Treatment of post-viral olfactory dysfunction: an evidence-based review with recommendations

Traditional Chinese medicine for post-viral olfactory dysfunction: A systematic review

Background

Post-viral olfactory dysfunction (PVOD) is the common symptoms of long COVID, lacking of effective treatments. Traditional Chinese medicine (TCM) is claimed to be effective in treating olfactory dysfunction, but the evidence has not yet been critically appraised. We conducted a systematic review to evaluate the effectiveness and safety of TCM for PVOD.

Methods

We searched eight databases to identified clinical controlled studies about TCM for PVOD. The Cochrane risk of bias tools and GRADE were used to evaluate the quality of evidence. Risk ratio (RR), mean differences (MD), and 95 % confidence interval (CI), were used for effect estimation and RevMan 5.4.1 was used for data analysis.

Results

Six randomized controlled trials (RCTs) (545 participants), two non-randomized controlled trials (non-RCTs) (112 participants), and one retrospective cohort study (30 participants) were included. The overall quality of included studies was low. Acupuncture (n = 8) and acupoint injection (n = 3) were the mainly used TCM therapies. Five RCTs showed a better effect in TCM group. Four trials used acupuncture, and three trials used acupoint injection. The results of two non-RCTs and one cohort study were not statistically significant. Two trials reported mild to moderate adverse events (pain and brief syncope caused by acupuncture or acupoint injection).

Conclusions

Limited evidence focus on acupuncture and acupoint injection for PVOD and suggests that acupuncture and acupoint injection may be effective in improving PVOD. More well-designed trials should focus on acupuncture to confirm the benefit.

Protocol registration

The protocol of this review was registered at PROSPERO: CRD42022366776.

Pro-inflammatory markers associated with COVID-19-related persistent olfactory dysfunction

INTRODUCTION

While localized inflammation has been implicated in the pathophysiology of acute coronavirus disease of 2019 (COVID-19) olfactory dysfunction (OD), persistent COVID-19 OD remains poorly understood with limited therapeutics. Our prospective study evaluated olfactory cleft (OC) biomarkers as predictors of persistent OD in mucus sampling.

METHODS

COVID-19 subjects with persistent OD >3 months confirmed by psychophysical olfaction tests were compared to COVID-19 subjects with no OD and those with no prior infection. OC mucus samples were evaluated for 13 anti-viral and inflammatory biomarkers. Cohorts were compared using analysis of variance (ANOVA) and Mann-Whitney tests with multi-comparison adjustment. Viral RNA was assessed through RT-PCR using the COVID-19 N2 primer.

RESULTS

Thirty-five samples were collected (20 COVID persistent OD, 8 COVID no OD, and 7 non-COVID no OD). Significant differences in IFN-λ1 (p = 0.007) and IFN-γ (p = 0.006) expression in OC mucus were found across all three groups, with the highest cytokine concentrations corresponding to COVID OD. IFN-α2 levels were elevated in COVID OD versus no OD (p = 0.026). Mean IFN-γ levels were the highest in COVID OD, but there were higher levels found in COVID no OD compared to non-COVID no OD (p = 0.008). No difference was seen in IL6. No N2 gene expression was detected in all cohorts.

CONCLUSION

IFN pathway cytokines were found elevated in the olfactory microenvironment of COVID-19 persistent OD compared to those with no OD and no prior history of COVID-19 infection.

Integrating the patient's voice into the research agenda for treatment of chemosensory disorders

World-wide some 658 million people were infected with coronavirus disease 2019 (COVID-19) and millions suffer from chemosensory impairment associated with long COVID. Current treatments for taste and smell disorders are limited. Involving patients has the potential to catalyze the dynamic exchange and development of new ideas and approaches to facilitate biomedical research and therapeutics. We assessed patients' perceptions of the efficacy of treatments for chemosensory impairment using an online questionnaire completed by 5,815 people in the US Logistic regression determined variables predictive of reported treatment efficacy for patients aged 18 to 24, 25 to 39, 40 to 60, and 60+ yrs. who were treated with nasal steroids, oral steroids, zinc, nasal rinse, smell training, theophylline, platelet-rich plasma, and Omega 3. The most consistent predictor was age, with the majority of those 40 to 60 and 60+ reporting that nasal steroids, oral steroids, zinc, nasal rinse, and smell training were only slightly effective or not effective at all. Many of these treatment strategies target regeneration and immune response, processes compromised by age. Only those under 40 reported more than slight efficacy of steroids or smell training. Findings emphasize the need to include patients of all ages in clinical trials. Older adults with olfactory impairment are at increased risk for Alzheimer's disease (AD). We speculate that olfactory impairment associated with long COVID introduces the potential for a significant rise in AD. Long COVID-associated chemosensory impairment increases the urgency for translational and clinical research on novel treatment strategies. Suggestions for high-priority areas for epidemiological, basic, and clinical research on chemosensory impairment follow.

Olfactory Dysfunction Following Moderate to Severe Traumatic Brain Injury: A Systematic Review and Meta-Analysis

OBJECTIVE

Reports of smell loss following traumatic brain injury (TBI) are a well-documented but understudied phenomenon. Given the broad consequences of olfactory loss, we characterized psychophysical olfactory dysfunction in individuals with moderate to severe TBI using systematic review and meta-analytic methods.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) protocol, five databases (PubMed, EMBASE, Cochrane Library, Web of Science, Scopus) were reviewed for studies investigating olfactory dysfunction in persons with moderate to severe TBI. Of the 5,223 studies reviewed, 19 met our inclusion criteria for the systematic review and 11 met inclusion criteria for meta-analysis. We calculated effect sizes (Hedges' g) to characterize the degree of olfactory dysfunction between patients with moderate to severe TBI and controls.

RESULTS

A total of 951 moderate-severe TBI patients from 19 studies were included in the systematic review, which largely demonstrated poorer olfactory psychophysical performances in this patient population. Meta-analysis demonstrated a large effect size for olfactory dysfunction in moderate-severe TBI relative to healthy controls (g=-2.43, 95%CI: -3.16 < δ<-1.69). The magnitude of the effect was moderated by age and patient sex, with larger effect sizes associated with older age (following exclusion of a pediatric population) and larger compositions of women in the patient group.

CONCLUSION

Moderate to severe TBI is associated with prominent olfactory dysfunction. Significant research gaps remain regarding the mechanism, recovery and natural history of olfactory dysfunction following moderate to severe TBI, which has significant clinical implications for the identification and treatment for those with post-traumatic olfactory dysfunction.

Local budesonide therapy in the management of persistent hyposmia in suspected non-severe COVID-19 patients: Results of a randomized controlled trial

OBJECTIVES

Consequences of COVID-19 on olfactory functions remained unclear during the pandemic. We assessed the efficacy of local budesonide in addition to olfactory rehabilitation when managing non-severe COVID-19 patients with persistent hyposmia.

