Olfactory Training for Postviral Olfactory Dysfunction: Systematic Review and Meta-analysis

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.

Null cross-modal effects of olfactory training on visual, auditory or olfactory working memory in 6- to 9-year-old children

Systematic exposure to odours (olfactory training, OT) is a method of smell loss treatment. Due to olfactory system projections to prefrontal brain areas, OT has been hypothesized to enhance cognitive functions, but its effects have been studied predominantly in adults. This study tested OT effects on working memory (WM), i.e., the ability to store and manipulate information for a short time, in healthy children aged 6-9 years. We expected OT to improve olfactory WM and establish cross-modal transfer to visual and auditory WM. Participants performed 12 weeks of bi-daily OT with either 4 odours (lemon, eucalyptus, rose, cloves; OT group) or odourless propylene glycol (placebo group). Pre- and post-training, participants' WM was measured utilizing odours (olfactory WM) or pictures (visual WM) and a word-span task (auditory WM). 84 children (40 girls) completed the study. The analyses revealed no changes in the WM performance following OT. The olfactory WM task was the most difficult for children, highlighting the need to include olfactory-related tasks in educational programmes to improve children's odour knowledge and memory, just as they learn about sounds and pictures. Further neuroimaging research is needed to fully understand the impact of OT on cognitive functions in children.

Olfactory dysfunction and the role of stem cells in the regeneration of olfactory neurons

The prevalence of COVID-19 has drawn increasing attention to olfactory dysfunction among researchers. Olfactory dysfunction manifests in various clinical types, influenced by numerous pathogenic factors. Despite this diversity, the underlying pathogenesis remains largely elusive, contributing to a lack of standardized treatment approaches. However, the potential regeneration of olfactory neurons within the nasal cavity presents a promising avenue for addressing olfactory dysfunction effectively. Our review aims to delve into the current research landscape and treatment modalities concerning olfactory dysfunction, emphasizing etiology, pathogenesis, clinical interventions, and the role of stem cells in regenerating olfactory nerves. Through this comprehensive examination, we aim to provide valuable insights into understanding the onset, progression, and treatment of olfactory dysfunction diseases.

Infectious disease for the rhinologist

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent literature relating to viral, fungal and bacterial infections and their interactions within the sinonasal tract in the past 18 months.

RECENT FINDINGS

Coronavirus disease 2019 (COVID-19)-associated olfactory dysfunction (OD) is variant dependent. Magnetic resonance imaging studies have found greater olfactory cleft opacification and higher olfactory bulb volume in post-COVID-19 OD. Olfactory training remains the mainstay of treatment, while platelet-rich plasma injections and ultramicronized palmitoylethanolamide and luteolin combination oral supplementation have shown early promise.Consensus statements on paranasal sinus fungal balls and acute invasive fungal sinusitis have been released.Studies on the nasal microbiome have reported Staphylococcus and Corynebacterium as the most abundant genera, with higher levels of Staphylococcus and Corynebacterium being found in patients with chronic rhinosinusitis (CRS) and healthy individuals respectively. However, there is conflicting evidence on the significance of biodiversity of the nasal microbiome found in CRS versus healthy patients.

SUMMARY

While the peak of the COVID-19 pandemic is behind us, its sequelae continue to pose treatment challenges. Further studies in OD have implications in managing the condition, beyond those afflicted post-COVID-19 infection. Similarly, more research is needed in studying the nasal microbiome and its implications in the development and treatment of CRS.

Olfactory training with four and eight odors: comparison with clinical testing and olfactory bulb volumetrics

PURPOSE

Post-infectious olfactory dysfunction (PIOD) is one of the most common causes of olfactory impairment but has limited treatment options. Recently, olfactory training (OT) has been considered an effective treatment method; however, several questions have arisen regarding its optimal scheme. The aim of this study was to assess whether an OT scheme with 8 odors is more effective than the classic OT scheme with 4 odors by comparing psychophysical test results and olfactory bulb (OB) volumetrics.

METHODS

In this prospective cohort study, 72 patients with PIOD were included. The patients followed either the classic 4-odor OT scheme (COT; n = 34 patients) or an extended 8-odor scheme (EOT; n = 38 patients) for 16 weeks. All patients underwent olfactory testing with a Sniffin'Sticks battery test at 0, 8, and 16 weeks. Of the patients, 38 underwent brain magnetic resonance imaging for OB volumetric assessment before and after treatment.

RESULTS

The comparison of the olfactory test results did not show any significant difference between the two study groups, in agreement with the OB volumetrics. The convex OB showed better test results than the non-convex OB, with significantly better improvement after treatment regardless of OT type. The EOT group presented significantly better adherence than the COT group.

CONCLUSION

The number of odors did not appear to play a significant role in the effect of the OT. However, the training scheme with more than four odors showed better adherence among the patients in a long-term treatment plan. The shape of the OB may have prognostic value in clinical assessment and warrants further investigation.

Olfactory dysfunction and training in children with COVID-19 infection: A prospective study Post-COVID pediatric olfactory training

OBJECTIVE

Postviral olfactory dysfunction (OD) including corona 2019 viral disease (COVID-19) OD occurs in both adults and children. Despite limited reports of efficacy in treating adult postviral including COVID-19 OD with olfactory training (OT), its effects on children in general, and post-COVID-19 in specific, is unknown. The study aimed at evaluating the effects of OT in a COVID-19 OD pediatric cohort.

