Altered structural connectivity in olfactory disfunction after mild COVID-19 using probabilistic tractography

Article Medicine, General & Internal

Aberrant olfactory network functional connectivity in people with olfactory dysfunction following COVID-19 infection: an exploratory, observational study

Jed Wingrove et al.

Summary: Individuals with COVID-19-related anosmia show functional differences in olfactory areas and regions involved in sensory processing and cognitive functioning, providing valuable insights for further research and therapeutic strategies.

ECLINICALMEDICINE (2023)

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Article Neurosciences

Olfactory loss and brain connectivity after COVID-19

Fabrizio Esposito et al.

Summary: This study analyzed the neural connectivity in the central olfactory system of individuals with persisting olfactory impairment due to COVID-19. The results showed that both the structural and functional connectivity were significantly increased in previously infected subjects compared to the control group. Greater residual olfactory impairment was associated with more segregated processing within certain regions. These findings suggest a characteristic brain connectivity response to residual hyposmia related to COVID-19.

HUMAN BRAIN MAPPING (2022)

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Review Medicine, Research & Experimental

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

Claire Jing-Wen Tan et al.

Summary: This study investigated the relationship between COVID-19 infection and olfactory dysfunction using radiological imaging. The results showed that the prevalence of olfactory cleft opacification was significantly higher in patients with COVID-19 infection and olfactory dysfunction compared to the control group. However, similar proportions of cases and controls demonstrated olfactory bulb signal abnormalities and olfactory mucosa abnormalities. Additionally, approximately half of the patients had abnormalities in the morphology of the olfactory bulb and olfactory nerve.

LARYNGOSCOPE (2022)

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Article Multidisciplinary Sciences

SARS-CoV-2 is associated with changes in brain structure in UK Biobank

Gwenaelle Douaud et al.

Summary: Through long-term observation of participants' MRI images, it was found that COVID-19 infection is associated with abnormal brain changes, including a reduction in gray matter thickness in the orbitofrontal cortex and parahippocampal gyrus, greater changes in markers of tissue damage in regions functionally connected to the primary olfactory cortex, and a greater reduction in global brain size. Infected individuals also showed significant cognitive decline.

NATURE (2022)

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Review Neurosciences

Quantitative mapping of the brain's structural connectivity using diffusion MRI tractography: A review

Fan Zhang et al.

Summary: This paper provides a high-level overview of how diffusion magnetic resonance imaging (dMRI) tractography is used for quantitative analysis of the brain's structural connectivity. The paper focuses on two types of quantitative analyses - tract-specific analysis and connectome-based analysis. It also reviews studies that have used quantitative tractography approaches to study the brain's white matter in various fields. The paper concludes that there is no consensus on the best methodology in quantitative analysis of tractography, and caution should be exercised when interpreting results.

NEUROIMAGE (2022)

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Article Clinical Neurology

Postmortem Assessment of Olfactory Tissue Degeneration and Microvasculopathy in Patients With COVID-19

Cheng-Ying Ho et al.

Summary: This postmortem study revealed that COVID-19 infection is associated with axon injuries and microvasculopathy in olfactory tissue, suggesting that olfactory dysfunction in COVID-19 infection may be severe and permanent.

JAMA NEUROLOGY (2022)

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Article Neurosciences

Changes in the Intranetwork and Internetwork Connectivity of the Default Mode Network and Olfactory Network in Patients with COVID-19 and Olfactory Dysfunction

Hui Zhang et al.

Summary: OD is a common symptom in COVID-19 patients, and many neurological manifestations have been reported. This study found increased intranetwork connectivity in the default mode network and stronger internetwork connectivity between the olfactory network and the default mode network in COVID-19 patients with OD. However, no significant difference was found in the intranetwork connectivity within the olfactory network. These results suggest that resting-state fMRI is an important tool for evaluating neurosensory dysfunction in COVID-19 patients.

