste secondary to COVID-19 compared to influenza.

CONCLUSIONS

Disorders of the smell and taste are more common among patients with COVID-19 compared to patients with Influenza. Beyond smell loss, patients experience additional nasal and sinus-related rhinological symptoms, pointing to COVID-19's and influenza's wider impact on overall rhinological health. We believe that due to the transient nature of these disorders, they might go underreported.

A Cross-Sectional Evaluation of Publication Bias in the Plastic Surgery Literature

BACKGROUND

Publication bias (PB) is the preferential publishing of studies with statistically significant results. PB can skew findings of systematic reviews (SRs) and meta-analyses (MAs), with potential consequences for patient care and health policy. This study aims to determine the extent to which SRs and MAs in the plastic surgery literature evaluate and report PB.

METHODS

This cross-sectional study assessed PB reporting and analysis from plastic surgery studies published between January 1, 2015, and June 19, 2020. Full texts of SRs and MAs were assessed by two reviewers for PB assessment methodology and analysis. Post hoc assessment of studies that did not originally analyze PB was performed using Egger regression, Duval, Tweedie trim-and-fill, and Copas selection models.

RESULTS

There were 549 studies evaluated, of which 531 full texts were included. PB was discussed by 183 studies (34.5%), and formally assessed by 97 studies (18.3%). Among SRs and MAs that formally assessed PB, PB was present in 24 studies (10.7%), not present in 52 (23.1%), and inconclusive in eight (3.6%); 141 studies (62.7%) did not report the results of their PB assessment. Funnel plots were the most common assessment method [ n = 88 (39.1%)], and 60 studies (68.2%) published funnel plots. The post hoc assessment revealed PB in 17 of 20 studies (85.0%).

CONCLUSIONS

PB is inadequately reported and analyzed among studies in the plastic surgery literature. Most studies that assessed PB found PB, as did post hoc analysis of nonreporting studies. Increased assessment and reporting of PB among SRs and MAs would improve the quality of evidence in plastic surgery.

Reduced olfactory performance is associated with changed microbial diversity, oralization, and accumulation of dead biomaterial in the nasal olfactory area

The partial or complete loss of the sense of smell, which affects about 20% of the population, impairs the quality of life in many ways. Dysosmia and anosmia are mainly caused by aging, trauma, infections, or even neurodegenerative disease. Recently, the olfactory area-a site containing the olfactory receptor cells responsible for odor perception-was shown to harbor a complex microbiome that reflects the state of olfactory function. This initially observed correlation between microbiome composition and olfactory performance needed to be confirmed using a larger study cohort and additional analyses. A total of 120 participants (middle-aged, no neurodegenerative disease) were enrolled in the study to further analyze the microbial role in human olfactory function. Olfactory performance was assessed using the Sniffin' Stick battery, and participants were grouped accordingly (normosmia: n = 93, dysosmia: n = 27). The olfactory microbiome was analyzed by 16S rRNA gene amplicon sequencing and supplemented by metatranscriptomics in a subset (Nose 2.0). Propidium monoazide (PMA) treatment was performed to distinguish between intact and non-intact microbiome components. The gastrointestinal microbiome of these participants was also characterized by amplicon sequencing and metabolomics and then correlated with food intake. Our results confirm that normosmics and dysosmics indeed possess a distinguishable olfactory microbiome. Alpha diversity (i.e., richness) was significantly increased in dysosmics, reflected by an increase in the number of specific taxa (e.g., Rickettsia, Spiroplasma, and Brachybacterium). Lower olfactory performance was associated with microbial signatures from the oral cavity and periodontitis (Fusobacterium, Porphyromonas, and Selenomonas). However, PMA treatment revealed a higher accumulation of dead microbial material in dysosmic subjects. The gastrointestinal microbiome partially overlapped with the nasal microbiome but did not show substantial variation with respect to olfactory performance, although the diet of dysosmic individuals was shifted toward a higher meat intake. Dysosmia is associated with a higher burden of dead microbial material in the olfactory area, indicating an impaired clearance mechanism. As the microbial community of dysosmics (hyposmics and anosmics) appears to be influenced by the oral microbiome, further studies should investigate the microbial oral-nasal interplay in individuals with partial or complete olfactory loss.IMPORTANCEThe loss of the sense of smell is an incisive event that is becoming increasingly common in today's world due to infections such as COVID-19. Although this loss usually recovers a few weeks after infection, in some cases, it becomes permanent-why is yet to be answered. Since this condition often represents a psychological burden in the long term, there is a need for therapeutic approaches. However, treatment options are limited or even not existing. Understanding the role of the microbiome in the impairment of olfaction may enable the prediction of olfactory disorders and/or could serve as a possible target for therapeutic interventions.

Effectiveness of platelet-rich plasma on post-COVID chronic olfactory dysfunction

OBJECTIVE

The aim of this study was to investigate the efficacy of platelet-rich plasma injection on the olfactory cleft of patients with post-COVID olfactory dysfunction lasting over 1 year, who were unresponsive to common treatments.

METHODS

Patients over 18 years of age with post-COVID olfactory dysfunction over 1 year whose complaints did not improve with intranasal steroids and D-panthenol/vitamin A combination nasal sprays with olfactory rehabilitation training for 1 month were prospectively collected and randomized into two groups: intranasal platelet-rich plasma group and control group. At the end of 1 month, Connecticut Chemosensory Clinical Research Center olfaction test scores of smell detection threshold and smell identification test were compared accordingly.

RESULTS

A total of 25 patients were randomized into platelet-rich plasma (n=12) and control (n=13) groups. In the platelet-rich plasma group, the mean smell detection threshold score increased from 5.63 (SD 0.68) to 6.46 (SD 0.45), and the mean smell identification test score increased from 11.42 (SD 1.17) to 15.17 (SD 0.39). In the control group, the mean smell detection threshold score changed from 5.69 (SD 0.66) to 5.77 (SD 0.70), and the mean smell identification test score changed from 11.20 (SD 1.12) to 11.85 (SD 1.57). Post-hoc analysis revealed that similar mean smell detection threshold (mean difference 0.07; p=0.994) and smell identification test (mean difference -0.50; p=0.703) scores were transformed into a significant difference between groups (smell detection threshold mean difference 0.69; p=0.037; smell identification test mean difference 3.32; p<0.001).

CONCLUSION

At the end of the first month, there was a significant improvement in olfactory threshold values in the platelet-rich plasma group compared to the control group. No side effect or adverse event related to platelet-rich plasma injection was observed.

Hyposmia and apathy in early, de novo Parkinson's disease: Lessons from structural brain connectivity

INTRODUCTION

The neuroanatomical structures implicated in olfactory and emotional processing overlap significantly. Our understanding of the relationship between hyposmia and apathy, common manifestations of early Parkinson's disease (PD), is inadequate.

