Inflammatory Obstruction of the Olfactory Clefts and Olfactory Loss in Humans: A New Syndrome?

Olfactory Loss in Rhinosinusitis: Mechanisms of Loss and Recovery

Chronic rhinosinusitis (CRS) is a highly prevalent disease and up to 83% of CRS patients suffer from olfactory dysfunction (OD). Because OD is specifically seen in those CRS patients that present with a type 2 eosinophilic inflammation, it is believed that type 2 inflammatory mediators at the level of the olfactory epithelium are involved in the development of this olfactory loss. However, due to the difficulties in obtaining tissue from the olfactory epithelium, little is known about the true mechanisms of inflammatory OD. Thanks to the COVID-19 pandemic, interest in olfaction has been growing rapidly and several studies have been focusing on disease mechanisms of OD in inflammatory conditions. In this paper, we summarize the most recent data exploring the pathophysiological mechanisms underlying OD in CRS. We also review what is known about the potential capacity of olfactory recovery of the currently available treatments in those patients.

Pathophysiology of SARS-CoV-2 Infection of Nasal Respiratory and Olfactory Epithelia and Its Clinical Impact

PURPOSE OF REVIEW

While the predominant cause for morbidity and mortality with SARS-CoV-2 infection is the lower respiratory tract manifestations of the disease, the effects of SARS-CoV-2 infection on the sinonasal tract have also come to the forefront especially with the increased recognition of olfactory symptom. This review presents a comprehensive summary of the mechanisms of action of the SARS-CoV-2 virus, sinonasal pathophysiology of COVID-19, and the correlation with the clinical and epidemiological impact on olfactory dysfunction.

RECENT FINDINGS

ACE2 and TMPRSS2 receptors are key players in the mechanism of infection of SARS-CoV-2. They are present within both the nasal respiratory as well as olfactory epithelia. There are however differences in susceptibility between different groups of individuals, as well as between the different SARS-CoV-2 variants. The sinonasal cavity is an important route for SARS-CoV-2 infection. While the mechanism of infection of SARS-CoV-2 in nasal respiratory and olfactory epithelia is similar, there exist small but significant differences in the susceptibility of these epithelia and consequently clinical manifestations of the disease. Understanding the differences and nuances in sinonasal pathophysiology in COVID-19 would allow the clinician to predict and counsel patients suffering from COVID-19. Future research into molecular pathways and cytokine responses at different stages of infection and different variants of SARS-CoV-2 would evaluate the individual clinical phenotype, prognosis, and possibly response to vaccines and therapeutics.

Magnetic Resonance Imaging as a Diagnostic and Research Tool in Patients with Olfactory Dysfunction: A Systematic Review

BACKGROUND

Patients with acquired, idiopathic olfactory dysfunction (OD) commonly undergo magnetic resonance imaging (MRI) evaluation to rule out intracranial pathologies. This practice is highly debated given the expense of MRI relative to the probability of detecting a treatable lesion. This, combined with the increasing use of MRI in research to investigate the mechanisms underlying OD, provided the impetus for this comprehensive review.

OBJECTIVE

The purpose of this systematic review was to both assess the utility of MRI in diagnosis of idiopathic OD and to describe MRI findings among mixed OD etiologies to better understand its role as a research tool in this patient population.

METHODS

A literature search of PubMed, Embase, Cochrane, Web of Science, and Scopus for studies with original MRI data for patients with OD was completed. Studies exclusively investigating patients with neurocognitive deficits or those studying traumatic or congenital etiologies of OD were excluded.

RESULTS

From 1758 candidate articles, 33 studies were included. Four studies reviewed patients with idiopathic OD for structural pathologies on MRI, of which 17 of 372 (4.6%) patients had a potential central cause identified, and 3 (0.8%) had an olfactory meningioma or olfactory neuroblastoma. Fourteen studies (42.4%) reported significant correlation between olfactory bulb volume and olfactory outcomes, and 6 studies (18.8%) reported gray matter volume reduction, specifically in the orbitofrontal cortex, anterior cingulate cortex, insular cortex, parahippocampal, and piriform cortex areas, in patients with mixed OD etiologies. Functional MRI studies reported reduced brain activation and functional connectivity in olfactory network areas.

CONCLUSION

MRI uncommonly detects intracranial pathology in patients with idiopathic OD. Among patients with mixed OD etiologies, reduced olfactory bulb and gray matter volume are the most common abnormal findings on MRI. Further research is required to better understand the role of MRI and its cost-effectiveness in patients with acquired, idiopathic OD.

Neuroradiological Basis of COVID-19 Olfactory Dysfunction: A Systematic Review and Meta-Analysis

Objective

Olfactory dysfunction (OD) is a common presenting symptom of COVID‐19 infection. Radiological imaging of the olfactory structures in patients with COVID‐19 and OD can potentially shed light on its pathogenesis, and guide clinicians in prognostication and intervention.

