Nervous system involvement after infection with COVID-19 and other coronaviruses.

Viral infections have detrimental impacts on neurological functions, and even to cause severe neurological damage. Very recently, coronaviruses (CoV), especially severe acute respiratory syndrome CoV 2 (SARS-CoV-2), exhibit neurotropic properties and may also cause neurological diseases. It is reported that CoV can be found in the brain or cerebrospinal fluid. The pathobiology of these neuroinvasive viruses is still incompletely known, and it is therefore important to explore the impact of CoV infections on the nervous system. Here, we review the research into neurological complications in CoV infections and the possible mechanisms of damage to the nervous system.

Self-reported symptom study of COVID-19 chemosensory dysfunction in Malaysia.

Alterations in the three chemosensory modalities-smell, taste, and chemesthesis-have been implicated in Coronavirus Disease 2019 (COVID-19), yet emerging data suggest a wide geographic and ethnic variation in the prevalence of these symptoms. Studies on chemosensory disorders in COVID-19 have predominantly focused on Caucasian populations whereas Asians remain understudied. We conducted a nationwide, multicentre cross-sectional study using an online questionnaire on a cohort of RT-PCR-confirmed adult COVID-19 patients in Malaysia between 6 June and 30 November 2020. The aim of our study was to investigate their presenting symptoms and assess their chemosensory function using self-ratings of perceived smell, taste, chemesthesis, and nasal blockage. In this cohort of 498 patients, 41.4% reported smell and/or taste loss when diagnosed with COVID-19, which was the commonest symptom. Blocked nose, loss of appetite, and gastrointestinal disturbances were independent predictors of smell and/or taste loss on multivariate analysis. Self-ratings of chemosensory function revealed a reduction in smell, taste, and chemesthesis across the entire cohort of patients that was more profound among those reporting smell and/or taste loss as their presenting symptom. Perceived nasal obstruction accounted for only a small proportion of changes in smell and taste, but not for chemesthesis, supporting viral disruption of sensorineural mechanisms as the dominant aetiology of chemosensory dysfunction. Our study suggests that chemosensory dysfunction in COVID-19 is more widespread than previously reported among Asians and may be related to the infectivity of viral strains.Study Registration: NMRR-20-934-54803 and NCT04390165.

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.

Predictors of smell recovery in a nationwide prospective cohort of patients with COVID-19.

OBJECTIVE: To determine which factors (demographic, symptoms, comorbidities, and treatments) are associated with recovery of smell in patients with COVID-19 associated olfactory loss. STUDY DESIGN: Prospective, longitudinal questionnaires. SETTING: National survey. METHODS: A longitudinal web-based nationwide survey of adults with COVID-19 associated smell and taste loss was launched April 10, 2020. After completing an initial entry survey, participants received detailed follow-up questionnaires 14 days, and 1, 3 and 6 months later. RESULTS: As of June 25, 2021, 798 participants met study inclusion criteria and completed 6-month questionnaires. Of demographic characteristics only age <40 years was positively associated with smell recovery (p < .003). Of symptoms, difficulty breathing was negatively associated with smell recovery (p < .004), and nasal congestion positively associated with smell recovery (p < .03). Of pre-existing comorbidities only previous head injury (p < .017) was negatively associated with smell recovery. None of the queried medications used to treat COVID were associated with better rates of smell recovery. CONCLUSIONS: Age <40 and presence of nasal congestion at time of COVID-19 infection were predictive of improved rates of smell recovery, while difficulty breathing at time of COVID-19 infection, and prior head trauma predicted worsened rates of recovery. Further study will be required to identify potential mechanisms for the other observed associations. Such information can be used by clinicians to counsel patients suffering COVID-19 associated smell loss as to prognosis for recovery.

Presence of gustatory and olfactory dysfunction in the time of the COVID-19 pandemic.