METHODS

A single-arm prospective study of pediatric COVID-19 OD subjects confirmed by the University of Pennsylvania Smell Identification Test (UPSIT), was conducted. All subjects underwent OT by sniffing 4 odorants (lavender, orange, peppermint, and eucalyptus) for 1 min twice a day for 3 months. Subjects underwent an odorant identification test (OIT) of the 4 odorants each visit. A repeat UPSIT was administered at the 4th visit.

RESULTS

The study enrolled a total of 37 subjects [11 males/26 females with mean age/standard deviation (std) of 15.6(2.1) years]. The time interval between COVID-19 and entry was 5.3(2.4) months. The mean pre/post study UPSIT score improvement was 2.3(4.7), p = .09. OIT scores between entry and 3 subsequent visits showed a mean improvement of 1.8(1.5), 1.8(1.9) and 2.3(1.9) odorants, respectively, with P < .001 for all 3 comparisons.

CONCLUSIONS

OT subjects were predominantly female teens with substantial OD lasting greater than 5 months. OT did not affect OD as measured by UPSIT but OIT scores improved during OT. We postulate that OT likely has a role in pediatric post-COVID OD recovery, but UPSIT likely is too rigid to detect disparate odorant improvement.

Effectiveness of Platelet-Rich Plasma for COVID-19-Related Olfactory Dysfunction: A Controlled Study

OBJECTIVE

To investigate the effectiveness of platelet-rich plasma (PRP) injection into the olfactory clefts of coronavirus disease 2019 (COVID-19) patients with persistent olfactory dysfunction (OD).

STUDY DESIGN

Controlled study.

SETTING

Multicenter study.

METHODS

From March 2022 to November 2022, COVID-19 patients with persistent OD were recruited from three European hospitals to undergo PRP injections into the olfactory clefts. Olfactory function was evaluated at baseline and 10 weeks postinjection with the Olfactory Disorder Questionnaire (ODQ) and threshold, discrimination, and identification (TDI) test. Data were compared with a control group of untreated patients.

RESULTS

Eighty-one patients who underwent PRP injection and 78 controls were included. Sixty-five PRP patients (80.3%) experienced subjective smell improvement after a mean duration of 3.4 ± 1.9 weeks. The parosmia, life quality statement, and ODQ sub- and total scores significantly decreased from pre- to 10-week postinjection in the PRP group. The TDI sub- and total scores significantly increased 10 weeks postinjection. In controls, the ODQ score did not change over time, while the discrimination, identification, and total TDI scores significantly increase after 10 weeks of follow-up. The 10-week TDI and ODQ scores were significantly better in the PRP group compared with the controls.

CONCLUSION

Patients who underwent PRP injection reported better 10-week subjective and objective smell outcomes than controls. Future randomized-controlled studies using saline injection into the olfactory cleft of controls are needed to determine the superiority of PRP over placebo.

Olfactory recovery following omicron variant infection: a psychophysical prospective case-control study with six-month follow up

OBJECTIVE

This study aimed to evaluate the recovery of olfactory function at six months in individuals infected with the coronavirus disease 2019 omicron variant, using psychophysical tests.

METHODS

A prospective case-control study that included severe acute respiratory syndrome coronavirus-2 patients infected in February and March 2022 was conducted. Patients underwent the Sniffin' Sticks test within 10 days of infection and again after at least 6 months. The olfactory scores were compared with those of a control group.

RESULTS

In all, 102 patients and 120 controls were enrolled in the study. At baseline, 26 patients (25.5 per cent) self-reported smell loss. The median threshold, discrimination and identification score was 33.6 (interquartile range, 12.5) for the cases and 36.5 (interquartile range, 4.38) for the controls (p < 0.001). Based on the threshold, discrimination and identification scores, 12 controls and 34 patients reported olfactory dysfunction (p < 0.001). Eighty cases underwent re-evaluation at six months; the median threshold, discrimination and identification score was 37.1 (interquartile range, 4.75) with no significant differences compared with the controls.

CONCLUSION

Six months after infection, the prevalence of olfactory dysfunction in patients did not differ significantly from the control population.

Comparative Analysis of Olfactory and Gustatory Function of Patients With COVID-19 Olfactory Dysfunction and Non-COVID-19 Postinfectious Olfactory Dysfunction

BACKGROUND

Coronavirus disease 2019 (COVID-19) is known to have a high incidence of loss of smell and taste. However, studies in the early stages of the COVID-19 pandemic have evaluated these symptoms using subjective surveys and simple olfactory tests only. Hence, we compared the olfactory and gustatory characteristics of patient groups with COVID-19 olfactory dysfunction (C19OD) and non-COVID-19 postinfectious olfactory dysfunction (PIOD) using an objective olfactory test and evaluated the significance of olfactory training in both patient groups.

METHODS

We retrospectively analyzed the medical records of 14 patients with a decreased sense of smell after having positive COVID-19 polymerase chain reaction results, and 56 patients with PIOD with no history of confirmed COVID-19. Participants were evaluated using the Korean version of the Sniffin' stick (KVSS) II, and chemical gustometry and olfactory training was assessed during their first visit. Olfactory training was then re-evaluated after an average of 8 (± 6) weeks.

RESULTS

The average age of participants in the C19OD group was lower than in those in the non-COVID-19 PIOD group. The proportion of men in the C19OD group was higher than in the non-COVID-19 PIOD group. At baseline assessment, the C19OD group had better olfactory and gustatory functions. After olfactory training, the non-COVID-19 PIOD patient group showed a significant increase in all KVSS II Total, T, D, and I scores, but there was a non-significant increase in all scores in the C19OD group.