METHODS

A multicentric, randomized, superiority trial was conducted (ClinicalTrials.gov NCT04361474). The experimental group (EG) received budesonide and physiological saline nasal irrigations administered via three syringes of 20 ml in each nasal cavity in the morning and evening for 30 days. The control group (CG) received a similar protocol without budesonide. Patients were included if they were >18 years old, with a SARS-CoV-2 infection and presenting an isolated hyposmia persisting 30 days after symptom onset. The primary endpoint was the percentage of patients with improvement of more than two points on the ODORATEST score after 30 days of treatment.

RESULTS

In total, 123 patients were included and randomized (EG: 62 vs CG: 61). Two patients from the EG met the primary endpoint with no statistical difference between the two groups (P = 0.5).

CONCLUSION

To our knowledge, this is the first study evaluating local budesonide for COVID-19 related hyposmia treatment even though previous trials were performed with other local corticosteroids. Local budesonide efficacy was not demonstrated for persistent hyposmia related to COVID-19.

The Olfactory System: Basic Anatomy and Physiology for General Otorhinolaryngologists

Olfaction is one of the five basic human senses, and it is known to be one of the most primitive senses. The sense of olfaction may have been critical for human survival in prehistoric society, and although many believe its importance has diminished over time, it continues to have an impact on human interaction, bonding, and propagation of the species. Even if we are unaware of it, the sense of smell greatly affects our lives and is closely related to overall quality of life and health. Nonetheless, olfaction has been neglected from a scientific perspective compared to other senses. However, olfaction has recently received substantial attention since the loss of smell and taste has been noted as a key symptom of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Studies investigating olfaction loss in association with coronavirus disease 2019 (COVID-19) have revealed that olfactory dysfunction can be both conductive and sensorineural, possibly causing structural changes in the brain. Olfactory training is an effective treatment for olfactory dysfunction, suggesting the reorganization of neural associations. A reduced ability to smell may also alert suspicion for neurodegenerative or psychiatric disorders. Here, we summarize the basic knowledge that we, as otorhinolaryngologists, should have about the sense of smell and the peripheral and central olfactory pathways for managing and helping patients with olfactory dysfunction.

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.

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.

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.

Post-COVID-19 Anosmia and Therapies: Stay Tuned for New Drugs to Sniff Out

Background: Anosmia is defined as the complete absence of olfactory function, which can be caused by a variety of causes, with upper respiratory tract infections being among the most frequent causes. Anosmia due to SARS-CoV-2 infection has attracted attention given its main role in symptomatology and the social impact of the pandemic. Methods: We conducted systematic research in a clinicaltrials.gov database to evaluate all active clinical trials worldwide regarding drug therapies in adult patients for anosmia following SARS-CoV-2 infection with the intention of identifying the nearby prospects to treat Anosmia. We use the following search terms: "Anosmia" AND "COVID-19" OR "SARS-CoV-2" OR "2019 novel coronavirus". Results: We found 18 active clinical trials that met our criteria: one phase 1, one phase 1-2, five phases 2, two phases 2-3, three phases 3, and six phases 4 studies were identified. The drug therapies that appear more effective and promising are PEA-LUT and Cerebrolysin. The other interesting drugs are 13-cis-retinoic acid plus aerosolized Vitamin D, dexamethasone, and corticosteroid nasal irrigation. Conclusions: COVID-19 has allowed us to highlight how much anosmia is an important and debilitating symptom for patients and, above all, to direct research to find a therapy aimed at curing the symptom, whether it derives from SARS-CoV-2 infection or other infections of the upper airways. Some of these therapies are very promising and are almost at the end of experimentation. They also provide hope in this field, which not addressed until recently.

Olfactory Nomenclature: An Orchestrated Effort to Clarify Terms and Definitions of Dysosmia, Anosmia, Hyposmia, Normosmia, Hyperosmia, Olfactory Intolerance, Parosmia, and Phantosmia/Olfactory Hallucination

BACKGROUND

Definitions are essential for effective communication and discourse, particularly in science. They allow the shared understanding of a thought or idea, generalization of knowledge, and comparison across scientific investigation. The current terms describing olfactory dysfunction are vague and overlapping.

SUMMARY

As a group of clinical olfactory researchers, we propose the standardization of the terms "dysosmia," "anosmia," "hyposmia," "normosmia," "hyperosmia," "olfactory intolerance," "parosmia," and "phantosmia" (or "olfactory hallucination") in olfaction-related communication, with specific definitions in this text.

KEY MESSAGES

The words included in this paper were determined as those which are most frequently used in the context of olfactory function and dysfunction, in both clinical and research settings. Despite widespread use in publications, however, there still exists some disagreement in the literature regarding the definitions of terms related to olfaction. Multiple overlapping and imprecise terms that are currently in use are confusing and hinder clarity and universal understanding of these concepts. There is a pressing need to have a unified agreement on the definitions of these olfactory terms by researchers working in the field of chemosensory sciences. With the increased interest in olfaction, precise use of these terms will improve the ability to integrate and advance knowledge in this field.

Assessment of factors influencing the olfactory bulb volume in patients with post-viral olfactory dysfunction

PURPOSE

To investigate the factors influencing the volume of the olfactory bulb (OB) in patients with post-viral olfactory dysfunction (PVOD).

METHODS

We collected 92 olfactory bulb volumes from patients with PVOD who underwent a sinus computed tomographic and magnetic resonance imaging (MRI) scan of the head and collected clinical information including gender, age, disease course, minimal cross-sectional area, nasal airway resistance, and olfactory function. OB volume was measured in MRI and the scans were evaluated according to the Lund-Mackay (LM) scoring system.

RESULTS

Male patients with PVOD had a larger OB volume (β = 0.284, P < 0.05). OB volume was smaller in patients with a longer course of olfactory dysfunction (β = - 0.254, P < 0.05). According to the LM scoring system, patients with a higher anterior ethmoidal sinus score had smaller OB volume (β = - 0.476, P < 0.05).

CONCLUSIONS

The study revealed that gender, disease course, and the score of anterior ethmoidal sinusitis can affect the OB volume in patients with PVOD.

Therapeutic options of post-COVID-19 related olfactory dysfunction: a systematic review and meta-analysis

BACKGROUND

Olfactory dysfunction is a typical post-COVID-19 presentation, affecting patients' quality of life. There are currently multiple treatment options in this group of patients such as oral and intranasal corticosteroids, olfactory training, oral vitamin-mineral supplementation, amongst others. This meta-analysis aims to consolidate existing evidence for current therapies in patients with persistent olfactory dysfunction related to COVID-19 infection and evaluate the possible role of corticosteroid add-on therapy in olfactory training.

METHODOLOGY

A systematic review and meta-analysis to study current treatments/interventions for olfactory dysfunction in post-COVID-19 infection were conducted. Data were pooled for the meta-analysis. The outcomes include subjective or objective olfactory assessment major and minor adverse reactions.