MATERIALS AND METHODS

We analyzed data on 40 patients with early de-novo idiopathic PD enrolled within 2 years of motor symptom onset in the Parkinson's Progression Markers Initiative (PPMI) study. To be included in the analysis, patients must have smell dysfunction but no apathy at the baseline visit and had completed a diffusion MRI (dMRI) at the baseline visit and at the 48-month follow-up visit. We used the FMRIB Software Library's diffusion tool kit to measure fractional anisotropy (FA) in six regions of interest on dMRI: bilateral anterior corona radiata, left cingulum, left superior corona radiata, genu and body of the corpus callosum. We compared the FA in each region from the dMRI done at the beginning of the study with the follow up studies at 4 years.

RESULTS

We found a significant decrease of FA at the bilateral anterior corona radiata, and the genu and body of the corpus callosum comparing baseline scans with follow up images at 4-years after starting the study.

CONCLUSION

Structural connectivity changes associated with apathy can be seen early in PD patients with smell dysfunction.

Vitamin D and smell impairment: a systematic literature review

OBJECTIVE

Smell impairment affects 60-80 per cent of individuals aged over 80 years. This review aimed to identify any association between vitamin D deficiency and smell impairment, and determine the efficacy of vitamin D to treat smell impairment.

METHODS

A literature search was conducted across four databases between the years 2000 and 2022. The literature screen was performed by two independent reviewers.

RESULTS

Seven articles were included in this review. Four studies examined the association between vitamin D deficiency and smell impairment, with three studies identifying a significant relationship. Three studies investigated the use of vitamin D as treatment for smell impairment, which found complete resolution or significant symptom improvement after vitamin D deficiency was treated.

CONCLUSION

This review identified limited studies on this topic. As vitamin D supplementation is relatively cost-efficient, further large-scale studies should be carried out to investigate the efficacy of vitamin D for treating anosmia.

Olfactory dysfunction incidence and resolution amongst 608 patients with COVID-19 infection

PURPOSE

Olfactory dysfunction (OD) is a common presenting sign of coronavirus-19 (COVID-19) infection and remains persistent in up to 7 % of patients one year after diagnosis. However, demographic, socioeconomic, and medical risk factors for persistent OD are not well understood. This study aims to determine risk factors for development and persistence of OD amongst patients with COVID-19 infection.

MATERIALS AND METHODS

This prospective, observational questionnaire study was performed at a tertiary-level, academic center. Patients with history of a positive COVID-19 diagnosis were sent an online questionnaire. Patients' self-reported survey responses for OD and resolution were assessed for associations with demographic variables, socioeconomic factors, and clinical data.

RESULTS

In total, 608 of 26,094 patients (77.6 % women, mean age 42.7 ± 17.4 years, range 9 months-92 years) completed the survey. OD was reported by 220 (36.2 %) patients, and 139 (63.2 %) patients achieved resolution. Patients with OD were more likely to have other sinonasal and flu-like symptoms, and had a hospitalization rate of 2.7 %. There were no significant differences in age, gender, occupational or residential factors, or medical comorbidities incidence of OD development. Women reported higher rates of persistent OD (88.9 % vs 77.0 %, p = 0.045). The OD recovery rates amongst active and resolved COVID-19 infections was 27.0 % and 70.0 %, respectively (p < 0.001).

CONCLUSIONS

There was a low hospitalization rate amongst patients reporting OD. One-third of patients with COVID-19 self-reported OD, and two-thirds of patients achieve OD resolution. Survey respondents with active COVID-19 infection and female gender were more likely to report persistent OD.

Assessment of COVID-19-related olfactory dysfunction and its association with psychological, neuropsychiatric, and cognitive symptoms

Purpose of review

To provide a detailed overview of the assessment of COVID-19-related olfactory dysfunction and its association with psychological, neuropsychiatric, and cognitive symptoms.

Recent findings

COVID-19-related olfactory dysfunction can have a detrimental impact to the quality of life of patients. Prior to the COVID-19 pandemic, olfactory and taste disorders were a common but under-rated, under-researched and under-treated sensory loss. The pandemic has exacerbated the current unmet need for accessing good healthcare for patients living with olfactory disorders and other symptoms secondary to COVID-19. This review thus explores the associations that COVID-19 has with psychological, neuropsychiatric, and cognitive symptoms, and provide a framework and rationale for the assessment of patients presenting with COVID-19 olfactory dysfunction.

Summary

Acute COVID-19 infection and long COVID is not solely a disease of the respiratory and vascular systems. These two conditions have strong associations with psychological, neuropsychiatric, and cognitive symptoms. A systematic approach with history taking and examination particularly with nasal endoscopy can determine the impact that this has on the patient. Specific olfactory disorder questionnaires can demonstrate the impact on quality of life, while psychophysical testing can objectively assess and monitor olfaction over time. The role of cross-sectional imaging is not yet described for COVID-19-related olfactory dysfunction. Management options are limited to conservative adjunctive measures, with some medical therapies described.

Olfactory Dysfunction following COVID-19 and the Potential Benefits of Olfactory Training

COVID-19 is associated with a common symptom of olfactory dysfunction, which may persist even after the infection is resolved. Olfactory training (OT) has emerged as the most effective intervention for post-viral olfactory dysfunction. OT involves daily exposure of the olfactory system to various odors. The current study aims to explore olfactory dysfunction following COVID-19 and the potential benefits of olfactory training.

METHODS

This is a cross-sectional study conducted among adults aged 18-60 living in Alahssa, Saudi Arabia. An online questionnaire containing an informed consent form and a survey to collect demographic data, vaccination status, level of loss of smell and taste, and the level of awareness about olfactory training (OT) was distributed among all participants who agreed to participate in this study.

RESULTS

The study included 524 participants and presented their baseline characteristics, including age, gender, COVID-19 infection status, and complaints. Most patients were female (66.0%), and 46.2% had previously been infected with COVID-19. About 54.8% of participants reported chemosensory dysfunction, while 286 had olfactory dysfunction. Of those, 29.8% had anosmia, 16.8% had hyposmia, and 8.0% had parosmia. Results suggest that being fully or partially vaccinated may offer some protection against olfactory dysfunction compared to being unvaccinated. Adherence to olfactory training was associated with improvement in the sense of smell.

CONCLUSIONS

The study highlights the importance of awareness and adherence to olfactory training, which may improve the sense of smell in individuals with chemosensory dysfunction. The findings of this study can inform public health policies and interventions aimed at reducing the burden of olfactory dysfunction associated with COVID-19 vaccination.

Post-traumatic olfactory dysfunction: a scoping review of assessment and rehabilitation approaches

Post-traumatic Olfactory Dysfunction (PTOD) consists of a complete or partial loss of olfactory function that may occur after a traumatic brain injury (TBI). PTOD may be linked to some neuropsychiatric features, such as social, cognitive and executive dysfunction, as well as behavioral symptoms, especially when TBI involves the orbito-frontal cortex. The diagnosis of PTOD is based on medical history and clinical data and it is supported by psychometric tests (i.e., subjective tools) as well as electrophysiological and neuroimaging measures (i.e., objective methods). The assessment methods allow monitoring the changes in olfactory function over time and help to establish the right therapeutic and rehabilitative approach. In this context, the use of the olfactory training (OT), which is a non-pharmacological and non-invasive treatment option, could promote olfactory function through top-down (central) and bottom-up (peripheral) processes. To better manage patients with TBI, PTOD should be detected early and properly treated using the various therapeutic rehabilitative possibilities, both conventional and advanced, also taking into consideration the emerging neuromodulation approach.