BACKGROUND: The unexpected outbreak of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused more than 49 million cases and an estimated 2,000,000 associated deaths worldwide. In Germany, there are currently more than 2,000,000 laboratory-confirmed coronavirus disease 2019 (COVID-19) cases including 51,800 deaths. However, regional differences also became apparent and with the second wave of infections, the detailed characterization of COVID-19 patients is crucial to early diagnosis and disruption of chains of infections. METHODS: Handing out detailed questionnaires to all individuals tested for COVID-19, we evaluated the clinical characteristics of negative and positive tested individuals. Expression of symptoms, symptom duration and association between predictor variables (i.e. age, gender) and a binary outcome (olfactory and gustatory dysfunction) were assessed. RESULTS: Overall, the most common symptoms among individuals who tested positive for SARS-CoV-2 were fatigue, headache, and cough. Olfactory and gustatory dysfunction were also reported by many SARS-CoV-2 negative individuals, more than 20% of SARS-CoV-2 negative tested individuals in our study reported olfactory and gustatory dysfunction. Independent of SARS-CoV-2 status, more females displayed symptoms of gustatory (29.8%, p = 0.0041) and olfactory dysfunction (22.9%, p = 0.0174) compared to men. CONCLUSIONS: Bringing early SARS-CoV-2 tests to the populations at risk must be a main focus for the upcoming months. The reliability of olfactory and gustatory dysfunction in COVID-19 negative tested individuals requires deeper investigation in the future.

Characteristics of COVID-19 smell and taste dysfunction in hospitalized patients.

The effects of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) exist on a spectrum. Clinical symptoms of smell and taste dysfunction are prominent features of COVID-19. The objective of this study was to elucidate the factors associated with smell and taste dysfunction amongst hospitalized COVID-19 patients. A retrospective review of a multi-hospital health network's COVID-19 database between March and June 2020 was performed. Patients with self-reported smell or taste loss were included. Demographic information, patient comorbidities, and mortality data was obtained. There were 2892 patients included in this analysis and 117 reported smell or taste loss (4.0%, 95% confidence interval [CI]: 3.4%-4.8%). The proportion of females with smell or taste loss was significantly higher than males (6.3% vs. 2.5%, P < 0.001), whereas no differences existed between ethnicity or smoking status. When compared with age of 30-40 years, the age group of 10-20 years were most likely to present with smell or taste dysfunction (odds ratio [OR] 6.59, 95% CI 1.32-26.12; P = 0.01). The majority of specific comorbidities were not associated with increased incidence of smell or taste dysfunction. Outpatient healthcare workers were more likely to present with smell or taste loss (OR 3.2, CI 1.8-5.47; P < 0.001). The mortality rate among COVID-19 patients with smell or taste dysfunction was significantly lower than those without (0% vs. 20.3%; P < 0.001). Smell or taste loss is more prevalent in women, younger age groups, and healthier individuals. It may be associated with lower mortality and a milder disease trajectory compared to the overall cohort.

Smell and taste disorders in COVID-19: From pathogenesis to clinical features and outcomes.

Patients with COVID-19 often complain of smell and taste disorders (STD). STD emerge early in the course of the disease, seem to be more common in SARS-CoV-2 infection than in other upper respiratory tract infections, and could in some cases persist for long after resolution of respiratory symptoms. Current evidence suggests that STD probably result from a loss of function of olfactory sensory neurons and taste buds, mainly caused by infection, inflammation, and subsequent dysfunction of supporting non-neuronal cells in the mucosa. However, the possible occurrence of other mechanisms leading to chemosensory dysfunction has also been hypothesized, and contrasting data have been reported regarding the direct infection of sensory neurons by SARS-CoV-2. In this mini-review, we summarize the currently available literature on pathogenesis, clinical manifestations, diagnosis, and outcomes of STD in COVID-19 and discuss possible future directions of research on this topic.

Risk Factors for Olfactory and Gustatory Dysfunctions in Patients with SARS-CoV-2 Infection.

INTRODUCTION: Smell and taste loss are characteristic symptoms of SARS-CoV-2 infection. The aim of this study is to investigate the prevalence and risk factors associated with olfactory and gustatory dysfunctions in coronavirus disease (COVID-19) patients. METHODS: We conducted an observational, retrospective study on 376 patients with documented SARS-CoV-2 infection admitted to the San Gerardo Hospital in Monza, Italy, from March to July 2020. All patients answered a phone questionnaire providing information on age, sex, smoking status, and clinical characteristics. Adjusted odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were estimated through logistic regression models including relevant covariates. RESULTS: The prevalence of olfactory and gustatory dysfunctions in COVID-19 patients was 33.5 and 35.6%, respectively. Olfactory dysfunctions were significantly directly associated with current smoking and history of allergy, the multivariable ORs being 6.53 (95% CI 1.16-36.86) for current smokers versus never smokers, and 1.89 (95% CI 1.05-3.39) for those with an allergy compared to those without any allergy. Respiratory allergy in particular was significantly associated with olfactory dysfunctions (multivariable OR 2.30, 95% CI 1.02-5.17). Significant inverse associations were observed for patients aged 60 years or more (multivariable OR 0.33, 95% CI 0.19-0.57) and hospitalization (multivariable OR 0.22, 95% CI 0.06-0.89). Considering gustatory dysfunctions, after allowance of other variables a significant direct association was found for respiratory allergies (OR 2.24, 95% CI 1.03-4.86), and an inverse association was found only for hospitalization (OR 0.21, 95% CI 0.06-0.76). CONCLUSION: Our study indicates that current smoking and history of allergy (particularly respiratory) significantly increase the risk for smell loss in COVID-19 patients; the latter is also significantly associated to taste loss. Hospitalization has an inverse association with the risk of olfactory and gustatory dysfunctions, suggesting that these may be symptoms characteristics of less severe SARS-CoV-2 infection.