RESULTS

Eleven studies (1414 participants) were included in this review, with six studies (916 participants) then assessed for the meta-analysis. Combined treatment of intranasal corticosteroid (INCS) with olfactory training (OT) has no benefit over OT monotherapy from both a VAS score improvement and identification component of Sniffin' Sticks test standpoint. In addition, there were no differences in improvement of TDI score between combined oral corticosteroid (OCS) with OT therapy compared to OT alone. Olfactory function was, however, significantly improved after OT.

CONCLUSION

There were no significant differences in the improvement of olfactory scores in combination INCS+OT or OCS+OT therapies compared to OT monotherapy. However, there is improvement in olfactory function after OT.

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.

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.

Olfactory Training Impacts Olfactory Dysfunction Induced by COVID-19: A Pilot Study

INTRODUCTION

Olfactory dysfunction is one of the main symptoms of COVID-19 and may last beyond resolution of the infection. The most promising intervention for post-viral olfactory dysfunction is olfactory training (OT), which involves exposing the olfactory system to a range of odors daily. This approach is thought of promoting the regeneration of olfactory receptor cells, but its effectiveness in patients with post-COVID-19 olfactory dysfunction has yet to be confirmed.

METHODS

This double-blind randomized pilot study compared the effectiveness of OT versus placebo in the treatment of post-COVID-19 olfactory dysfunction. Twenty-five participants were recruited in each group. OT protocol consisted of sniffing 4 scents (rose, orange, clove, and eucalyptus) for 5 min twice daily for 12 weeks. Olfactory function was assessed before and after the training using (1) a validated odor identification test (UPSIT-40) and (2) a 10-point visual analog scale; we further assessed the presence of (3) parosmia.

RESULTS

While we did not observe any effect of OT on olfactory test scores, we observed a significant improvement of subjective olfactory function in the intervention group, while no such effect was observed in the placebo group. Finally, the frequency of parosmia was significantly lower in the intervention group.

CONCLUSIONS

This study highlights an increase in subjective but not objective olfactory function when performing OT for 12 weeks. Further, parosmia seems to be positively affected by OT. These results may serve as a starting point for larger scale studies to assess the efficacy of OT for treatment of post-COVID-19 olfactory dysfunction.

A multicenter real-life study to determine the efficacy of corticosteroids and olfactory training in improving persistent COVID-19-related olfactory dysfunction

Background

No definitive treatment exists to effectively restore function in patients with persistent post-infectious olfactory dysfunction (OD). Corticosteroids have been considered as a therapeutic option in post-infectious OD but their benefit in COVID-19-related OD remains unexplored. We aim to determine the role of the combination of corticosteroids plus olfactory training (OT) in improving persistent COVID-19-related OD.

Methods

A multicenter real-life cohort study was conducted between December 2020 and April 2022 on patients with reported COVID-19-related OD. Only patients with confirmed OD at Sniffin' Sticks (S'S) and those who attended their 6-month follow-up were included. Patients were started on a combined treatment of corticosteroids and OT. Patients refusing corticosteroids or not doing any treatment formed the control groups. Visual analogue scale (VAS) for sense of smell and SNOT-22 were used to assess patients reported symptoms.

Results

Sixty-seven subjects with reported COVID-19-related OD were initially seen. Normosmic patients at S'S (n = 14) and those not attending their follow-up (n = 9) were excluded. Of the 44 patients included in the analysis, 19 patients had the combined treatment (group A), 16 patients refused to take corticosteroids and did the OT alone (group B) whereas 9 patients did not do any treatment (group C). An improvement of threshold + discrimination + identification (TDI) score (p = .01) and VAS for smell (p = .01) was found in group A whereas only the TDI score improved in group B (p = .04). Presence of comorbidities, age, sex (male), and length of OD negatively influenced olfactory recovery.

Conclusions

Our study confirms the importance of OT in long-term OD suggesting that the addition of corticosteroids may give a benefit in terms of patient's perceived olfaction.

Level of Evidence

2b.

Post Viral Olfactory Dysfunction After SARS-CoV-2 Infection: Anticipated Post-pandemic Clinical Challenge

Persistent olfactory dysfunction (OD) is the second most common symptom of post coronavirus disease-19 (COVID-19) now being termed long-COVID. Its prevalence after recovery from COVID-19 is estimated to be 12% after nearly 6 months of follow-up. It thus becomes imperative for the treating clinicians to update themselves with the pathophysiology of this post COVID disability as well as the tools for diagnosis and the available treatment options. A systematic literature search was performed as per PRISMA guidelines in MEDLINE, Cochrane Library, LILACS, Google Scholar, ClinicalTrials.gov, and medRxiv databases. The keywords used were covid-19, Olfactory Disorders, Smell, Anosmia, PVOD, Post Viral Olfactory Disorders, post-covid and post haul. All articles were studied for definition, mechanism, diagnostic tests and treatment options for post COVID OD. 33 published articles and 8 ongoing trials were found relevant and included after full-text review. SARS-CoV-2 can cause conductive, neural and central OD. Olfactory evaluation can be done both subjectively (visual analogue scale) and objectively (Sniffin' sticks, Sinonasal Outcome Test, University of Pennsylvania Smell Identification Test and modified Davidson's alcohol sniff test). They can be used to detect and follow-up patients. Despite several on-going clinical trials, the most reliable and advisable treatment option available till date is olfactory training.

Prednisolone does not improve olfactory function after COVID-19: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Prednisolone has been suggested as a treatment for olfactory disorders after COVID-19, but evidence is scarce. Hence, we aimed to determine the efficacy of a short oral prednisolone treatment on patients with persistent olfactory disorders after COVID-19.

METHODS

We performed a randomized, double-blind, placebo-controlled, single-centered trial in the Netherlands. Patients were included if they were > 18 years old and if they had persistent (> 4 weeks) olfactory disorders within 12 weeks after a confirmed COVID-19 test. The treatment group received oral prednisolone 40 mg once daily for 10 days and the placebo group received matching placebo. In addition, all patients performed olfactory training. The primary outcome was the objective olfactory function on Sniffin' Sticks Test (SST) 12 weeks after the start of treatment, measured in Threshold-Discrimination-Identification (TDI) score. Secondary outcomes were objective gustatory function assessed by the Taste Strip Test (TST) and subjective self-reported outcomes on questionnaires about olfactory, gustatory and trigeminal function, quality of life, and nasal symptoms. The CONSORT 2010 guideline was performed.

RESULTS

Between November 2021 and February 2022, we included 115 eligible patients, randomly assigned to the treatment (n = 58) or placebo group (n = 57). No difference in olfactory function between groups was obtained after 12 weeks. Median TDI score on SST was 26.8 (IQR 23.6-29.3) in the placebo group and 28.8 (IQR 24.0-30.9) in the prednisolone group, with a median difference of 2.0 (95% CI 0.75 to 1.5). There was similar improvement on olfactory function in both groups after 12 weeks. Furthermore, on secondary outcomes, we obtained no differences between groups.

