Paranasal sinuses computed tomography findings in anosmia of COVID-19

Magnetic resonance spectroscopy findings of brain olfactory areas in patients with COVID-19-related anosmia: A preliminary comparative study

Objectives

2019 novel coronavirus disease (COVID-19) infection is commonly associated with olfactory dysfunctions, but the basic pathogenesis of these complications remains controversial. This study seeks to evaluate the value of magnetic resonance spectroscopy (MRS) in determining the molecular neurometabolite alterations within the main brain olfactory areas in patients with COVID-19-related anosmia.

Methods

In a cross-sectional study, seven patients with persistent COVID-19-related anosmia (mean age: 29.57 years) and seven healthy volunteers (mean age: 27.28 years) underwent MRS in which N-acetyl-aspartate (NAA), choline (Cho), creatine (Cr), and their ratios were measured in the anterior cingulate cortex, dorsolateral prefrontal cortex, orbitofrontal cortex (OFC), insular cortex, and ventromedial prefrontal cortex. Data were analyzed using TARQUIN software (version 4.3.10), and the results were compared with an independent sample t-test and nonparametric Mann-Whitney test based on the normality of the MRS data distribution.

Results

The mean duration of anosmia before imaging was 8.5 months in COVID-19-related anosmia group. MRS analysis elucidated a significant association between MRS findings within OFC and COVID-19-related anosmia (P disease < 0.01), and NAA was among the most important neurometabolites (P interaction = 0.006). Reduced levels of NAA (P < 0.001), Cr (P < 0.001) and NAA/Cho ratio (P = 0.007) within OFC characterize COVID-19-related anosmia.

Conclusions

This study emphasizes that MRS can be illuminating in COVID-19-related anosmia and indicates a possible association between central nervous system impairment and persistent COVID-19-related anosmia.

COVID-19 and anosmia: The story so far

OBJECTIVES

The pandemic has affected over 182 million coronavirus disease 2019 (COVID-19) cases worldwide. Accumulated evidence indicates that anosmia is one of the significant characteristics of COVID-19 with a high prevalence. However, many aspects of COVID-19-induced anosmia are still far from being fully understood. The purpose of this review is to summarize recent developments in COVID-19-induced anosmia to increase awareness of the condition.

METHODS

A literature search was carried out using the PubMed, Embase, Web of Science, and Scopus. We reviewed the latest literature on COVID-19-induced anosmia, including mechanisms of pathogenesis, olfactory testing, anosmia as predictive tool, pathological examinations, imaging findings, affected factors, co-existing diseases, treatments, prognosis, hypothesis theories, and future directions.

RESULTS

The possible pathogenesis of COVID-19-induced anosmia may involve inflammation of the olfactory clefts and damage to the olfactory epithelium or olfactory central nervous system by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The D614G spike variant may also play a role in the increased number of anosmia patients. Anosmia may also be an essential indicator of COVID-19 spread and an early indicator of the effectiveness of political decisions. The occurrence and development of COVID-19-induced anosmia may be influenced by smoking behaviors and underlying diseases such as type 2 diabetes, gastroesophageal disorders, and rhinitis. Most patients with COVID-19-induced anosmia can fully or partially recover their olfactory function for varying durations. COVID-19-induced anosmia can be treated with various approaches such as glucocorticoids and olfactory training.

CONCLUSION

Anosmia is one of the main features of COVID-19 and the underlying disease of the patient may also influence its occurrence and development. The possible pathogenesis of COVID-19-induced anosmia is very complicated, which may involve inflammation of the olfactory clefts and damage to the olfactory epithelium or olfactory central nervous system.

Anosmia in COVID-19: Investigating the Role of Paranasal Sinus Mucosal Thickening

Background Anosmia has been identified as a distinctive symptom of COVID-19, leading to hypotheses about its pathophysiological underpinnings, including the potential role of paranasal sinus mucosal thickening. Objective To investigate the association between paranasal sinus mucosal thickening and anosmia in COVID-19 patients, providing insights into the complex clinical manifestations of the disease. Methods This retrospective cohort study analyzed CT paranasal sinus from 270 confirmed COVID-19 patients, divided into those with anosmia (n = 23, 8.52%) and those without anosmia (n = 247, 91.48%). Statistical analysis, including independent t-tests, was employed to compare mucosal thickening between the groups. Results The study found an average mucosal thickening of 0.03 in patients with anosmia and 0.02 in those without, with no statistically significant difference between the groups (p = 0.480, which is greater than 0.05). The findings suggest that mucosal thickening in the paranasal sinuses does not serve as a definitive correlate of anosmia among COVID-19 patients. Conclusion The absence of a significant correlation between paranasal sinus mucosal thickening and anosmia in COVID-19 patients indicates that the pathophysiology of anosmia may involve factors beyond anatomical changes, including direct viral effects and systemic inflammatory responses.

