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Taking a Closer Look at COVID-19’s Effects on the Brain

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MRI of a brain damaged by COVID-19
Caption: Magnetic resonance microscopy showing lower part of a COVID-19 patient’s brain stem postmortem. Arrows point to light and dark spots indicative of blood vessel damage with no signs of infection by the coronavirus that causes COVID-19. Credit: National Institute of Neurological Disorders and Stroke, NIH

While primarily a respiratory disease, COVID-19 can also lead to neurological problems. The first of these symptoms might be the loss of smell and taste, while some people also may later battle headaches, debilitating fatigue, and trouble thinking clearly, sometimes referred to as “brain fog.” All of these symptoms have researchers wondering how exactly the coronavirus that causes COVID-19, SARS-CoV-2, affects the human brain.

In search of clues, researchers at NIH’s National Institute of Neurological Disorders and Stroke (NINDS) have now conducted the first in-depth examinations of human brain tissue samples from people who died after contracting COVID-19. Their findings, published in the New England Journal of Medicine, suggest that COVID-19’s many neurological symptoms are likely explained by the body’s widespread inflammatory response to infection and associated blood vessel injury—not by infection of the brain tissue itself [1].

The NIH team, led by Avindra Nath, used a high-powered magnetic resonance imaging (MRI) scanner (up to 10 times as sensitive as a typical MRI) to examine postmortem brain tissue from 19 patients. They ranged in age from 5 to 73, and some had preexisting conditions, such as diabetes, obesity, and cardiovascular disease.
The team focused on the brain’s olfactory bulb that controls our ability to smell and the brainstem, which regulates breathing and heart rate. Based on earlier evidence, both areas are thought to be highly susceptible to COVID-19.

Indeed, the MRI images revealed in both regions an unusual number of bright spots, a sign of inflammation. They also showed dark spots, which indicate bleeding. A closer look at the bright spots showed that tiny blood vessels in those areas were thinner than normal and, in some cases, leaked blood proteins into the brain. This leakage appeared to trigger an immune reaction that included T cells from the blood and the brain’s scavenging microglia. The dark spots showed a different pattern, with leaky vessels and clots but no evidence of an immune reaction.

While those findings are certainly interesting, perhaps equally noteworthy is what Nath and colleagues didn’t see in those samples. They could find no evidence in the brain tissue samples that SARS-CoV-2 had invaded the brain tissue. In fact, several methods to detect genetic material or proteins from the virus all turned up empty.

The findings are especially intriguing because there has been some suggestion based on studies in mice that SARS-CoV-2 might cross the blood-brain barrier and invade the brain. Indeed, a recent report by NIH-funded researchers in Nature Neuroscience showed that the viral spike protein, when injected into mice, readily entered the brain along with many other organs [2].

Another recent report in the Journal of Experimental Medicine, which used mouse and human brain tissue, suggests that SARS-CoV-2 may indeed directly infect the central nervous system, including the brain [3]. In autopsies of three people who died from complications of COVID-19, the NIH-supported researchers detected signs of SARS-CoV-2 in neurons in the brain’s cerebral cortex. This work was done using the microscopy-based technique of immunohistochemistry, which uses antibodies to bind to a target, in this case, the virus’s spike protein. Also last month, in a study published in the journal Neurobiology of Disease, another NIH-supported team demonstrated in a series of experiments in cell culture that the SARS-CoV-2 spike protein could cross a 3D model of the blood-brain barrier and infect the endothelial cells that line blood vessels in the brain [4].

Clearly, more research is needed, and NIH’s National Institute of Neurological Disorders and Stroke has just launched the COVID-19 Neuro Databank/Biobank (NeuroCOVID) to collect more clinical information, primarily about COVID-19-related neurological symptoms, complications, and outcomes. Meanwhile, Nath and colleagues continue to explore how COVID-19 affects the brain and triggers the neurological symptoms often seen in people with COVID-19. As we learn more about the many ways COVID-19 wreaks havoc on the body, understanding the neurological symptoms will be critical in helping people, including the so-called Long Haulers bounce back from this terrible viral infection.

References:

[1] Microvascular Injury in the Brains of Patients with Covid-19. Lee MH, Perl DP, Nair G, Li W, Maric D, Murray H, Dodd SJ, Koretsky AP, Watts JA, Cheung V, Masliah E, Horkayne-Szakaly I, Jones R, Stram MN, Moncur J, Hefti M, Folkerth RD, Nath A. N Engl J Med. 2020 Dec 30.