The Association of Peripheral and Central Olfaction With Frailty in Older Adults

BACKGROUND

Olfactory impairment is increasingly recognized as a biomarker of frailty, but the relationship between olfactory subdomains that describe peripheral or central dysfunction and frailty remains unexplored.

METHODS

We examined 1 160 older adults from the National Social Life, Health, and Aging Project Wave 3. Olfactory identification (OI): the ability to identify an odorant; and olfactory sensitivity (OS): the ability to detect the presence of an odorant, were assessed using 5- and 6-point measures, respectively. Frailty was operationalized as both a 37-item frailty index (FI) and the 5-item Physical Frailty Phenotype (PFP). Mixed models were fit to examine the association between OI, OS, FI, and PFP, while adjusting for demographic and clinical covariates.

RESULTS

Participants in the most-frail PFP category had lower OI and OS scores (OI: 3.88 vs 4.19, p = .016; OS: 3.15 vs 3.47, p = .031), whereas participants in the most-frail FI category exhibited lower OI scores but not OS scores when compared to nonfrail participants (OI: 3.72 vs 4.27, p = .014; OS: 3.19 vs 3.43, p = .476). Adjusted mixed models showed that a point increase in OI was associated with a lower PFP score (β = -0.107, p = .006) and FI score (β = -0.009, p = .010). A point increase in OS was associated with a lower PFP score (β = -0.058, p = .016) but not FI score (β = -0.004, p = .064).

CONCLUSION

Both OS and OI, predominantly peripheral and central measures of olfaction, respectively, are associated with frailty implicating olfaction as a potential biomarker and risk factor for frailty.

An olfactory-based Brain-Computer Interface: electroencephalography changes during odor perception and discrimination

Brain-Computer Interfaces (BCIs) are devices designed for establishing communication between the central nervous system and a computer. The communication can occur through different sensory modalities, and most commonly visual and auditory modalities are used. Here we propose that BCIs can be expanded by the incorporation of olfaction and discuss the potential applications of such olfactory BCIs. To substantiate this idea, we present results from two olfactory tasks: one that required attentive perception of odors without any overt report, and the second one where participants discriminated consecutively presented odors. In these experiments, EEG recordings were conducted in healthy participants while they performed the tasks guided by computer-generated verbal instructions. We emphasize the importance of relating EEG modulations to the breath cycle to improve the performance of an olfactory-based BCI. Furthermore, theta-activity could be used for olfactory-BCI decoding. In our experiments, we observed modulations of theta activity over the frontal EEG leads approximately 2 s after the inhalation of an odor. Overall, frontal theta rhythms and other types of EEG activity could be incorporated in the olfactory-based BCIs which utilize odors either as inputs or outputs. These BCIs could improve olfactory training required for conditions like anosmia and hyposmia, and mild cognitive impairment.

The use of Platelet rich Plasma in COVID-19 Induced Olfactory Dysfunction: Systematic Review

PURPOSE

Different modalities of treatment have been suggested in the treatment for post COVID-19 olfactory dysfunction (OD). Starting with lifestyle modification, smoking cessation, for example, was shown to improve the symptoms for patients with OD. Intranasal and oral corticosteroids have been described in the literature for the treatment of OD. In this review, we are looking at a novel intervention using platelet-rich plasma injection into the nasal cleft for treatment of post COVID-19 infection olfactory dysfunction.

METHODS

A literature search was done using the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) 2020 Guidelines, the databases of PMC, Medline, CINAHL, Wiley online library were searched from their year of inception until February 2023. Search terms were used and included a combination of the following keywords; "platelet-rich plasma", "platelet rich plasma", "PRP", "Anosmia", "olfactory dysfunction" and "COVID".

RESULTS

The four studies in this review included a total of 238 adult patients who presented with olfactory dysfunction. The studies were heterogenic in terms of follow up period which was not long enough through all the included studies. Additionally, different protocol of injecting was seen in different studies.

CONCLUSION

Injecting PRP for treatment of COVID-19 induced olfactory dysfunction is a safe technique with what seems like promising initial results with low complication rate. However, there are not enough studies assessing its effectiveness compared to other treatment modalities. Further randomized controlled trials with shared protocol are needed to establish further understanding of its role in treatment of COVID-19 induced OD.

Comparable responses to a wide range of olfactory stimulation in women and men

The evidence for differences between women and men in terms of olfactory abilities is contradictory. We analyzed women and men's performance and reactions to a wider range of odour exposure outcomes than usually studied, to assess possible differences and similarities between sexes. Measures of sensitivity and sensory decision rule were established in 37 women and 39 men. Perceptual, cognitive, symptom-related and autonomic nervous system (skin conductance level and heart-rate variability) reactions were also assessed during extended ambient odour exposure, as well as participants' self-rated chemical intolerance. Bayesian analyses consistently revealed greater support for sex-related similarities than differences, suggesting that women and men perform and react comparably not only in terms of basic olfactory measures, but also to environmental odour exposure mimicking everyday situations.

Olfactory Function and Olfactory Disorders

The sense of smell is important. This became especially clear to patients with infection-related olfactory loss during the SARS-CoV-2 pandemic. We react, for example, to the body odors of other humans. The sense of smell warns us of danger, and it allows us to perceive flavors when eating and drinking. In essence, this means quality of life. Therefore, anosmia must be taken seriously. Although olfactory receptor neurons are characterized by regenerative capacity, anosmia is relatively common with about 5 % of anosmic people in the general population. Olfactory disorders are classified according to their causes (e. g., infections of the upper respiratory tract, traumatic brain injury, chronic rhinosinusitis, age) with the resulting different therapeutic options and prognoses. Thorough history taking is therefore important. A wide variety of tools are available for diagnosis, ranging from short screening tests and detailed multidimensional test procedures to electrophysiological and imaging methods. Thus, quantitative olfactory disorders are easily assessable and traceable. For qualitative olfactory disorders such as parosmia, however, no objectifying diagnostic procedures are currently available. Therapeutic options for olfactory disorders are limited. Nevertheless, there are effective options consisting of olfactory training as well as various additive drug therapies. The consultation and the competent discussion with the patients are of major importance.

