Neuro-PASC is characterized by enhanced CD4+ and diminished CD8+ T cell responses to SARS-CoV-2 Nucleocapsid protein.

Introduction: Many people with long COVID symptoms suffer from debilitating neurologic post-acute sequelae of SARS-CoV-2 infection (Neuro-PASC). Although symptoms of Neuro-PASC are widely documented, it is still unclear whether PASC symptoms impact virus-specific immune responses. Therefore, we examined T cell and antibody responses to SARS-CoV-2 Nucleocapsid protein to identify activation signatures distinguishing Neuro-PASC patients from healthy COVID convalescents. Results: We report that Neuro-PASC patients exhibit distinct immunological signatures composed of elevated CD4+ T cell responses and diminished CD8+ memory T cell activation toward the C-terminal region of SARS-CoV-2 Nucleocapsid protein when examined both functionally and using TCR sequencing. CD8+ T cell production of IL-6 correlated with increased plasma IL-6 levels as well as heightened severity of neurologic symptoms, including pain. Elevated plasma immunoregulatory and reduced pro-inflammatory and antiviral response signatures were evident in Neuro-PASC patients compared with COVID convalescent controls without lasting symptoms, correlating with worse neurocognitive dysfunction. Discussion: We conclude that these data provide new insight into the impact of virus-specific cellular immunity on the pathogenesis of long COVID and pave the way for the rational design of predictive biomarkers and therapeutic interventions.

Multidisciplinary Center Care for Long COVID Syndrome-A Retrospective Cohort Study.

BACKGROUND: Persistent multi-organ symptoms after coronavirus disease 2019 (COVID-19) have been termed "long COVID" or "post-acute sequelae of SARS-CoV-2 infection." The complexity of these clinical manifestations posed challenges early in the pandemic as different ambulatory models formed out of necessity to manage the influx of patients. Little is known about the characteristics and outcomes of patients seeking care at multidisciplinary post-COVID centers. METHODS: We performed a retrospective cohort study of patients evaluated at our multidisciplinary comprehensive COVID-19 center in Chicago, Ill, between May 2020 and February 2022. We analyzed specialty clinic utilization and clinical test results according to severity of acute COVID-19. RESULTS: We evaluated 1802 patients a median of 8 months from acute COVID-19 onset, including 350 post-hospitalization and 1452 non-hospitalized patients. Patients were seen in 2361 initial visits in 12 specialty clinics, with 1151 (48.8%) in neurology, 591 (25%) in pulmonology, and 284 (12%) in cardiology. Among the patients tested, 742/878 (85%) reported decreased quality of life, 284/553 (51%) had cognitive impairment, 195/434 (44.9%) had alteration of lung function, 249/299 (83.3%) had abnormal computed tomography chest scans, and 14/116 (12.1%) had elevated heart rate on rhythm monitoring. Frequency of cognitive impairment and pulmonary dysfunction was associated with severity of acute COVID-19. Non-hospitalized patients with positive SARS-CoV-2 testing had findings similar to those with negative or no test results. CONCLUSIONS: The experience at our multidisciplinary comprehensive COVID-19 center shows common utilization of multiple specialists by long COVID patients, who harbor frequent neurologic, pulmonary, and cardiologic abnormalities. Differences in post-hospitalization and non-hospitalized groups suggest distinct pathogenic mechanisms of long COVID in these populations.

Neurologic Manifestations of Long COVID Differ Based on Acute COVID-19 Severity.

OBJECTIVE: To characterize neurologic manifestations in post-hospitalization Neuro-PASC (PNP) and non-hospitalized Neuro-PASC (NNP) patients. METHODS: Prospective study of the first 100 consecutive PNP and 500 NNP patients evaluated at a Neuro-COVID-19 clinic between 5/2020 and 8/2021. RESULTS: PNP were older than NNP patients (mean 53.9 vs 44.9 y; p < 0.0001) with a higher prevalence of pre-existing comorbidities. An average 6.8 months from onset, the main neurologic symptoms were "brain fog" (81.2%), headache (70.3%), and dizziness (49.5%) with only anosmia, dysgeusia and myalgias being more frequent in the NNP compared to the PNP group (59 vs 39%, 57.6 vs 39% and 50.4 vs 33%, all p < 0.003). Moreover, 85.8% of patients experienced fatigue. PNP more frequently had an abnormal neurologic exam than NNP patients (62.2 vs 37%, p < 0.0001). Both groups had impaired quality of life in cognitive, fatigue, sleep, anxiety, and depression domains. PNP patients performed worse on processing speed, attention, and working memory tasks than NNP patients (T-score 41.5 vs 55, 42.5 vs 47 and 45.5 vs 49, all p < 0.001) and a US normative population. NNP patients had lower results in attention task only. Subjective impression of cognitive ability correlated with cognitive test results in NNP but not in PNP patients. INTERPRETATION: PNP and NNP patients both experience persistent neurologic symptoms affecting their quality of life. However, they harbor significant differences in demographics, comorbidities, neurologic symptoms and findings, as well as pattern of cognitive dysfunction. Such differences suggest distinct etiologies of Neuro-PASC in these populations warranting targeted interventions. ANN NEUROL 2023;94:146-159.