[2] The S1 protein of SARS-CoV-2 crosses the blood-brain barrier in mice. Rhea EM, Logsdon AF, Hansen KM, Williams LM, Reed MJ, Baumann KK, Holden SJ, Raber J, Banks WA, Erickson MA. Nat Neurosci. 2020 Dec 16.

[3] Neuroinvasion of SARS-CoV-2 in human and mouse brain. Song E, Zhang C, Israelow B, et al. J Exp Med (2021) 218 (3): e20202135.

[4] The SARS-CoV-2 spike protein alters barrier function in 2D static and 3D microfluidic in-vitro models of the human blood-brain barrier. Buzhdygan TP, DeOre BJ, Baldwin-Leclair A, Bullock TA, McGary HM, Khan JA, Razmpour R, Hale JF, Galie PA, Potula R, Andrews AM, Ramirez SH. Neurobiol Dis. 2020 Dec;146:105131.

Links:

COVID-19 Research (NIH)

Avindra Nath (National Institute of Neurological Disorders and Stroke/NIH)

NIH Support: National Institute of Neurological Disorders and Stroke; National Institute on Aging; National Institute of General Medical Sciences; National Cancer Institute; National Institute of Mental Health


Study Highlights Need for Continued Care of COVID-19 Survivors

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Collage of people being cared for after contracting COVID-19
Credit: Composed of images from Getty

The past several months have shown that most people hospitalized with COVID-19 will get better. As inspiring as it is to see these patients breathe on their own and converse with their loved ones again, we are learning that many will leave the hospital still quite ill and in need of further care. But little has been published to offer a detailed demographic picture of those being discharged from our nation’s hospitals and the types of community-based care and monitoring that will be needed to keep them on the road to recovery.

A recent study in the journal EClinicalMedicine helps to fill in those gaps by chronicling the early COVID-19 experience of three prominent hospitals in the Boston area: Massachusetts General Hospital, Brigham and Women’s Hospital, and Newton-Wellesley Hospital. These data were reported from a patient registry of 247 middle-aged and older COVID-19 patients. The patients were admitted over three weeks last March into one of these hospitals, which are part of New England’s largest integrated health network.

The data confirm numerous previous reports that COVID-19 disproportionately affects people of color. The researchers, led by Jason H. Wasfy and Cian P. McCarthy, Massachusetts General Hospital and Harvard Medical School, Boston, found a large number of their patients were Hispanic (30 percent) or Black (10 percent). Wasfy said these numbers could be driven by many factors, including a low income, more family members living in one home, greater difficulty accessing healthcare, presence of chronic illness (health disparities), and serving as essential workers during the pandemic.

The researchers also tracked the patients after discharge for about 80 days. About a third of patients left the hospital for a post-acute care facility to continue their rehabilitation. After discharge, many required supplemental oxygen (15 percent), tube feeding (9 percent), or treatment with medications including antipsychotics and prescription painkillers (16 percent). About 10 percent were readmitted to the hospital within weeks or months of their initial discharge.

Wasfy and colleagues also found:

· Many patients undergoing treatment were enrolled in Medicaid (20 percent) or both Medicaid and Medicare (12 percent).

· A substantial number also were retired (36 percent) or unemployed (8.5 percent), highlighting the role of non-occupational spread. Many others worked in the hospitality industry, healthcare, or public transportation.

· A large proportion (42 percent) of hospitalized patients required intensive care. The good news is that most of them (86 percent) ultimately recovered enough to be discharged from the hospital. Tragically, 14 percent—34 of 247 people—died in the hospital.

These findings represent hospitals in just one notable American city hard hit early in the pandemic. But they spotlight the importance of public health efforts to prevent COVID-19 among the most vulnerable and reduce its most devastating social impacts. These are critical points, and NIH has recently begun supporting community engagement research efforts in areas hardest hit by COVID-19. With this support and access to needed post-discharge care, we aim to help more COVID survivors stay on the road to a full recovery.

Reference:

[1] Early clinical and sociodemographic experience with patients hospitalized with COVID-19 at a large American healthcare system. McCarthy CP et al. EClinicalMedicine. August 19, 2020.