CONCLUSION

The C19OD group had better olfactory and gustatory function than the non-COVID-19 PIOD group at the initial assessment. After olfactory training, there was an increase in olfactory function test scores in both groups. Olfactory training may be helpful in C19OD, as in non-COVID-19 PIOD.

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.

A double-blinded randomised controlled trial of vitamin A drops to treat post-viral olfactory loss: study protocol for a proof-of-concept study for vitamin A nasal drops in post-viral olfactory loss (APOLLO)

BACKGROUND

Smell loss is a common problem with an estimated 5% of the population having no functioning sense of smell. Viral causes of smell loss are the second most common cause and the coronavirus (COVID-19) pandemic is estimated to have caused 20,000 more people this year to have a lasting loss of smell. Isolation, depression, anxiety, and risk of danger from hazards such as toxic gas and spoiled food are all negative impacts. It also affects appetite with weight loss/gain in two-thirds of those affected. Phantosmia or smell distortion can also occur making most foods seem unpalatable. Smell training has been tried with good results in the immediate post-viral phase. Evidence behind treatment with steroids has not shown to have proven effectiveness. With this, a key problem for patients and their clinicians is the lack of proven effective therapeutic treatment options. Based on previous studies, there is some evidence supporting the regenerative potential of retinoic acid, the metabolically active form of vitamin A in the regeneration of olfactory receptor neurons. It is based on this concept that we have chosen vitamin A as our study comparator.

AIM

To undertake a two-arm randomised trial of intranasally delivered vitamin A vs no intervention to determine proof of concept.

METHODS/DESIGN

The study will compare 10,000 IU once daily Vitamin A self-administered intranasal drops versus peanut oil drops (placebo) delivered over 12 weeks in patients with post-viral olfactory loss. Potentially eligible patients will be recruited from the Smell & Taste Clinic and via the charity Fifth Sense. They will be invited to attend the Brain Imaging Centre at the University of East Anglia on two occasions, 3 months apart. If they meet the eligibility criteria, they will be consented to enter the study and randomised to receive vitamin A drops or no treatment in a 2:1 ratio. MRI scanning will enable volumetric measurement of the OB and ROS; fMRI will then be conducted using an olfactometer to deliver pulsed odours-phenethylalcohol (rose-like) and hydrogen sulphide (rotten eggs). Participants will also perform a standard smell test at both visits as well as complete a quality-of-life questionnaire. Change in OB volume will be the primary outcome measure.

DISCUSSION

We expect the outputs of this study to enable a subsequent randomised controlled trial of Vitamin A versus placebo. With PPI input we will make the outputs publicly available using journals, conferences, and social media via Fifth Sense. We have already prepared a draft RCT proposal in partnership with the Norwich Clinical Trials Unit and plan to develop this further in light of the findings.

TRIAL REGISTRATION

ISRCTN registry 39523. Date of registration in the primary registry: 23rd February 2021.

Outcome and Safety of Insulin in the Management of Smell Loss: A Systematic Review

Background: Olfactory dysfunction can negatively impact the quality of life and increase the risk of danger from warning odors. Various factors can cause olfactory dysfunction, including COVID-19 infection, which has increased anosmia cases. No medications are approved; however, recent studies have suggested that intranasal insulin could effectively treat olfactory dysfunction. Aim: To comprehensively evaluate the effectiveness and safety of intranasal insulin in treating olfactory dysfunction. Materials and Methods: PubMed, Google Scholar, and CENTRAL databases were searched using specific keywords, and the outputs were screened using the Rayyan AI system. Original research articles published without time frame limitations that reported the relevant outcomes were included. The reviewers performed the screening and data extraction, and any disagreements were resolved by a third senior author. Results: This systematic review identified 66 references from 3 databases, with 45 articles meeting the criteria for review after duplicates were removed. Six articles met the inclusion criteria and were selected, including 177 subjects. The selected studies consisted of various study designs, including pilot studies, placebo-controlled trials, crossover studies, and randomized clinical trials. The findings showed that intranasal insulin therapy had beneficial effects on olfactory function. Specifically, improvements were observed in olfactory detection and discrimination in patients with post-COVID-19 anosmia, olfactory threshold performance in healthy participants, and odor identification in hyposmic patients. However, there were variations in the observed effects based on different doses of insulin administered and gender differences. It also shows that using insulin provides good outcomes. Using it intranasally was safe and did not cause any complications. Conclusion: Intranasal insulin has shown promising results as a potentially safe treatment for olfactory dysfunction. Studies suggest that it can improve olfactory thresholds. Further studies are needed to investigate optimal doses and potential gender differences in response.

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.

Efficacy of Palmitoylethanolamide and Luteolin Association on Post-Covid Olfactory Dysfunction: A Systematic Review and Meta-Analysis of Clinical Studies

Post-Covid Olfactory Dysfunction (PCOD) is characterized by olfactory abnormalities, hyposmia, and anosmia, which are among the most often enduring symptoms in individuals who have recovered from SARS-CoV-2 infection. This disorder has been reported to persist in subsets of patients well after 12 months following infection, significantly affecting their quality of life. Despite the high prevalence of PCOD among patients who suffered from SARS-CoV-2 infection, specific therapeutic strategies are still limited. Among these, emerging evidence seems to indicate the administration of CoUltraPEALut, a combination of micronized Palmitoylethanolamide (PEA), an endogenous fatty acid amide, and Luteolin, a natural antioxidant flavonoid, as a viable therapy, especially when given as an adjuvant to olfactory training. Based on the above, a systematic review and a meta-analysis of the literature were conducted, with the aim of evaluating the efficacy of CoUltraPEALut as an addition to olfactory training (OT), in treating PCOD symptoms. Pubmed (MEDLINE), Embase (OVID), and Web of Science scientific databases were screened from the inception until 31 May 2023, and a total of 407 articles were recovered; only five of these studies (441 total patients between treated and control groups) were included in the systematic review. CoUltraPEALut demonstrated significant efficacy in the overall recovery of the olfactory function, compared to the conventional therapy, suggesting that it could represent a possible future adjuvant treatment for PCOD.

