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Anosmia has been recognized as a prevalent and early symptom by many COVID-19 patients. However, most researchers have recorded smell dysfunction solely as present or absent and based on subjective evaluation by patients. We described the results of 57 consecutive COVID-19 patients seen at FIOCRUZ, Rio de Janeiro, Brazil, from April to May 2020. Data about the presence of smell loss, the onset of smell loss and other COVID-19 symptoms such as ageusia and nasal congestion or rhinorrhea were recorded. All patients at the initial consultation and 34 healthy controls underwent the Q-SIT, which is a quick disposable three-item smell identification test, by a trained physician. We compared three groups: healthy controls, COVID+ patients with reported smell loss (COVID w/ SL) and COVID+ patients without smell loss (COVID+ w/o SL). The mean age of patients was 41.4 years (SD ± 10.4), and 54.4% were women. Smell loss was reported by 40.4% of COVID-19 patients. We observed a gradual effect with higher Q-SIT scores in healthy controls, followed by COVID+ w/o SL and COVID+ w/ SL (medians = 3, 2 and 0; respectively, p, Highlights • Smell dysfunction is frequent in COVID-19 patients. • Subtle olfactory dysfunction is frequently not perceived by patients when inquired during medical visits. • Q-SIT is a quick and reliable screening test for the detection of smell dysfunction during the pandemics.

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., Impairments of smell and taste perception are two of the main symptoms of COVID–19. In this issue of Neuron, Cooper et al. focus on these chemosensory symptoms and review recent hypotheses of the putative mechanisms mediating the loss of taste and smell through COVID–19.

Introduction Hyposmia is a common non-motor symptom occurring in Parkinson’s disease (PD), and has been included in the diagnostic criteria. Although a version of the Brief Smell Identification Test (B-SIT) has been developed specifically for Chinese populations, there have been no reports of the utility of this test in the diagnosis of PD in China. Objective Considering the influence of cultural factors on olfactory test findings, we sought to investigate the utility and efficiency of the B-SIT in Chinese PD patients. Methods PD patients were recruited from the Movement Disorder Clinic of Xuanwu Hospital, and healthy controls were recruited from the Beijing Longitudinal Study on Aging Cohort II, between 2015 and 2016. The B-SIT was used for olfactory function testing in all subjects, and the familiarity of 59 odors questionnaire was performed for the investigation of familiarity of odors. Results A sample of 275 subjects participated in the study, including 112 healthy controls and 163 PD patients. The sensitivity (64.1%), specificity (83.9%), positive predictive value (83.5%) and negative predictive value (64.8%) for identifying PD were measured with the B-SIT. The consistency values between the results of self-reported smell loss and hyposmia identified by B-SIT in control and PD groups were 74.8% and 64.2%, respectively. Most of the odors in the B-SIT were familiar to people in the Chinese population, based on a survey of 3356 subjects using a familiarity questionnaire. Conclusions It is recommended to use the B-SIT olfactory test instead of self-reported smell loss for PD diagnosis for Chinese.

Introduction Individuals with unexplained smell loss constitute an at-risk population for the development of Parkinson's disease (PD). Currently, no specific MRI patterns are known for early PD diagnosis. In this study, we measured the fractional anisotropy (FA) in the substantia nigra (SN) in PD patients, in patients with idiopathic smell loss, and in healthy controls. Methods All subjects underwent extensive olfactory testing and MR imaging data were obtained to explore SN diffusion characteristics. The SN regions were manually identified by two independent raters on the individual imaging data. Results FA measurements in the SN revealed significant group differences, with reduced values clearly distinguishing PD patients and patients with idiopathic smell loss from healthy controls. Conclusion These findings indicate a reduced intrinsic integrity of the SN in PD at-risk subjects and support the risk status of patients with idiopathic smell loss.

The loss of smell and taste is one of the most consistent symptoms of covid-19, so what can that tell us about the condition, asks Kayt Sukel

Objective Olfaction plays an important role in human daily life. The olfactory bulb size is dependent on stimulation. Smell loss is one of the main symptoms in chronic rhinonasal sinusitis. MRI has been indicated to evaluate the size of the olfactory bulb in such patients. The aim of this study was to assess the volumetric changes of the olfactory bulb in patients with sinonasal polyposis before and after treatment using MRI. Patients and methods Fifteen control subjects and 30 patients were included in the study, 24 of them patients underwent endoscopic sinus surgery. Volumetric analysis of their olfactory bulb volume was done using MRI and specialized software. Results It was found that the olfactory bulb volume was significantly smaller in patients (19.98 ± 5.88 mm 3 ) when compared to control mean (39.6 ± 13.8 mm 3 ) and there was a significant increase in the olfactory bulb volumes in patients who underwent surgery 6 months postoperatively (24.79 ± 5.11 mm 3 ). Conclusions MRI with volumetric analysis is a useful tool in assessment of the olfactory bulb volume in patients with olfactory loss and appears to be of help in assessment of the degree of recovery in patients after sinus surgery.

