Multifocal and Microvascular Involvement in Ischemic Stroke During COVID-19: A Cohort Study With Comparison With Non-COVID-19 Stroke

The possible causal relationship between COVID-19 and imaging markers of cerebral small vessel disease: a Mendelian randomization study

OBJECTIVES

Observational studies have suggested that SARS-CoV-2 infection may increase the burden of cerebral small vessel disease (CSVD). This study aims to explore the causal correlation between COVID-19 and the imaging markers of CSVD using Mendelian randomization (MR) methods.

METHODS

Summary-level genome-wide association study (GWAS) statistics for COVID-19 susceptibility, hospitalization, and severity were utilized as proxies for exposure. Large-scale meta-analysis GWAS data on three neuroimaging markers of white matter hyperintensity, lacunar stroke, and brain microbleeds, were employed as outcomes. Our primary MR analysis employed the inverse variance weighted (IVW) approach, supplemented by MR-Egger, weighted median, and MR-PRESSO methods. We also conducted multivariable MR analysis to address confounding bias and validate the robustness of the established causal estimates. Comprehensive sensitivity analyses included Cochran's Q test, Egger-intercept analysis, MR-PRESSO, and leave-one-out analysis.

RESULTS

The MR analysis revealed a significant causal correlation between the severity of COVID-19 and an increased risk of lacunar stroke, as demonstrated by the IVW method (ORivw = 1.08, 95% CI: 1.03-1.16, pivw = 0.005, FDR = 0.047). Nevertheless, no causal correlations were observed between COVID-19 susceptibility or hospitalization and any CSVD imaging markers. The robustness and stability of these findings were further confirmed by multivariable MR analysis and comprehensive sensitivity analyses.

DISCUSSION

This study provides compelling evidence of a potential causal effect of severe COVID-19 on the incidence of lacunar stroke, which may bring fresh insights into the understanding of the comorbidity between COVID-19 and CSVD.

Basic implications on three pathways associated with SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) interacts between the host and virus and govern induction, resulting in multiorgan impacts. Its pathophysiology involves the followings: 1) the angiotensin-converting enzyme (ACE2) and Toll-like receptor (TLR) pathways: 2) the neuropilin (NRP) pathway: 3) the spike protein pathway. Therefore, it is necessary to block the pathological course with modulating innate lymphoid cells against diverse corona variants in the future.

Ischemic strokes in COVID-19: risk factors, obesity paradox, and distinction between trigger and causal association

Background and purpose

Stroke has been described as a COVID-19 complication. However, its occurrence rate, risk factors, and causal relationships are still not well established.

Methods

We describe the characteristics of confirmed COVID-19-related strokes among all cases of COVID-19 hospitalized in our health network, from November 1, 2020 to April 30, 2021. Risk factor analysis has been conducted for ischemic stroke (IS), which represents 92% of all confirmed cases of Covid-19-related strokes, and a "causal attribution to infection" classification is provided.

Results

In all, 62/4105 hospitalized COVID-19 patients had an acute stroke (1.51%). Severe COVID-19 (OR 2.27-CI 1.06-4.77; p = 0.032), atrial fibrillation (OR 3.65-CI 1.63-7.98; p = 0.001), and ischemic heart disease (OR 4.590-CI 1.714-12.137; p = 0.002) proved to be independent risk factors for IS, while obesity was a protective factor (OR 0.90-CI 0.82-0.97; p = 0.012). COVID-19 had a causal role in 32.1% of IS cases, was a relevant cofactor in 28.6% of cases of IS, and was a possible trigger in 39.3% of events.

Conclusion

Our stroke occurrence rate is consistent with other population-based reports (range 0.34-2.7%). Prespecified peculiar clinical and radiological features allow the distinction between "IS caused by COVID-19" and "IS triggered by COVID-19." Clinical history of vascular diseases and risk factors is crucial in determining the risk of IS in patients with COVID-19. However, the protective effect of a BMI > 30 kg/m2 seems to suggest an obesity paradox.

Cerebral small vessel disease pathology in COVID-19 patients: A systematic review

Cerebral small vessel disease (CSVD) is the leading cause of vascular cognitive impairment and is associated with COVID-19. However, contributing factors that often accompany CSVD pathology in COVID-19 patients may influence the incidence of cerebrovascular complications. Thus, a mechanism linking COVID-19 and CSVD has yet to be uncovered and differentiated from age-related comorbidities (i.e., hypertension), and medical interventions during acute infection. We aimed to evaluate CSVD in acute and recovered COVID-19 patients and to differentiate COVID-19-related cerebrovascular pathology from the above-mentioned contributing factors by assessing the localization of microbleeds and ischemic lesions/infarctions in the cerebrum, cerebellum, and brainstem. A systematic search was performed in December 2022 on PubMed, Web of Science, and Embase using a pre-established search criterion related to history of, or active COVID-19 with CSVD pathology in adults. From a pool of 161 studies, 59 met eligibility criteria and were included. Microbleeds and ischemic lesions had a strong predilection for the corpus callosum and subcortical/deep white matter in COVID-19 patients, suggesting a distinct CSVD pathology. These findings have important implications for clinical practice and biomedical research as COVID-19 may independently, and through exacerbation of age-related mechanisms, contribute to increased incidence of CSVD.

Role of tRNA-Derived Fragments in Neurological Disorders: a Review

tRFs are small tRNA derived fragments that are emerging as novel therapeutic targets and regulatory molecules in the pathophysiology of various neurological disorders. These are derived from precursor or mature tRNA, forming different subtypes that have been reported to be involved in neurological disorders like stroke, Alzheimer's, epilepsy, Parkinson's, MELAS, autism, and Huntington's disorder. tRFs were earlier believed to be random degradation debris of tRNAs. The significant variation in the expression level of tRFs in disease conditions indicates their salient role as key players in regulation of these disorders. Various animal studies are being carried out to decipher their exact role; however, more inputs are required to transform this research knowledge into clinical application. Future investigations also call for high-throughput technologies that could help to bring out the other hidden aspects of these entities. However, studies on tRFs require further research efforts to overcome the challenges posed in quantifying tRFs, their interactions with other molecules, and the exact mechanism of function. In this review, we are abridging the current understanding of tRFs, including their biogenesis, function, relevance in clinical therapies, and potential as diagnostic and prognostic biomarkers of these neurological disorders.