Pre-existing immunity modulates responses to mRNA boosters.

mRNA vaccines are effective in preventing severe COVID-19, but breakthrough infections, emerging variants, and waning immunity warrant the use of boosters. Although mRNA boosters are being implemented, the extent to which pre-existing immunity influences the efficacy of boosters remains unclear. In a cohort of individuals primed with the mRNA-1273 or BNT162b2 vaccines, we report that lower antibody levels before boost are associated with higher fold-increase in antibody levels after boost, suggesting that pre-existing antibody modulates the immunogenicity of mRNA vaccines. Our studies in mice show that pre-existing antibodies accelerate the clearance of vaccine antigen via Fc-dependent mechanisms, limiting the amount of antigen available to prime B cell responses after mRNA boosters. These data demonstrate a "tug of war" between pre-existing antibody responses and de novo B cell responses following mRNA vaccination, and they suggest that transient downmodulation of antibody effector function may improve the efficacy of mRNA boosters.

Case report: Treatment of long COVID with a SARS-CoV-2 antiviral and IL-6 blockade in a patient with rheumatoid arthritis and SARS-CoV-2 antigen persistence.

Introduction: Long COVID, or post-acute sequelae of SARS-CoV-2 infection (PASC) in ∼30% of all infected individuals. Here, we present a case of PASC in a patient with rheumatoid arthritis characterized by viral persistence in the nasopharynx for 6 months after acute infection. We demonstrate transient disappearance of antigen persistence and decreased antiviral and autoimmune T cell responses after nirmatrelvir/ritonavir and tocilizumab treatment. Case presentation: A 37-year-old female with a 7-year history of rheumatoid arthritis enrolled in a COVID-19 research study was found to continuously test SARS-CoV-2 antigen positive in the nasopharynx for 6 months after acute infection. She simultaneously presented with new-onset PASC symptoms including chronic occipital headache and periods of intense fatigue 8 weeks after acute infection. The patient was prescribed nirmatrelvir/ritonavir to treat SARS-CoV-2 persistence at 3.5 months post-acute infection and observed a reduction in PASC symptoms 3 weeks after completing antiviral treatment. After resurgence of PASC symptoms, she stopped treatment with tocilizumab for rheumatoid arthritis to attempt complete SARS-CoV-2 viral clearance. The severity of the patient's PASC symptoms subsequently increased, and she developed new-onset brain fog in addition to previous symptoms, which resolved after resumption of tocilizumab treatment. Assessment of adaptive immune responses demonstrated that nirmatrelvir/ritonavir and tocilizumab treatment decreased antiviral and autoreactive T cell activation. After resuming tocilizumab treatment, the patient's PASC symptoms were significantly reduced, but nasopharyngeal antigen positivity remained. Conclusion: These data suggest that nirmatrelvir/ritonavir should be considered in the treatment of PASC in patients who have SARS-CoV-2 antigen persistence, though care must be taken to monitor the patient for symptom resurgence or viral reactivation. In addition, the IL-6 inhibitor tocilizumab may ameliorate PASC symptoms in patients with persistent headache, fatigue, and brain fog.

Improved control of SARS-CoV-2 by treatment with a nucleocapsid-specific monoclonal antibody.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein is the main antigen in all approved COVID-19 vaccines and is also the only target for monoclonal antibody (mAb) therapies. Immune responses to other viral antigens are generated after SARS-CoV-2 infection, but their contribution to the antiviral response remains unclear. Here, we interrogated whether nucleocapsid-specific antibodies can improve protection against SARS-CoV-2. We first immunized mice with a nucleocapsid-based vaccine and then transferred sera from these mice into naive mice, followed by challenge with SARS-CoV-2. We show that mice that received nucleocapsid-specific sera or a nucleocapsid-specific mAb exhibited enhanced control of SARS-CoV-2. Nucleocapsid-specific antibodies elicited NK-mediated, antibody-dependent cellular cytotoxicity (ADCC) against infected cells. To our knowledge, these findings provide the first demonstration in the coronavirus literature that antibody responses specific to the nucleocapsid protein can improve viral clearance, providing a rationale for the clinical evaluation of nucleocapsid-based mAb therapies to treat COVID-19.