Objective The objective of this study was to determine whether there are genetic factors associated with Type II congenital smell loss. Study design The expression frequencies of 16 erythrocyte antigens among patients with Type II congenital smell loss were determined and compared to those of a large control group. Methods Blood samples were obtained from 99 patients with Type II congenital smell loss. Presence of the erythrocyte surface antigens A, B, M, N, S, s, Fy a , Fy b , D, C, c, E, e, K, Jk a , and Jk b was analyzed by blood group serology. Comparisons of expression frequencies of these antigens were made between the patients and a large control group. Results Patients tested for the Duffy b antigen (Fy b haplotype) exhibited a statistically significant 11% decrease in expression frequency compared to the controls. There were no significant differences between patients and controls in the expression frequencies for all other erythrocyte antigens (A, B, M, N, S, s, Fy a , D, C, c, E, e, K, Jk a , or Jk b ). Conclusions These findings describe the presence of a previously unrevealed genetic tendency among patients with Type II congenital smell loss related to erythrocyte surface antigen expression. The deviation in expression rate of Duffy b suggests a target gene and chromosome region in which future research into this form of congenital smell loss may reveal a more specific genetic basis for Type II congenital smell loss.

Objective: Olfactory dysfunction is known to have significant social, psychological, and safety implications. Despite increasingly recognized prevalence, potential risk factors for olfactory loss have been arbitrarily documented and knowledge is limited in scale. The aim of this study is to identify potential demographic and exposure variables correlating with olfactory dysfunction. Methods: Cross-sectional analysis of the 2011â2012 and 2013â2014 editions of the National Health Examination and Nutrition Survey was performed. The utilized survey reports from a nationally representative sample of about 5000 persons each year located in counties across the United States. There is an interview and physical examination component which includes demographic, socioeconomic, dietary, and health-related questions as well as medical, dental, physiologic measurements, and laboratory tests. 3594 adult respondents from 2011 to 2012 and 3708 respondents from 2013 to 2014 were identified from the above population-based database. The frequency of self-reported disorders as well as performance on odor identification testing was determined in relation to demographic factors, occupational or environmental exposures, and urinary levels of environmental and industrial compounds. Results: In both subjective and objective analysis, smell disorders were significantly more common with increasing age. While the non-Hispanic Black and non-Hispanic Asian populations were less likely to report subjective olfactory loss, they, along with Hispanics, performed more poorly on odor identification than Caucasians. Those with limited education had a decreased prevalence of hyposmia. Women outperformed men on smell testing. Those reporting exposure to vapors were more likely to experience olfactory dysfunction, and urinary levels of manganese, 2-Thioxothiazolidine-4-carboxylic acid, and 2-Aminothiazoline-4-carboxylic acid were lower among respondents with subjective smell disturbance. In odor detection, elevated serum levels of lead and urinary levels of 2,4 dichlorophenol were associated with anosmia and hyposmia, respectively. Conclusions: This study provides current, population-based data identifying demographic and exposure elements related to smell disturbances in U.S. adults. Age, race, gender, education, exposure to vapors, urinary levels of manganese, 2-Thioxothiazolidine-4-carboxylic acid, 2-Aminothiazoline-4-carboxylic acid, 2,4 dichlorophenol, and serum lead levels were all implicated in smell disturbance. Care should be taken in interpretation due to lack of consistency between subjective and objective measures of olfaction as well as limitations related to population-based data. Prospective trials are indicated to further elucidate these relationships. Keywords: Population based study, Olfaction, Olfactory loss, Olfactory dysfunction, Smell loss, Risk factors

Chemosensory disorders have been receiving increasing clinical attention but remain a difficult diagnostic problem. With the development of several well-standardized testing methods, taste or smell loss can now be verified, and this has added to knowledge concerning the common causes of dysfunction. Diagnosis typically rests upon the history and physical examination, but, except in the case of obstructive nasal and sinus pathologic conditions, therapy usually remains elusive.

This article has reviewed studies that document a relationship between loss of smell function and disturbances in nasal airflow function. In some cases (for example, hypertrophied adenoids and nasal sinus disease), medical or surgical intervention appears to be useful in restoring some, if not all, of the smell loss associated with the disorder. In other cases (for example, septoplasty), empirical evidence of such efficacy is wanting. Given the current research interest on these topics, however, a clear understanding of both the positive and negative influences of surgical and medical interventions in most cases of obstructive nasal disease or malformities will be forthcoming.