SARS-CoV-2 induces inflammation and intracranial infection through the olfactory epithelium-olfactory bulb pathway in non-human primates

We examined the histopathological changes in the olfactory mucosa of cynomolgus and rhesus macaque models of SARS-CoV-2 infection. SARS-CoV-2 infection induced severe inflammatory changes in the olfactory mucosa. A major histocompatibility complex (MHC) class II molecule, HLA-DR was expressed in macrophage and supporting cells, and melanocytes were increased in olfactory mucosa. Supporting cells and olfactory neurons were infected, and SARS-CoV-2 N protein was detected in the axons of olfactory neurons and in olfactory bulbs. Viral RNA was detected in olfactory bulbs and brain tissues. The olfactory epithelium-olfactory bulb pathway may be important as a route for intracranial infection by SARS-CoV-2.

Olfactory dysfunction among patients with COVID-19

OBJECTIVES

To assess the frequency of olfactory dysfunction (OD) among individuals afflicted with coronavirus disease of 2019 (COVID-19).

METHODS

A comprehensive literature search was carried out across several bibliographical databases (PubMed, Scopus, Google Scholar, and Web of Science) to extract publications in the English language between January 2020 and December 2021 to report the incidence of OD alone or together with gustatory dysfunction (GD) among COVID-19 patients.

RESULTS

Based on eligibility criteria, 84 articles were included from 27 countries, comprising 36,903 patients, of whom 58.1% were females. The generality rates of olfactory impairment alone was 34.60% and in conjunction with GD was 11.36%. Patients with OD were subclassified into various categories, and the prevalence of anosmia was 20.85%, 5.04% for hyposmia, 8.88% for anosmia or hyposmia, 1.84% for parosmia, 0.78% for phantosmia, and 0.02% for hyperosmia, among COVID-19 patients.

CONCLUSION

Clinical features associated with OD, either isolated or in combination with GD, are common in patients with COVID-19 and consider important signs of COVID-19 that may guide clinicians in the early phase of the disease.PROSPERO Reg. No.: 417296.

Acute and long-term immune responses to SARS-CoV-2 infection in unvaccinated children and young adults with inborn errors of immunity

Purpose

To describe SARS-CoV-2 infection outcome in unvaccinated children and young adults with inborn errors of immunity (IEI) and to compare their specific acute and long-term immune responses with a sex-, age-, and severity-matched healthy population (HC).

Methods

Unvaccinated IEI patients up to 22 years old infected with SARS-CoV-2 were recruited along with a cohort of HC. SARS-CoV-2 serology and ELISpot were performed in the acute phase of infection (up to 6 weeks) and at 3, 6, 9, and 12 months.

Results

Twenty-five IEI patients (median age 14.3 years, min.-max. range 4.5-22.8; 15/25 males; syndromic combined immunodeficiencies: 48.0%, antibody deficiencies: 16.0%) and 17 HC (median age 15.3 years, min.-max. range 5.4-20.0; 6/17 males, 35.3%) were included. Pneumonia occurred in 4/25 IEI patients. In the acute phase SARS-CoV-2 specific immunoglobulins were positive in all HC but in only half of IEI in whom it could be measured (n=17/25): IgG⁺ 58.8% (10/17) (p=0.009); IgM⁺ 41.2% (7/17)(p<0.001); IgA⁺ 52.9% (9/17)(p=0.003). Quantitative response (index) was also lower compared with HC: IgG IEI (3.1 ± 4.4) vs. HC (3.5 ± 1.5)(p=0.06); IgM IEI (1.9 ± 2.4) vs. HC (3.9 ± 2.4)(p=0.007); IgA IEI (3.3 ± 4.7) vs. HC (4.6 ± 2.5)(p=0.04). ELISpots positivity was qualitatively lower in IEI vs. HC (S-ELISpot IEI: 3/11, 27.3% vs. HC: 10/11, 90.9%; p=0.008; N-ELISpot IEI: 3/9, 33.3% vs. HC: 11/11, 100%; p=0.002) and also quantitatively lower (S-ELISpot IEI: mean index 3.2 ± 5.0 vs. HC 21.2 ± 17.0; p=0.001; N-ELISpot IEI: mean index 9.3 ± 16.6 vs. HC: 39.1 ± 23.7; p=0.004). As for long term response, SARS-CoV-2-IgM⁺ at 6 months was qualitatively lower in IEI(3/8, 37.5% vs. 9/10 HC: 90.0%; p=0.043), and quantitatively lower in all serologies IgG, M, and A (IEI n=9, 1.1 ± 0.9 vs. HC n=10, 2.1 ± 0.9, p=0.03; IEI n=9, 1.3 ± 1.5 vs. HC n=10, 2.9 ± 2.8, p=0.02; and IEI n=9, 0.6 ± 0.5 vs. HC n=10, 1.7 ± 0.8, p=0.002 -respectively) but there were no differences at remaining time points.

Conclusions

Our IEI pediatric cohort had a higher COVID-19 pneumonia rate than the general age-range population, with lower humoral and cellular responses in the acute phase (even lower compared to the reported IEI serological response after SARS-CoV-2 vaccination), and weaker humoral responses at 6 months after infection compared with HC.