Effect of any form of steroids in comparison with that of other medications on the duration of olfactory dysfunction in patients with COVID-19: A systematic review of randomized trials and quasi-experimental studies

BACKGROUND

The life quality of about two-thirds of patients with COVID-19 is affected by related olfactory dysfunctions. The negative impact of olfactory dysfunction ranged from the decreased pleasure of eating to impaired quality of life. This research aimed to provide a comprehensive understanding of the effects of corticosteroid treatments by comparing that to other currently available treatments and interventions.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist's 27-point checklist was used to conduct this review. PubMed (Public/Publisher MEDLINE), PubMed Central and EMBASE (Excerpta Medica Database) databases were conveniently selected and Boolean search commands were used for a comprehensive literature search. Five core search terms were "effects of treatments", " COVID-19-related olfactory dysfunction", "corticosteroids", "treatments" and "interventions". The reporting qualities of the included studies were appraised using JBI (Joanna Briggs Institute) appraisal tools. The characteristics of the 21 experimental studies with a total sample (of 130,550) were aggregated using frequencies and percentages and presented descriptively. The main interventions and their effects on the duration of the COVID-19-related olfactory dysfunction were narratively analyzed.

RESULTS

Among patients with COVID-19, the normal functions of the olfactory lobe were about 23 days earlier to gain with the treatments of fluticasone and triamcinolone acetonide nasal spray compared with that of mometasone furoate nasal spray and oral corticosteroid. The smell loss duration was reduced by fluticasone and triamcinolone acetonide nasal spray 9 days earlier than the inflawell syrup and 16 days earlier than the lavender syrup. The nasal spray of corticosteroids ended the COVID-19-related smell loss symptoms 2 days earlier than the zinc supplementation, about 47 days earlier than carbamazepine treatment and was more effective than palmitoylethanolamide (PEA) and luteolin and omega-3 supplementations and olfactory training. Treatment with oral corticosteroid plus olfactory training significantly improved Threshold, Discrimination and Identification (TDI) scores compared with olfactory training alone. A full dose of the COVID-19 vaccination was not uncertain to reduce the COVID-19-related smell loss duration.

CONCLUSION

Corticosteroid treatment is effective in reducing the duration of COVID-19-related smell loss and olfactory training, the basic, essential and effective intervention, should be used as a combination therapy.

Persistent post-COVID-19 dysosmia: Practices survey of members of the French National Union of Otorhinolaryngology-Head and Neck Surgery Specialists. CROSS analysis

INTRODUCTION

Persistent dysosmia more than 3 months after SARS-CoV-2 disease (COVID-19) is considered as long-COVID olfactory disease (LCOD). The primary objective of this study was to evaluate the diagnostic and therapeutic management of LCOD in the daily clinical practice of members of the National Union of Otorhinolaryngology-Head and Neck Surgery Specialists (Syndicat national des médecins spécialisés en ORL et chirurgie cervico-faciale) (SNORL). The secondary objective was to identify factors influencing management within the descriptive survey data.

MATERIALS AND METHODS

A questionnaire was designed (GoogleForm®) and e-mailed to all 715 SNORL members in January 2022.

RESULTS

The response rate was 7.4% (n=53/715). In total, 94.3% of respondents (n=50) had managed LCOD cases, and 56% (n=28) used psychophysical olfactory tests. Specific olfactory medical therapy involved local corticosteroid nasal sprays in 49.1% of cases (n=26) and oral corticosteroids in 32.1% (n=17). Olfactory self-training was prescribed by 81.1% of respondents, with associated speech pathologist therapy in 15.1% (n=8) of cases. No predictive factors for specific management were identified.

CONCLUSION

Olfactometry is currently under-applied. Consistent with guidelines, non-drug therapy (olfactory training) is the first-line treatment for LCOD.

Considerations in Children and Adolescents Related to Coronavirus Disease 2019 (COVID-19)

Pediatric post-acute sequelae of SARS-CoV-2 (PASC) or "long COVID" are a complex multisystemic disease that affects children's physical, social, and mental health. PASC has a variable presentation, time course, and severity and can affect children even with mild or asymptomatic acute COVID-19 symptoms. Screening for PASC in children with a history of SARS-CoV-2 infection is important for early detection and intervention. A multifaceted treatment approach and utilization of multidisciplinary care, if available, are beneficial in managing the complexities of PASC. Lifestyle interventions, physical rehabilitation, and mental health management are important treatment approaches to improve pediatric PASC patients' quality of life.

