Project Summary/Abstract More than half of individuals infected with COVID-19 continue to experience debilitating symptoms beyond the initial phase of their infection – a syndrome that is now known as Post-Acute Sequelae of COVID-19 (PASC). When neurological manifestations such as altered smell or taste, post-exertional malaise, “brain fog” (impaired cognition, executive function, and memory), fatigue, dizziness, abnormal movements, headache, sleep disturbances, mood disorders, and/or dysautonomia, are concerned, this syndrome is termed neuroPASC. Knowledge of the specific mechanisms by which SARS-CoV-2 causes damage to the brain and brainstem is vitally important to inform clinical treatment of patients suffering from neuroPASC, but at this point, our knowledge is severely lacking. We hypothesize that SARS-CoV-2 infection causes immune-mediated injury to the neurovascular endothelium, causing microhemorrhages, microinfarctions, and vascular leakage followed by secondary damage to the neural parenchyma due to immune-mediated inflammation in response to breakdown of the blood-brain barrier. The consequences of this tissue injury will manifest as a specific spatiotemporal distribution of neuroimaging findings on in vivo MRI, associated with neurological signs and symptoms and markers of inflammation. The results of this project will rigorously confirm the mechanisms by which SARS-CoV- 2 infection causes tissue damage that leads to neuroPASC, and by leveraging ex vivo MRI to link in vivo neuroimaging findings on a clinically translatable MRI protocol and the presence and temporal evolution of neurological signs and symptoms to a detailed histopathological explanation of the underlying mechanisms by which neural tissue is damaged in neuroPASC, this project will establish a foundation of knowledge for targeted interventions and provide protocols and biomarkers to evaluate the efficacy of those interventions. The specific aims of this project are as follows: Aim 1: we will acquire high-resolution, multi-contrast, quantitative ex vivo MRI and detailed histological datasets in hemibrains from 25 neuroPASC-positive decedents and 15 neuroPASC- negative control decedents who recovered from their acute course of COVID-19 without persistent neurological sequelae. We will compare frequencies of MRI and histological findings in neuroPASC and controls throughout the regions of the brain and brainstem implicated by prominent symptoms to confirm the aforementioned mechanistic hypothesis, and also identify additional spatial patterns of neuroPASC-related abnormalities through data-driven analyses. Aim 2: we will apply an in vivo 7 T structural, vascular, perfusion, and diffusion MRI protocol and perform neuropsychological testing and quantification of blood inflammatory markers in 60 neuroPASC-positive patients at two time points, and 60 neuroPASC-negative control subjects at a single time point. We will analyze the spatial distribution of neuroimaging findings and their evolution over time as neuroPASC symptoms abate to support a hypothesis that resolution of symptoms is closely temporally linked with resolution of specific spatial distributions of neuroimaging findings.

Project Narrative More than half of individuals infected with COVID-19 continue to experience debilitating symptoms beyond the initial phase of their infection – a syndrome that is now known as Post-Acute Sequelae of COVID-19 (PASC) and, when neurological manifestations such as impaired cognition, executive function, and memory, headache, sleep disturbances, mood disorders, fatigue, dizziness, dysautonomia, are concerned, this syndrome is termed neuroPASC. Knowledge of the mechanisms by which SARS-CoV-2 causes damage to the brain and brainstem is vitally important to inform clinical treatment of patients suffering from neuroPASC, but at this point, our knowledge is severely lacking. In this project, we propose to use high-resolution quantitative ex vivo and in vivo 7 Tesla magnetic resonance imaging (MRI) to image the brains and brainstems of neuroPASC patients and individuals who died with neuroPASC, perform neuropsychological testing and quantification of blood inflammatory markers in patients, and both systematically sampled and image-guided targeted histology in postmortem specimens, and using ex vivo MRI as a bridge, interpret the resulting imaging, clinical, and histological findings in order to comprehensively understand the mechanisms by which SARS-CoV-2 injures the central nervous system and causes neuroPASC.