Sinus, middle-ear and mastoid radiological findings of severe acute respiratory syndrome coronavirus-2

OBJECTIVE

To assess the incidence of radiological inflammation within the paranasal sinuses, middle ear and mastoid in patients with confirmed severe acute respiratory syndrome coronavirus-2.

METHODS

A retrospective cohort study was conducted to examine consecutive adults (aged over 18 years) with coronavirus disease 2019 (confirmed on polymerase chain reaction within 7 days of imaging) who underwent computed tomography of the head between 1 March 2020 and 24 June 2020. Lund-Mackay and mastoid and middle-ear opacification scores were used to categorise the extent of sinus and mastoid opacification on axial and coronal computed tomography images.

RESULTS

Of 147 patients originally identified, only 83 met the inclusion criteria. Sinus opacification was present in 51.8 per cent of patients (n = 43), and middle-ear or mastoid opacification was observed in 24.1 per cent (n = 20). There was no statistically significant difference in sinus or middle-ear and mastoid opacification between patients after stratification based on 30-day all-cause mortality.

CONCLUSION

Radiological computed tomography findings suggest mild mucosal disease within the sinuses, middle ear and mastoid. There was no statistical correlation between such opacification and 30-day mortality.

Oral SARS-CoV-2 Inoculation Causes Nasal Viral Infection Leading to Olfactory Bulb Infection: An Experimental Study

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections can cause long-lasting anosmia, but the impact of SARS-CoV-2 infection, which can spread to the nasal cavity via the oral route, on the olfactory receptor neuron (ORN) lineage and olfactory bulb (OB) remains undetermined. Using Syrian hamsters, we explored whether oral SARS-CoV-2 inoculation can lead to nasal viral infection, examined how SARS-CoV-2 affects the ORN lineage by site, and investigated whether SARS-CoV-2 infection can spread to the OB and induce inflammation. On post-inoculation day 7, SARS-CoV-2 presence was confirmed in the lateral area (OCAM-positive) but not the nasal septum of NQO1-positive and OCAM-positive areas. The virus was observed partially infiltrating the olfactory epithelium, and ORN progenitor cells, immature ORNs, and mature ORNs were fewer than in controls. The virus was found in the olfactory nerve bundles to the OB, suggesting the nasal cavity as a route for SARS-CoV-2 brain infection. We demonstrated that transoral SARS-CoV-2 infection can spread from the nasal cavity to the central nervous system and the possibility of central olfactory dysfunction due to SARS-CoV-2 infection. The virus was localized at the infection site and could damage all ORN-lineage cells.

COVID-19 and rhinological surgery

The Coronavirus-19 (COVID-19) pandemic has caused disruptions in the normal patient care workflow, necessitating adaptations within the healthcare profession. The objective of this article is to outline some of these adaptations and considerations necessitated by COVID-19 within the subspeciality of rhinology and endoscopic skull base surgery.

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

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

Pathogenesis of Olfactory Disorders in COVID-19

Since the outbreak of the SARS-CoV-2 pandemic, olfactory disorders have been reported as a frequent symptom of COVID-19; however, its pathogenesis is still debated. The aim of this review is to summarize the current understanding of the pathogenesis of smell impairment in the course of COVID-19 and to highlight potential avenues for future research on this issue. Several theories have been proposed to explain the pathogenesis of COVID-19-related anosmia, including nasal obstruction and rhinorrhea, oedema of the olfactory cleft mucosa, olfactory epithelial damage either within the olfactory receptor cells or the supporting non-neural cells (either direct or immune-mediated), damage to the olfactory bulb, and impairment of the central olfactory pathways. Although the pathogenesis of COVID-19-related anosmia is still not fully elucidated, it appears to be mainly due to sensorineural damage, with infection of the olfactory epithelium support cells via the ACE1 receptor and disruption of the OE caused by immense inflammatory reaction, and possibly with direct olfactory sensory neurons infection mediated by the NRP-1 receptor. Involvement of the higher olfactory pathways and a conductive component of olfactory disorders, as well as genetic factors, may also be considered.

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.

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.

Clinical, virological and immunological evolution of the olfactory and gustatory dysfunction in COVID-19

Purpose

New-onset olfactory and gustatory dysfunction (OGD) represents a well-acknowledged COVID-19 red flag. Nevertheless, its clinical, virological and serological features are still a matter of debate.

Materials and methods

For this cohort study, 170 consecutive subjects with new-onset OGD were consecutively recruited. Otolaryngological examination, OGD subjective grading, nasopharyngeal swabs (NS) for SARS-CoV-2 RNA detection and serum samples (SS) collection for SARS-CoV-2 IgG quantification were conducted at baseline and after one (T1), two (T2) and four weeks (T3).

Results

SARS-CoV-2 infection was confirmed in 79% of patients. Specifically, 43% of positive patients were detected only by SS analysis. The OGD was the only clinical complaint in 10% of cases. Concurrent sinonasal symptoms were reported by 45% of patients. Subjective improvement at T3 was reported by 97% of patients, with 40% recovering completely. Hormonal disorders and RNA detectability in NS were the only variables associated with OGD severity. Recovery rate was higher in case of seasonal influenza vaccination, lower in patients with systemic involvement and severe OGD. Not RNA levels nor IgG titers were correlated with recovery.