A Review on the Nasal Microbiome and Various Disease Conditions for Newer Approaches to Treatments

Introduction: Commensal bacteria have always played a significant role in the maintenance of health and disease but are being unravelled only recently. Studies suggest that the nasal microbiome has a significant role in the development of various disease conditions. Search engines were used for searching articles having a nasal microbiome and disease correlation. In olfactory dysfunction, dysbiosis of the microbiome may have a significant role to play in the pathogenesis. The nasal microbiome influences the phenotype of CRS and is also capable of modulating the immune response and plays a role in polyp formation. Microbiome dysbiosis has a pivotal role in the development of Allergic Rhinitis; but, yet known how is this role played. The nasal microbiome has a close association with the severity and phenotype of asthma. They contribute significantly to the onset, severity, and development of asthma. The nasal microbiome has a significant impact on the immunity and protection of its host. The nasal microbiome has been a stimulus in the development of Otitis Media and its manifestations. Studies suggest that the resident nasal microbiome is responsible for the initiation of neurodegenerative diseases like Parkinson's Disease.Materials and Methods: Literature search from PubMed, Medline, and Google with the Mesh terms: nasal microbiome AND diseases. Conclusion: With increasing evidence on the role of the nasal microbiome on various diseases, it would be interesting to see how this microbiome can be modulated by pro/pre/post biotics to prevent a disease or the severity of illness.

Liu D, A. Müller C, A. Stuck B, Welge-Lüssen A, Hähner A. Olfactory Dysfunction: Etiology, Diagnosis, and Treatment

BACKGROUND

Disorders of the sense of smell have received greater attention because of the frequency with which they occur as a symptom of SARS-CoV-2 infection. Olfactory dysfunction can lead to profound reduction in quality of life and may arise from many different causes.

METHODS

A selective literature review was conducted with consideration of the current version of the guideline issued by the Association of the Scientific Medical Societies in Germany.

RESULTS

The cornerstones of diagnosis are the relevant medical history and psychophysical testing of olfactory function using standardized validated tests. Modern treatment strategies are oriented on the cause of the dysfunction. While treatment of the underlying inflammation takes precedence in patients with sinunasal dysosmia, olfactory training is the primary treatment option for other forms of the disorder. The prognosis is determined not only by the cause of the olfactory dysfunction and the patient's age, but also by the olfactory performance as measured at the time of diagnosis.

CONCLUSION

Options for the treatment of olfactory dysfunction are available but limited, depending on the cause. It is therefore important to carry out a detailed diagnostic work-up and keep the patient informed of the expected course and prognosis.

Late onset and persistent parosmia and dysgeusia as neurosensorial complication by the SARS virus COV 2

About the neurological manifestations of COVID-19, smell impairment with some distortion or parosmia is currently one of the longest-lasting post-covid sequelae affecting many young adults around the world, we present a case of a 25yo patient that after the COVID-19 infection initiates with anosmia and dysgeusia of difficult control and some weeks later begins with parosmia associated to general discomfort and vomiting preceded by nausea, accompanied by poor oral intake, generating weight loss in 3 weeks, and depression probably related to the clinical profile and the confinement due to the pandemic. She was treated with prednisone, gabapentin, nasal irrigations and olfactory rehabilitation, with mild improvement, which was greater after the second dose of covid-19 vaccine.

Effects of classical olfactory training in patients with COVID-19-related persistent loss of smell

PURPOSE

The management of post-COVID-19 persistent olfactory dysfunction (OD) is uncertain. Currently, olfactory training is the only evidence-based therapy for post-viral OD. In this study, we evaluated the effectiveness of classical olfactory training (COT) in the treatment of post-COVID-19 persistent OD.

MATERIALS AND METHODS

Patients with persistent OD after COVID-19 were assessed using the Sniffin' Sticks test. Fifty-one patients were then divided into two groups based on personal preference: the COT group (n = 31) included subjects who performed COT over 12 weeks, and the control group (n = 20) included subjects who did not receive any treatment. After the exclusion of eight patients, the olfactory performances of 43 patients were re-evaluated and compared to the baseline values.

RESULTS

A significantly higher proportion of patients in the COT group improved their olfactory scores above the clinically important difference compared to the control group (40% versus 6%) (p = 0.014). The subjective smell improvement by COT was independent of age, gender, OD duration, presence of parosmia, or the initial olfactory score (all p > 0.05).

CONCLUSION

Twelve weeks of COT appears to increase the olfactory sensitivity in patients with persistent OD following COVID-19.

Olfaction in (Social) Context: The Role of Social Complexity in Trajectories of Older Adults' Olfactory Abilities

Objectives: Olfaction is an important correlate of later-life health, including cognition and mortality risk. Environmental enrichment protects against olfactory decline, yet little research considers the social context as a source of sensory enrichment or stimulation. This study examines how exposure to social complexity (i.e., diversity or novelty in social networks and activities) shapes later-life olfaction. Methods: Cross-sectional and longitudinal ordered logit models analyze data from 1,447 older adults interviewed at Rounds 1 and 2 of the National Social Life, Health, and Aging Project. Results: Exposure to greater social complexity (larger social networks, greater network diversity) is associated with significantly better olfaction at baseline. Increases in network diversity and fewer network losses significantly protect against olfactory decline over time. Discussion: Findings highlight the social context as an important, yet relatively overlooked source of sensory enrichment, and underscore the need for biological applications to integrate social life dynamics into studies of health trajectories.

Long-term Consequences of COVID-19: Chemosensory Disorders

PURPOSE OF REVIEW

A number of sequelae after acute coronavirus disease 2019 (COVID-19) significantly affect the quality of life of patients. The chemosensory disorders including olfactory dysfunction (OD) and gustatory dysfunction (GD) are two of the commonest symptoms complained by patients with COVID-19. Although chemosensory function has been reported improved in over 60% of COVID-19 patients in a short time after acute infection, it may last as a major symptom for patients with long COVID-19. This narrative review discussed current literatures on OD and GD in long COVID-19 including the prevalence, risk factors, possible mechanisms, and potential therapies.

RECENT FINDINGS

Although the prevalence of OD and GD has declined continuously after acute COVID-19, a considerable number of patients had persistent chemosensory disorders 3 months to 2 years after symptom onset. Female gender, initial severity of dysfunction, nasal congestion, emotional distress and depression, and SARS-CoV-2 variants have been identified as risk factors for persistent OD and GD in long COVID-19. The pathogenesis of OD and GD in long COVID-19 remains unknown, but may be analogous to the persistent OD and GD post common respiratory viral infection. Corticosteroids and olfactory training might be a potential choice regarding the treatment of lasting OD and GD after SARS-CoV-2 infection; however, more studies are needed to prove it. OD and GD are common long-term consequences of COVID-19 and influenced by gender, initial severity of dysfunction, emotional distress and depression, and SARS-CoV-2 variants. More studies are needed to illustrate their pathogenesis and to establish therapeutic strategies.

Study on a Flexible Odor-Releasing Device for Olfactory Training

Olfactory training has been shown to be effective in treating olfactory dysfunction. However, there are hardly any devices that can regularly and quantificationally release odors for olfactory training. A new odor-releasing device, which is low-cost, customizable, semi-automatic, and flexible, was developed in this study. The operation of the device can be easily achieved by the examiner, or even by the participant, simply by pressing a few buttons. A controller system with 15 individual relays was employed to master the working logic for the whole process. The device allows the examiner to isolate from the participants using the Bluetooth module in the control board. The odorants and their concentrations stored in the scent bottles can be customized by the specific requirements of different participants. The odors for training are provided by ultrasonic atomizers, which have simple structures, but powerful features. The flow rates of the odors can also be controlled by altering the rotation speed of the fans. Final experiments on practical odor generation further proved the potential of the developed device for olfactory training. More attention should be paid to the improvements of odor generation devices for olfactory training.