CONCLUSIONS

This trial shows that prednisolone does not improve olfactory function after COVID-19. Therefore, we recommend not prescribing prednisolone for patients with persistent olfactory disorders after COVID-19.

TRIAL REGISTRATION

This trial is registered on the ISRCTN registry with trial ID ISRCTN70794078.

Mucosal plasma cells are required to protect the upper airway and brain from infection

While blood antibodies mediate protective immunity in most organs, whether they protect nasal surfaces in the upper airway is unclear. Using multiple viral infection models in mice, we found that blood-borne antibodies could not defend the olfactory epithelium. Despite high serum antibody titers, pathogens infected nasal turbinates, and neurotropic microbes invaded the brain. Using passive antibody transfers and parabiosis, we identified a restrictive blood-endothelial barrier that excluded circulating antibodies from the olfactory mucosa. Plasma cell depletions demonstrated that plasma cells must reside within olfactory tissue to achieve sterilizing immunity. Antibody blockade and genetically deficient models revealed that this local immunity required CD4+ T cells and CXCR3. Many vaccine adjuvants failed to generate olfactory plasma cells, but mucosal immunizations established humoral protection of the olfactory surface. Our identification of a blood-olfactory barrier and the requirement for tissue-derived antibody has implications for vaccinology, respiratory and CNS pathogen transmission, and B cell fate decisions.

Novel Therapies in Olfactory Disorders

Purpose of Review

To summarize and critically review the recent literature on novel treatments for olfactory disorders (OD).

Recent Findings

Emerging therapies in the management of OD include multiple vitamins and supplements, biologics, neuromodulators, and intranasal agents. There is also an active investigation into treatments that harness the neuroregenerative properties of the olfactory epithelium, such as platelet-rich plasma and stem cell transplantation.

Summary

Successful management of OD is multimodal and tailored to the underlying etiology. As the findings of further investigations accrue, the management of OD will undoubtedly continue to be advanced and refined, and likely harness the intrinsic neuroregenerative properties of the olfactory system.

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.

Revealing the mystery of persistent smell loss in Long COVID patients

COVID-19 is hopefully approaching its end in many countries as herd immunity develops and weaker strains of SARS-CoV-2 dominate. However, a new concern occurs over the long-term effects of COVID-19, collectively called "Long COVID", as some symptoms of the nervous system last even after patients recover from COVID-19. This review focuses on studies of anosmia, i.e., impairment of smell, which is the most common sensory defect during the disease course and is caused by olfactory dysfunctions. It remains mysterious how the olfactory functions are affected since the virus can't invade olfactory receptor neurons. We describe several leading hypotheses about the mystery in hope to provide insights into the pathophysiology and treatment strategies for anosmia.

Intensive Olfactory Training in Post-COVID-19 Patients: A Multicenter Randomized Clinical Trial

BACKGROUND

Olfactory dysfunction (OD)-including anosmia and hyposmia-is a common symptom of COVID-19. Previous studies have identified olfactory training (OT) as an important treatment for postinfectious OD; however, little is known about its benefits and optimizations after SARS-CoV-2 infection.

OBJECTIVE

This study aimed to assess whether olfactory training performance can be optimized using more fragrances over a shorter period of time in patients with persistent OD after COVID-19. In addition, we determined the presence of other variables related to OD and treatment response in this population.

METHODS

This multicenter randomized clinical trial recruited 80 patients with persistent OD and prior COVID-19 infection for less than 3 months. The patients were divided into 2 groups receiving either 4 or 8 essences over 4 weeks. Subjective assessments and the University of Pennsylvania Smell Identification Test (UPSIT) were performed before and after the treatment.

RESULTS

Significant olfactory improvement was measured subjectively and using the UPSIT in both groups; however, no significant differences between the groups were observed. Additionally, the presence of olfactory fluctuations was associated with higher UPSIT scores.

CONCLUSION

These data suggest that training intensification by increasing the number of essences for 4 weeks does not show superiority over the classical method. Moreover, fluctuant olfaction seems to be related to a higher score on the UPSIT.

Therapeutic Potential of Valproic Acid for Postviral Olfactory Dysfunction: A Single-Arm Pilot Study

OBJECTIVES

Although some patients with postviral olfactory dysfunction (PVOD) recover spontaneously, many others are left with the degree of smell loss and there are no established drugs for the treatment of patients with PVOD. Valproic acid (VPA) has been widely used for the treatment of epilepsy. Its potential neuroregenerative effects have been shown via animal studies. This is the first study to treat PVOD patients with VPA. This open-label, single-arm, phase II study was conducted to investigate the effects of VPA in patients with PVOD.

METHODS

The patients received oral tablets of VPA 200 mg twice a day for 24 weeks. In total, 11 patients with PVOD were recruited. Oder scores of recognition and detection threshold (measured with a T&T olfactometer), and visual analog scale were examined during the treatment.

RESULTS

All odor scores significantly improved over time. Although the mean duration of olfactory dysfunction in this study was 11.5 months, both odor recognition threshold and odor detection threshold scores significantly improved 4 weeks after treatment initiation compared to the pre-treatment threshold scores. The olfactory recovery rates in patients treated with VPA were clearly better than those we previously reported in PVOD patients who received Toki-shakuyaku-san, the traditional treatment in Japan. The olfactory recovery rates of patients with PVOD at 12 weeks and 24 weeks of VPA treatment were both 77.8%, and the olfactory cure rates at 12 weeks and 24 weeks of VPA treatment were 33.3% and 44.4%, respectively. No serious adverse events were observed.

CONCLUSIONS

VPA seems to be a safe treatment option in patients with PVOD. The effects of VPA treatment for PVOD patients should be studied with a controlled study design in the future.

Tailored Approach for Persistent Olfactory Dysfunction After SARS-CoV-2 Infection: A Pilot Study

OBJECTIVE

So far, no original studies explored non-randomized, standardized protocols for COVID-19 associated olfactory dysfunction. The main objective was to determine the efficacy of a new protocol for post-COVID olfactopathy while assessing the benefit of adding adjuvant therapies to olfactory training.

METHODS

Patients suffering from long-lasting post-COVID-19 olfactory dysfunction were evaluated. A non-randomized protocol based on individual nasal endoscopy findings and patient's preferences was applied. Patients were assigned for olfactory training alone or olfactory training + adjuvant therapy. Participants performed olfactory objective and subjective evaluations at first consultation and 3 months after treatment, and results were compared.