[The odor stick identification test for Japanese (OSIT-J) in a case of coronavirus disease 2019 (COVID-19) without pneumonia].

Anosmia is a frequently experienced symptom in coronavirus disease 2019 (COVID-19). Previous studies have suggested the potential use of olfactometry to identify infected individuals. We performed a sequential olfactometry using the odor stick identification test for Japanese (OSIT-J) in a COVID-19 patient without pneumonia. The test uses 12 odorants that are familiar to the Japanese population. Our patient was a 56-year-old man diagnosed with COVID-19 who was admitted to our hospital following the development of anosmia. He had no respiratory symptoms except pharyngeal pain. Chest CT findings did not reveal the presence of pneumonia. The patient underwent OSIT-J on the 1st hospital day, and his score was 1 out of 12. Following the olfactometry, ciclesonide was administered. The patient did not develop any new symptoms during hospitalization, and his anosmia was gradually improved. The OSIT-J scores were 9 and 11 on the 7th and 16th hospital day, respectively. The patient was discharged on the 25th hospital day after two negative PCR test results. In our case, OSIT-J could identify anosmia in a COVID-19 patient. Some COVID-19 patients are asymptomatic, expect for olfactory disturbances, and OSIT-J may help identify such patients in the Japanese population.

A Follow-Up Study of Lung Function and Chest Computed Tomography at 6 Months after Discharge in Patients with Coronavirus Disease 2019.

We aimed to investigate changes in pulmonary function and computed tomography (CT) findings in patients with coronavirus disease 2019 (COVID-19) during the recovery period. COVID-19 patients underwent symptom assessment, pulmonary function tests, and high-resolution chest CT 6 months after discharge from the hospital. Of the 54 patients enrolled, 31 and 23 were in the moderate and severe group, respectively. The main symptoms 6 months after discharge were fatigue and exertional dyspnea, experienced by 24.1% and 18.5% of patients, respectively, followed by smell and taste dysfunction (9.3%) and cough (5.6%). One patient dropped out of the pulmonary function tests. Of the remaining 54 patients, 41.5% had pulmonary dysfunction. Specifically, 7.5% presented with restrictive ventilatory dysfunction (forced vital capacity <80% of the predicted value), 18.9% presented with small airway dysfunction, and 32.1% presented with pulmonary diffusion impairment (diffusing capacity for carbon monoxide <80% of the predicted value). Of the 54 patients enrolled, six patients dropped out of the chest CT tests. Eleven of the remaining 48 patients presented with abnormal lung CT findings 6 months after discharge. Patients with residual lung lesions were more common in the severe group (52.6%) than in the moderate group (3.4%); a higher proportion of patients had involvement of both lungs (42.1% vs. 3.4%) in the severe group. The residual lung lesions were mainly ground-glass opacities (20.8%) and linear opacities (14.6%). Semiquantitative visual scoring of the CT findings revealed significantly higher scores in the left, right, and both lungs in the severe group than in the moderate group. COVID-19 patients 6 months after discharge mostly presented with fatigue and exertional dyspnea, and their pulmonary dysfunction was mostly characterized by pulmonary diffusion impairment. As revealed by chest CT, the severe group had a higher prevalence of residual lesions than the moderate group, and the residual lesions mostly manifested as ground-glass opacities and linear opacities.

Incidence, clinical, risk factors and outcomes of Guillain-Barré in Covid-19.