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.

Olfactory training - Thirteen years of research reviewed

The sense of smell is interrelated with psychosocial functioning. Olfactory disorders often decrease quality of life but treatment options for people with olfactory loss are limited. Additionally, olfactory loss accompanies and precedes psychiatric and neurodegenerative diseases. Regular, systematic exposure to a set of odors, i.e., olfactory training (OT) has been offered for rehabilitation of the sense of smell in clinical practice. As signals from the olfactory bulb are directly projected to the limbic system it has been also debated whether OT might benefit psychological functioning, i.e., mitigate cognitive deterioration or improve emotional processing. In this review we synthesize key findings on OT utility in the clinical practice and highlight the molecular, cellular, and neuroanatomical changes accompanying olfactory recovery in people with smell loss as well as in experimental animal models. We discuss how OT and its modifications have been used in interventions aiming to support cognitive functions and improve well-being. We delineate main methodological challenges in research on OT and suggest areas requiring further scientific attention.

COVID-19 loss of taste and smell: potential psychological repercussions

The novel coronavirus (COVID-19) has become a cause for global concern. Apart from a multitude of symptoms, the virus is known for its ability to cause loss of taste and smell that can be irreversible in a few cases. In fact, even after recovery, post-covid syndrome can still lead to devastating outcomes, specifically with reference to loss of smell and taste. A number of mechanisms that have been postulated include receptor-mediated uptake, increased inflammation, transneuronal migration, and direct damage to the olfactory pathway. Considering how important these two senses are, many psychological, social, and emotional repercussions can be expected. These repercussions include lowering of self-esteem and developmental of mental health issues. Long-term altered taste sensation can also lead to the development of unhealthy eating habits that can result in increasing risk for diabetes and hypertension. A few solutions have been investigated for treating these chemosensory dysfunctions, such as olfactory training, corticosteroids, theophylline and acupuncture. Although the results have been promising but a new modality, virtual reality, requires more in-depth exploration because it targets not only the dysfunction but also the mental health issues being experienced. It is important that affected individuals be provided with strong emotional and family support. Additionally, physicians can help the patients through support groups, cognitive behavioural therapy, olfactory, and virtual reality training.

Interventions for the treatment of persistent post-COVID-19 olfactory dysfunction

BACKGROUND

Olfactory dysfunction is a common consequence of COVID-19 infection and persistent symptoms can have a profound impact on quality of life. At present there is little guidance on how best to treat this condition. A variety of interventions have been suggested to promote recovery, including medication and olfactory training. However, it is uncertain whether any intervention is of benefit. This is an update of the 2021 review with one additional study added.  OBJECTIVES: 1) To evaluate the benefits and harms of any intervention versus no treatment for people with persisting olfactory dysfunction due to COVID-19 infection.  2) To keep the evidence up-to-date, using a living systematic review approach.  SEARCH METHODS: The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the latest search was 20 October 2021.   SELECTION CRITERIA: We included randomised controlled trials (RCTs) in people with COVID-19 related olfactory disturbance that had persisted for at least four weeks. We included any intervention compared to no treatment or placebo.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were the recovery of sense of smell, disease-related quality of life and serious adverse effects. Secondary outcomes were the change in sense of smell, general quality of life, prevalence of parosmia and other adverse effects (including nosebleeds/bloody discharge). We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included two studies with 30 participants. The studies evaluated the following interventions: systemic corticosteroids plus intranasal corticosteroid/mucolytic/decongestant and palmitoylethanolamide plus luteolin.  Systemic corticosteroids plus intranasal corticosteroid/mucolytic/decongestant compared to no intervention We included a single RCT with 18 participants who had anosmia for at least 30 days following COVID-19 infection. Participants received a 15-day course of oral corticosteroids combined with nasal irrigation (consisting of an intranasal corticosteroid/mucolytic/decongestant solution) or no intervention. Psychophysical testing was used to assess olfactory function at 40 days. This is a single, small study and for all outcomes the certainty of evidence was very low. We are unable to draw meaningful conclusions from the numerical results. Palmitoylethanolamide plus luteolin compared to no intervention We included a single RCT with 12 participants who had anosmia or hyposmia for at least 90 days following COVID-19 infection. Participants received a 30-day course of palmitoylethanolamide and luteolin or no intervention. Psychophysical testing was used to assess olfactory function at 30 days. This is a single, small study and for all outcomes the certainty of evidence was very low. We are unable to draw meaningful conclusions from the numerical results.

AUTHORS' CONCLUSIONS

There is very limited evidence available on the efficacy and harms of treatments for persistent olfactory dysfunction following COVID-19 infection. However, we have identified a number of ongoing trials in this area. As this is a living systematic review we will update the data regularly, as new results become available.

Interventions for the prevention of persistent post-COVID-19 olfactory dysfunction

BACKGROUND

Loss of olfactory function is well recognised as a symptom of COVID-19 infection, and the pandemic has resulted in a large number of individuals with abnormalities in their sense of smell. For many, the condition is temporary and resolves within two to four weeks. However, in a significant minority the symptoms persist. At present, it is not known whether early intervention with any form of treatment (such as medication or olfactory training) can promote recovery and prevent persisting olfactory disturbance. This is an update of the 2021 review with four studies added.