Conclusion

Clinical, virological and serological features of COVID-19 related OGD were monitored longitudinally, offering valuable hints for future research on the relationship between host characteristics and chemosensory dysfunctions.

Anosmia in COVID-19: Underlying Mechanisms and Assessment of an Olfactory Route to Brain Infection

In recent months it has emerged that the novel coronavirus-responsible for the COVID-19 pandemic-causes reduction of smell and taste in a large fraction of patients. The chemosensory deficits are often the earliest, and sometimes the only signs in otherwise asymptomatic carriers of the SARS-CoV-2 virus. The reasons for the surprisingly early and specific chemosensory dysfunction in COVID-19 are now beginning to be elucidated. In this hypothesis review, we discuss implications of the recent finding that the prevalence of smell and taste dysfunction in COVID-19 patients differs between populations, possibly because of differences in the spike protein of different virus strains or because of differences in the host proteins that enable virus entry, thus modifying infectivity. We review recent progress in defining underlying cellular and molecular mechanisms of the virus-induced anosmia, with a focus on the emerging crucial role of sustentacular cells in the olfactory epithelium. We critically examine the current evidence whether and how the SARS-CoV-2 virus can follow a route from the olfactory epithelium in the nose to the brain to achieve brain infection, and we discuss the prospects for using the smell and taste dysfunctions seen in COVID-19 as an early and rapid diagnostic screening tool.

Olfactory dysfunction as a screening tool for mild and moderate cases of COVID-19: a single-center prevalence study of 646 patients in flu clinic

Background

To evaluate the prevalence of olfactory dysfunction (OD) in the Indian population and to establish olfactory dysfunction as a screening tool in COVID-19-positive patients. Data was collected using a questionnaire from laboratory-confirmed COVID-19 patients. The patient’s demographic and clinical details were analyzed to calculate the prevalence of olfactory dysfunction, general symptoms like fever, cough, malaise, diarrhea, along with the sinonasal symptoms. All the symptoms were self-reported, and no objective tests were carried out.

Results

Out of 646 laboratory-confirmed cases of COVID-19 infection, olfactory dysfunction was self-reported by 465 (72%) patients and gustatory dysfunction (GD) was seen in 406 (62.8%) patients. The affected males (416) were proportionately more than females (230), with the mean age of our study population being 39.47 ± 13.85 (range 18–85 years). The most common symptoms were myalgia (n = 494, 76.5%), cough (n = 471, 72.9%), and fever (n = 444, 68.7%). Out of 465 patients with olfactory dysfunction, only 108 (23.2%) reported nasal obstruction. Five hundred thirty-three (82.5%) RT-PCR-positive patients did not give a history of smoking; however, co-morbidity was reported by 163 patients, of which 117 were found to have olfactory dysfunction. One hundred seventy (26.3%) patients gave a positive contact history.

13.6% reported olfactory dysfunction as their first symptom. A positive association was seen between olfactory dysfunction and gustatory dysfunction

Conclusions

Our study demonstrates a high prevalence of 72% in the Indian population. We recommend that anosmia be used as a screening tool to identify mild to moderate cases of COVID-19.

A Systematic Review of Imaging Studies in Olfactory Dysfunction Secondary to COVID-19

RATIONALE AND OBJECTIVES

Hyposmia/anosmia is common among patients with coronavirus disease-2019 (COVID-19). Various imaging modalities have been used to assess olfactory dysfunction in COVID-19. In this systematic review, we sought to categorize and summarize the imaging data in COVID-19-induced anosmia.

MATERIAL AND METHODS

Eligible articles were included after a comprehensive review using online databases including Google scholar, Scopus, PubMed, Web of science and Elsevier. Duplicate results, conference abstracts, reviews, and studies in languages other than English were excluded.

RESULTS

In total, 305 patients undergoing MRI/functional MRI (177), CT of paranasal sinuses (129), and PET/CT or PET/MRI scans (14) were included. Out of a total of 218 findings reported on MRI, 80 were reported on early (≤ 1 month) and 85 on late (>1 month) imaging in relation to the onset of anosmia. Overall, OB morphology and T2-weighted or FLAIR signal intensity were normal in 68/218 (31.2%), while partial or complete opacification of OC was observed in 60/218 (27.5%). T2 hyperintensity in OB was detected in 11/80 (13.75%) and 18/85 (21.17%) on early and late imaging, respectively. Moreover, OB atrophy was reported in 1/80 (1.25%) on early and in 9/85 (10.58%) on late imaging. Last, among a total of 129 CT scans included, paranasal sinuses were evalualted in 88 (68.21%), which were reported as normal in most cases (77/88, [87.5%]).

CONCLUSION

In this systematic review, normal morphology and T2/FLAIR signal intensity in OB and OC obstruction were the most common findings in COVID-19-induced anosmia, while paranasal sinuses were normal in most cases. OC obstruction is the likely mechanism for olfactory dysfunction in COVID-19. Abnormalities in OB signal intensity and OB atrophy suggest that central mechanisms may also play a role in late stage in COVID-19-induced anosmia.