Methods

PubMed, Embase, Cochrane, SCOPUS were searched from inception to August 1, 2021. Three reviewers selected observational studies, case series, and case reports reporting radiological changes in the olfactory structures, detected on magnetic resonance imaging, computed tomography, or other imaging modalities, in patients aged ≥18 years with COVID‐19 infection and OD, following preferred reporting items for systematic reviews and meta‐analyses guidelines and a PROSPERO‐registered protocol (CRD42021275211). We described the proportion of radiological outcomes, and used random‐effects meta‐analyses to pool the prevalence of olfactory cleft opacification, olfactory bulb signal abnormalities, and olfactory mucosa abnormalities in patients with and without COVID‐19‐associated OD.

Results

We included 7 case–control studies (N = 353), 11 case series (N = 154), and 12 case reports (N = 12). The pooled prevalence of olfactory cleft opacification in patients with COVID‐19 infection and OD (63%, 95% CI = 0.38–0.82) was significantly higher than that in controls (4%, 95% CI = 0.01–0.13). Conversely, similar proportions of cases and controls demonstrated olfactory bulb signal abnormalities (88% and 94%) and olfactory mucosa abnormalities (2% and 0%). Descriptive analysis found that 55.6% and 43.5% of patients with COVID‐19 infection and OD had morphological abnormalities of the olfactory bulb and olfactory nerve, respectively, while 60.0% had abnormal olfactory bulb volumes.

Conclusion

Our findings implicate a conductive mechanism of OD, localized to the olfactory cleft, in approximately half of the affected COVID‐19 patients. Laryngoscope, 132:1260–1274, 2022

Magnetic Resonance Imaging Findings of Olfactory Bulb in Anosmic Patients with COVID-19: A Systematic Review

Background Anosmia is one of the symptoms in individuals with SARS-CoV-2 infection. In anosmic patients, SARS-CoV-2 temporarily alters the signaling process in olfactory nerve cells and olfactory bulb (OB), which eventually damages the structure of the olfactory epithelium, leading to a permanent disorder in the olfactory pathway that this damaged structure is showed in MRI imaging Methods Two investigators independently searched four databases consisting of PubMed, ProQuest, Scopus, and Web of Science for relevant records as of November 11, 2020 with no time, space, and language restrictions. Google Scholar was also searched for the related resources within the time limit of 2020. All the found articles were reviewed based on the PRISMA flow diagram. Qualitative studies, case reports, editorials, letters, and other non-original studies were excluded from this systematic analysis. Results Initial search yielded 434 records. After reviewing the titles and abstracts, we selected 74 articles; finally, 8 articles were depicted to be investigated and read in full text. The obtained results showed an increase in the width and volume of the olfactory cleft (OC), complete or partial destruction of OC, and complete occlusion of OC in COVID-19 patients. Deformation and degeneration as well as a subtle asymmetry were evident in the OBs. Computed tomography (CT), meganetic resonance imaging (MRI), and positron emission tomography (PET) were used to detect the outcomes of anosmia in these studies. Conclusions The changes in OC are greater than those in OB in patients with COVID-19, mainly due to the inflammatory and immune responses in OC. However, fewer changes in OB are due to neurological or vascular disorders. Topical steroid therapy and topical saline can be helpful.

“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.

COVID-19 Anosmia: High Prevalence, Plural Neuropathogenic Mechanisms, and Scarce Neurotropism of SARS-CoV-2?

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative pathogen of coronavirus disease 2019 (COVID-19). It is known as a respiratory virus, but SARS-CoV-2 appears equally, or even more, infectious for the olfactory epithelium (OE) than for the respiratory epithelium in the nasal cavity. In light of the small area of the OE relative to the respiratory epithelium, the high prevalence of olfactory dysfunctions (ODs) in COVID-19 has been bewildering and has attracted much attention. This review aims to first examine the cytological and molecular biological characteristics of the OE, especially the microvillous apical surfaces of sustentacular cells and the abundant SARS-CoV-2 receptor molecules thereof, that may underlie the high susceptibility of this neuroepithelium to SARS-CoV-2 infection and damages. The possibility of SARS-CoV-2 neurotropism, or the lack of it, is then analyzed with regard to the expression of the receptor (angiotensin-converting enzyme 2) or priming protease (transmembrane serine protease 2), and cellular targets of infection. Neuropathology of COVID-19 in the OE, olfactory bulb, and other related neural structures are also reviewed. Toward the end, we present our perspectives regarding possible mechanisms of SARS-CoV-2 neuropathogenesis and ODs, in the absence of substantial viral infection of neurons. Plausible causes for persistent ODs in some COVID-19 convalescents are also examined.