We diagnosed 11 Guillain-Barré syndrome (GBS) cases among 71,904 COVID patients attended at 61 Spanish emergency departments (EDs) during the 2-month pandemic peak. The relative frequency of GBS among ED patients was higher in COVID (0.15‰) than non-COVID (0.02‰) patients (odds ratio [OR] = 6.30, 95% confidence interval [CI] = 3.18-12.5), as was the standardized incidence (9.44 and 0.69 cases/100,000 inhabitant-years, respectively, OR = 13.5, 95% CI = 9.87-18.4). Regarding clinical characteristics, olfactory-gustatory disorders were more frequent in COVID-GBS than non-COVID-GBS (OR = 27.59, 95% CI = 1.296-587) and COVID-non-GBS (OR = 7.875, 95% CI = 1.587-39.09) patients. Although COVID-GBS patients were more frequently admitted to intensive care, mortality was not increased versus control groups. Our results suggest SARS-CoV-2 could be another viral infection causing GBS. ANN NEUROL 2021;89:598-603.

Six-Month Psychophysical Evaluation of Olfactory Dysfunction in Patients with COVID-19.

This study prospectively assessed the 6-month prevalence of self-reported and psychophysically measured olfactory dysfunction in subjects with mild-to-moderate COVID-19. Self-reported smell or taste impairment was prospectively evaluated by SNOT-22 at diagnosis, 4-week, 8-week, and 6-month. At 6 months from the diagnosis, psychophysical evaluation of olfactory function was also performed using the 34-item culturally adapted University of Pennsylvania Smell Identification Test (CA-UPSIT). 145 completed both the 6-month subjective and psychophysical olfactory evaluation. According to CA-UPSIT, 87 subjects (60.0%) exhibited some smell dysfunction, with 10 patients being anosmic (6.9%) and seven being severely microsmic (4.8%). At the time CA-UPSIT was administered, a weak correlation was observed between the self-reported alteration of the sense of smell or taste and olfactory test scores (Spearman's r = -0.26). Among 112 patients who self-reported normal sense of smell at last follow-up, CA-UPSIT revealed normal smell in 46 (41.1%), mild microsmia in 46 (41.1%), moderate microsmia in 11 (9.8%), severe microsmia in 3 (2.3%), and anosmia in 6 (5.4%) patients; however, of those patients self-reporting normal smell but who were found to have hypofunction on testing, 62 out of 66 had a self-reported reduction in sense of smell or taste at an earlier time point. Despite most patients report a subjectively normal sense of smell, we observed a high percentage of persistent smell dysfunction at 6 months from the diagnosis of syndrome coronavirus 2 (SARS-CoV-2) infection, with 11.7% of patients being anosmic or severely microsmic. These data highlight a significant long-term rate of smell alteration in patients with previous SARS-COV-2 infection.

Loss of smell and taste in COVID-19 infection in adolescents.

OBJECTIVES: To study the prevalence, clinical course and outcomes of olfactory and taste dysfunction in COVID-19 positive adolescents. METHODS: This prospective study was carried out from May to August 2020. The adolescents, aged 10-19 years, who were detected COVID-19 positive by RT-PCR with mild to moderate disease were included in the study. The following epidemiological and clinical outcomes were studied: age, sex, general symptoms, olfactory and taste dysfunction. RESULTS: Out of 141 patients included in the study, there were 83 males (58.9%) and 58 females (41.1%). The age varied from 10 to 19 years with an average of 15.2 years. Forty patients (28.4%) had olfactory or taste dysfunction. Out of these 40 patients, 28 patients (19.8%) had both olfactory and taste dysfunction. Of the 34 patients (24.1%) who complained of olfactory dysfunction, 16 patients complained of hyposmia and 18 patients complained of anosmia. Dysgeusia was reported by 34 patients (24.1%). The duration of OTD varied from 2 to 15 days with an average of 5.7 days. CONCLUSION: Loss of smell and taste are common symptoms in COVID-19 positive adolescents. It recovers spontaneously within a few weeks, along with the resolution of other symptoms.

Olfactory function and viral recovery in COVID-19.