RESULTS

A total of 47 patients were enrolled. All groups showed significant improvement in olfactory thresholds at 3-month follow-up suggesting protocol effectiveness (olfactory training group alone showed a mean threshold difference of 2.9, P < .001; Olfactory training + Topical Corticosteroid showed a mean threshold difference of 4, P = .006; Olfactory training + Topical Corticosteroid + Vitamin B complex showed a mean threshold difference of 4.4, P = .006; Olfactory training + Intranasal Vitamin A and E showed a mean threshold difference of 4.4, P < .001). Olfactory training alone showed lower mean olfactory threshold improvement, when compared to patients undergoing olfactory training + adjuvant therapy (olfactory training alone mean improvement 2.9 ± 2.3 vs olfactory training + adjuvants mean improvement 4.3 ± 2.458, P = .03).

CONCLUSIONS

This is one of the first studies to demonstrate results in the treatment of post-COVID-19 persistent olfactory impairment. A customized approach based on endoscopy findings and patient's preferences may be a valid option for the management of persistent post-COVID-19 olfactory disorder. Adjuvant therapy could be considered in addition to olfactory training, but further studies are needed in order to confirm their effectiveness in this setting.

LEVEL OF EVIDENCE

2c (outcomes research).

Anosmia Testing as Early Detection of SARS-CoV-2 Positivity; A Prospective Study under Screening Conditions

Sudden onset of anosmia is a phenomenon often associated with developing COVID-19 disease and has even been described as an initial isolated symptom in individual cases. In this case-control study, we investigated the feasibility of this condition as a suitable screening test in a population at risk. We performed a prospective study with a total of 313 subjects with suspected SARS-CoV-2 infection. In parallel to routine PCR analysis, a modified commercial scent test was performed to objectify the presence of potential anosmia as a predictor of SARS-CoV-2 positivity. Furthermore, a structured interview assessment of the participants was conducted. A total of 12.1% of the study participants had molecular genetic detection of SARS-CoV-2 infection in the nasopharyngeal swab. It could be demonstrated that these subjects had a significantly weaker olfactory identification performance of the scents. Further analysis of the collected data from the scent test and medical history via random forest (Boruta) algorithm showed that no improvement of the prediction power was achieved by this design. The assay investigated in this study may be suitable for screening general olfactory function. For the screening of COVID-19, it seems to be affected by too many external and internal biases and requires too elaborate and selective pre-test screening.

Knowledge Mapping of Olfactory Dysfunction: A Bibliometric Study

Background

Olfaction is one of the five basic senses of human beings. As such, olfactory dysfunction seriously affects patients' quality of life and can even endanger them. In recent years, olfactory dysfunction has attracted greater research interest, and numerous studies have been published on olfactory dysfunction. However, there are few studies on olfactory dysfunction through bibliometric analysis. This study aims to describe the current situation and identify the foci and potential new research directions of olfactory dysfunction using a bibliometric approach.

Methods

Articles related to olfactory dysfunction published from 2002 to 2021 were located in the Web of Science Core Collection of Clarivate Analytics (London, UK). Bibliometric analyses were conducted with the CiteSpace (Chaomei Chen, Drexel University, Philadelphia, PA, USA) and VOSviewer (Center for Science and Technology Studies, Leiden University, Leiden, Netherlands) software programs.

Results

The number of articles published each year showed an upward trend, especially in 2020, where a sharp increase had occurred due to the coronavirus disease 2019 (COVID-19) pandemic. The United States was the country with the most publications and the strongest international cooperation. In terms of institutions, the greatest number of publications from a single institution came from Dresden University of Technology. Thomas Hummel was the author who had contributed the most articles. An analysis of co-citation networks and burst keywords in the field revealed a shift from “gonadotropin-releasing hormone” and “apoptosis” earlier on to “olfactory training,” “COVID-19,” and “Parkinson's disease” more recently. “Outcome,” “COVID-19,” “infection,” and “pathogenesis” are topics of the research frontier and hotspots.

Conclusion

More attention has been paid to olfactory dysfunction as the understanding of it has improved in the past 20 years. This study provides researchers with an objective, systematic, and comprehensive analysis of the literature on olfactory dysfunction. The current frontier areas and hotspots in the field focus on the pathological mechanisms of olfactory dysfunction after infection with COVID-19 and its different prognoses. The pathophysiological mechanism of olfactory dysfunction in neurodegenerative diseases and COVID-19 will be a primary future research direction.

Clinical Symptoms in Hospitalized and Self-Quarantined Patients with SARS-CoV-2 Infection in Northwestern Greece - Association with Olfactory and Gustatory Dysfunction

Backround: We aimed to assess the relation of chemosensory dysfunction with the reported symptoms in two subgroups of patients in Northwestern Greece: the first one included patients with moderate to severe symptomatology who needed hospitalization and the second one, patients with mild symptoms who recovered at home. Methods:We used a questionnaire to select information about patient demographics, medical history and reported symptoms during infection. Three hundred COVID-19 positive patients who were identified via RT-PCR test in the University Hospital of Ioannina, Greece, were included in the present study, of which 150 recovered at home and the remaining 150 needed hospitalization. Statistical analysis was based on IBM-SPSS Statistics 26.0. Results:The majority of patients had fever during infection, while o minor percentage of those who needed hospitalization (12.67%) suffered from sore throat. There was a statistically significant difference between the loss of smell and clinical symptoms including fatigue, nose congestion, body aches and headache, and loss of taste and reported symptoms including fatigue, body aches, runny nose, headache and sore throat. Conclusion: Fever was the symptom with the highest percentage rate, while sore throat was the symptom with the lowest percentage rate. There are reported clinical symptoms related with olfactory and gustatory dysfunction during COVID-19 infection.

Riech- und Schmeckstörungen

Ziel der vorliegenden Übersicht ist es, einen Überblick über die Ätiologie und Diagnostik von Riech- und Schmeckstörungen zu geben. Da etwa 5 % der Allgemeinbevölkerung betroffen sind, ist es ein häufiges Krankheitsbild. Riechen und Schmecken erhielten v. a. zuletzt Aufmerksamkeit während des Aufkommens der SARS-CoV-2-Pandemie, wobei eine plötzlich aufgetretene Riech- und/oder Schmeckstörung zu den typischen Symptomen zählt. Daneben sind Riechstörungen in der Frühdiagnostik neurodegenerativer Erkrankungen von Bedeutung. Häufig zeigen Patienten mit Riechstörungen Zeichen einer Depression. Die Auswirkungen von Riech‑/Schmeckstörungen sind also umfangreich, die Therapiemöglichkeiten aktuell begrenzt. Nach einem Einblick in die Ätiologie werden Diagnostik und Therapiemöglichkeiten auf dem aktuellen Stand der Literatur erörtert. Auch zukunftsweisende Behandlungsvorstellungen, wie z. B. autologe Schleimhauttransplantationen oder olfaktorische Implantate, werden angesprochen.

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.

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.