Links:

Coronavirus (COVID-19) (NIH)

Massachusetts General Hospital (Boston)

Brigham and Women’s Hospital (Boston)

Newton-Wellesley Hospital (Newton, MA)

Jason Wasfy (Massachusetts General Hospital)


Months After Recovery, COVID-19 Survivors Often Have Persistent Lung Trouble

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Lung function test
Caption: Testing breathing capacity with a spirometer. Credit: iStock/Koldunov

The pandemic has already claimed far too many lives in the United States and around the world. Fortunately, as doctors have gained more experience in treating coronavirus disease 2019 (COVID-19), more people who’ve been hospitalized eventually will recover. This raises an important question: what does recovery look like for them?

Because COVID-19 is still a new condition, there aren’t a lot of data out there yet to answer that question. But a recent study of 55 people recovering from COVID-19 in China offers some early insight into the recovery of lung function [1]. The results make clear that—even in those with a mild-to-moderate infection—the effects of COVID-19 can persist in the lungs for months. In fact, three months after leaving the hospital about 70 percent of those in the study continued to have abnormal lung scans, an indication that the lungs are still damaged and trying to heal.

The findings in EClinicalMedicine come from a team in Henan Province, China, led by Aiguo Xu, The First Affiliated Hospital of Zhengzhou University; Yanfeng Gao, Zhengzhou University; and Hong Luo, Guangshan People’s Hospital. They’d heard about reports of lung abnormalities in patients discharged from the hospital. But it wasn’t clear how long those problems stuck around.

To find out, the researchers enrolled 55 men and women who’d been admitted to the hospital with COVID-19 three months earlier. Some of the participants, whose average age was 48, had other health conditions, such as diabetes or heart disease. But none had any pre-existing lung problems.

Most of the patients had mild or moderate respiratory illness while hospitalized. Only four of the 55 had been classified as severely ill. Fourteen patients required supplemental oxygen while in the hospital, but none needed mechanical ventilation.

Three months after discharge from the hospital, all of the patients were able to return to work. But they continued to have lingering symptoms of COVID-19, including shortness of breath, cough, gastrointestinal problems, headache, or fatigue.

Evidence of this continued trouble also showed up in their lungs. Thirty-nine of the study’s participants had an abnormal result in their computed tomography (CT) lung scan, which creates cross-sectional images of the lungs. Fourteen individuals (1 in 4) also showed reduced lung function in breathing tests.

Interestingly, the researchers found that those who went on to have more lasting lung problems also had elevated levels of D-dimer, a protein fragment that arises when a blood clot dissolves. They suggest that a D-dimer test might help to identify those with COVID-19 who would benefit from pulmonary rehabilitation to rebuild their lung function, even in the absence of severe respiratory symptoms.

This finding also points to the way in which the SARS-CoV-2 virus seems to enhance a tendency toward blood clotting—a problem addressed in our Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV) public-private partnership. The partnership recently initiated a trial of blood thinners. That trial will start out by focusing on newly diagnosed outpatients and hospitalized patients, but will go on to include a component related to convalescence.

Moving forward, it will be important to conduct larger and longer-term studies of COVID-19 recovery in people of diverse backgrounds to continue to learn more about what it means to survive COVID-19. The new findings certainly indicate that for many people who’ve been hospitalized with COVID-19, regaining normal lung function may take a while. As we learn even more about the underlying causes and long-term consequences of this new infectious disease, let’s hope it will soon lead to insights that will help many more COVID-19 long-haulers and their concerned loved ones breathe easier.

Reference:

[1] Follow-up study of the pulmonary function and related physiological characteristics of COVID-19 survivors three months after recovery. Zhao YM, Shang YM, Song WB, Li QQ, Xie H, Xu QF, Jia JL, Li LM, Mao HL, Zhou XM, Luo H, Gao YF, Xu AG. EClinicalMedicine.2020 Aug 25:100463

Links:

Coronavirus (COVID-19) (NIH)

How the Lungs Work (National Heart, Lung, and Blood Institute/NIH)

Computed Tomography (CT) (National Institute of Biomedical Imaging and Bioengineering/NIH)

Zhengzhou University (Zhengzhou City, Henan Province, China)

Accelerating COVID-19 Therapeutic Interventions and Vaccines (ACTIV) (NIH)


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