Patient Income Does Not Predict Disability or Mortality in Hospitalized COVID-19 Patients in a Large Health Care System in the Chicago Metropolitan Area.

Race, income, and their role in COVID-19 infection in the community have been extensively reported, but their impact on outcomes in hospitalized patients is less well defined. We retrospectively analyzed the first 509 COVID-19 patients in our hospital network, examining associations between median household income, 30-day mortality, and ambulatory state at discharge (using the modified Rankin scale (mRS)), adjusting for hospitalization at the academic medical center (AMC) and other variables. Income did not predict mortality. Higher income was associated with slightly increased odds of ability to ambulate at discharge only when accounting for hospital type. At the AMC, income and mortality were lower and functional outcomes more favorable. Patients with lower incomes had greater comorbidity burden. That income was not associated with measures of morbidity and mortality from COVID-19 is a remarkable and encouraging finding. Academic medical centers may mitigate detrimental effects of socioeconomic disparities on COVID-19 seen at the community level.

Therapeutic Approaches to the Neurologic Manifestations of COVID-19.

As of May 2022, there have been more than 527 million infections with severe acute respiratory disease coronavirus type 2 (SARS-CoV-2) and over 6.2 million deaths from Coronavirus Disease 2019 (COVID-19) worldwide. COVID-19 is a multisystem illness with important neurologic consequences that impact long-term morbidity and mortality. In the acutely ill, the neurologic manifestations of COVID-19 can include distressing but relatively benign symptoms such as headache, myalgias, and anosmia; however, entities such as encephalopathy, stroke, seizures, encephalitis, and Guillain-Barre Syndrome can cause neurologic injury and resulting disability that persists long after the acute pulmonary illness. Furthermore, as many as one-third of patients may experience persistent neurologic symptoms as part of a Post-Acute Sequelae of SARS-CoV-2 infection (Neuro-PASC) syndrome. This Neuro-PASC syndrome can affect patients who required hospitalization for COVID-19 or patients who did not require hospitalization and who may have had minor or no pulmonary symptoms. Given the large number of individuals affected and the ability of neurologic complications to impair quality of life and productivity, the neurologic manifestations of COVID-19 are likely to have major and long-lasting personal, public health, and economic consequences. While knowledge of disease mechanisms and therapies acquired prior to the pandemic can inform us on how to manage patients with the neurologic manifestations of COVID-19, there is a critical need for improved understanding of specific COVID-19 disease mechanisms and development of therapies that target the neurologic morbidities of COVID-19. This current perspective reviews evidence for proposed disease mechanisms as they inform the neurologic management of COVID-19 in adult patients while also identifying areas in need of further research.

Evolution of neurologic symptoms in non-hospitalized COVID-19 "long haulers".

OBJECTIVE: We characterized the evolution of neurologic symptoms and self-perceived recovery of non-hospitalized COVID-19 "long haulers" 6-9 months after their initial Neuro-COVID-19 clinic evaluation. METHODS: In this follow-up study on the first 100 patients, 50 SARS-CoV-2 laboratory-positive (SARS-CoV-2+ ), and 50 laboratory-negative (SARS-CoV-2- ), evaluated at our Neuro-COVID-19 clinic between May and November 2020, patients completed phone questionnaires on their neurologic symptoms, subjective impression of recovery and quality of life. RESULTS: Of 52 patients who completed the study (27 SARS-CoV-2+ , 25 SARS-CoV-2- ) a median 14.8 (range 11-18) months after symptom onset, mean age was 42.8 years, 73% were female, and 77% were vaccinated for SARS-CoV-2. Overall, there was no significant change in the frequency of most neurologic symptoms between first and follow-up evaluations, including "brain fog" (81 vs. 71%), numbness/tingling (69 vs. 65%), headache (67 vs. 54%), dizziness (50 vs. 54%), blurred vision (34 vs. 44%), tinnitus (33 vs. 42%), and fatigue (87 vs. 81%). However, dysgeusia and anosmia decreased overall (63 vs. 27%, 58 vs. 21%, both p < 0.001). Conversely, heart rate and blood pressure variation (35 vs. 56%, p = 0.01) and gastrointestinal symptoms (27 vs. 48%, p = 0.04) increased at follow-up. Patients reported improvements in their recovery, cognitive function, and fatigue, but quality of life measures remained lower than the US normative population (p < 0.001). SARS-CoV-2 vaccination did not have a positive or detrimental impact on cognitive function or fatigue. INTERPRETATION: Non-hospitalized COVID-19 "long haulers" continue to experience neurologic symptoms, fatigue, and compromised quality of life 14.8 months after initial infection.