SARS-CoV-2 infection in the mouse olfactory system

SARS-CoV-2 infection causes a wide spectrum of clinical manifestations in humans, and olfactory dysfunction is one of the most predictive and common symptoms in COVID-19 patients. However, the underlying mechanism by which SARS-CoV-2 infection leads to olfactory disorders remains elusive. Herein, we demonstrate that intranasal inoculation with SARS-CoV-2 induces robust viral replication in the olfactory epithelium (OE), not the olfactory bulb (OB), resulting in transient olfactory dysfunction in humanized ACE2 (hACE2) mice. The sustentacular cells and Bowman’s gland cells in the OE were identified as the major target cells of SARS-CoV-2 before invasion into olfactory sensory neurons (OSNs). Remarkably, SARS-CoV-2 infection triggers massive cell death and immune cell infiltration and directly impairs the uniformity of the OE structure. Combined transcriptomic and quantitative proteomic analyses revealed the induction of antiviral and inflammatory responses, as well as the downregulation of olfactory receptor (OR) genes in the OE from the infected animals. Overall, our mouse model recapitulates olfactory dysfunction in COVID-19 patients and provides critical clues for understanding the physiological basis for extrapulmonary manifestations of COVID-19.

Comparison of Magnetic Resonance Imaging and Computed Tomography in the Evaluation of the Olfactory Cleft and Ethmoidal Cells

ABSTRACT

No study has examined whether magnetic resonance imaging (MRI) alone can be used for evaluating olfactory cleft and ethmoidal sinus in patients with olfactory disorders. Therefore, we analyzed the discrepancies between computed tomography (CT) and MRI in the imaging of the olfactory cleft and ethmoidal sinus. Patients who underwent CT and MRI within 30 days were evaluated. Age, sex, diagnosis, presence of bronchial asthma (BA), peripheral blood eosinophil percentage, and CT and MRI findings were retrospectively reviewed, and the sinuses were assessed on a scale of 0 to 3. Overall, 146 patients with 292 sinuses were enrolled. The ethmoid sinus score and the olfactory cleft score had 77.1% and 72.6% image similarity in CT and MRI. Sex and BA status were not associated with olfactory cleft score discrepancies (sex: P = 0.52, BA: P = 0.41). Magnetic resonance imaging scores tended to be rated higher than the CT scores as age increased, although this difference was not statistically significant (P = 0.09). The higher the peripheral blood eosinophil percentage, the more the magnitude by which the CT score tended to exceed the MRI score; however, this finding was also not statistically significant (P = 0.11). Magnetic resonance imaging scans should be limited to the evaluation of intracranial regions. Scans of olfactory cleft and ethmoid cells are not accurate for the assessment of olfactory dysfunction.

Olfactory Dysfunction is Associated with More Severe Clinical Course in COVID-19

To perform a quantitative olfactory test in positive COVID19 RT-PCR admitted patients and asymptomatic ones, to evaluate the association between hyposmia and disease severity. This is a Cross sectional study. Ninety-one patients including 68 inpatients and 23 asymptomatic healthcare workers with positive COVID-19 RT-PCRs. Methods: Demographics and clinical characteristics were collected. Iran Smell Identification Test (IR-SIT), a highly accurate 6-odorant test was used to evaluate the reliability of self-reported hyposmia and determine the correlation of the measured olfactory dysfunction with disease severity. Twenty-two of 91 patients (24%) reported hyposmia, while 41/91 (45%) patients had measurable olfactory dysfunction (IR-SIT score 1–4, p < 0.05). Mean age of the 68 inpatients and 23 asymptomatic patients were 43.97 ± 16.13 years; M:F 43:25, and 43.87 ± 12.76 years; M:F 8:15 respectively. Of 68 patients, 20 were graded as severe, and 48/68 had mild course of disease. IR-SIT detected hyposmia in 80% of patients with severe disease, and 50% with mild disease, respectively. The risk of disease severity was significantly increased for patients with olfactory dysfunction and was detected 4 times higher when compared to patients with mild disease (OR 4, 95% CI: 1.166–13.728, p = 0.028). Olfactory Dysfunction was present in 80% of patients with severe course. The risk of disease severity is significantly increased with olfactory dysfunction in admitted patients.

Olfactory Bulb MRI and Paranasal Sinus CT Findings in Persistent COVID-19 Anosmia

Background and purpose

There is limited literature consisting of case reports or series on olfactory bulb imaging in COVID-19 olfactory dysfunction. An imaging study with objective clinical correlation is needed in COVID-19 anosmia in order to better understand underlying pathogenesis.

