Cerebral blood flow in patients recovered from mild COVID-19

Cerebral blood flow alterations and host genetic association in individuals with long COVID: A transcriptomic-neuroimaging study

Neuroimaging studies have indicated that altered cerebral blood flow (CBF) was associated with the long-term symptoms of postacute sequelae of SARS-CoV-2 infection (PASC), also known as "long COVID". COVID-19 and long COVID were found to be strongly associated with host gene expression. Nevertheless, the relationships between altered CBF, clinical symptoms, and gene expression in the central nervous system (CNS) remain unclear in individuals with long COVID. This study aimed to explore the genetic mechanisms of CBF abnormalities in individuals with long COVID by transcriptomic-neuroimaging spatial association. Lower CBF in the left frontal-temporal gyrus was associated with higher fatigue and worse cognition in individuals with long COVID. This CBF pattern was spatially associated with the expression of 2,178 genes, which were enriched in the molecular functions and biological pathways of COVID-19. Our study suggested that lower CBF is associated with persistent clinical symptoms in long COVID individuals, possibly as a consequence of the complex interactions among multiple COVID-19-related genes, which contributes to our understanding of the impact of adverse CNS outcomes and the trajectory of development to long COVID.

Neuroimaging insights into lung disease-related brain changes: from structure to function

Lung diseases induce changes in brain structure and function, leading to a range of cognitive, emotional, and motor deficits. The concept of the lung-brain axis has been proposed through neuroanatomy, endocrine, and immune pathway, while a considerable number of studies also explored the existence of the lung-brain axis from a neuroimaging perspective. This survey summarizes studies exploring the relationship between lung disease and brain structure and function from neuroimaging perspective, particular in magnetic resonance imaging (MRI). We have collated existing lung diseases studies and categorized them into four types: chronic obstructive pulmonary disease (COPD), coronavirus disease 2019 (COVID-19), lung cancer and other lung diseases. The observed structural and functional changes in the brain and cognitive dysfunction induced by lung diseases are discussed. We also present distinct pattern of brain changes in various lung diseases. Neuroimaging changes in COPD are concentrated in the frontal lobes, including gray matter atrophy, white matter damage, and reduced perfusion. Patients with COVID-19 exhibit extensive microhemorrhages and neuroinflammation, brain regions functionally connected to the primary olfactory cortex show greater changes. For lung cancer patients, brain changes are mainly attributed to the neurotoxicity of radiotherapy and chemotherapy, with damage concentrated in subcortical structures, patients with cancer pain demonstrate hyperconnectivity in motor and visual networks. The survey also discusses the pathological mechanisms revealed in neuroimaging studies and clinical significance of current studies. Finally, we analyzed current limitations, mainly in terms of small sample size, non-standardized criteria, reliance on correlation analyses, lack of longitudinal studies, and absence of reliable biomarkers. We suggest future research directions should include leveraging artificial intelligence for biomarker development, conducting longitudinal and multicenter studies, and investigating the systemic effects of lung disease on the brain and neuromodulation strategies.

On the merits and potential of advanced neuroimaging techniques in COVID-19: A scoping review

Many Coronavirus Disease 2019 (COVID-19) patients are suffering from long-term neuropsychological sequelae. These patients may benefit from a better understanding of the underlying neuropathophysiological mechanisms and identification of potential biomarkers and treatment targets. Structural clinical neuroimaging techniques have limited ability to visualize subtle cerebral abnormalities and to investigate brain function. This scoping review assesses the merits and potential of advanced neuroimaging techniques in COVID-19 using literature including advanced neuroimaging or postmortem analyses in adult COVID-19 patients published from the start of the pandemic until December 2023. Findings were summarized according to distinct categories of reported cerebral abnormalities revealed by different imaging techniques. Although no unified COVID-19-specific pattern could be subtracted, a broad range of cerebral abnormalities were revealed by advanced neuroimaging (likely attributable to hypoxic, vascular, and inflammatory pathology), even in absence of structural clinical imaging findings. These abnormalities are validated by postmortem examinations. This scoping review emphasizes the added value of advanced neuroimaging compared to structural clinical imaging and highlights implications for brain functioning and long-term consequences in COVID-19.