Neuroimaging findings in COVID-19: A narrative review

Hippocampal neurometabolic and structural changes from pre-to post-COVID-19: A case-series study

BACKGROUND

Neurological complications of the COVID-19 infection may be caused in part by local neurochemical and structural abnormalities that could not be detected during routine medical examinations. We examined within subject neurometabolic and structural brain alterations from pre-to post-COVID-19 in the hippocampal region of three elderly individuals (aged 63-68 years) who had a COVID-19 infection with mild symptoms. Patients were participating in an interventional study in which they were closely monitored at the time they were diagnosed with COVID-19. Patients 1 and 2 just completed 18-20 resistance training sessions prior to their diagnosis. Patient 3 was assigned to a non-training condition in the same study.

METHODS

Whole brain magnetic resonance imaging (MRI) images and proton magnetic resonance spectroscopy (1H-MRS) of the left hippocampus were collected before and after infection. Structural and spectroscopic imaging measures post-COVID-19 were contrasted to the pre-COVID-19 measures and were compared with values for Minimal Detectable Change at 95% (MDC95) and 90% (MDC90) confidence from a group of six elderly (aged 60-79 years) without COVID-19 that participated in the same study.

RESULTS

After SARS-COV-2 infection, we observed a reduction of glutamate-glutamine (Glx) in Patients 1 and 2 (≥ 42.0%) and elevation of myo-inositol (mIns) and N-acetyl-aspartate (NAA) in Patient 3 (≥ 36.4%); all > MDC90. MRI findings showed increased (Patients 1 and 2) or unchanged (Patient 3) hippocampal volume.

CONCLUSIONS

Overall, findings from this exploratory study suggest that mild COVID-19 infection could be associated with development of local neuroinflammation and reduced glutamate levels in the hippocampus. Our 1H-MRS findings may have clinical value for explaining chronic neurological and psychological complaints in COVID-19 long-haulers.

The Impact of COVID-19 Pandemic on Clinical Findings in Medical Imaging Exams: An Observational Study in a Nationwide Israeli Health Organization (Preprint)

BACKGROUND

The outbreak of the COVID-19 pandemic had a major effect on consumption of healthcare services. Changes in the use of routine diagnostic exams, increased incidences of post-acute COVID-19 syndrome (PCS), and other pandemic-related factors, may have influenced detected clinical conditions.

OBJECTIVE

The study aimed to analyze the impact of COVID-19 on the use of outpatient medical imaging services and clinical findings therein, specifically focusing on the time period after the launch of the Israeli COVID-19 vaccination campaign. In addition, the study tested whether the observed gains in abnormal findings may be linked to PCS or COVID-19 vaccination.

METHODS

Our dataset included 572,480 ambulatory medical imaging patients in a national health organization, from January 1, 2019 to August 31, 2021. We compared different measures of medical imaging utilization and clinical findings therein, before and after the surge of the pandemic, to identify significant changes. We also inspected the changes in the rate of abnormal findings during the pandemic after adjusting for changes in medical imaging utilization. Finally, for imaging classes that showed increased rates of abnormal findings, we measured the causal associations between COVID-19 infection, hospitalization (indicative of COVID-19 complications), and vaccination and future risk for abnormal finding. To allow adjustment for a multitude of confounding factors, we used causal inference methodologies.

RESULTS

After the initial drop in the utilization of routine medical imaging due to the first COVID-19 wave, the number of these exams has increased, but with lower proportions of older patients, patients with comorbidities, women, and vaccine-hesitant patients. Furthermore, we observed significant gains in the rate of abnormal findings, specifically in musculoskeletal magnetic resonance (MR-MSK) and brain computed tomography (CT-brain) exams. These results also persisted after adjusting for the changes in medical imaging utilization. Demonstrated causal associations included: COVID-19 infection increasing the risk for an abnormal finding in a CT-brain exams (odds ratio [OR] of 1.4, with 95% confidence interval [CI] 1.1 to 1.7); and COVID-19-related hospitalization increasing the risk for abnormal findings in an MR-MSK exam (OR 3.1, 95% CI 1.9 to 5.3).

CONCLUSIONS

COVID-19 impacted the use of ambulatory imaging exams, with greater avoidance among patients at higher risk for COVID-19 complications: older patients, patients with comorbidities, and non-vaccinated patients. Causal analysis results imply that PCS may have contributed to the observed gains in abnormal findings in MR-MSK and CT-brain exams, respectively.

CLINICALTRIAL

Clinical, Laboratory and Imaging Characteristics of Hospitalized COVID-19 Patients with Neurologic Involvement; a Cross-Sectional Study

Introduction

Although neurologic involvement and neuroimaging abnormalities have been frequently identified in COVID-19 patients, the underlying factors remain unclear. In this study, we assessed the association of the neurological manifestations and neuroimaging features of hospitalized COVID-19 patients with their clinical, laboratory, and imaging characteristics.