Material and methods

We evaluated 23 patients with persistent COVID-19 olfactory dysfunction. Patients included in this study had a minimum 1-month duration between onset of olfactory dysfunction and evaluation. Olfactory functions were evaluated with Sniffin’ Sticks Test. Paranasal sinus CTs and MRI dedicated to olfactory nerves were acquired. On MRI, quantitative measurements of olfactory bulb volumes and olfactory sulcus depth and qualitative assessment of olfactory bulb morphology, signal intensity, and olfactory nerve filia architecture were performed.

Results

All patients were anosmic at the time of imaging based on olfactory test results. On CT, Olfactory cleft opacification was seen in 73.9% of cases with a mid and posterior segment dominance. 43.5% of cases had below normal olfactory bulb volumes and 60.9% of cases had shallow olfactory sulci. Of all, 54.2% of cases had changes in normal inverted J shape of the bulb. 91.3% of cases had abnormality in olfactory bulb signal intensity in the forms of diffusely increased signal intensity, scattered hyperintense foci or microhemorrhages. Evident clumping of olfactory filia was seen in 34.8% of cases and thinning with scarcity of filia in 17.4%. Primary olfactory cortical signal abnormality was seen in 21.7% of cases.

Conclusion

Our findings indicate olfactory cleft and olfactory bulb abnormalities are seen in COVID-19 anosmia. There was a relatively high percentage of olfactory bulb degeneration. Further longitudinal imaging studies could shed light on the mechanism of olfactory neuronal pathway injury in COVID-19 anosmia.

Complications and Pathophysiology of COVID-19 in the Nervous System

The coronavirus disease (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global public health threat. Majority of the patients with COVID-19 have fever, cough, and fatigue. Critically ill patients can develop dyspnea and acute respiratory distress syndrome. In addition to respiratory symptoms, neurological damage also occurs in some patients. However, the mechanisms by which SARS-CoV-2 invades the nervous system have not been elucidated yet. In order to provide some reference for designing optimal therapeutic strategies, we have discussed the complications and potential mechanisms of COVID-19 in the nervous system in this review.

Study of Clinical and Biological Characteristics of Moroccan Covid-19 Patients With and Without Olfactory and/or Gustatory Dysfunction

Background

The epidemic of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19), presents a significant and urgent threat to global health. This alarming viral infection, declared as pandemic by the WHO in February 2020, has resulted millions of infected patients and thousands of deaths around the world. In Morocco, despite the efforts made by the authorities, the SARS-CoV-2 continues to spread and constitutes a burden of morbidity and mortality. The objective of this study is to describe clinical characteristics of COVID-19 Moroccan patients and to establish the relationship between specific clinical symptoms, namely ageusia and/or anosmia, with these characteristics.

Methods

We performed a descriptive, non-interventional cross-sectional study analyzing data from 108 patients admitted to the VINCI clinic, Casablanca (Morocco). The database includes 39 parameters including epidemiological characteristics, anthropometric measurements and biological analyzes.

Results

The average of age of the patients was 43.80 ± 15.75 years with a sex ratio of 1:1. The mean body mass index of the patients was 25.54 ± 4.63 Kg/m². The majority of patients had, at least, one comorbidity and among 75% symptomatic patients, about 50% had, at least, three symptoms namely, fever (40.7%), cough (39.8%), myalgia (28.7%), and anosmia and/or ageusia (20.4%). From biological analyzes, we noticed lymphopenia and an elevated protein C reactive and lactate dehydrogenases levels in 24.1, 36.1, and 35.2% of patients, respectively. A disturbance in liver function markers was observed in 15.7% of cases. For the other hemostasis parameters, high levels of prothrombin and platelets were reported in 14.6 and 14.8% of patients, respectively. Comparisons related to the presence of anosmia and/or ageusia did not show any difference for demographic and anthropometric characteristics, while a possibility of a significant difference was revealed for certain biological parameters, particularly the levels of lymphocytes, D-dimer and troponin.

Conclusion

This study provides significant findings that will be used not only to supplement previous studies carried out in Morocco in order to resume the epidemiological situation in comparison with other countries, but also to improve the quality of the diagnosis of COVID-19 patients by identifying all the symptoms of the disease and better understanding its clinical outcomes.

Factors affecting flavor perception in space: Does the spacecraft environment influence food intake by astronauts?