Post-viral effects of COVID-19 in the olfactory system and their implications

BACKGROUND

The mechanisms by which any upper respiratory virus, including SARS-CoV-2, impairs chemosensory function are not known. COVID-19 is frequently associated with olfactory dysfunction after viral infection, which provides a research opportunity to evaluate the natural course of this neurological finding. Clinical trials and prospective and histological studies of new-onset post-viral olfactory dysfunction have been limited by small sample sizes and a paucity of advanced neuroimaging data and neuropathological samples. Although data from neuropathological specimens are now available, neuroimaging of the olfactory system during the acute phase of infection is still rare due to infection control concerns and critical illness and represents a substantial gap in knowledge.

RECENT DEVELOPMENTS

The active replication of SARS-CoV-2 within the brain parenchyma (ie, in neurons and glia) has not been proven. Nevertheless, post-viral olfactory dysfunction can be viewed as a focal neurological deficit in patients with COVID-19. Evidence is also sparse for a direct causal relation between SARS-CoV-2 infection and abnormal brain findings at autopsy, and for trans-synaptic spread of the virus from the olfactory epithelium to the olfactory bulb. Taken together, clinical, radiological, histological, ultrastructural, and molecular data implicate inflammation, with or without infection, in either the olfactory epithelium, the olfactory bulb, or both. This inflammation leads to persistent olfactory deficits in a subset of people who have recovered from COVID-19. Neuroimaging has revealed localised inflammation in intracranial olfactory structures. To date, histopathological, ultrastructural, and molecular evidence does not suggest that SARS-CoV-2 is an obligate neuropathogen. WHERE NEXT?: The prevalence of CNS and olfactory bulb pathosis in patients with COVID-19 is not known. We postulate that, in people who have recovered from COVID-19, a chronic, recrudescent, or permanent olfactory deficit could be prognostic for an increased likelihood of neurological sequelae or neurodegenerative disorders in the long term. An inflammatory stimulus from the nasal olfactory epithelium to the olfactory bulbs and connected brain regions might accelerate pathological processes and symptomatic progression of neurodegenerative disease. Persistent olfactory impairment with or without perceptual distortions (ie, parosmias or phantosmias) after SARS-CoV-2 infection could, therefore, serve as a marker to identify people with an increased long-term risk of neurological disease.

The effect of coronaviruses on olfaction: systematic review

BACKGROUND

Unlike other respiratory viruses, SARS-CoV-2 causes anosmia without sinonasal inflammation. Here we systematically review the effects of the 7 known human coronaviruses on olfaction to determine if SARS-CoV-2 distinctly affects the olfactory system.

METHOD

PubMed, EMBASE, Web of Science, bioRxiv, medRxiv and DOAJ were searched for studies describing pathophysiological, immunohistochemical, cytological and clinical data.

RESULTS

49 studies were included. Common cold coronaviruses lead to sinonasal inflammation which can cause transient and chronic loss of smell. MERS-CoV entry receptors were not found in the nasal mucosa and it did not impair olfaction. SARS-CoV-1 had low affinity for its receptor ACE2, limiting olfactory effects. Anosmia is frequent in SARS-CoV-2 infections. SARS-CoV-2’s entry factors ACE2 and TMPRSS2 are expressed in the nasal respiratory epithelium and olfactory supporting cells. SARS-CoV-2 appeared to target the olfactory cleft while diffuse nasal inflammation was not observed. Damage of the olfactory epithelium was observed in animal models. Alternative receptors such as furin and neuropilin-1 and the similarity of viral proteins to odourant receptors could amplify olfactory impairment in SARS-CoV-2 infection.

CONCLUSIONS

The pathophysiology of anosmia in SARS-CoV-2 infection is distinct from other coronaviruses due to preferentially targeting olfactory supporting cells. However, SARS-CoV-2 does not cause sinonasal inflammation in spite of preferred entry factor expression in the nasal respiratory epithelium. This raises doubts about the attention given to ACE2. Alternative receptors, odourant receptor mimicry and other as yet unknown mechanisms may be crucial in the pathogenesis of anosmia in SARS-CoV-2 infection. Further studies are warranted to investigate infection mechanisms beyond ACE2.

Structural and metabolic brain abnormalities in COVID-19 patients with sudden loss of smell

OBJECTIVES

Sudden loss of smell is a very common symptom of coronavirus disease 19 (COVID-19). This study characterizes the structural and metabolic cerebral correlates of dysosmia in patients with COVID-19.

METHODS

Structural brain magnetic resonance imaging (MRI) and positron emission tomography with [18F]-fluorodeoxyglucose (FDG-PET) were prospectively acquired simultaneously on a hybrid PET-MR in 12 patients (2 males, 10 females, mean age: 42.6 years, age range: 23-60 years) with sudden dysosmia and positive detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on nasopharyngeal swab specimens. FDG-PET data were analyzed using a voxel-based approach and compared with that of a group of healthy subjects.

