Orthonasal and retronasal odor identification in patients with parosmia

Objective: To compare retronasal and orthonasal perception in parosmic COVID-19 patients, in order to determine whether COVID-19 has a differential effect on these functions. Methods: Using the Sniffin Sticks test battery orthonasal function was examined for odor threshold, discrimination and identification. Retronasal function was assessed using 20 tasteless aromatized powders. Gustatory function was measured using the Taste Strips test. Results: This study included 177 patients (127 women, 50 men; mean age 45 years), of whom 127 (72%) were hyposmic and 50 (28%) normosmic. Compared to patients without parosmia, parosmic patients performed worse in odor identification for both orthonasal (F = 4.94, p = 0.03) and retronasal tests (F = 11.95, p < 0.01). However, an interaction effect between route of odor identification (orthonasal or retronasal) and parosmia status was found (F = 4.67, p = 0.03): patients with parosmia had relatively lower retronasal scores than patients without parosmia. Conclusion: Our results suggest that COVID-19 may affect the olfactory mucosa differently along the anterior-posterior axis, thereby possibly contributing to the pathophysiology of parosmia. Patients with parosmia also exhibit a higher degree of impairment when odors are presented through the retronasal route during eating and drinking

Functional septorhinoplasty alters brain structure and function: Neuroanatomical correlates of olfactory dysfunction

Introduction: We previously demonstrated functionally significant structural plasticity within the central olfactory networks, in association with improved olfaction after surgical treatment of chronic rhinosinusitis (CRS). In order to confirm and expand on these findings, the primary aim of this study was to determine whether these same regions undergo functionally significant structural plasticity following functional septorhinoplasty (fSRP), in patients with non-CRS olfactory dysfunction (OD) of mixed cause. fSRP has previously been shown to improve olfactory function, and the secondary aim of this study was to provide initial insights into the mechanism by which fSRP affects olfaction.// Methods: We performed a pilot prospective, multimodal neuroimaging study in 20 participants undergoing fSRP, including patients with non-CRS OD of mixed cause, as well as normosmic surgical controls. Participants underwent psychophysical olfactory testing, assessment of nasal airway, structural and functional neuroimaging. This was performed pre- and postoperatively in patients, and preoperatively in controls.// Results: There was a statistically and clinically significant improvement in mean psychophysical olfactory scores after surgery. This was associated with structural and functional plasticity within areas of the central olfactory network (anterior cingulate, orbitofrontal cortex, insula, temporal pole). Improved psychophysical scores were significantly correlated with change in bilateral measures of nasal airflow, not measures of airflow symmetry, suggesting that improved overall airflow was more important than correction of septal deviation.// Conclusion: This work highlights the importance of these neuroanatomical regions as potential structural correlates of olfactory function and dysfunction. Our results also provide initial insight into the mechanistic effects of fSRP on olfaction. Further work could investigate the utility of these regions as personalised biomarkers of OD, as well as the role of fSRP in treating OD

Comparison of COVID-19 and common cold chemosensory dysfunction

Anosmia constitutes a prominent symptom of COVID-19. However, anosmia is also a common symptom of acute colds of various origins. In contrast to an acute cold, it appears from several questionnaire-based studies that in the context of COVID-19 infection, anosmia is the main rhinological symptom and is usually not associated with other rhinological symptoms such as rhinorrhoea or nasal obstruction. Until now, no study has directly compared smell and taste function between COVID-19 patients and patients with other causes of upper respiratory tract infection (URTI) using valid and reliable psychophysical tests. In this study, we aimed to objectively assess and compare olfactory and gustatory functions in 10 COVID-19 patients (PCR diagnosed, assessed on average 2 weeks after infection), 10 acute cold (AC) patients (assessed before the COVID-19 outbreak) and 10 healthy controls, matched for age and sex. Smell performance was assessed using the extended "Sniffin' Sticks" test battery (4), while taste function was assessed using "taste strips" (5). Receiver Operating Characteristic (ROC) curves were built to probe olfactory and gustatory scores in terms of their discrimination between COVID-19 and AC patients. Our results suggest that mechanisms of COVID-19 related olfactory dysfunction are different from those seen in an AC and may reflect, at least to some extent, a specific involvement at the level of central nervous system in some COVID-19 patients. In the future, studies to assess the prevalence of persistent anosmia and neuroanatomical changes on MRI correlated to chemosensory function, will be useful to understand these mechanisms

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

Management of new onset loss of sense of smell during the COVID-19 pandemic - BRS Consensus Guidelines

OBJECTIVES: The primary aim of the study is to provide recommendations for the investigation and management of patients with new onset loss of sense of smell during the COVID-19 pandemic. DESIGN: After undertaking a literature review, we used the RAND/UCLA methodology with a multi-step process to reach consensus about treatment options, onward referral, and imaging. SETTING AND PARTICIPANTS: An expert panel consisting of 15 members was assembled. A literature review was undertaken prior to the study and evidence was summarised for the panellists. MAIN OUTCOME MEASURES: The panel undertook a process of ranking and classifying appropriateness of different investigations and treatment options for new onset loss of sense of smell during the COVID-19 pandemic. Using a 9-point Likert scale, panellists scored whether a treatment was: Not recommended, optional, or recommended. Consensus was achieved when more than 70% of responses fell into the category defined by the mean. RESULTS: Consensus was reached on the majority of statements after 2 rounds of ranking. Disagreement meant no recommendation was made regarding one treatment, using Vitamin A drops. Alpha-lipoic acid was not recommended, olfactory training was recommended for all patients with persistent loss of sense of smell of more than 2 weeks duration, and oral steroids, steroid rinses, and omega 3 supplements may be considered on an individual basis. Recommendations regarding the need for referral and investigation have been made. CONCLUSION: This study identified the appropriateness of olfactory training, different medical treatment options, referral guidelines and imaging for patients with COVID-19-related loss of sense of smell. The guideline may evolve as our experience of COVID-19 develops