The intention to send a crewed mission to Mars involves a huge amount of planning to ensure a safe and successful mission. Providing adequate amounts of food for the crew is a major task, but 20 years of feeding astronauts on the International Space Station (ISS) have resulted in a good knowledge base. A crucial observation from the ISS is that astronauts typically consume only 80% of their daily calorie requirements when in space. This is despite daily exercise regimes that keep energy usage at very similar levels to those found on Earth. This calorie deficit seems to have little effect on astronauts who spend up to 12 months on the ISS, but given that a mission to Mars would take 30 to 36 months to complete, there is concern that a calorie deficit over this period may lead to adverse effects in crew members. The key question is why astronauts undereat when they have a supply of food designed to fully deliver their nutritional needs. This review focuses on evidence from astronauts that foods taste different in space, compared to on Earth. The underlying hypothesis is that conditions in space may change the perceived flavor of the food, and this flavor change may, in turn, lead to underconsumption by astronauts. The key areas investigated in this review for their potential impact on food intake are the effects of food shelf life, physiological changes, noise, air and water quality on the perception of food flavor, as well as the link between food flavor and food intake.

Loss of smell in patients with COVID-19

Objective

To assess the physiopathology of olfactory function loss (OFL) in patients with coronavirus disease 2019 (COVID-19), we evaluated the olfactory clefts (OC) on MRI during the early stage of the disease and 1 month later.

Methods

This was a prospective, monocentric, case-controlled study. Twenty severe acute respiratory syndrome coronavirus 2 (SARS-CoV2)–infected patients with OFL were included and compared to 20 age-matched healthy controls. All infected patients underwent olfactory function assessment and 3T MRI, performed both at the early stage of the disease and at the 1-month follow-up.

Results

At the early stage, SARS-CoV2–infected patients had a mean olfactory score of 2.8 ± 2.7 (range 0–8), and MRI displayed a complete obstruction of the OC in 19 of 20 patients. Controls had normal olfactory scores and no obstruction of the OC on MRI. At the 1 month follow-up, the olfactory score had improved to 8.3 ± 1.9 (range 4–10) in patients, and only 7 of 20 patients still had an obstruction of the OC. There was a correlation between olfactory score and obstruction of the OC (p = 0.004).

Conclusion

OFL in SARS-CoV2–infected patients is associated with a reversible obstruction of the OC.

Anosmia and ageusia associated with coronavirus infection (COVID-19) - what is known?

In 2020 a new pandemic caused by the SARS-CoV-2 coronavirus is affecting the lives of millions of patients and healthcare workers worldwide. The clinical picture of this infection is in a dynamic process of discovery, and more symptoms emerge as the clinicians observe and diagnose manifestations that affect multiple organs. Anosmia (loss of smell), and ageusia (loss of taste) become more frequently cited as independent symptoms or in association with the most common manifestations of the disease, such as fever, cough and dyspnea. A thorough screening program will prevent most nosocomial and community-acquired infections by promoting efficient triage and specific measures such as isolation of the patients. Therefore, it is important to include frequent symptoms in the anamnesis and questionnaires to select those patients who might benefit from testing, isolation, and treatment. This study summarizes the existing data regarding the association of anosmia and ageusia with the SARS-CoV-2 infection. It also aims to describe manifestations of these, particularly in the clinical picture of all symptomatic patients.

Clinical and Radiological Evaluations of COVID-19 Patients With Anosmia: Preliminary Report

OBJECTIVES/HYPOTHESIS

To investigate clinical and radiological features of olfactory clefts of patients with mild coronavirus disease 2019 (COVID-19).

STUDY DESIGN

Prospective non controlled study.

METHODS

Sixteen COVID-19 patients were recruited. The epidemiological and clinical data were extracted. Nasal complaints were assessed through the 22-item Sino-Nasal Outcome Test. Patients underwent psychophysical olfactory testing, olfactory cleft examination, and computed tomography (CT) scans.

RESULTS

Sixteen anosmic patients were included. The mean Sniffin' Sticks score was 4.6 ± 1.7. The majority of patients had no endoscopical abnormality, with a mean olfactory cleft endoscopy score of 0.6 ± 0.9. The olfactory clefts were opacified in three patients on the CT scan. The mean radiological olfactory cleft score was 0.7 ± 0.8. There were no significant correlations between clinical, radiological, and psychophysical olfactory testing.

CONCLUSIONS

The olfactory cleft of anosmic COVID-19 patients is free regarding endoscopic examination and imaging. The anosmia etiology is not related to edema of the olfactory cleft.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:2526-2531, 2020.

The diagnostic value of detecting sudden smell loss among asymptomatic COVID-19 patients in early stage: The possible early sign of COVID-19

IMPORTANCE

The newly emerged coronavirus disease 19 (COVID-19), is threatening the world. Olfactory or gustatory dysfunction is reported as one of the symptoms worldwide. As reported so far, different clinical features have been reported according to outbreak sites and gender; most of the patients, who complained of anosmia or hyposmia, were Europeans. We had a fast review for novel articles about COVID-19 infection and olfactory function.