BRAIN SCIENCES (2022)

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Article Clinical Neurology

Widespread white matter oedema in subacute COVID-19 patients with neurological symptoms

Alexander Rau et al.

Summary: Using diffusion microstructure imaging, researchers found widespread interstitial oedema in subacute COVID-19 inpatients, which is associated with cognitive impairment and changes in brain metabolism.

BRAIN (2022)

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Article Clinical Neurology

Brain microstructural changes and fatigue after COVID-19

Diogenes Diego de Carvalho Bispo et al.

Summary: This study aimed to assess fatigue and neuropsychological performance and investigate changes in the thickness and volume of gray matter and microstructural abnormalities in the white matter in patients recovering from COVID-19. The results showed that COVID-19 patients had higher levels of fatigue and lower fiber density in certain brain regions compared to the control group. These findings suggest that there may be underlying brain substrates for the symptoms caused by SARS-CoV-2 during medium- to long-term recovery.

FRONTIERS IN NEUROLOGY (2022)

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Article Clinical Neurology

Mid-term MRI evaluation reveals microstructural white matter alterations in COVID-19 fully recovered subjects with anosmia presentation

Laura Pelizzari et al.

Summary: This neuroimaging exploratory study analyzed the medium-term effect of COVID-19 on the brain of people who recovered from COVID-19, experienced anosmia during the acute phase of the disease, and have never been hospitalized due to the infection. The results showed that COVID-19 may produce mid/long-term microstructural effects on the brain, even in cases of mild-to-moderate disease not requiring hospitalization. Further investigation and follow-ups are needed to assess the recovery of these alterations over time.

THERAPEUTIC ADVANCES IN NEUROLOGICAL DISORDERS (2022)

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Review Radiology, Nuclear Medicine & Medical Imaging

Mapping Structural Connectivity Using DiffusionMRI: Challenges and Opportunities

Chun-Hung Yeh et al.

Summary: Diffusion MRI-based tractography is commonly used for inferring the structural brain connectome, and applying graph theory to analyze these connectomes provides important opportunities to explore connectivity patterns. However, challenges exist in this framework, particularly regarding methodological and biological plausibility.

JOURNAL OF MAGNETIC RESONANCE IMAGING (2021)

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Article Clinical Neurology

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

Rafal Butowt et al.

Summary: The prevalence of smell and taste dysfunction in COVID-19 differs between populations, possibly due to differences in virus strains or host proteins. Recent progress has been made in defining the cellular and molecular mechanisms of virus-induced anosmia, focusing on the role of sustentacular cells in the olfactory epithelium. The potential for using smell and taste dysfunctions as early diagnostic tools in COVID-19 is discussed.

NEUROSCIENTIST (2021)

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Article Otorhinolaryngology

Olfactory Cleft Measurements and COVID-19-Related Anosmia

Aytug Altundag et al.

Summary: This study found that patients with COVID-19 anosmia had significantly wider OC widths and volumes compared to control subjects, and showed potential inflammatory changes on MRI.

OTOLARYNGOLOGY-HEAD AND NECK SURGERY (2021)

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Article Biochemistry & Molecular Biology

Article Visualizing in deceased COVID-19 patients how SARS-CoV-2 attacks the respiratory and olfactory mucosae but spares the olfactory bulb

Mona Khan et al.

Summary: Anosmia, the loss of smell, is a common symptom of COVID-19, but it is caused by the virus attacking sustentacular cells in the olfactory mucosa rather than infecting olfactory sensory neurons. This suggests that SARS-CoV-2 is not a neurotropic virus.

CELL (2021)

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Article Medicine, General & Internal

Prevalence and 6-month recovery of olfactory dysfunction: a multicentre study of 1363 COVID-19 patients

J. R. Lechien et al.

Summary: This study found that olfactory dysfunction (OD) is more prevalent in mild cases of COVID-19 compared to moderate-to-critical forms. Additionally, 24.1% of patients did not subjectively recover olfaction 60 days after the onset of the dysfunction. Objective olfactory evaluations identified hyposmia/anosmia in a significant percentage of patients, with higher baseline severity of objective olfactory evaluations strongly predictive of persistent OD.