RESULTS

Bilateral blocking of the olfactory cleft was observed in six patients, while subtle olfactory bulb asymmetry was found in three patients. No MRI signal abnormality downstream of the olfactory tract was observed. Decrease or increase in glucose metabolism abnormalities was observed (p < .001 uncorrected, k ≥ 50 voxels) in core olfactory and high-order neocortical areas. A modulation of regional cerebral glucose metabolism by the severity and the duration of COVID-19-related dysosmia was disclosed using correlation analyses.

CONCLUSIONS

This PET-MR study suggests that sudden loss of smell in COVID-19 is not related to central involvement due to SARS-CoV-2 neuroinvasiveness. Loss of smell is associated with subtle cerebral metabolic changes in core olfactory and high-order cortical areas likely related to combined processes of deafferentation and active functional reorganization secondary to the lack of olfactory stimulation.

Extrathoracic manifestations of COVID-19 in adults and presentation of the disease in children

In March 2020, the World Health Organization declared a global pandemic of COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2); epidemic conditions continue in nearly all countries today. Although the symptoms and imaging manifestations of COVID-19 predominantly involve the respiratory system, it is fundamental to know the manifestations of the disease and its possible complications in other organs to help in diagnosis and orient the prognosis. To improve the diagnostic process without increasing the risk of contagion unnecessarily, it is crucial to know when extrathoracic imaging tests are indicated and which tests are best in each situation. This paper aims to provide answers to these questions. To this end, we describe and illustrate the extrathoracic imaging manifestations of COVID-19 in adults as well as the entire spectrum of imaging findings in children.

COVID-19 and Parkinson's disease: Defects in neurogenesis as the potential cause of olfactory system impairments and anosmia

Anosmia, a neuropathogenic condition of loss of smell, has been recognized as a key pathogenic hallmark of the current pandemic SARS-CoV-2 infection responsible for COVID-19. While the anosmia resulting from olfactory bulb (OB) pathology is the prominent clinical characteristic of Parkinson's disease (PD), SARS-CoV-2 infection has been predicted as a potential risk factor for developing Parkinsonism-related symptoms in a significant portion of COVID-19 patients and survivors. SARS-CoV-2 infection appears to alter the dopamine system and induce the loss of dopaminergic neurons that have been known to be the cause of PD. However, the underlying biological basis of anosmia and the potential link between COVID-19 and PD remains obscure. Ample experimental studies in rodents suggest that the occurrence of neural stem cell (NSC) mediated neurogenesis in the olfactory epithelium (OE) and OB is important for olfaction. Though the occurrence of neurogenesis in the human forebrain has been a subject of debate, considerable experimental evidence strongly supports the incidence of neurogenesis in the human OB in adulthood. To note, various viral infections and neuropathogenic conditions including PD with olfactory dysfunctions have been characterized by impaired neurogenesis in OB and OE. Therefore, this article describes and examines the recent reports on SARS-CoV-2 mediated OB dysfunctions and defects in the dopaminergic system responsible for PD. Further, the article emphasizes that COVID-19 and PD associated anosmia could result from the regenerative failure in the replenishment of the dopaminergic neurons in OB and olfactory sensory neurons in OE.

Extrathoracic manifestations of COVID-19 in adults and presentation of the disease in children

El síndrome de distrés respiratorio grave por el virus coronavirus 2, conocido como SARS-CoV-2, fue declarado pandemia mundial en marzo de 2020 por la Organización Mundial de la Salud y sigue activo actualmente en casi todos los países del mundo. Aunque los síntomas y manifestaciones en pruebas de imagen predominan en el aparato respiratorio, conocer las manifestaciones y posibles complicaciones en otros órganos será fundamental para ayudar al diagnóstico y orientar hacia el pronóstico de la enfermedad. Saber cuándo están indicadas las pruebas de imagen extratorácicas y cuáles son más rentables en cada circunstancia será crucial para mejorar el proceso diagnóstico sin aumentar innecesariamente el riesgo de contagio. En este trabajo hemos tratado de proporcionar estas respuestas, y hemos descrito iconográficamente las manifestaciones radiológicas de la enfermedad COVID-19 en regiones extratorácicas en adultos, así como en su conjunto en el paciente pediátrico.

Sinus computed tomography findings in patients with COVID-19

OBJECTIVE

To analyze computed tomography scans of paranasal sinuses of a series of patients with coronavirus disease 2019, and correlate the findings with the disease.

METHODS

Computed tomography scans of 95 adult patients who underwent a polymerase chain reaction test for severe acute respiratory syndrome coronavirus 2 were analyzed. Clinical data were obtained from patients' records and telephone calls. Paranasal sinus opacification was graded and compared according to severe acute respiratory syndrome coronavirus 2 positivity.