OBJECTIVES

1) To evaluate the benefits and harms of any intervention versus no treatment for people with acute olfactory dysfunction due to COVID-19 infection.  2) To keep the evidence up-to-date, using a living systematic review approach.  SEARCH METHODS: The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the latest search was 20 October 2021.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in people with COVID-19 related olfactory disturbance, which had been present for less than four weeks. We included any intervention compared to no treatment or placebo.  DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. Our primary outcomes were the presence of normal olfactory function, serious adverse effects and change in sense of smell. Secondary outcomes were the prevalence of parosmia, change in sense of taste, disease-related quality of life and other adverse effects (including nosebleeds/bloody discharge). We used GRADE to assess the certainty of the evidence for each outcome.  MAIN RESULTS: We included five studies with 691 participants. The studies evaluated the following interventions: intranasal corticosteroid sprays, intranasal corticosteroid drops, intranasal hypertonic saline and zinc sulphate.  Intranasal corticosteroid spray compared to no intervention/placebo We included three studies with 288 participants who had olfactory dysfunction for less than four weeks following COVID-19. Presence of normal olfactory function The evidence is very uncertain about the effect of intranasal corticosteroid spray on both self-rated recovery of olfactory function and recovery of olfactory function using psychophysical tests at up to four weeks follow-up (self-rated: risk ratio (RR) 1.19, 95% confidence interval (CI) 0.85 to 1.68; 1 study; 100 participants; psychophysical testing: RR 2.3, 95% CI 1.16 to 4.63; 1 study; 77 participants; very low-certainty evidence).  Change in sense of smell The evidence is also very uncertain about the effect of intranasal corticosteroid spray on self-rated change in the sense of smell (at less than 4 weeks: mean difference (MD) 0.5 points lower, 95% CI 1.38 lower to 0.38 higher; 1 study; 77 participants; at > 4 weeks to 3 months: MD 2.4 points higher, 95% CI 1.32 higher to 3.48 higher; 1 study; 100 participants; very low-certainty evidence, rated on a scale of 1 to 10, higher scores mean better olfactory function). Intranasal corticosteroids may make little or no difference to the change in sense of smell when assessed with psychophysical testing (MD 0.2 points, 95% CI 2.06 points lower to 2.06 points higher; 1 study; 77 participants; low-certainty evidence, 0- to 24-point scale, higher scores mean better olfactory function).  Serious adverse effects The authors of one study reported no adverse effects, but their intention to collect these data was not pre-specified so we are uncertain if these were systematically sought and identified. The remaining two studies did not report on adverse effects.  Intranasal corticosteroid drops compared to no intervention/placebo We included one study with 248 participants who had olfactory dysfunction for ≤ 15 days following COVID-19. Presence of normal olfactory function Intranasal corticosteroid drops may make little or no difference to self-rated recovery at > 4 weeks to 3 months (RR 1.00, 95% CI 0.89 to 1.11; 1 study; 248 participants; low-certainty evidence). No other outcomes were assessed by this study.  Data on the use of hypertonic saline nasal irrigation and the use of zinc sulphate to prevent persistent olfactory dysfunction are included in the full text of the review.

AUTHORS' CONCLUSIONS

There is very limited evidence available on the efficacy and harms of treatments for preventing persistent olfactory dysfunction following COVID-19 infection. However, we have identified a number of ongoing trials in this area. As this is a living systematic review we will update the data regularly, as new results become available.

Persisting Smell and Taste Disorders in Patients Who Recovered from SARS-CoV-2 Virus Infection-Data from the Polish PoLoCOV-CVD Study

In the majority of cases, patients infected with the SARS-CoV-2 virus experience a complete resolution of symptoms within six weeks of acquiring the infection, but an increasing number of patients report persistent symptoms. This study aimed to analyse the prevalence of self-reported smell and/or taste disorders (STDs) in a group of convalescent patients after infection with the SARS-CoV-2 virus and to identify risk factors for the disease. The study included 2218 COVID-19 convalescents after both inpatient and outpatient treatment. The sample group was analysed with regard to chronic diseases, place of isolation and clinical symptoms occurring during COVID-19 along with their duration. The assessment also included the most common symptoms of COVID-19 and the severity of the disease course. A total of 98 patients reported persistent smell and taste disorders up to three months after the end of isolation (67.4% of men and 32.6% of women). The mean age of the participants was 53.8 ± 13.5 years (49.19 ± 14.68 in patients with an STD vs. 54.01 ± 13.44 in patients without an STD). The patients treated for COVID-19 at home (p < 0.001) constituted almost the entire group of patients with persistent smell and taste disorders (97%). Among the patients with persistent smell and taste disorders, 57.1% suffered from at least one chronic condition (vs. 71.4% of patients without an STD). In patients with an STD, the number of symptoms per patient was higher than in the other group at 8.87 ± 3.65 (p = 0.018), while the most common clinical symptoms during the acute phase of COVID-19 were smell and taste disorders (84%) (p < 0.001), significant weakness (70%), headache (60%), cough (55%), arthralgia (51%) (p = 0.034) and back muscle pain (51%). Based on the results obtained, the following conclusions were drawn: the risk of developing persistent smell and taste disorders after COVID-19 is greater in younger people with less comorbidities and a higher number of symptoms during the acute phase of COVID-19. The risk is associated with clinical symptoms occurring during the acute phase of COVID-19, i.e., smell and taste disorders and arthralgia. In addition, this risk is higher in patients receiving outpatient treatment for COVID-19.

Management of Post-Infectious Anosmia and Hyposmia: A Systematic Review

BACKGROUND

Anosmia and hyposmia significantly affect patients' quality of life and have many etiologies, including trauma, inflammatory conditions including chronic rhinosinusitis, neoplasm, and viral infections, such as rhinovirus and SARS-CoV-2.

OBJECTIVE

Our purpose was to establish whether a consensus exists regarding optimal management of olfactory dysfunction and to provide insight into the treatment of anosmia in the current climate of increased prevalence secondary to COVID-19. Thus, we aimed to systematically review the literature on the management of non-Chronic-rhinosinusitis- related anosmia/hyposmia.

METHODS

PubMed, EMBASE, and Cochrane databases were searched for articles published since January 1990 using terms combined with Medical Subject Headings (MeSH). We included articles evaluating management of anosmia and hyposmia written in the English language, with original data, a minimum of 3 months of follow-up except for COVID-related studies, at least 2 patients, and well-defined and measurable outcomes.

RESULTS

A total of 3013 unique titles were returned upon the initial search. Of these, 297 abstracts were examined, yielding 19 full texts meeting inclusion criteria (8 with level 1 evidence, 3 with level 2, 1 with level 3, and 7 with level 4). The studies included a total of 1522 subjects, with follow up ranging from 3 to 72 months, with an exception for COVID related studies. Endpoints were based on clinically significant improvements of olfactory functions as measured through validated smell tests. Treatments with the most robust data were intranasal corticosteroids and olfactory training.

CONCLUSION

The literature on the treatment of anosmia and hyposmia includes randomized trials showing the efficacy of a few modalities. While further research is needed to expand therapeutic options for this debilitating condition, the current literature supports the use of olfactory training and topical corticosteroids.

Total laryngectomy negatively impacts sinonasal and olfactory-specific quality of life

PURPOSE

The purpose of this study is to characterize deficits in olfactory-specific and sinonasal-specific QoL after total laryngectomy (TL) with validated patient reported outcome measures.

METHODS

Thirty patients who had a TL were prospectively enrolled. Patient demographics, as well as scores from the Questionnaire of Olfactory Disorders Negative Statements (QOD-NS) and the Sino-nasal Outcome Test-22 (SNOT-22) were collected. Univariate analysis was performed to assess associations between patient characteristics and QoL scores.

RESULTS

The average QOD-NS score was 37.9 ± 11.4 (<38.5 is considered abnormal) and average SNOT-22 score was 32.0 ± 3.8 (>20 indicates a moderate/severe impact on QoL). The abnormal QOD-NS group had a greater percentage of former smokers compared to the normal group (77.8% vs. 58.1%; P = 0.56) and more median days from surgery compared to the normal group (904 vs. 477 days; P = 0.24).

CONCLUSIONS

Olfactory dysfunction associated with TL results in blunting of olfactory-specific QoL.