Methods

This multicenter cross-sectional study was conducted between September 2020 and March 2021 at two large academic hospitals in Tehran, Iran. We used census sampling from medical records to enroll hospitalized patients with a positive COVID-19 Polymerase chain reaction (PCR) test who underwent brain imaging due to presenting any acute neurologic symptom during hospital stay.

Results

Of the 4372 hospitalized patients with COVID-19, only 211 met the inclusion criteria (35.5% with severe infection). Central nervous system and psychiatric manifestations were significantly more common in severe cases (p ≤ 0.044). Approximately, 30% had a new abnormality on their neuroimaging, with ischemic (38/63) and hemorrhagic (16/63) insults being the most common. The most frequent reasons that provoked cranial imaging were headache (27%), altered consciousness (25.6%), focal neurologic signs (19.9%), and delirium (18%). Analysis revealed a positive correlation for age, neutrophilia, lymphopenia, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) with the emergence of neuroimaging abnormalities (p ≤ 0.018). In addition, patients with new neuroimaging abnormalities had a significantly higher lung CT score than those without any pathologic findings (11.1 ± 4.8 vs. 5.9 ± 4.8, p < 0.001).

Conclusion

Approximately 30% of the study population had various acute neuroimaging findings. The lung CT score, neutrophil count, and age were strong predictors of acute neuroimaging abnormalities in hospitalized COVID-19 patients.

FDG-PET/CT of COVID-19 and Other Lung Infections

While not conventionally used as the first-line modality, [¹⁸F]-2-fluoro-2-deoxy-D-glucose (FDG) - positron emission tomography/computed tomography (PET/CT) can identify infection and inflammation both earlier and with higher sensitivity than anatomic imaging modalities [including chest X-ray (CXR), computed tomography (CT), and magnetic resonance imaging (MRI)]. The extent of inflammation and, conversely, recovery within the lungs, can be roughly quantified on FDG-PET/CT using maximum standardized uptake value (SUVmax) values. The Coronavirus disease 2019 (COVID-19) pandemic has highlighted the value of FDG-PET/CT in diagnosis, elucidation of acute pulmonary and extrapulmonary manifestations, and long-term follow up. Similarly, many other pulmonary infections such as previously documented coronaviruses, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, cryptococcosis, histoplasmosis, mucormycosis, and typical/atypical mycobacterial infections have all been identified and characterized using FDG-PET/CT imaging. The goal of this review is to summarize the actual and potential benefits of FDG-PET/CT in the imaging of COVID-19 and other lung infections. Further research is necessary to determine the best indications and clinical applications of FDG-PET/CT, improve its specificity, and ultimately ascertain how this modality can best be utilized in the diagnostic work up of infectious pathologies.

Central Nervous System Effects of COVID-19 in People with HIV Infection

The convergence of the HIV and SARS-CoV-2 pandemics is an emerging field of interest. In this review, we outline the central nervous system (CNS) effects of COVID-19 in the general population and how these effects may manifest in people with HIV (PWH). We discuss the hypothetical mechanisms through which SARS-CoV-2 could impact the CNS during both the acute and recovery phases of infection and the potential selective vulnerability of PWH to these effects as a result of epidemiologic, clinical, and biologic factors. Finally, we define key research questions and considerations for the investigation of CNS sequelae of COVID-19 in PWH.

The Immunopathogenesis of Neuroinvasive Lesions of SARS-CoV-2 Infection in COVID-19 Patients

The new coronavirus disease COVID-19 was identified in December 2019. It subsequently spread across the world with over 125 M reported cases and 2.75 M deaths in 190 countries. COVID-19 causes severe respiratory distress; however, recent studies have reported neurological consequences of infection by the COVID-19 virus SARS-CoV-2 even in subjects with mild infection and no initial neurological effects. It is likely that the virus uses the olfactory nerve to reach the CNS and that this transport mechanism enables virus access to areas of the brain stem that regulates respiratory rhythm and may even trigger cell death by alteration of these neuronal nuclei. In addition, the long-term neuronal effects of COVID-19 suggest a role for SARS-CoV-2 in the development or progression of neurodegerative disease as a result of inflammation and/or hypercoagulation. In this review recent findings on the mechanism(s) by which SARS-CoV-2 accesses the CNS and induces neurological dysregulation are summarized.