Olfactory dysfunction as a post-infectious symptom of SARS-CoV-2 infection

The unexpected onset smell and taste disability was being recognized as a COVID-19 related symptom. Loss of smell might occur alone or be followed by other COVID-19 symptoms, such as a dry cough, fever, headache, and shortness of breath. Other virus infections have been linked to anosmia (parainfluenza, rhinovirus, SARS, and others), affecting up to 20% of the adult population, which is much less common than SARS-CoV-2 infection. A hypothesis about the pathophysiology of post-infectious olfactory loss is that viruses could make an inflammatory response of the nasal mucosa or directly damage the olfactory neuroepithelium. However, in patients with COVID-19, loss of smell may occur without other rhino logic symptoms or suggestive nasal inflammation. According to evidence, anosmia-related SARS-CoV-2 could be a new viral syndrome unique to COVID-19. Furthermore, through experimental intranasal inoculation in mice, SARS-CoV-2 can be inoculated into the olfactory neural circuitry. This disease has not had the required focus, most likely because it is not life-threatening in and of itself. Though patients' quality of living is significantly reduced as their olfactory ability is lost, resulting in lowering and inadequate appetite, excessive or unbalanced food consumption, as well as an overall sense of insecurity. This review aims to give a quick overview of the latest epidemiological research, pathological mechanisms for the dysfunction of smell, and taste in patients infected with SARS-CoV-2. In addition, the initial diagnosis and treatment options for dysfunction are also discussed.

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The pathological mechanism of SARS-CoV-2 infection in olfactory dysfunction.

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Pathognomonic symptoms of sinonasal impairment in COVID-19 patients.

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Treatment of olfactory dysfunction after SARS-CoV-2 infection.

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.

Olfactory training for Olfactory dysfunction in COVID-19: A promising mitigation amidst looming neurocognitive sequelae of the pandemic

Olfactory dysfunction (OD) is a recognized symptom of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is independently associated with neurodegenerative disorders. Moreover, the central nervous system manifestations in patients infected with the coronavirus -2019 (COVID-19) have demonstrated cognitive decline and neuropsychiatric manifestations. Hence, OD in COVID -19 necessitates perusal of its' mechanism and available treatment options to avert possible development of neurocognitive sequelae of the pandemic. The article presents a literature review organized from the published information about olfactory training (OT) for OD during COVID-19. The methodology comprised retrieval of available literature from database searches and subsequent scrutinization of relevant information. Inferentially, Injury to the sustentacular cells, possessing angiotensin-converting enzyme 2 (ACE-2) receptors, is an important mechanism causing OD in COVID-19. OD may be prolonged in severe cases of anosmia predisposing to neurodegenerative and cognitive impairment in COVID-19 infection. OT demonstrates an effective treatment for OD based on human and animal-derived evidence through recent studies. It curtails the progression of OD, besides inducing neural rearrangement and changes in functional connectivity in patients receiving OT. Additionally, contemporary reports support that the administration of OT for COVID-induced anosmia is effective and encompasses no significant adverse effects. The present review highlights the prominence of olfactory training as a recommended intervention for OD in COVID-19. This review can guide the clinicians in curbing neurological repercussions of COVID besides enhancing cognitive rehabilitation through olfactory training.

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.

[Olfactory and gustatory disorders]

Ziel der vorliegenden Übersicht ist es, einen Überblick über die Ätiologie und Diagnostik von Riech- und Schmeckstörungen zu geben. Da etwa 5 % der Allgemeinbevölkerung betroffen sind, ist es ein häufiges Krankheitsbild. Riechen und Schmecken erhielten v. a. zuletzt Aufmerksamkeit während des Aufkommens der SARS-CoV-2-Pandemie, wobei eine plötzlich aufgetretene Riech- und/oder Schmeckstörung zu den typischen Symptomen zählt. Daneben sind Riechstörungen in der Frühdiagnostik neurodegenerativer Erkrankungen von Bedeutung. Häufig zeigen Patienten mit Riechstörungen Zeichen einer Depression. Die Auswirkungen von Riech‑/Schmeckstörungen sind also umfangreich, die Therapiemöglichkeiten aktuell begrenzt. Nach einem Einblick in die Ätiologie werden Diagnostik und Therapiemöglichkeiten auf dem aktuellen Stand der Literatur erörtert. Auch zukunftsweisende Behandlungsvorstellungen, wie z. B. autologe Schleimhauttransplantationen oder olfaktorische Implantate, werden angesprochen.

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.

Preliminary Guidelines for the Clinical Evaluation and Management of Long COVID

Long-lasting coronavirus disease 2019 (COVID-19) symptoms beyond 12 weeks, the so-called ‘long COVID’ have been increasingly reported worldwide. Long COVID can be manifested in various forms, and there is an increasing demand for proper assessment and management. However, it is challenging when trying to determine the best-practice standards of care based on the current evidence because there is no internationally agreed clinical definition or clear treatment pathway. Therefore, the present guidelines have been drafted to provide advice on diagnosis and management based on the latest updated available evidence and the consensus of expert opinion. So far, no standard test and drug treatment can be strongly recommended for patients with long COVID because of a lack of evidence. The present guidelines provide advice based on 12 key questions, including appropriate interventions for long COVID that can be used in clinical practice. Continuous careful observation and studies related to long COVID are needed for the long-term impact of COVID-19 and proper management for long COVID to be determined.

[Prognostic value of olfactory bulb volume in patients with post-viral olfactory dysfunction]

Objective:The purpose of this study was to compare the olfactory function examination results of patients with post-viral olfactory dysfunction（PVOD） in different prognostic groups and analyze prognostic factors, especially the influence of olfactory bulb volume（OBV） on prognosis, so as to provide objective basis for clinical diagnosis and treatment. Methods:After approval by the hospital ethics committee, the patients with PVOD admitted to Beijing Anzhen Hospital's outpatient department from January 2019 to December 2019 were followed up for at least 1 year. These patients completed the Sniffin' Sticks test and MRI examination of the olfactory pathway before treatment. According to the results of the Sniffin' Sticks test after 1 year follow-up（threshold-discrimination-identification（TDI） score of the patients was increased at least 6 points）, the patients were divided into two groups as the improvement group and the non-improvement group. The prognostic factors of PVOD patients were preliminarily determined by comparing the differences of various factors and the results of olfactory function examination between the two groups. Results:In this study, 47 patients with PVOD were included, with the smell improvement rate was 53.2%. Compared with the improvement group, the patients in the non-improvement group had longer duration, poorer initial olfactory function, higher olfactory threshold, and poorer olfactory discrimination and recognition ability（All P<0.01）. There was no statistical difference in terms of gender, age, allergic rhinitis and smoking between the two groups（All P>0.05）.The OBV of the non-improvement group was （59.48±23.92） mm³, which was significantly lower than that in the improvement group（[92.77±14.35]mm³, P<0.001）. Multiple logistic regression analysis showed that prognostic factors included course of disease（OR 0.677, 95%CI 0.461-0.993, P=0.046）, initial T value（OR 263.806, 95%CI 1.028-67 675.884, P=0.049） and OBV（OR 1.160, 95%CI 1.002-1.343, P=0.047）. The area under the receiver operating characteristic curve（ROC curve） of OBV was 0.888（0.797-0.979, P<0.001）. The correct diagnostic index of OBV≥78.50 mm³was used to determine the prognosis of olfactory function, with a specificity of 0.818 and a sensitivity of 0.840. The ROC curve analysis showed that the area under the ROC curve of duration was 0.822（0.703-0.940, P<0.001）. The correct diagnostic index of the duration ≤6 months was used to determine the prognosis of olfactory function, with a specificity of 0.727 and a sensitivity of 0.800. The area of T score was 0.793（0.662-0.924, P=0.001）. T score ≥1.25 was used as the correct diagnostic index to determine the prognosis of olfactory function. The specificity and sensitivity were 0.818 and 0.680, respectively. Conclusion:The prognosis of olfactory function in PVOD patients is related to the course of disease, the degree of olfactory loss and OBV. Those with no improvement in olfactory function have a longer disease course, aggravated olfactory damage and reduced OBV than those with improved olfactory function. The factors of Duration ≤6 months, T value ≥1.25 and OBV≥78.50 mm³suggested better prognosis, and the results of objective olfactory examination have greater value in evaluating the prognosis of olfactory function.