RESULTS

Of the patients 28 (29.5%) tested positive for severe acute respiratory syndrome coronavirus 2 (median age 52 [range 26-95] years) and 67 were negative (median age 50 [range 18-95] years). Mucosal thickening was present in 97.4% of maxillary sinuses, 80% of anterior ethmoid air cells, 75.3% of posterior ethmoid air cells, 74.7% of frontal sinuses, and 66.3% of sphenoid sinuses. Minimal or mild mucosal thickening (score 1)and normally aerated sinuses (score 0) corresponded to 71.4% and 21.3% of all paranasal sinuses, respectively. The mean score of each paranasal sinus among severe acute respiratory syndrome coronavirus 2 positive and negative patients was 0.85±0.27 and 0.87±0.38, respectively (p=0.74). Median paranasal sinus opacification score among severe acute respiratory syndrome coronavirus 2 positive patients was 9 (interquartile range 8-10) compared to 9 (interquartile range 5-10) in negative patients (p=0.89). There was no difference in mean score adjusted for age and sex. Nasal congestion was more frequent in severe acute respiratory syndrome coronavirus 2 positive than negative patients (p=0.05).

CONCLUSION

Severe acute respiratory syndrome coronavirus 2 infection was associated with patient recall of nasal congestion, but showed no correlation with opacification of paranasal sinuses.

International consensus statement on allergy and rhinology: rhinosinusitis 2021

I.

EXECUTIVE SUMMARY

BACKGROUND: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR-RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR-RS-2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence-based findings of the document.

METHODS

ICAR-RS presents over 180 topics in the forms of evidence-based reviews with recommendations (EBRRs), evidence-based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary.

RESULTS

ICAR-RS-2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence-based management algorithm is provided.

CONCLUSION

This ICAR-RS-2021 executive summary provides a compilation of the evidence-based recommendations for medical and surgical treatment of the most common forms of RS.

Anosmia and dysgeusia in SARS-CoV-2 infection: incidence and effects on COVID-19 severity and mortality, and the possible pathobiology mechanisms - a systematic review and meta-analysis

Background: The present study aimed to determine the global prevalence of anosmia and dysgeusia in coronavirus disease 2019 (COVID-19) patients and to assess their association with severity and mortality of COVID-19. Moreover, this study aimed to discuss the possible pathobiological mechanisms of anosmia and dysgeusia in COVID-19. Methods: Available articles from PubMed, Scopus, Web of Science, and preprint databases (MedRxiv, BioRxiv, and Researchsquare) were searched on November 10th, 2020. Data on the characteristics of the study (anosmia, dysgeusia, and COVID-19) were extracted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Newcastle-Ottawa scale was used to assess research quality. Moreover, the pooled prevalence of anosmia and dysgeusia were calculated, and the association between anosmia and dysgeusia in presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was assessed using the Z test. Results: Out of 32,142 COVID-19 patients from 107 studies, anosmia was reported in 12,038 patients with a prevalence of 38.2% (95% CI: 36.5%, 47.2%); whereas, dysgeusia was reported in 11,337 patients out of 30,901 COVID-19 patients from 101 studies, with prevalence of 36.6% (95% CI: 35.2%, 45.2%), worldwide. Furthermore, the prevalence of anosmia was 10.2-fold higher (OR: 10.21; 95% CI: 6.53, 15.96, p < 0.001) and that of dysgeusia was 8.6-fold higher (OR: 8.61; 95% CI: 5.26, 14.11, p < 0.001) in COVID-19 patients compared to those with other respiratory infections or COVID-19 like illness. To date, no study has assessed the association of anosmia and dysgeusia with severity and mortality of COVID-19. Conclusion: Anosmia and dysgeusia are prevalent in COVID-19 patients compared to those with the other non-COVID-19 respiratory infections. Several possible mechanisms have been hypothesized; however, future studies are warranted to elucidate the definitive mechanisms of anosmia and dysgeusia in COVID-19. Protocol registration: PROSPERO CRD42020223204.

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.

Global prevalence and pathogenesis of headache in COVID-19: A systematic review and meta-analysis

Background: This study was conducted to determine the prevalence of headache in coronavirus disease 2019 (COVID-19) and to assess its association as a predictor for COVID-19. This study also aimed to discuss the possible pathogenesis of headache in COVID-19. Methods: Available articles from PubMed, Scopus, and Web of Science were searched as of September 2 nd, 2020. Data on characteristics of the study, headache and COVID-19 were extracted following the PRISMA guidelines. Biases were assessed using the Newcastle-Ottawa scale. The cumulative prevalence of headache was calculated for the general population (i.e. adults and children). The pooled odd ratio (OR) with 95% confidence intervals (95%CI) was calculated using the Z test to assess the association between headache and the presence of COVID-19 cases. Results: We included 104,751 COVID-19 cases from 78 eligible studies to calculate the global prevalence of headache in COVID-19 and 17 studies were included to calculate the association of headache and COVID-19. The cumulative prevalence of headache in COVID-19 was 25.2% (26,464 out of 104,751 cases). Headache was found to be more prevalent, approximately by two-fold, in COVID-19 patients than in non-COVID-19 patients with symptoms of other respiratory viral infections, OR: 1.73; 95% CI: 1.94, 2.5 with p=0.04. Conclusion: Headache is common among COVID-19 patients and seems to be more common in COVID-19 patients compared to those with the non-COVID-19 viral infection. No definitive mechanisms on how headache  emerges in COVID-19 patients but several possible hypotheses have been proposed. However, extensive studies are warranted to elucidate the mechanisms. PROSPERO registration: CRD42020210332 (28/09/2020).