OBSERVATIONS

Rapid reviews for COVID-19 or other viral infection and olfactory and/or gustatory dysfunctions were done in this review. Up to date, a lot of reports have shown that olfactory dysfunction is related to viral infections but no exact mechanism, clinical course, and definite treatment have been discovered, which is also same in COVID-19. In general, intranasal steroid (INS) and oral steroid for short time help improve the recovery of the olfactory function in case of olfactory dysfunction after virus infection. Considering severe respiratory complications and immunocompromised state of COVID-19, the use of steroid should be limited and cautious because we do not have enough data to support the usage of steroid to treat olfactory dysfunction in the clinical course of COVID-19.

CONCLUSIONS AND RELEVANCE

In the days of pandemic COVID-19, we should keep in mind that olfactory dysfunctions, even without other upper respiratory infection or otolaryngologic symptoms, might be the early signs of COVID-19.

COVID-19 and the Chemical Senses: Supporting Players Take Center Stage

The main neurological manifestation of COVID-19 is loss of smell or taste. The high incidence of smell loss without significant rhinorrhea or nasal congestion suggests that SARS-CoV-2 targets the chemical senses through mechanisms distinct from those used by endemic coronaviruses or other common cold-causing agents. Here we review recently developed hypotheses about how SARS-CoV-2 might alter the cells and circuits involved in chemosensory processing and thereby change perception. Given our limited understanding of SARS-CoV-2 pathogenesis, we propose future experiments to elucidate disease mechanisms and highlight the relevance of this ongoing work to understanding how the virus might alter brain function more broadly.

Frequency and outcome of olfactory impairment and sinonasal involvement in hospitalized patients with COVID-19

Background

Olfactory dysfunction has shown to accompany COVID-19. There are varying data regarding the exact frequency in the various study population. The outcome of the olfactory impairment is also not clearly defined.

Objective

To find the frequency of olfactory impairment and its outcome in hospitalized patients with positive swab test for COVID-19.

Methods

This is a prospective descriptive study of 100 hospitalized COVID-19 patients, randomly sampled, from February to March 2020. Demographics, comorbidities, and laboratory findings were analyzed according to the olfactory loss or sinonasal symptoms. The olfactory impairment and sinonasal symptoms were evaluated by 9 Likert scale questions asked from the patients.

Results

Ninety-two patients completed the follow-up (means 20.1 (± 7.42) days). Twenty-two (23.91%) patients complained of olfactory loss and in 6 (6.52%) patients olfactory loss was the first symptom of the disease. The olfactory loss was reported to be completely resolved in all but one patient. Thirty-nine (42.39%) patients had notable sinonasal symptoms while rhinorrhea was the first symptom in 3 (3.26%). Fifteen patients (16.3%) had a taste impairment. Patients with sinonasal symptoms had a lower age (p = 0.01). There was no significant relation between olfactory loss and sinonasal symptoms (p = 0.07).

Conclusions

Sudden olfactory dysfunction and sinonasal symptoms have a considerable prevalence in patients with COVID-19. No significant association was noted between the sinonasal symptoms and the olfactory loss, which may suggest that other mechanisms beyond upper respiratory tract involvement are responsible for the olfactory loss.

Olfaction in Juvenile Nasopharyngeal Angiofibroma: The first study

BACKGROUND

To study the pattern of olfactory dysfunction/recovery in juvenile nasopharyngeal angiofibroma (JNA).

METHODS

Olfactory assessment was undertaken in 30 patients (category1) both pre- & post-operatively and in another 18 (category 2) only postoperative. All patients underwent transpalatal excision and variables of interest included age, radiological stage/parameters & tumor size.

RESULTS

Objective olfactory dysfunction was seen in 60% while involvement of olfactory strip was suggested in 50%. Despite some marginal trends only noted between size/age with change of olfaction, Pearson's correlation test did not reveal any significance amongst multiple variables. However a better recovery of olfaction following surgery was evident in Category-2 where Chi-Square test (p < 0.05) significantly revealed this to be a function of postoperative duration. This regenerative course in JNA suggests an optimum period of 4 years for full recovery after surgery.

CONCLUSION

In this first study of olfaction in JNA many new trends have been appreciated. In general, deteriorations of olfaction were seen due to 'vascular-concussion' effect in early postoperative phase where post-surgical clearance of airway showed minimal effect in terms of improvement. The hypervascularity of olfactory epithelium with possible hormonal effects may be responsible for the unique pattern of olfactory function and recovery in JNA.

Olfactory and gustatory abnormalities in COVID-19 cases

Purpose

At the time of writing, there is a pandemic affecting virtually every country on Earth. There is considerable discussion amongst clinicians as well as lay people about anosmia and ageusia in COVID-19 sufferers. We aimed to report the results from comprehensive olfactory and gustatory testing in a series of hospital in-patients.