Chemical Constituents of Essential Oils Used in Olfactory Training: Focus on COVID-19 Induced Olfactory Dysfunction

The recent increase in the number of patients with post-viral olfactory dysfunction (PVOD) following the outbreak of COVID-19 has raised the general interest in and concern about olfactory dysfunction. At present, no clear method of treatment for PVOD has been established. Currently the most well-known method to improve the symptoms of olfactory dysfunction is "olfactory training" using essential oils. The essential oils used in olfactory training typically include rose, lemon, clove, and eucalyptus, which were selected based on the odor prism hypothesis proposed by Hans Henning in 1916. He classified odors based on six primary categories or dimensions and suggested that any olfactory stimulus fits into his smell prism, a three-dimensional space. The term "olfactory training" has been used based on the concept of training olfactory sensory neurons to relearn and distinguish olfactory stimuli. However, other mechanisms might contribute to how olfactory training can improve the recovery of the olfactory sense. Possibly, the essential oils contain chemical constituents with bioactive properties that facilitate the recovery of the olfactory sense by suppressing inflammation and enhancing regeneration. In this review, we summarize the chemical constituents of the essential oils of rose, lemon, clove, and eucalyptus and raise the possibility that the chemical constituents with bioactive properties are involved in improving the symptoms of olfactory dysfunction. We also propose that other essential oils that contain chemical constituents with anti-inflammatory effects and have binding affinity with SARS-CoV-2 can be new candidates to test their efficiencies in facilitating the recovery.

Olfactory and gustatory disorders in COVID-19

Loss of olfaction is one of the symptoms most commonly reported by patients with coronavirus disease 2019 (COVID-19). Although the spontaneous recovery rate is high, recent studies have shown that up to 7% of patients remain anosmic for more than 12 months after the onset of infection, leaving millions of people worldwide suffering from severe olfactory impairment. Olfactory training remains the first recommended treatment. With the continued lack of approved drug treatments, new therapeutic options are being explored. This article reviews the current state of science on COVID-19-related olfactory disorders, focusing on epidemiology, pathophysiology, cure rates, currently available treatment options, and research on new treatments.

Odor Identification by Parkinson’s Disease Patients Tested by Using Sniffin’ Sticks versus Natural Spices

Introduction

Hyposmia is a frequent symptom of Parkinson's disease (PD), which greatly impacts patients' flavor perception and their quality of life. However, PD patients recognize some odors better than others. Identifying which food odors are still recognized by PD patients may be useful for flavor enhancement. Our aim was to evaluate the olfactory identification of Sniffin' Sticks and spice odorants in PD patients and healthy controls (HC), to identify the impact of synthetic odorants compared with real-life food and the impact of odor familiarity and pleasantness on odorant identification in PD patients.

Methods

Sniffin' Sticks odorant identification was evaluated in 80 PD patients and 105 age-matched HC. In a subset, the spice odorant identification was evaluated.

Results

The mean total score was higher for the Sniffin' Sticks than for the spice odor identification test in all participants (55.4% versus 22.5%). Sniffin' Sticks orange, peppermint, rose, and fish odorants were best correctly identified by PD patients, by 62.5, 53.8, 52.9, and 57.5%, respectively. Of the spice odor identification test, garlic and “no stimulus” were best correctly identified by PD patients, by, respectively, 38.2 and 67.6%. HC identified most Sniffin' Sticks odorants and spices better than PD patients. Odorant familiarity determined real-life food odorant identification.

Conclusion

This study demonstrates that some food odorants, both the commercial Sniffin' Sticks as natural odorants, are still recognized by PD patients. Sniffin' Sticks were better recognized compared with real-life odorants, by both HC and PD patients. Odorant familiarity determined PD patients' odorant identification; therefore, familiar food odorants may have potential for a future flavor enhancement. Implications. This is the first study, to our knowledge, to evaluate real-life food odor identification in PD patients. Our results provide a first step towards patient-appropriate flavor enhancement strategies in PD.

Effect of early olfactory training on olfactory recovery after nasal endoscopy in patients with chronic rhinosinusitis and olfactory impairment

OBJECTIVE

To analyze the effect of early comprehensive olfactory rehabilitation training on olfactory recovery after nasal endoscopy in patients with chronic rhinosinusitis and olfactory impairment.

METHODS

A retrospective study was conducted on 67 patients with chronic rhinosinusitis combined with olfactory impairment in our hospital from July 2018 to August 2020. Patients were divided into control group and observation group according to the time of implementing comprehensive olfactory rehabilitation training. The control group received non-early comprehensive olfactory rehabilitation training at 2 weeks after nasal endoscopy, and the observation group received early comprehensive olfactory rehabilitation training at 1 week after nasal endoscopy. The minimum detection/recognition threshold, olfactory threshold, olfactory function and quality of life were compared between the two groups.

RESULTS

After 3 months of training, T&T olfactory test scores in the observation group were significantly lower than those in the control group (P<0.05). The minimum detection scores in the observation group were lower than those in the control group after 1, 2 and 3 months of training, and the recognition scores in the observation group were higher than those in the control group (P<0.05). The scores of olfactory threshold, odor discrimination, and odor identification of the observation group after 1, 2 and 3 months of training were higher than those of the control group (P<0.05). After 3 months of training, the self-description scores of quality-of-life questionnaires in the observation group were higher than those in the control group, and visual analogue scale (VAS) scores in the observation group were lower than those in the control group (P<0.05).

CONCLUSION

Early comprehensive olfactory training can improve the olfactory threshold and odor discrimination of patients with chronic rhinosinusitis combined with olfactory impairment after nasal endoscopy, improve the quality of life, and have a positive effect on olfactory recovery.

A three-factor benefits framework for understanding consumer preference for scented household products: psychological interactions and implications for future development

Humans have deliberately scented their environment for purpose or pleasure for millennia. In the contemporary marketplace most consumers prefer and purchase scented versions of common household products. However, the drivers of this consumer preference have not been elucidated. To explain the attraction to scent in household products we propose a novel three-factor framework, comprising functional benefits (malodor mitigation, base odor coverage, freshening), in-use experience benefits (cleanliness, efficacy, pleasure), and emotional benefits (increasing in confidence, mood and nostalgia). To support this framework, we present new data from a market research survey on US consumer purchasing habits and attitudes towards home cleaning, laundry, and air freshening products. Further substantiating our framework, a focused review of olfactory psychological science illustrating the central role of scent in cognition, wellbeing, motivated behavior, and social behavior, as well as sensory marketing research highlights the benefits and implications of scent in consumer household products. Based on our three-factor framework we go on to discuss the potential for scent to influence health and raise issues to consider (such as potential negative responding to fragranced products). We conclude by showcasing new opportunities for future research in olfactory science and on scented household products that can advance the positive impacts of scent.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

“Anosmia” the mysterious collateral damage of COVID-19

COVID-19 pandemic spreads worldwide, with more than 100 million positive cases and more than 2 million deaths. From the beginning of the COVID-19 pandemic, several otolaryngologists described many cases of a sudden loss of smell (anosmia) associated with the disease with or without additional symptoms. Anosmia is often the first and sometimes the only sign in the asymptomatic carriers of COVID-19. Still, this disorder is underestimated, and it is not life-threatening. However, it significantly decreases the quality of life. This olfactory dysfunction continues in several cases even after the nasopharyngeal swab was negative. The occurrence of anosmia can be used as a screening tool for COVID-19 patients and can be used to identify these patients to accomplish the isolation and tracking procedures. In this review, we highlighted the possible mechanisms of anosmia in COVID-19 patients, major pathologies and features of anosmia, implications of anosmia in early diagnosis of COVID-19, evaluation of the smell function during COVID-19, and management and treatment options of COVID-19 anosmia.