Efficacy of Stellate Ganglion Block in Treating Long-Term COVID-19-Related Olfactory and Gustatory Dysfunction: A Case Series

Olfactory and gustatory dysfunction, including anosmia, parosmia, ageusia, and dysgeusia, are common long-term symptoms of coronavirus disease 2019 (COVID-19) infection. These symptoms can have a severe impact on quality of life of a patient, including psychological well-being. Stellate ganglion block (SGB) has recently been explored as a potential therapeutic intervention for these symptoms. In this case series, we present six patients with long-term COVID-19 symptoms and we detail how their symptoms evolved after an SGB. All SGB were performed under ultrasound guidance by the same physician. Patients had a right SGB during the initial visit, followed by a left SGB at a subsequent visit. All but one patient reported improvements in olfaction and gustation after the SGB. Our findings suggest that SGB may be a promising therapeutic intervention for patients with olfactory and gustatory dysfunction related to long-term COVID-19 symptoms. Further research is needed to confirm these findings and to explore the optimal treatment protocol.

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.

SARS-CoV-2 Effects on Psychophysical Olfactory Scores: Prospective Study With Evaluation Before and 60-Days After Infection

The aim of this study was to prospectively evaluate the olfactory function in a series of individuals infected with SARS-CoV-2 and who had undergone psychophysical olfactory assessment prior to infection. Individuals unexposed to SARS-CoV-2 infection underwent a psychophysical evaluation of smell with the Sniffin' Sticks test. The subjects were followed prospectively and included in the study if they developed SARS-CoV-2 infection with a second test 60 days after recovery. At the 60-day follow-up of the 41 included subjects, 2 (4.9%) self-reported persistent olfactory dysfunction (OD). The differences between TDI scores before and after infection were statistically significant (37 [interquartile range (IQR), 34.25-39.25] vs 34.75 [IQR, 32.25-38]; p = .021). Analyzing the individual olfactory domains, the differences were significant for threshold (T) (9.75 [IQR, 9-11.25] vs 8.25 [IQR, 7.25-10.25]; p = .009) but not for odor discrimination (D) (p = .443) and identification (I) (p = .159). SARS-CoV-2 causes a significant reduction in the olfactory function, in particular affecting the olfactory threshold, even in subjects who do not self-report an OD.

Efficacy of Combined Visual-Olfactory Training With Patient-Preferred Scents as Treatment for Patients With COVID-19 Resultant Olfactory Loss: A Randomized Clinical Trial

Importance

The number of olfactory dysfunction cases has increased dramatically because of the COVID-19 pandemic. Identifying therapies that aid and accelerate recovery is essential.

Objective

To determine the efficacy of bimodal visual-olfactory training and patient-preferred scents vs unimodal olfactory training and physician-assigned scents in COVID-19 olfactory loss.

Design, Setting, and Participants

This was a randomized, single-blinded trial with a 2-by-2 factorial design (bimodal, patient preferred; unimodal, physician assigned; bimodal, physician assigned; unimodal, patient preferred) and an independent control group. Enrollment occurred from February 1 to May 27, 2021. Participants were adults 18 to 71 years old with current olfactory loss defined as University of Pennsylvania Smell Identification Test (UPSIT) score less than 34 for men and less than 35 for women and duration of 3 months or longer. Olfactory loss was initially diagnosed within 2 weeks of COVID-19 infection.

Interventions

Participants sniffed 4 essential oils for 15 seconds with a 30-second rest in between odors for 3 months. Participants in the physician-assigned odor arms trained with rose, lemon, eucalyptus, and clove. Participants randomized to the patient-preferred arms chose 4 of 24 available scents. If assigned to the bimodal arm, participants were shown digital images of the essential oil they were smelling.

Main Outcomes and Measures

The primary end point was postintervention change in UPSIT score from baseline; measures used were the UPSIT (validated, objective psychometric test of olfaction), Clinical Global Impressions Impression-Improvement (CGI-I; self-report improvement scale), and Olfactory Dysfunction Outcomes Rating (ODOR; olfaction-related quality-of-life questionnaire).

Results

Among the 275 enrolled participants, the mean (SD) age was 41 (12) years, and 236 (86%) were female. The change in UPSIT scores preintervention to postintervention was similar between the study arms. The marginal mean difference for change in UPSIT scores preintervention to postintervention between participants randomized to patient-preferred vs physician-assigned olfactory training was 0.73 (95% CI, -1.10 to 2.56), and between participants randomized to bimodal vs unimodal olfactory training was 1.10 (95% CI, -2.92 to 0.74). Five (24%) participants in the control arm had clinically important improvement on UPSIT compared with 18 (53%) in the bimodal, patient-preferred arm for a difference of 29% (95% CI, 4%-54%). Four (19%) participants in the control group self-reported improvement on CGI-I compared with 12 (35%) in the bimodal, patient-preferred arm for a difference of 16% (95% CI, -7% to 39%). The mean change in ODOR score preintervention to postintervention was 11.6 points (95% CI, 9.2-13.9), which was not deemed clinically important nor significantly different between arms.

Conclusions and Relevance

Based on the change in UPSIT scores, this randomized clinical trial did not show any difference between intervention arms, but when exploring within-patient change in UPSIT as well as self-reported impression of improvement, active interventions were associated with larger improvement than controls with a potential advantage of bimodal intervention. While not definitive, these results suggest that patients with COVID-19 olfactory loss may benefit from bimodal visual-olfactory training with patient-preferred scents.

Trial Registration

ClinicalTrials.gov Identifier: NCT04710394.

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.

Platelet-rich plasma injection in the olfactory clefts of COVID-19 patients with long-term olfactory dysfunction

OBJECTIVE

To investigate safety, feasibility, and effectiveness of platelet-rich plasma (PRP) injection into the olfactory clefts of COVID-19 patients with persistent olfactory dysfunction (OD).