Methods

The prospective study evaluated 81 individuals with a COVID-19 infection, as confirmed by 2019 n-cov Real-Time PCR laboratory testing. The control group consisted of forty individuals with COVID-19 negative. Olfactory and gustatory testings were carried out by an examiner utilizing stringent safety standards and wearing full personal protective equipment. The results obtained in the case group were then compared with those obtained for the controls.

Results

In the case group, 41(50.6%) of patients were male and 40 (49.4%) were female, mean age of 54.16 ± 16.98 years (18–95). In the control group, 21 (52.5%) of subjects were male and 19 (47.5%) were female, and mean age was 55 ± 15.39 years (18–90). Fifty (61.7%) COVID-19-positive patients had complaints related to olfaction. The distribution of olfactory symptoms in the case group differed at the level of statistical significance from the control group (p < 0.001). Turning to gustatory abnormalities, within the case group, 22 individuals (27.2%) had taste malfunction. A statistically significant difference was found in the distribution of gustatory abnormalities between cases and controls (p < 0.001).

Conclusions

Olfactory and gustatory dysfunctions are strongly associated with SARS-CoV-2 infection. Hyposmia with or without hypogeusia is potentially a reliable indicator of latent COVID-19.

The Effect of Endoscopic Olfactory Cleft Opening on Obstructed Olfactory Cleft Disease

Purpose

This study was conducted to evaluate the effect of endoscopic olfactory cleft (OC) opening on olfaction in patients with obstructed OC disease. Materials and Methods. Patients with obstructed OC disease who underwent endoscopic OC opening for treatment were enrolled. The endoscopic olfactory cleft opening was performed under local anesthesia. Under an endoscopy, the middle and superior turbinates were gently lateralized to open the OC using an elevator. The phenyl ethyl alcohol threshold test was performed to evaluate the olfactory function both before and after surgery.

Results

An endoscopic OC opening was performed on 42 patients. Amongst them, the etiology of OC obstruction revealed anatomic anomalies in 14 patients, inflammatory process in 14, and anatomic anomalies as well as inflammatory process in 14. The phenyl ethyl alcohol threshold levels improved in 32 (76.2%) of the patients after surgery. The olfactory function was better improved in patients experiencing OC obstructed by inflammatory process than those by anatomic anomalies.

Conclusions

This study showed that endoscopic OC opening seemed to be effective in treating olfactory dysfunction in patients with obstructed OC disease caused by inflammatory process.

Olfactory cleft proteome does not reflect olfactory performance in patients with idiopathic and postinfectious olfactory disorder: A pilot study

Technical advances including liquid chromatography–tandem mass spectrometry and its data analysis enable detailed proteomic analysis of the nasal mucus. Alterations of the nasal mucus proteome may provoke substantial changes of the nasal physiology and have already been associated with rhinologic diseases such as allergic rhinitis. This study was conducted as a pilot study to map the olfactory cleft proteome using current techniques for proteomic analysis. Furthermore, we aimed to investigate proteomic changes as potential biomarkers in patients suffering from idiopathic and postinfectious olfactory disorders compared to healthy controls. Seven patients with idiopathic hyposmia and anosmia, seven patients with postinfectious hyposmia and anosmia and seven healthy controls were included in this study. In total, 1117 different proteins were detected in at least five patients in at least one group. Results of this study did not reveal significant differences regarding the proteomic composition of the olfactory cleft mucus between patients versus healthy controls. Among proteins involved in olfactory perception the G protein family was detected but also found unchanged between groups. Investigation of protein composition by liquid chromatography–tandem mass spectrometry enabled us to perform an in–depth analysis of the olfactory cleft mucus proteome regarding the diversity of different proteins in individual patients. However untargeted proteomics of the olfactory cleft mucus may not be an applicable approach to develop biomarkers for olfactory disorders. Targeted analyses of distinct proteins known to be involved in olfactory perception but not detected by our approach, e.g. odorant binding proteins, may provide more information regarding pathophysiology of olfactory diseases.

Olfactory cleft dilatation

The surgical technique of olfactory cleft dilatation consists in transmucosal lateral fracture-dislocation of the lateral wall of each olfactory cleft (i.e., of the turbinate wall of the ethmoid, composed, from anterior to posterior, of the middle, superior and supreme turbinates), in order to get access to the recess hosting the human olfactory mucosa and to the roof of the olfactory cleft (i.e., cribriform plate), with minimal trauma to the mucosa. Olfactory cleft dilatation is indicated for dysosmia secondary to constitutional stenosis of the olfactory clefts due to abnormal development of the ethmoid. Constitutional stenosis of the olfactory clefts should be differentiated from inflammatory obstruction and other diseases of the olfactory clefts, and especially from respiratory epithelial adenomatoid hamartoma, which enlarges the olfactory clefts and must be treated by resection. The technique of olfactory cleft dilatation is illustrated by three surgical cases. There was clear improvement in dysosmia in all three cases, without any complications. The place of constitutional olfactory cleft stenosis needs still to be defined in both diagnosis and treatment of dysosmia.