Persistent viral RNA shedding of SARS-CoV-2 is associated with delirium incidence and six-month mortality in hospitalized COVID-19 patients.

BACKGROUND: Persistent viral RNA shedding of SARS-CoV-2 following COVID-19 has increasingly been recognized, with limited understanding of its implications on outcomes in hospitalized COVID-19 patients. METHODS: We retrospectively assessed for persistent viral shedding across Northwestern Medicine Healthcare (NMHC) patients between March and August 2020. We assessed for predictors of persistent viral shedding, in-hospital delirium, and six-month mortality using binary logistic regression. RESULTS: Of the 2,518 hospitalized patients with an RT-PCR-confirmed diagnosis of COVID-19, 959 underwent repeat SARS-CoV-2 RT-PCR at least fourteen days from initial positive testing. Of those, 405 (42.2%) patients were found to have persistent viral shedding. Persistent viral shedding was associated with male sex, increased BMI, diabetes mellitus, chronic kidney disease, and exposure to corticosteroids during initial COVID-19 hospitalization. Persistent viral shedding was independently associated with incidence of in-hospital delirium after adjusting for factors including severity of respiratory dysfunction (OR 2.45; 95% CI 1.75, 3.45). Even after adjusting for age, severity of respiratory dysfunction, and occurrence of in-hospital delirium, persistent viral shedding remained significantly associated with increased six-month mortality (OR 2.43; 95% CI 1.42, 4.29). CONCLUSIONS: Persistent viral shedding occurs frequently in hospitalized COVID-19 patients and is associated with in-hospital delirium and increased six-month mortality.

Plasma Biomarkers of Neuropathogenesis in Hospitalized Patients With COVID-19 and Those With Postacute Sequelae of SARS-CoV-2 Infection.

BACKGROUND AND OBJECTIVES: Although patients hospitalized with COVID-19 frequently present with encephalopathy, those with mild initial COVID-19 disease who never required hospitalization also often develop neurologic symptoms as part of postacute sequelae of severe acute respiratory coronavirus type 2 (SARS-CoV-2) infection (neuro-PASC). The pathogenic mechanisms of COVID-19 encephalopathy and neuro-PASC are unknown. We sought to establish biochemical evidence of CNS injury in those patients and their association with neuropsychiatric manifestations and SARS-CoV-2 antigenemia. METHODS: We recruited hospitalized, posthospitalized, and nonhospitalized patients with confirmed diagnosis of COVID-19 with neurologic symptoms in addition to healthy control (HC) subjects. Plasma neurofilament light chain (pNfL), plasma glial fibrillary acidic protein (pGFAP), and plasma SARS-CoV-2 Nucleocapsid antigen (pN Ag) were measured by HD-X Simoa analyzer (Quanterix) and compared with neuropsychiatric symptoms, patient-reported quality-of-life measures, and standardized cognitive assessments. Neuroglial scores (pGFAP/pNfL) were calculated to estimate the relative contribution of astroglial and neuronal involvement. RESULTS: We enrolled a total of 64 study participants, including 9 hospitalized patients with COVID-19 encephalopathy (CE), 9 posthospitalization neuro-PASC (PNP) patients, 38 nonhospitalized neuro-PASC (NNP) patients, and 8 HC subjects. Patients with CE were older, had higher pNfL and pGFAP concentrations, and more frequent pN Ag detection than all neuro-PASC groups. PNP and NNP patients exhibited similar PASC symptoms, decreased quality-of-life measures, and cognitive dysfunction, and 1 of the 38 (2.6%) NNP patients had pN Ag detectable 3 weeks postsymptoms onset. Patients with neuro-PASC presenting with anxiety/depression had higher neuroglial scores, which were correlated with increased anxiety on quality-of-life measures. DISCUSSION: pNfL, pGFAP, and pN Ag measurements indicate neuronal dysfunction and systemic involvement in hospitalized COVID-19 patients with encephalopathy. Detection of SARS-CoV-2 N Ag in blood 3 weeks after symptoms onset in a nonhospitalized patient suggests that prolonged antigenic stimulation, or possibly latent infection, may occur. Anxiety was associated with evidence of astroglial activation in patients with neuro-PASC. These data shed new light on SARS-Cov-2 neuropathogenesis and demonstrate the value of plasma biomarkers across the COVID-19 disease spectrum.