Smell Changes and Efficacy of Nasal Theophylline (SCENT) irrigation: A randomized controlled trial for treatment of post-viral olfactory dysfunction

OBJECTIVE

To evaluate the efficacy and safety of intranasal theophylline saline irrigation on olfactory recovery in patients with post-viral olfactory dysfunction (PVOD).

METHODS

Between May 2019 and April 2020, we conducted a double-blinded, placebo-controlled randomized clinical trial of adults with 6-36 months of PVOD. Patients were randomized to nasal theophylline saline irrigation or placebo saline irrigation twice a day for 6 weeks. The primary outcome was the Global Rating of Smell Change. Secondary outcomes were changes in the University of Pennsylvania Smell Identification Test (UPSIT) and Questionnaire of Olfactory Disorders-Negative Statements (QOD-NS).

RESULTS

Twenty-two patients (n = 12, theophylline; n = 10, placebo) completed the study. Slightly more patients in the theophylline group (33%) reported improved smell compared to the placebo group (30%, difference 3.3%, 95% CI -35.6% to 42.3%). The median differences in pre- and post-treatment UPSIT and QOD-NS change between the two groups were 1 (95% CI -3 to 5) and -10 (95% CI -15 to -4), respectively in favor of theophylline. Three patients receiving theophylline and 2 receiving placebo had clinically meaningful improvements on the UPSIT (difference 5%, 95% CI -30% to 40%). There were no adverse events, and serum theophylline levels were undetectable in 10/10 patients.

CONCLUSIONS

While safe, there were no clinically meaningful differences in olfactory change between the two groups except for olfaction-related quality of life, which was better with theophylline. The imprecise estimates suggest future trials will need substantially larger sample sizes or treatment modifications, such as increasing the theophylline dose, to observe larger treatment effects.

Treatment strategies for postviral olfactory dysfunction: A systematic review

Background: The coronavirus disease 2019 (COVID-19) pandemic has been associated with a dramatic increase in postviral olfactory dysfunction (PVOD) among patients who are infected. A contemporary evidence-based review of current treatment options for PVOD is both timely and relevant to improve patient care. Objective: This review seeks to impact patient care by qualitatively reviewing available evidence in support of medical and procedural treatment options for PVOD. Systematic evaluation of data quality and of the level of evidence was completed to generate current treatment recommendations. Methods: A systematic review was conducted to identify primary studies that evaluated treatment outcomes for PVOD. A number of medical literature data bases were queried from January 1998 to May 2020, with completion of subsequent reference searches of retrieved articles to identify all relevant studies. Validated tools for the assessment of bias among both interventional and observational studies were used to complete quality assessment. The summary level of evidence and associated outcomes were used to generate treatment recommendations. Results: Twenty-two publications were identified for qualitative review. Outcomes of alpha-lipoic acid, intranasal and systemic corticosteroids, minocycline, zinc sulfate, vitamin A, sodium citrate, caroverine, intranasal insulin, theophylline, and Gingko biloba are reported. In addition, outcomes of traditional Chinese acupuncture and olfactory training are reviewed. Conclusion: Several medical and procedural treatments may expedite the return of olfactory function after PVOD. Current evidence supports olfactory training as a first-line intervention. Additional study is required to define specific treatment recommendations and expected outcomes for PVOD in the setting of COVID-19.

COVID-19 related olfactory dysfunction

PURPOSE OF REVIEW

This article reviews the literature on COVID-19 related anosmia, focusing on the epidemiology, pathophysiology recovery rates, current available treatment options, and research regarding novel treatments.

RECENT FINDINGS

Loss of sense of smell is one of the most prevalent symptoms reported by patients after COVID-19 infection. Even though there is a high self-reported recovery rate, recent studies have demonstrated that up to 7% of the patients remain anosmic more than 12 months after onset, leaving millions worldwide with severe olfactory dysfunction. Olfactory training remains the first line recommended treatment. Given the paucity of effective medical treatments options researchers are exploring novel therapeutic options.

SUMMARY

Olfactory dysfunction remains a significant and persistent legacy of the COVID-19 pandemic, but heightened awareness may stimulate research that leads to the development of much-needed treatment options.

Olfactory Dysfunction in Patients With Coronavirus Disease 2019: A Review

The coronavirus disease 2019 (COVID-19) pandemic is wreaking havoc on public-health and economic systems worldwide. Among the several neurological symptoms of patients with COVID-19 reported in clinical practice, olfactory dysfunction (OD) is the most common. OD occurs as the earliest or the only clinical manifestation in some patients. Increasing research attention has focused on OD, which is listed as one of the main diagnostic symptoms of severe acute respiratory syndrome-coronavirus-2 infection. Multiple clinical and basic-science studies on COVID-19-induced OD are underway to clarify the underlying mechanism of action. In this review, we summarize the clinical characteristics, mechanisms, evaluation methods, prognosis, and treatment options of COVID-19-induced OD. In this way, we hope to improve the understanding of COVID-19-induced OD to aid early identification and precise intervention.

Management of post-COVID-19 olfactory dysfunction

Purpose of Review

Olfactory dysfunction is a frequent complication of SARS-CoV-2 infection. This review presents the current literature regarding the management of post-COVID-19 olfactory dysfunction (PCOD).

Recent Findings

A systematic review of the literature using the PubMed/MEDLINE, EMBASE, and Cochrane databases for the following keywords, “Covid-19,” “SARS-CoV-2,” “anosmia,” “olfactory,” “treatment,” and “management” was performed. While most cases of post-COVID-19 olfactory dysfunction resolve spontaneously within 2 weeks of symptom onset, patients with symptoms that persist past 2 weeks require medical management. The intervention with the greatest degree of supporting evidence is olfactory training, wherein patients are repeatedly exposed to potent olfactory stimuli. To date, no large-scale randomized clinical trials exist that examine the efficacy of pharmacologic therapies for PCOD. Limited clinical trials and prospective controlled trials suggest intranasal corticosteroids and oral corticosteroids may alleviate symptoms.

Summary

Olfactory training should be initiated as soon as possible for patients with PCOD. Patients may benefit from a limited intranasal or oral corticosteroid course. Further research on effective pharmacologic therapies for PCOD is required to manage the growing number of patients with this condition.