Do sinus computed tomography findings predict olfactory dysfunction and its postoperative recovery in chronic rhinosinusitis patients?

BACKGROUND

Olfactory dysfunction secondary to chronic rhinosinusitis (CRS) is a mixed disorder of conductive and sensorineural olfactory impairment. Although endoscopic sinus surgery has some beneficial effects on olfaction, the outcomes are challenging to predict. The aim of this study was to assess the olfactory outcomes after surgery, to investigate the correlation between the severity of regional computed tomography (CT) findings and olfactory performance, and to identify the predictors of postoperative outcomes based on unilateral olfactory threshold analysis.

METHODS

This study included 167 CRS nostrils of 97 patients with/without polyps (68/99 nostrils) undergoing sinus surgery between January 2007 and December 2011. Olfactory function was evaluated using the butanol threshold test (BTT) before and 6 months after surgery. Clinical and nasal factors from sinus CT scan (sinuses, ostiomeatal complex, olfactory cleft [OC], nasal polyps, and unilateral Lund-Mackay CT score) were analyzed to correlate them with pre- and postoperative olfactory performances.

RESULTS

Eighty-two percent of the CRS nostrils had anosmia or hyposmia. After surgery, 42% of them showed an improvement in BTT score. Despite improvement, most of the subjects remained with residual hyposmia. The BTT scores deteriorated after surgery in 23% of the total subjects. The disease severity of the OC, posterior ethmoid, and frontal sinus were the significant risk factors for CRS-related anosmia. The strongest risk factor for anosmia was totally obstructed OC (odds ratio [OR], 16.56; 95% CI, 4.31-63.71; p = 0.000). The nostrils with anosmia or partly opacified anterior ethmoid benefited from surgery with respect to olfaction.

CONCLUSION

Our results can give support to the combined use of the butanol threshold and sinonasal CT findings in the evaluation of olfaction in CRS patients and help us counsel the patients about the likelihood of postoperative olfactory recovery.

The olfactory system

Any dysfunction in olfaction requires a radiological exploration comprising the nasal cavity, the anterior base of the skull, in particular the frontal and temporal lobes. MRI is the reference examination, due to the frontal plane and the T1, T2 volume maps. In the child, aplasia of the olfactory bulbs falls within a polymalformation (CHARGE) or endocrine (Kallman) context. In the adult, rhino sinus disease and meningiomas are the most common etiologies. Frontal or temporal impairment: tumoral or vascular and neurodegenerative disorders (Parkinson's disease) may accompany a loss of olfaction.

Smell and taste disorders

Smell and taste disorders can markedly affect the quality of life. In recent years we have become much better in the assessment of the ability to smell and taste. In addition, information is now available to say something about the prognosis of individual patients. With regard to therapy there also seems to be low but steady progress. Of special importance for the treatment is the ability of the olfactory epithelium to regenerate.

Diagnostic tools in Rhinology EAACI position paper

This EAACI Task Force document aims at providing the readers with a comprehensive and complete overview of the currently available tools for diagnosis of nasal and sino-nasal disease. We have tried to logically order the different important issues related to history taking, clinical examination and additional investigative tools for evaluation of the severity of sinonasal disease into a consensus document. A panel of European experts in the field of Rhinology has contributed to this consensus document on Diagnostic Tools in Rhinology.

Digital volume tomography (DVT) measurements of the olfactory cleft and olfactory fossa

CONCLUSION

Preoperative imaging is important, because of the small size of the cribriform plate, different anatomical variants of the olfactory fossa in varied patients and unequal width of the cribriform plate in the anterior and posterior third.

OBJECTIVE

Digital volume tomography (DVT) is a rather new imaging technique for the diagnosis of diseases of paranasal sinuses. This technology is dedicated to the evaluation of the distinctive structures of the anterior skull base due to the high resolution of the DVT. Based on the Keros classification this anatomic area was analyzed radiologically and also in relation to the uncinate process.

METHODS

The investigation was performed on 111 patients. The Accu-I-tomo F17 was used. Patients with total nasal polyposis and patients who had undergone sinus surgery were excluded from the study.

RESULTS

Keros type I was found in 11.25% of the patients, type II in 68.05% and type III in 20.7%. Significant asymmetry of the olfactory fossa was identified in nine patients (8.1%). The width of the olfactory cleft varied from 0 to 3.25 mm. No relation between Keros type and a particular onset of the uncinate process to orbit, skull base or middle turbinate could be detected.