Relevance of BET Family Proteins in SARS-CoV-2 Infection

The recent pandemic we are experiencing caused by the coronavirus disease 2019 (COVID-19) has put the world's population on the rack, with more than 191 million cases and more than 4.1 million deaths confirmed to date. This disease is caused by a new type of coronavirus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). A massive proteomic analysis has revealed that one of the structural proteins of the virus, the E protein, interacts with BRD2 and BRD4 proteins of the Bromodomain and Extra Terminal domain (BET) family of proteins. BETs are essential to cell cycle progression, inflammation and immune response and have also been strongly associated with infection by different types of viruses. The fundamental role BET proteins play in transcription makes them appropriate targets for the propagation strategies of some viruses. Recognition of histone acetylation by BET bromodomains is essential for transcription control. The development of drugs mimicking acetyl groups, and thereby able to displace BET proteins from chromatin, has boosted interest on BETs as attractive targets for therapeutic intervention. The success of these drugs against a variety of diseases in cellular and animal models has been recently enlarged with promising results from SARS-CoV-2 infection studies.

Brain Stress Mapping in COVID-19 Survivors Using MR Spectroscopy: New Avenue of Mental Health Status Monitoring$

Coronavirus (COVID-19) has emerged as a human catastrophe worldwide, and it has impacted human life more detrimentally than the combined effect of World Wars I and II. Various research studies reported that the disease is not confined to the respiratory system but also leads to neurological and neuropsychiatric disorders suggesting that the virus is potent to affect the central nervous system (CNS). Moreover, the damage to CNS may continue to rise even after the COVID-19 infection subsides which may further induce a long-term impact on the brain, resulting in cognitive impairment. Neuroimaging techniques is the ideal platform to detect and quantify pathological manifestations in the brain of COVID-19 survivors. In this context, a scheme based on structural, spectroscopic, and behavioral studies could be executed to monitor the gradual changes in the brain non-invasively due to COVID-19 which may further help in quantifying the impact of COVID-19 on the mental health of the survivors. Extensive research is required in this direction for identifying the mechanism and implications of COVID-19 in the brain. Cohort studies are urgently required for monitoring the effects of this pandemic on individuals of various subtypes longitudinally.

Serum neurofilament light protein correlates with unfavorable clinical outcomes in hospitalized patients with COVID-19

SARS-CoV-2 infection, the cause of coronavirus disease 2019 (COVID-19), causes neurological manifestations in a substantial proportion of patients. Determining the extent of neuronal injury is essential to better understand disease pathophysiology and to evaluate potential therapies. Prudencio et al. analyzed serum from 142 patients hospitalized with COVID-19 and showed that the expression of the neurofilament light protein (NFL), a marker of neuroaxonal injury, was elevated compared to healthy controls. In addition, serum NFL expression correlated with disease severity and tended to be reduced in subjects treated with remdesivir. The results suggest that serum NFL analysis should be incorporated when evaluating therapeutic trials for COVID-19.

Brain imaging studies of patients with COVID-19 show evidence of macro- and microhemorrhagic lesions, multifocal white matter hyperintensities, and lesions consistent with posterior reversible leukoencephalopathy. Imaging studies, however, are subject to selection bias, and prospective studies are challenging to scale. Here, we evaluated whether serum neurofilament light chain (NFL), a neuroaxonal injury marker, could predict the extent of neuronal damage in a cohort of 142 hospitalized patients with COVID-19. NFL was elevated in the serum of patients with COVID-19 compared to healthy controls, including those without overt neurological manifestations. Higher NFL serum concentrations were associated with worse clinical outcomes. In 100 hospitalized patients with COVID-19 treated with remdesivir, a trend toward lower NFL serum concentrations was observed. These data suggest that patients with COVID-19 may experience neuroaxonal injury and may be at risk for long-term neurological sequelae. Neuroaxonal injury should be considered as an outcome in acute pharmacotherapeutic trials for COVID-19.

Confronting COVID-19-associated cough and the post-COVID syndrome: role of viral neurotropism, neuroinflammation, and neuroimmune responses

Cough is one of the most common presenting symptoms of COVID-19, along with fever and loss of taste and smell. Cough can persist for weeks or months after SARS-CoV-2 infection, often accompanied by chronic fatigue, cognitive impairment, dyspnoea, or pain-a collection of long-term effects referred to as the post-COVID syndrome or long COVID. We hypothesise that the pathways of neurotropism, neuroinflammation, and neuroimmunomodulation through the vagal sensory nerves, which are implicated in SARS-CoV-2 infection, lead to a cough hypersensitivity state. The post-COVID syndrome might also result from neuroinflammatory events in the brain. We highlight gaps in understanding of the mechanisms of acute and chronic COVID-19-associated cough and post-COVID syndrome, consider potential ways to reduce the effect of COVID-19 by controlling cough, and suggest future directions for research and clinical practice. Although neuromodulators such as gabapentin or opioids might be considered for acute and chronic COVID-19 cough, we discuss the possible mechanisms of COVID-19-associated cough and the promise of new anti-inflammatories or neuromodulators that might successfully target both the cough of COVID-19 and the post-COVID syndrome.