METHODS

From March 2022 to July 2022, COVID-19 patients with persistent OD were consecutively recruited to benefit from PRP injection into the olfactory clefts. Patient pain, annoyance, time of procedure, and adverse events were evaluated. Olfactory function was evaluated at baseline and 2-month post-injection with the olfactory disorder questionnaire (ODQ) and threshold, discrimination, and identification (TDI) test.

RESULTS

Eighty-seven patients with anosmia (N = 30), hyposmia (N = 40), or parosmia (N = 17) with a mean OD duration of 15.7 months completed the evaluations. The PRP injection was successfully performed in all patients with a mean procedure time of 18.4 ± 3.4 min. The adverse events included transient epistaxis (N = 31), parosmia related to xylocaine spray (N = 10), and vasovagal episode (N = 2). The injection procedure was evaluated as somewhat or moderately painful by 41 (47%) and 22 (25%) patients, respectively. Thirty-seven patients were assessed after 2 months post-injection. The mean ODQ and TDI scores significantly improved from baseline to 2-month post-injection (p < 0.01). The olfactory improvement occurred after a mean of 3.6 ± 1.9 weeks.

CONCLUSION

The injection of PRP into the olfactory clefts is safe and associated with adequate patient-reported outcomes. The findings of this preliminary study suggest possible efficacy on subjective and psychophysical evaluations, but future randomized controlled studies are needed to determine the superiority of PRP injection over placebo.

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.

Corticosteroid nasal irrigation as early treatment of olfactory dysfunction in COVID-19: A prospective randomised controlled trial

OBJECTIVE

This study aimed to evaluate the efficacy of corticosteroid irrigation compared to saline to no nasal irrigation in COVID-19 patients with olfactory loss.

DESIGN AND SETTING

A randomised controlled study was conducted at the Otolaryngology-Head & Neck Surgery Department, Ramathibodi Hospital, Faculty of Medicine, Mahidol University.

PARTICIPANTS

Two hundred thirty-seven COVID-19 participants with a new-onset smell loss were recruited into the study. Two hundred twenty-two participants met the inclusion criteria and were randomised into three groups: corticosteroid irrigation, saline irrigation and no treatment.

MAIN OUTCOME MEASURES

The primary outcome was the mean difference in the smell sensation score among the groups after treatment at 1, 2 and 6 weeks. The secondary outcomes measurements included (1) a self-rating quality of life (QOL)-related smell dysfunction score, (2) the change over time in smell sensation score and self-rating QOL-related smell dysfunction score and (3) the median time to complete recovery of smell loss.

RESULTS

The mean differences in smell sensation scores among the three groups were not statistically significant at any follow-up period. The mean score of self-rating QOL-related smell dysfunction in the corticosteroid group was significantly better than the other groups at 1 week. The change of outcome scores showed significant improvement over time, regardless of the treatments. The median time to complete smell recovery was similar: 3 weeks.

CONCLUSION

This study emphasised that corticosteroid nasal irrigation is not superior to saline or no nasal irrigation in restoring the sense of smell in COVID-19-associated olfactory loss.

Proof-of-concept: SCENTinel 1.1 rapidly discriminates COVID-19 related olfactory disorders

It is estimated that 20-67% of those with COVID-19 develop olfactory disorders, depending on the SARS-CoV-2 variant. However, there is an absence of quick, population-wide olfactory tests to screen for olfactory disorders. The purpose of this study was to provide a proof-of-concept that SCENTinel 1.1, a rapid, inexpensive, population-wide olfactory test, can discriminate between anosmia (total smell loss), hyposmia (reduced sense of smell), parosmia (distorted odor perception), and phantosmia (odor sensation without a source). Participants were mailed a SCENTinel 1.1 test, which measures odor detection, intensity, identification, and pleasantness, using one of four possible odors. Those who completed the test (N = 381) were divided into groups based on their self-reported olfactory function: quantitative olfactory disorder (anosmia or hyposmia, N = 135), qualitative olfactory disorder (parosmia and/or phantosmia; N = 86), and normosmia (normal sense of smell; N = 66). SCENTinel 1.1 accurately discriminates quantitative olfactory disorders, qualitative olfactory disorders, and normosmia groups. When olfactory disorders were assessed individually, SCENTinel 1.1 discriminates between hyposmia, parosmia and anosmia. Participants with parosmia rated common odors less pleasant than those without parosmia. We provide proof-of-concept that SCENTinel 1.1, a rapid smell test, can discriminate quantitative and qualitative olfactory disorders, and is the only direct test to rapidly discriminate parosmia.

A Review of Current Evaluation and Management Strategies in Pediatric Postacute Sequelae of COVID-19

Pediatric postacute sequelae of COVID-19 (pPASC), or long COVID, is a complex, heterogeneous, multisystem syndrome that leads to disruption in the lives of children and adolescents for months, and possibly years, after recovery from acute SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection. While the underlying pathophysiologic mechanisms of PASC are still under investigation, clinicians are facing the immediate challenges of treating these patients. In this article, we provide an overview of the current multidisciplinary evaluation of patients with pPASC. We also offer guidance on the medical, psychological, and rehabilitative management strategies based on experience with both pPASC and patients with other postviral syndromes. [Pediatr Ann. 2022;51(11):e421-e425.].

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.

Managing Post-traumatic Olfactory Disorders

Purpose of Review

This study aims to summarize and critically review recent literature on management of post-traumatic olfactory dysfunction (PTOD) with emphasis on the diagnostic procedure and treatment options.