Cross-protective immunity following coronavirus vaccination and coronavirus infection.

Although severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines have shown efficacy against SARS-CoV-2, it is unknown if coronavirus vaccines can also protect against other coronaviruses that may infect humans in the future. Here, we show that coronavirus vaccines elicited cross-protective immune responses against heterologous coronaviruses. In particular, we show that a severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) vaccine developed in 2004 and known to protect against SARS-CoV-1 conferred robust heterologous protection against SARS-CoV-2 in mice. Similarly, prior coronavirus infections conferred heterologous protection against distinct coronaviruses. Cross-reactive immunity was also reported in patients with coronavirus disease 2019 (COVID-19) and in individuals who received SARS-CoV-2 vaccines, and transfer of plasma from these individuals into mice improved protection against coronavirus challenges. These findings provide the first demonstration to our knowledge that coronavirus vaccines (and prior coronavirus infections) can confer broad protection against heterologous coronaviruses and establish a rationale for universal coronavirus vaccines.

Acute-care hospital reencounters in COVID-19 patients.

Acute-care hospital reencounters (ACHEs)-encompassing emergency department visits, observation stays, and hospital readmissions-following COVID-19 hospitalization may exacerbate health care system strain and impair recovery from illness. We sought to characterize these reencounters and factors associated with reencounters. We identified the first consecutive 509 patients hospitalized for COVID-19 within an IL hospital network, and examined ACHEs, experienced within 30 days and 4 months of index hospitalization. We identified independent predictors of reencounter using binary logistic regression. Of 509 patients, 466 (91.6%) were discharged alive from index COVID-19 hospitalization. Within 30 days and 4 months, 12.4% and 21.5% of patients, respectively, experienced ACHEs. The median time to first ACHE was 24.2 (IQR 6.5, 55) days. COVID-19 symptom exacerbation was the leading reason for early ACHE (44.8%). Reencounters, both within 30 days and 4 months, were associated with a history of a neurological disorder before COVID-19 (OR 2.78 [95% CI 1.53, 5.03] and OR 2.75 [95% CI 1.67, 4.53], respectively). Older patients and those with diabetes mellitus, chronic obstructive pulmonary disease, or organ transplantation tended towards more frequent ACHEs. Steroid treatment during COVID-19 hospitalization demonstrated reduced odds of 30-day reencounter (OR 0.31 [95% CI 0.091, 0.79]). Forty-nine patients had repeat SARS-CoV-2 nasopharyngeal testing during a reencounter; twelve (24.5%) patients had positive reencounter tests and experienced more frequent reencounters than those testing negative. COVID-19 symptom exacerbation is a leading cause of early ACHE after COVID-19 hospitalization, and steroid use during index hospitalization may reduce early reencounters. Neurologic illness before COVID-19 predicts ACHEs.

Diaphragm and Phrenic Nerve Ultrasound in COVID-19 Patients and Beyond: Imaging Technique, Findings, and Clinical Applications.

The diaphragm, the principle muscle of inspiration, is an under-recognized contributor to respiratory disease. Dysfunction of the diaphragm can occur secondary to lung disease, prolonged ventilation, phrenic nerve injury, neuromuscular disease, and central nervous system pathology. In light of the global pandemic of coronavirus disease 2019 (COVID-19), there has been growing interest in the utility of ultrasound for evaluation of respiratory symptoms including lung and diaphragm sonography. Diaphragm ultrasound can be utilized to diagnose diaphragm dysfunction, assess severity of dysfunction, and monitor disease progression. This article reviews diaphragm and phrenic nerve ultrasound and describes clinical applications in the context of COVID-19.

Persistent neurologic symptoms and cognitive dysfunction in non-hospitalized Covid-19 "long haulers".