International clinical assessment of smell:An international, cross-sectional survey of current practice in the assessment of olfaction

Objectives: Olfactory dysfunction (OD) is common and carries significant personal and societal burden. Accurate assessment is necessary for good clinical and research practice but is highly dependent on the assessment technique used. Current practice with regards to UK/international clinical assessment is unknown. We aimed to capture current clinical practice, with reference to contemporaneously available guidelines. We further aimed to compare UK to international practice. Design: Anonymous online questionnaire with cross-sectional non-probability sampling. Subgroup analysis according to subspeciality training in rhinology (‘rhinologists’ and ‘non-rhinologists’) was performed, with geographical comparisons only made according to subgroup. Participants: ENT surgeons who assess olfaction. Results: Responses were received from 465 clinicians (217 from UK and 17 countries total). Country-specific response rate varied, with the lowest rate being obtained from Japan (1.4%) and highest from Greece (72.5%). Most UK clinicians do not perform psychophysical smell testing during any of the presented clinical scenarios—though rhinologists did so more often than non-rhinologists. The most frequent barriers to testing related to service provision (e.g., time/funding limitations). Whilst there was variability in practice, in general, international respondents performed psychophysical testing more frequently than those from the UK. Approximately 3/4 of all respondents said they would like to receive training in psychophysical smell testing. Patient reported outcome measures were infrequently used in the UK/internationally. More UK respondents performed diagnostic MRI scanning than international respondents. Conclusions: To our knowledge, this is the most comprehensive UK-based, and only international survey of clinical practice in the assessment of OD. We present recommendations to improve practice, including increased education and funding for psychophysical smell testing. We hope this will promote accurate and reliable olfactory assessment, as is the accepted standard in other sensory systems

Clinical Olfactory Working Group Consensus statement on the treatment of post infectious olfactory dysfunction

Background: Respiratory tract viruses are the second most common cause of olfactory dysfunction. As we learn more about the effects of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with the recognition that olfactory dysfunction is a key symptom of this disease process, there is a greater need than ever for evidence-based management of postinfectious olfactory dysfunction (PIOD). Objective: Our aim was to provide an evidence-based practical guide to the management of PIOD (including post–coronavirus 2019 cases) for both primary care practitioners and hospital specialists. Methods: A systematic review of the treatment options available for the management of PIOD was performed. The written systematic review was then circulated among the members of the Clinical Olfactory Working Group for their perusal before roundtable expert discussion of the treatment options. The group also undertook a survey to determine their current clinical practice with regard to treatment of PIOD. Results: The search resulted in 467 citations, of which 107 articles were fully reviewed and analyzed for eligibility; 40 citations fulfilled the inclusion criteria, 11 of which were randomized controlled trials. In total, 15 of the articles specifically looked at PIOD whereas the other 25 included other etiologies for olfactory dysfunction. Conclusions: The Clinical Olfactory Working Group members made an overwhelming recommendation for olfactory training; none recommended monocycline antibiotics. The diagnostic role of oral steroids was discussed; some group members were in favor of vitamin A drops. Further research is needed to confirm the place of other therapeutic options

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

Systemic corticosteroids in coronavirus disease 2019 (COVID‐19)‐related smell dysfunction: an international view

The frequent association between coronavirus disease 2019 (COVID‐19) and olfactory dysfunction is creating an unprecedented demand for a treatment of the olfactory loss. Systemic corticosteroids have been considered as a therapeutic option. However, based on current literature, we call for caution using these treatments in early COVID‐19–related olfactory dysfunction because: (1) evidence supporting their usefulness is weak; (2) the rate of spontaneous recovery of COVID‐19–related olfactory dysfunction is high; and (3) corticosteroids have well‐known potential adverse effects. We encourage randomized placebo‐controlled trials investigating the efficacy of systemic steroids in this indication and strongly emphasize to initially consider smell training, which is supported by a robust evidence base and has no known side effects

Recent smell loss is the best predictor of COVID-19 among individuals with recent respiratory symptoms

In a preregistered, cross-sectional study we investigated whether olfactory loss is a reliable predictor of COVID-19 using a crowdsourced questionnaire in 23 languages to assess symptoms in individuals self-reporting recent respiratory illness. We quantified changes in chemosensory abilities during the course of the respiratory illness using 0-100 visual analog scales (VAS) for participants reporting a positive (C19+; n=4148) or negative (C19-; n=546) COVID-19 laboratory test outcome. Logistic regression models identified univariate and multivariate predictors of COVID-19 status and post-COVID-19 olfactory recovery. Both C19+ and C19- groups exhibited smell loss, but it was significantly larger in C19+ participants (mean±SD, C19+: -82.5±27.2 points; C19-: -59.8±37.7). Smell loss during illness was the best predictor of COVID-19 in both univariate and multivariate models (ROC AUC=0.72). Additional variables provide negligible model improvement. VAS ratings of smell loss were more predictive than binary chemosensory yes/no-questions or other cardinal symptoms (e.g., fever). Olfactory recovery within 40 days of respiratory symptom onset was reported for ~50% of participants and was best predicted by time since respiratory symptom onset. We find that quantified smell loss is the best predictor of COVID-19 amongst those with symptoms of respiratory illness. To aid clinicians and contact tracers in identifying individuals with a high likelihood of having COVID-19, we propose a novel 0-10 scale to screen for recent olfactory loss, the ODoR-19. We find that numeric ratings ≤2 indicate high odds of symptomatic COVID-19 (4&lt;10). Once independently validated, this tool could be deployed when viral lab tests are impractical or unavailable