Recent Findings

Magnetic resonance imaging and olfactory testing are the basis of the diagnostic procedure. Time of diagnosis is critical as the most improvement occurs within the first year after trauma. Olfactory training and oral steroids seem to be a relatively evidence-based therapeutic option but with non-optimal results. Surgery has a limited place in the management of PTOD. Promising future options could be the development of olfactory implants and transplantation of olfactory epithelium or stem cells.

Summary

PTOD management is challenging as it has several pathogenetic mechanisms and relatively poor prognosis. Patients with olfactory impairment and head trauma have diminished quality of life, and increased risk for harmful events and development of depression. Thus, clinicians should not only focus to therapeutic options but equally to appropriate counseling to their patients in order to decrease risks of personal injury and improve their daily life.

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.

Effectiveness of olfactory training in COVID-19 patients with olfactory dysfunction: a prospective study

OBJECTIVES

To investigate effectiveness of olfactory training (OT) in COVID-19 patients with persistent olfactory dysfunction (OD).

METHODS

From March 2020 to March 2022, COVID-19 patients with OD were prospectively followed in three European medical centers for a period of 18 months. A standardized OT protocol were recommended to patients. Patient-reported outcome questionnaires and psychophysical evaluations were used to evaluate olfaction at baseline, 6, 12, and 18 months after the start of OT. The evolution of olfactory outcome was compared according to the adherence to the OT protocol.

RESULTS

Fifty-seven patients completed the evaluations. Thirty-two patients fully adhered to the OT, while 25 did not adhere. The psychophysical scores significantly improved from baseline to 6-month post-infection in both groups. In the OT group, the psychophysical scores continued to significantly improve from 6 to 12 months after the start of OT (p = 0.032). The mean duration of OT was 15.4 weeks. The mean delay of patient recovery perception was comparable between groups (27.4 weeks). The occurrence of cacosmia (35.1%) and parosmia (43.9%) throughout the follow-up period was comparable between groups. There proportion of phantosmia was higher in training (34.4%) compared with no-OT (16.0%; p = 0.007) group. The baseline Sniffin'Sticks tests was positively associated with the 6-month Sniffin'Sticks tests (r_s = 0.685; p < 0.001) and negatively associated with the time of recovery (r_s = - 0.369; p = 0.034).

CONCLUSIONS

The adherence to an OT protocol was associated with better mid-term improvement of psychophysical scores. Future large-cohort randomized-controlled studies are needed to confirm the effectiveness of OT in COVID-19 patients.

Improving taste sensitivity in healthy adults using taste recall training: a randomized controlled trial

Although many patients suffer from taste disorder, methods to improve taste sensitivity are limited. To develop a taste recall training method to improve the perception of taste, 42 healthy individuals were randomly assigned to either the training or the control group. Using the filter paper disc method, participants in the training group were asked to match the four tastes (sweetness, saltiness, sourness, and bitterness) between those of taste recognition thresholds and those of a one-step higher concentration until they get them right. Then, they were asked to match the four tastes between those of one-step lower and one-step higher in concentration from their taste recognition thresholds until they get them right. Finally, they were asked to match the four tastes between those of one-step lower concentration and those of their taste recognition thresholds until they get them right. This training was repeated until perfectly matched. The taste recall training program led to a lowered taste recognition threshold in healthy adults for each taste quality, suggesting the improvement of taste sensitivity. This lowered threshold for each taste was observed with each additional training session. We conclude that this taste recall training method might be a therapeutic approach for treating taste disorder.

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.

Assessment of Smell and Taste Disturbances among COVID-19 Convalescent Patients: A Cross-Sectional Study in Armenia

Background and Objectives: Neurological manifestations of Coronavirus Disease 2019 (COVID-19) such as olfactory and gustatory disturbance have been reported among convalescent COVID-19 patients. However, scientific data on the prevalence of smell and taste disturbance are lacking. Therefore, we present findings on the degree of smell and taste disturbances among the Armenian population. Methods: Study participants were randomly recruited and then categorized into two groups based on their course of the disease. A cross-sectional study was performed to assess participants’ sensitivity to smell triggered by the olfactory and the trigeminal nerves; their ability to differentiate between various odors; and to evaluate their gustatory perception. Results: The smell test revealed that the degree of olfactory nerve disturbance was different by 30.7% in those participants of the early group as compared to those of the late group, and the degree of trigeminal nerve disturbance was different by 71.3% in the early group as compared to the late group. A variation of the differentiating ability among the participants of the early and late groups was detected. Gustatory disturbances for all flavors were also found to be different in both the groups. A moderate positive correlation (0.51) was found between the overall sensitivity of smell and the ability to differentiate between various odors as cumulatively stimulated by both the olfactory and trigeminal nerves. Also, a moderate positive correlation (0.33) was found between headache and smell sensitivity through the olfactory nerve and a high negative correlation (−0.71) was found between headache and smell sensitivity through the trigeminal nerve. Conclusion: Pathological changes in the olfactory and trigeminal perceptive abilities caused disturbances in smell sensation, with the trigeminal nerve being more affected. The capacity to differentiate fragrances did not improve with time and the disturbance severity of bitter taste perception was higher among the study participants.