Global prevalence and pathogenesis of headache in COVID-19: A systematic review and meta-analysis

Background: This study was conducted to determine the prevalence of headache in coronavirus disease 2019 (COVID-19) and to assess its association as a predictor for COVID-19. This study also aimed to discuss the possible pathogenesis of headache in COVID-19. Methods: Available articles from PubMed, Scopus, and Web of Science were searched as of September 2 nd, 2020. Data on characteristics of the study, headache and COVID-19 were extracted following the PRISMA guidelines. Biases were assessed using the Newcastle-Ottawa scale. The cumulative prevalence of headache was calculated for the general population (i.e. adults and children). The pooled odd ratio (OR) with 95% confidence intervals (95%CI) was calculated using the Z test to assess the association between headache and the presence of COVID-19 cases. Results: We included 104,751 COVID-19 cases from 78 eligible studies to calculate the global prevalence of headache in COVID-19 and 17 studies were included to calculate the association of headache and COVID-19. The cumulative prevalence of headache in COVID-19 was 25.2% (26,464 out of 104,751 cases). Headache was found to be more prevalent, approximately by two-fold, in COVID-19 patients than in non-COVID-19 patients (other respiratory viral infections), OR: 1.73; 95% CI: 1.94, 2.5 with p=0.04. Conclusion: Headache is common among COVID-19 patients and seems to be more common in COVID-19 patients compared to those with the non-COVID-19 viral infection. No definitive mechanisms on how headache  emerges in COVID-19 patients but several possible hypotheses have been proposed. However, extensive studies are warranted to elucidate the mechanisms. PROSPERO registration: CRD42020210332 (28/09/2020).

Objective evaluation of the nasal mucosal secretion in COVID-19 patients with anosmia

Background

COVID-19 is a new disease caused by the SARS-CoV-2 virus. The olfactory dysfunction linked to COVID-19 is not associated with rhinorrhea but there is no objective evaluation.

Aims

To evaluate nasal mucosal secretion objectively in COVID-19 patients with anosmia.

Methods

Fifty-two COVID-19 patients with anosmia and 51 healthy individuals included. Anosmia was diagnosed by subjective questionnaires. Nasal Schirmer test was done to the left and the right nasal cavity separately.

Results

All patients had anosmia and 82.6% had gustatory dysfunction. In group 1, the mean of the nasal Schirmer test results in the right cavity was 12.4 mm, 12.01 mm in the left nasal cavity. The median wetting distance (right plus left divided by two) was calculated 12.21 mm. In group 2, the mean of the nasal Schirmer test results in the right cavity was 12.1 mm, 11.8 mm in the left nasal cavity. The median wetting distance (right plus left divided by two) was calculated11.97 mm. There was no difference between the two groups in terms of nasal schirmer.

Conclusion

Olfactory dysfunction and gustatory dysfunction are the two of the unknown for this disease. We evaluated the nasal mucosa secretions in COVID-19 patients with anosmia objectively to evaluate if there is inflammation in the nasal mucosa. We found no difference between healthy individuals. According to our study, SARS-CoV-2 causes anosmia without causing nasal mucosal inflammation. Invasion of the olfactory bulb and central nervous system by SARS-CoV-2 may lead to anosmia in COVID-19, which may cause olfactory dysfunction.

Neurological complications of coronavirus infection; a comparative review and lessons learned during the COVID-19 pandemic

INTRODUCTION

Coronavirus disease-19 (COVID-19) pandemic continues to grow all over the world. Several studies have been performed, focusing on understanding the acute respiratory syndrome and treatment strategies. However, there is growing evidence indicating neurological manifestations occur in patients with COVID-19. Similarly, the other coronaviruses (CoV) epidemics; severe acute respiratory syndrome (SARS-CoV-1) and Middle East respiratory syndrome (MERS-CoV) have been associated with neurological complications.

METHODS

This systematic review serves to summarize available information regarding the potential effects of different types of CoV on the nervous system and describes the range of clinical neurological complications that have been reported thus far in COVID-19.

RESULTS

Two hundred and twenty-five studies on CoV infections associated neurological manifestations in human were reviewed. Of those, 208 articles were pertinent to COVID-19. The most common neurological complaints in COVID-19 were anosmia, ageusia, and headache, but more serious complications, such as stroke, impairment of consciousness, seizures, and encephalopathy, have also been reported.

CONCLUSION

There are several similarities between neurological complications after SARS-CoV-1, MERS-CoV and COVID-19, however, the scope of the epidemics and number of patients are very different. Reports on the neurological complications after and during COVID-19 are growing on a daily basis. Accordingly, comprehensive knowledge of these complications will help health care providers to be attentive to these complications and diagnose and treat them timely.