JOURNAL OF INTERNAL MEDICINE (2021)

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Article Neurosciences

Olfactory transmucosal SARS-CoV-2 invasion as a port of central nervous system entry in individuals with COVID-19

Jenny Meinhardt et al.

Summary: The study demonstrates the presence of SARS-CoV-2 in the nasopharynx and brain, suggesting the virus may enter the CNS through the olfactory mucosa. The virus utilizes the neural-mucosal interface in the olfactory mucosa to penetrate the nervous system, affecting various neuroanatomical areas, including the primary respiratory and cardiovascular control center.

NATURE NEUROSCIENCE (2021)

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Article Multidisciplinary Sciences

High-dimensional characterization of post-acute sequelae of COVID-19

Ziyad Al-Aly et al.

Summary: This study comprehensively describes the post-acute sequelae of COVID-19 using national healthcare databases, finding increased risk of death and use of health resources beyond the first 30 days of illness, as well as incident sequelae in various organ systems, increased use of therapeutic agents, and evidence of laboratory abnormalities. The findings show a risk gradient according to the severity of acute COVID-19 infection and highlight the burden of health loss experienced by patients who survive the acute phase.

NATURE (2021)

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Review Biochemistry & Molecular Biology

Post-acute COVID-19 syndrome

Ani Nalbandian et al.

Summary: SARS-CoV-2 is responsible for the COVID-19 pandemic, causing global healthcare crises. Recovery from COVID-19 may lead to persistent symptoms and long-term complications, prompting the need for multidisciplinary care and follow-up for survivors.

NATURE MEDICINE (2021)

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Article Cell Biology

COVID-19-related anosmia is associated with viral persistence and inflammation in human olfactory epithelium and brain infection in hamsters

Guilherme Dias de Melo et al.

Summary: Recent investigations have shown that olfactory and taste dysfunction are common in mildly symptomatic COVID-19 patients. Research on the olfactory neuroepithelium revealed that SARS-CoV-2 infection can cause local inflammation and lead to acute loss of smell, which may account for prolonged symptoms of COVID-19 such as anosmia.

SCIENCE TRANSLATIONAL MEDICINE (2021)

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Review Cell Biology

Olfactory dysfunction in aging and neurodegenerative diseases

Xiuli Dan et al.

Summary: This study explores alterations in olfactory functions as early biomarkers for neurodegeneration, particularly in early-stage Parkinson's and Alzheimer's disease. Implementing early treatment to postpone or avert pathological development is crucial for these diseases.

AGEING RESEARCH REVIEWS (2021)

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Article Clinical Neurology

Quantitative Analysis of the Olfactory System in COVID-19: An MR Imaging Study

E. Altunisik et al.

Summary: This study compared quantitative measurements of olfactory anatomic structures between patients diagnosed with COVID-19 associated with persistent olfactory dysfunction and healthy controls using MRI. The results showed significantly lower olfactory bulb volume, olfactory sulcus depth, and olfactory tract length in COVID-19 patients compared to healthy controls. MRI findings suggested olfactory injury in COVID-19 patients and the olfactory pathway may serve as an alternative route for virus entry into the central nervous system.

AMERICAN JOURNAL OF NEURORADIOLOGY (2021)

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Article Multidisciplinary Sciences

Acquired olfactory loss alters functional connectivity and morphology

Behzad Iravani et al.

Summary: The study found that recently acquired sensory loss is associated with changes in cerebral morphology within core olfactory areas and an increase in dynamic functional connectivity from olfactory cortex to cerebral areas processing multisensory integration.

SCIENTIFIC REPORTS (2021)

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Article Neurosciences