OBJECTIVE: Most SARS-CoV-2-infected individuals never require hospitalization. However, some develop prolonged symptoms. We sought to characterize the spectrum of neurologic manifestations in non-hospitalized Covid-19 "long haulers". METHODS: This is a prospective study of the first 100 consecutive patients (50 SARS-CoV-2 laboratory-positive (SARS-CoV-2+ ) and 50 laboratory-negative (SARS-CoV-2- ) individuals) presenting to our Neuro-Covid-19 clinic between May and November 2020. Due to early pandemic testing limitations, patients were included if they met Infectious Diseases Society of America symptoms of Covid-19, were never hospitalized for pneumonia or hypoxemia, and had neurologic symptoms lasting over 6 weeks. We recorded the frequency of neurologic symptoms and analyzed patient-reported quality of life measures and standardized cognitive assessments. RESULTS: Mean age was 43.2 ± 11.3 years, 70% were female, and 48% were evaluated in televisits. The most frequent comorbidities were depression/anxiety (42%) and autoimmune disease (16%). The main neurologic manifestations were: "brain fog" (81%), headache (68%), numbness/tingling (60%), dysgeusia (59%), anosmia (55%), and myalgias (55%), with only anosmia being more frequent in SARS-CoV-2+ than SARS-CoV-2- patients (37/50 [74%] vs. 18/50 [36%]; p < 0.001). Moreover, 85% also experienced fatigue. There was no correlation between time from disease onset and subjective impression of recovery. Both groups exhibited impaired quality of life in cognitive and fatigue domains. SARS-CoV-2+ patients performed worse in attention and working memory cognitive tasks compared to a demographic-matched US population (T-score 41.5 [37, 48.25] and 43 [37.5, 48.75], respectively; both p < 0.01). INTERPRETATION: Non-hospitalized Covid-19 "long haulers" experience prominent and persistent "brain fog" and fatigue that affect their cognition and quality of life.

Abnormal movements in hospitalized COVID-19 patients: A case series.

BACKGROUND: Abnormal movements in Covid-19 patients have been reported with varying degree of frequency, prompting neurologic consultation and additional diagnostic evaluation. We sought to evaluate the frequency and etiology of abnormal movements among hospitalized Covid-19 patients undergoing neurologic consultation. METHODS: We retrospectively analyzed the first 50 consecutive patients with confirmed Covid-19 hospitalized at our tertiary medical care center who underwent acute inpatient neurology consultation from March 2020 through May 2020. Indication for neurologic consultation and diagnostic studies performed were identified by electronic medical record review. RESULTS: Of the 50 initial consultation requests, 11 (22.0%) patients were evaluated for abnormal movements (nine male and two female). Myoclonus was diagnosed in 6/11 (54.5%) patients. Additionally, two patients were diagnosed with seizures (confirmed on EEG in one), while two additional patients were diagnosed with tremor (physiologic and probable functional). A single case of serotonin syndrome was also identified. CONCLUSION: Abnormal movements observed in hospitalized Covid-19 patients can have a wide range of etiologies and were a frequent initial indication for neurologic consultation. Myoclonus was the most frequent type of abnormal movement observed. Early clinical recognition and directed diagnostic work-up is essential for accurate diagnoses in these patients.

Transcranial Doppler Ultrasound Evidence of Active Cerebral Embolization in COVID-19.

OBJECTIVE: To report six consecutive patients with confirmed coronavirus disease-2019 (COVID-19) who underwent Transcranial Doppler (TCD) ultrasonography evaluation for cerebral microemboli in the setting of suspected or confirmed acute ischemic stroke. METHODS: Patient data were obtained from medical records from Northwestern Memorial Hospital, Chicago, IL between May and June 2020. All patients with confirmed COVID-19 who underwent clinical TCD ultrasonography for microemboli detection were included. RESULTS: A total of eight TCD studies were performed in six patients with COVID-19 (4 men and 2 women, median age 65±5), four with confirmed ischemic stroke and two with refractory encephalopathy. Microemboli were detected in three male patients, two patients had suffered a confirmed ischemic stroke and one who developed prolonged encephalopathy. Microemboli of varying intensity were identified in multiple vascular territories in two patients, and microemboli persisted despite therapeutic anticoagulation in a third patient. Of the three patients without evidence of microemboli on TCD ultrasonography, two patients had suffered a confirmed ischemic stroke, while one remained with refractory encephalopathy. CONCLUSIONS: TCD ultrasonography for microemboli detection identified three patients with confirmed COVID-19 with evidence of cerebral arterial microemboli, including one who was therapeutically anticoagulated. TCD ultrasonography provides a non-invasive method for evaluating cerebral microemboli in patients with COVID-19 and may be useful in assessing response to treatment in cases with suspected or confirmed disorders of hypercoagulability. Further studies investigating the prevalence of cerebral microemboli and associated risk factors are needed to characterize their pathogenic mechanism and guide therapeutic interventions in hospitalized COVID-19 patients.