Acupoint stimulation improves pain and quality of life in head and neck cancer patients with chemoradiotherapy: a randomized controlled trial

Objective

This study aimed to evaluate the effect of acupoint stimulation on pain, negative moods, and quality of life for head and neck cancer (HNC) patients who underwent concurrent chemoradiotherapy (CCRT).

Methods

This randomized controlled trial recruited participants from a medical center and randomly assigned using a permuted block randomization list with computer-generated random serial numbers into the AcuCare group (n ​= ​46) receiving acupoint stimulation with transcutaneous acupoint electrical stimulation (TAES) and auricular acupressure (AA) or the control group (n ​= ​46) without any acupoint stimulation. Outcomes were repeatedly assessed pain intensity using the visual analogue scale, negative moods using the hospital anxiety and depression scale, and quality of life (QoL) using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire—Head and Neck 35.

Results

After adjusting varying mucositis grades and time-dependent growth effects, the generalized estimating equations showed a significantly increase in pain intensity at weeks 1, 2, 3, and 6 (P ​< ​0.05), but not in negative moods (P ​> ​0.05), compared to baseline and control group. Analysis of covariance showed a significant group-difference in the senses problems of QoL (F ​= ​7.33, P ​= ​0.01) at Week 6.

Conclusions

This study supports that acupoint stimulation could effectively reduce pain and improve senses problem of QoL for patients with HNC.

Trial registration

This study was registered at https://clinicaltrials.gov/NCT03640195.

[Predictors of posttreatment olfactory improvement in patients with postviral olfactory dysfunction]

Objective:To analyzed the results of olfactory function test in patients with post-viral olfactory dysfunction（PVOD）, and evaluated the prognostic factors, so as to provide a basis for clinical diagnosis and treatment. Methods:This study included patients who were diagnosed with PVOD at least one year ago in Beijing Anzhen Hospital and whose telephone interviews of subjective olfactory function were available. The general condition of the patients, the results Sniffin' Sticks olfactory test and the event-related potentials（ERPs） were analyzed in different improvement groups. This study retrospectively analyzed PVOD patients treated in the outpatient department of Beijing Anzhen Hospital. They were given olfactory training for 4 months. The Sniffin' Sticks test was performed on the patients before and after the treatment. The Sniffin' Sticks test and event-related potentials（ERPs） results were used to evaluate the prognostic factors. Results:In this study, the olfactory improvement rate of 63 PVOD patients was 52.38%（33/63）. Compared to the non-improvement group, the course of disease in the group with improved subjective olfactory function was significantly shorter（P<0.001）, the initial olfactory function was significantly better（P<0.001）, and the olfactory threshold was much lower（P<0.001）. The presence of olfactory event-related potentials and trigeminal ERPs（tERPs） were 52.38%（33/63） and 87.30%（55/63）, respectively. The presence of oERPs in the olfactory function improvement group was significantly higher than that in the non-improvement group（P<0.05）, but there was no difference in the presence of tERPs（P>0.05）. Latency of N1 and P2 waves in oERPs with improvement group（ON1L, OP2L） were longer than those in the non-improvement group（P<0.05）, N1 and P2 wave amplitudes（ON1A, OP2A） had no difference（P>0.05）. The N1 and P2 amplitudes and latency of tERPs showed no difference between the two groups. Multivariate Logistic regression analysis showed that threshold value before treatment（OR=21.376, 95%CI: 2.172-210.377, P=0.009）; ON1L（OR=0.994, 95%CI: 0.988-0.999, P=0.029） and course of disease（OR=0.607, 95%CI: 0.405-0.920, P=0.016） was significantly associated with olfactory prognosis. Conclusion:The course of olfactory dysfunction, the severity of olfactory dysfunction, the threshold of olfactory function, and the latency of N1 wave of oERPs can be used to evaluate the prognosis of PVOD patients. However, age, olfactory discrimination, recognition ability, oERPs amplitude and tERPs wave value had less prognostic value.

Olfactory recovery following infection with COVID-19: A systematic review

Olfactory loss has been identified as one of the common symptoms related to COVID-19 infection. Although olfactory loss is recognized, our understanding of both the extent of loss and time to olfactory recovery following infection is less well known. Similarly, knowledge of potential impactful patient factors and therapies that influence olfactory recovery is desirable but is not overtly clear in the literature. Our systematic review sought to fill this knowledge gap. We included studies that: involved either an observational or an interventional design that reported data on patients with olfactory dysfunction due to Reverse Transcription Polymerase Chain Reaction (RT-PCR) diagnosed COVID-19 infection; and reported data regarding olfactory recovery measured by an objective olfactory test, Likert scale and/or visual analog scale (VAS). The study methods were determined a priori and registered in PROSPERO (Registration Number CRD42020204354). An information specialist searched Medline, Embase, LitCovid and the Cochrane Register of Controlled Trials up to March 2021, and two reviewers were involved in all aspects of study selection and data collection. After screening 2788 citations, a total of 44 studies of assorted observational designs were included. Patients had undergone objective COVID-19 testing, and most were adult patients with mild to moderate COVID-19. Olfactory recovery was found to occur as early as 7 days, with most patients recovering olfaction within 30 days. Few studies included prolonged follow-up to 6 months or longer duration. Poor olfaction at initial presentation was associated with poor recovery rates. Only a small number of studies assessed olfactory retraining and steroid therapy. Additional trials are underway.

Treatment and Prognosis of COVID-19 Associated Olfactory and Gustatory Dysfunctions

Olfactory and gustatory dysfunctions are important initial symptoms of coronavirus disease 2019 (COVID-19). However, the treatment modality for these conditions has yet to be clearly established. Therefore, most physicians have been administering empirical treatments for COVID-19-associated olfactory dysfunction, including topical or systemic steroid supplementation and olfactory training. In this literature review, we summarize the clinical course and effects of various treatments currently being conducted in patients with COVID-19-associated olfactory and gustatory dysfunctions.