BACKGROUND: Olfactory and taste disorders were reported in up to 30%-80% of COVID-19 patients. The purpose of our study was to objectively assess smell impairment in COVID-19 patients and to correlate olfactory function with viral recovery. METHODS: Between 15 and 30 April 2020, hospitalized patients with confirmed SARS-CoV-2 infection underwent an objective assessment of olfactory function with the Smell Identification subtest of the Sniffin' Sticks Test (SI-SST). Association between viral recovery and SI-SST performance was evaluated. RESULTS: 51 patients were enrolled (49% males, mean age 66.2 ± 14.6 years). At the time of test administration, 45% were clinically recovered and 39% were virus-free. Objective hyposmia/anosmia was found in 45% of the patients. Subjective olfactory disorders showed no association with the clinical or viral recovery status of the patients. On the contrary, none of the patients with anosmia and the 5% of hyposmic patients at test had viral recovery. The relative risk for hyposmic patients to be still positive at swab test was 10.323 (95% CI 1.483-71.869, p < .0001). Logistic regression analysis showed an independent and significant correlation between viral clearance and SI-SST scores (OR = 2.242; 95% CI 1.322-3.802, p < .003). ROC curve analysis confirmed that a SI-SST > 10.5 predicts viral clearance with 79% sensitivity and 87% specificity (AUC = 0.883). CONCLUSION: Hyposmia is part of COVID-19 symptoms; however, only objectively assessed olfactory function is associated with viral recovery. SI-SST is an easy and safe instrument, and further large multicentric studies should assess its value to predict infection and recovery.

Regional and Chronological Variation of Chemosensory Dysfunction in COVID-19: a Meta-Analysis.

BACKGROUND: Olfactory and gustatory dysfunction are frequently reported in patients with coronavirus disease 2019 (COVID-19). However, the reported prevalence of olfactory and/or gustatory dysfunction varies widely, and the reason for the inter-study differences is unclear. Hence, in this meta-analysis, we performed subgroup analyses to investigate the factors that contribute to the inter-study variability in the prevalence of olfactory and gustatory dysfunction. METHODS: Out of 943 citations, we included 55 eligible studies with 13,527 patients with COVID-19 for a meta-analysis. Calculating the data extracted from each study, the weighted summary prevalence of olfactory and gustatory dysfunction was estimated using a Freeman-Tukey transformation with models based on random-effects assumptions. A meta-analysis of variance compared the prevalence of olfactory and gustatory dysfunction according to regional, chronological, demographic, and methodologic factors, respectively. RESULTS: The overall pooled prevalence rates of olfactory and gustatory dysfunction were 51.4% and 47.5%, respectively, in the random-effect model. In subgroup analyses, the prevalence rates of olfactory and gustatory dysfunction were significantly different among four geographical regions (both P < 0.001, respectively). Although the prevalence rates of olfactory and gustatory dysfunction did not significantly differ according to the time of enrollment, the subgroup analyses including only studies from the same geographical region (Europe) revealed a significant difference in olfactory dysfunction according to the time of enrollment. CONCLUSION: The regional and chronological differences in the prevalence rates of olfactory and gustatory dysfunctions partly explain the wide inter-study variability.

Objective evaluation and predictive value of olfactory dysfunction among patients hospitalized with COVID-19.

OBJECTIVES: Olfactory dysfunction is a frequent feature of COVID-19. Despite the growing evidence, current knowledge on the subject remains insufficient, so that data obtained with different tools, from multiple centers and in distinct scenarios are welcome. Yet, the predictive value of olfactory dysfunction in terms of the overall prognosis of COVID-19 is unknown. This study aims to evaluate the olfactory function of hospitalized patients with COVID-19 and the impact of the results on their clinical outcomes. METHODS: Patients with severe acute respiratory distress syndrome (ARDS) admitted to a university tertiary hospital were recruited and divided into those with ARDS due to COVID-19, and those with ARDS of any other cause. Sociodemographic and clinical data were collected at baseline and the patients had their objective olfactory function evaluated by the Alcohol Sniff Test on admission and during hospital stay. The participants were then followed up until reaching an endpoint: hospital discharge, endotracheal intubation, transfer to the intensive care unit, or death. Patients with COVID-19 were also subgrouped and compared according to their olfactory thresholds and to their overall clinical outcomes. The obtained data was analyzed using R software. Level of significance was set at 0.05. RESULTS: Eighty-two patients were included (of which 58 had COVID-19). 87.93% of the patients with COVID-19 had diminished olfactory dysfunction on admission. The mean length of hospital stay among patients with olfactory dysfunction was greater (7.84 vs 6.14 days) and nine individuals in this subgroup had poor overall outcomes. None of those with normal olfactory function developed critical COVID-19. The mean olfactory function was significantly worse among patients with COVID-19 and poor outcomes (3.97 vs 7.90 cm, P = .023). CONCLUSION: Objective olfactory dysfunction is frequent in ARDS caused by SARS-CoV-2 infection. Patients with longitudinal poorer outcomes present worse olfactory thresholds on admission.