Olfactory Training in Post-COVID-19 Persistent Olfactory Disorders: Value Normalization for Threshold but Not Identification

(1) Background: Persistent post-viral olfactory disorders (PPVOD) are estimated at 30% of patients one year after COVID-19 infection. No treatment is, to date, significantly effective on PPVOD with the exception of olfactory training (OT). The main objective of this work was to evaluate OT efficiency on post-COVID-19 PPVOD. (2) Methods: Consecutive patients consulting to the ENT department with post-COVID-19 PPVOD were included after completing clinical examination, the complete Sniffin’ Stick Test (TDI), the short version of the Questionnaire of olfactory disorders and the SF-36. Patients were trained to practice a self-olfactory training with a dedicated olfactory training kit twice a day for 6 months before returning to undergo the same assessments. (3) Results: Forty-three patients were included and performed 3.5 months of OT in average. We observed a significant TDI score improvement, increasing from 24.7 (±8.9) before the OT to 30.9 (±9.8) (p < 0.001). Based on normative data, a significant increase in the number of normosmic participants was observed only for the threshold values (p < 0.001). Specific and general olfaction-related quality of life improved after the OT. (4) Conclusions: Olfactory function appeared to improve only in peripheral aspects of post-COVID-19 PPVOD after OT. Future controlled studies must be performed to confirm the OT role and justify new therapeutic strategies that may focus on the central aspects of post-COVID-19 PPVOD.

Chronic Rhinosinusitis and COVID-19

The COVID-19 pandemic has raised awareness about olfactory dysfunction, although a loss of smell was present in the general population before COVID-19. Chronic rhinosinusitis (CRS) is a common upper airway chronic inflammatory disease that is also one of the most common causes of olfactory dysfunction. It can be classified into different phenotypes (ie, with and without nasal polyps) and endotypes (ie, type 2 and non-type 2 inflammation). However, scientific information regarding CRS within the context of COVID-19 is still scarce. This review focuses on (1) the potential effects of severe acute respiratory syndrome coronavirus 2 infection on CRS symptoms, including a loss of smell, and comorbidities; (2) the pathophysiologic mechanisms involved in the olfactory dysfunction; (3) CRS diagnosis in the context of COVID-19, including telemedicine; (4) the protective hypothesis of CRS in COVID-19; and (5) the efficacy and safety of therapeutic options for CRS within the context of COVID-19.

Long COVID: current status in Japan and knowledge about its molecular background

Even after recovering from coronavirus disease 2019 (COVID-19), patients can experience prolonged complaints, referred to as "long COVID". Similar to reports in Caucasians, a follow-up study in Japan revealed that fatigue, dyspnea, cough, anosmia/dysgeusia, and dyssomnia are common symptoms. Although the precise mode of long COVID remains elusive, multiple etiologies such as direct organ damage by infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), autoimmunity, prolonged inflammatory reactions, and psychiatric impairment seem to be involved. Notably, SARS-CoV-2 is neurotropic, and viral RNA and proteins are continuously detectable in multiple organs, including the brain. Viral proteins exert a number of different toxic effects on cells, suggesting that persistent infection is a key element for understanding long COVID. Here, we first reviewed the current status of long COVID in Japan, and then summarized literature that help us understand the molecular background of the symptoms. Finally, we discuss the feasibility of vaccination as a treatment for patients with long COVID.

Smell and Taste Symptoms Among Patients With Mild and Moderately Severe COVID-19 Infection in Uganda

Objective

Patients with coronavirus disease 2019 (COVID-19) may present with smell/taste dysfunctions in addition to the most frequent symptoms (fever, cough, and shortness of breath) or as the first symptom or even the only symptom. There is paucity of documentation of prevalence and characteristics of smell/taste dysfunction in COVID-19 in sub-Saharan Africa. The aim of this study was to determine the prevalence of smell/taste symptoms in our setting to institute local evidence-based practice.

Study Design

Cross-sectional study.

Setting

COVID-19 treatment centers in Uganda.

Methods

Patients hospitalized for COVID-19 at 3 treatment sites from November 2020 to March 2021 were recruited. Following written informed consent, their demographics, comorbidities, and smell/taste symptoms data were collected using a questionnaire.

Results

Of 614 patients recruited, 409 (63.8%) had mild symptoms and 232 (36.2%) had moderate to severe symptoms; 64.3% were male, and the mean age was 48.6 ± 15.51 years. In total, 23.1% were health responders and 12.2% had contact with a positive case. Smell and taste impairment was seen in 425 (66.3%) patients, second to cough (71.6%). Smell and taste impairment was seen in 162 (38.1%) as the first symptom, in 128 (30%) as the only symptom, and significantly more in those with mild COVID-19 symptoms (P < .001).

Conclusion

COVID-19 manifests with various symptoms, including impairment of smell and taste. This study shows that smell and taste impairment is common and can be the first and only symptom in less severe COVID-19 infections. Therefore, inclusion in the Ministry of Health guidelines is strongly recommended.

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.

Research Progress of Olfactory Nerve Regeneration Mechanism and Olfactory Training

The olfactory nerve (ON) is the only cranial nerve exposed to the external environment. Hence, it is susceptible to damage from head trauma, viral infection, inflammatory stimulation, and chemical toxins, which can lead to olfactory dysfunction. However, compared with all other cranial nerves, the ON is unique due to its inherent ability to regenerate. This characteristic provides a theoretical basis for treatment of olfactory dysfunction. Olfactory training (OT) is one of the main treatments for olfactory dysfunction. It is easy to apply and has few side-effects, and has been shown to be efficacious for patients with olfactory dysfunction of various causes. To further understand the application value of ON regeneration and OT on olfactory dysfunction, we review the research progress on the mechanism of ON regeneration and OT.

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 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.

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.