Prevalence of subjective impairments of the sense of smell and taste in employees of retirement and nursing homes during SARS-CoV-2 pandemic

Aim

To investigate the usability of querying subjective impairments of the sense of smell and taste in order to improve pre‐test probability in testing for SARS‐CoV‐2. To achieve this, exploring the prevalence of these restrictions in the COVID‐19‐negative population, as well as nasal co‐symptoms.

Design

A cross‐sectional study was carried out as part of the secondary prophylaxis, following the STROBE guidelines of the EQUATOR network.

Methods

In total, 1,734 employees of retirement and nursing homes were tested for COVID‐19 and asked for subjective reduction or loss in the sense of smell and taste, furthermore about nasal co‐symptoms such as nasal obstruction and rhinorrhoea.

Results

All employees tested negative for COVID‐19. Subjective hyposmia and hypogeusia rarely occurred and were usually accompanied by other nasal symptoms such as nasal obstruction. Querying subjective hyposmia/anosmia or hypogeusia/ageusia appears to be a useful anamnestic instrument for the clinical assessment of the probability of SARS‐CoV‐2 infection.

Contemporary Review of Olfactory Dysfunction in COVID-19

The pandemic of coronavirus disease 2019 (COVID-19) is an extreme threat to international health care, resulting in more than two million deaths. Data reveal that olfactory disorder is a characteristic symptom of COVID-19 and has unique clinical manifestations. The olfactory dysfunction induced by COVID-19 has sudden onset, short duration, and rapid recovery, with anosmia often the only symptom. Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) affects the human body by binding to angiotensin converting enzyme 2 (ACE2) of the olfactory epithelium. However, the etiology of COVID-19-induced olfactory dysfunction is unclear. In many countries, vaccines for COVID-19 in human are beginning to be administered. Conventional conservative treatments are common for olfactory disorders caused by COVID-19. Rhinologists should be aware of olfactory dysfunction to avoid delayed diagnosis of COVID-19. The article reviews the latest scientific evidence of anosmia in COVID-19.

Comparison of the Healing Effect of Nasal Saline Irrigation with Triamcinolone Acetonide Versus Nasal Saline Irrigation alone in COVID-19 Related Olfactory Dysfunction: A Randomized Controlled Study

There is no routinely determined treatment for olfactory dysfunction because of COVID-19. Saline irrigation and nasal corticosteroid treatments are safe and inexpensive methods, and have low side effects. In our study, we argue that saline nasal irrigation and topical corticosteroid treatment can be used in the treatment of patients with olfactory loss in all areas of rhinology. A total of 150 patients who admitted to our clinic with other symptoms or with only acute odor loss, diagnosed with COVID-19 with RT-PCR were divided into 3 equal groups.Fifty patients in Group 1 were not given any extra treatments. The other 50 patients in Group 2 were given saline irrigation for treatment; and the 50 people in Group 3 were given both saline irrigation and nasal steroid spray for treatment. The “Subjective Olfactory Capability (SOC)” was used for olfactory function evaluation of patients. Self-Rating Olfactory Score (SROS), and Olfactory Dysfunction Duration (ODD) were recorded on the 1st, 15th and 30th days. SROS of the group receiving Nasal Saline + Triamcinolone Acetonide treatment on the 30th day was significantly higher than in other groups (p^−1–3 = 0.018, p²⁻³ =0.033). Also, the ODD was significantly reduced in this group compared to other groups (p^−1–3 =0.022, p²⁻³ =0.028,). Topical triamcinolone treatment was found to be successful in the treatment of olfactory dysfunction due to COVID-19. Nasal steroids, which are both inexpensive and have low side effect profiles, can be used safely in the treatment of patients with olfactory losses.

Effects of olfactory training on posttraumatic olfactory dysfunction: a systematic review and meta-analysis

BACKGROUND

Posttraumatic olfactory dysfunction is a clinical challenge due to refractory characteristics and limited therapeutic options. Olfactory training has been proved to be effective for olfactory dysfunction with varied etiologies. We pooled existing studies to evaluate the effects of olfactory training in patients with posttraumatic olfactory dysfunction.

METHODS

A systematic literature review using PubMed, Embase, Cochrane Library, and Web of Science was conducted to identify studies assessing olfactory change in patients with posttraumatic olfactory dysfunction after olfactory training.

RESULTS

Of the initial 812 abstracts reviewed, 13 full-text articles were included. Clinically significant results after olfactory training were defined as an improvement of threshold, discrimination, and identification (TDI) score ≥6 or University of Pennsylvania Smell Identification Test (UPSIT) score ≥4. Six studies were included in the meta-analysis, 36.31% (95% confidence interval [CI], 0.28 to 0.45) of posttraumatic patients would achieve clinically significant results after olfactory training with a mean increase of TDI score of 4.61.

CONCLUSION

Olfactory training might be a promising modality for the treatment of posttraumatic olfactory dysfunction. More high-quality studies with controls are needed to clarify the effect of olfactory training on total olfactory performance and subcomponents of olfaction.

Postinfectious Olfactory Dysfunction: Oral Steroids and Olfactory Training versus Olfactory Training Alone: Is There any Benefit from Steroids?

INTRODUCTION

There are limited treatment options for postinfectious olfactory dysfunction (PIOD). Olfactory training has recently been used in clinical practice, but no medical treatment is widely accepted. Although there is weak evidence for their value, some physicians use oral corticosteroids as first-line treatment. The aim of this study was to compare combined oral methylprednisolone and olfactory training with olfactory training alone in the management of PIOD.

METHODS

This prospective cohort study included 131 patients with PIOD over a 2-year period before the COVID-19 pandemic. Seventy-eight patients who were treated with oral methylprednisolone and olfactory training (group A) were compared with 53 patients who were treated with olfactory training only (group B). Olfactory function was evaluated with "Sniffin' Sticks" at baseline and 2, 8, and 16 weeks after initial assessment. Patients who improved after steroid treatment underwent magnetic resonance imaging of the paranasal sinuses, skin prick tests, lung spirometry, and sputum eosinophil assessment.

RESULTS

Oral steroids improved 19.23% of patients (n = 15) of group A. History, clinical evaluation, imaging, and laboratory tests identified an inflammatory background in half of them (n = 8). The remaining 7 had no findings of nasal inflammation, and all had a short history of olfactory dysfunction. Both groups significantly improved in olfactory testing results at the end of the olfactory training scheme without significant difference between them.

CONCLUSIONS

The percentage of improved patients after oral methylprednisolone was relatively low to suggest it as first-line treatment. Half of the improved patients had an underlying upper airway inflammatory condition not related to the infection that caused the acute loss of olfactory function.