Study finds new evidence of SARS-CoV-2 damaging brain blood vessels

 

Scientists have found no trace of SARS-CoV-2 in the brains of people with the infection. However, they have observed blood vessel damage caused by the body’s inflammatory response in the post-mortem brains of patients who tested positive for the virus, which suggests the virus may indirectly attack the organ.

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The scientific advances researchers made this past year have helped tremendously in learning about the new coronavirus that first appeared in Wuhan, China.

Initially, COVID-19 was characterized by fever, sore throat, cough, and dyspnea, all manifestations of a respiratory illness.

However, a spectrum of other clinical manifestations, including headaches, abdominal pain, diarrhea, and loss of taste and smell, have been reported. Researchers also now have evidence of the novel coronavirus damaging the heart, creating blood clots, and causing gastrointestinal issues.

While the pandemic has disproportionally affected older adults and people with preexisting health conditions, younger adults are not immune.

Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.

Earlier this year, reports showed that younger adults who contracted the new coronavirus exhibited more neurological symptoms, including mental confusion, headaches, dizziness, uncoordinated muscle movements, seizures, and a rise in the risk of stroke.

These are but a few examples of how much we have learned and how much we are yet to learn in order to fully understand the SARS-CoV-2 virus. Now, new research suggests that the virus may also cause brain vessel injury.

The research authors published their findings as a correspondence article in the New England Journal of Medicine.

Study design

The study was conducted by researchers from the National Institute of Neurological Disorders and Stroke (NINDS) in Bethesda, MD, and other institutions across the United States.

They examined post-mortem brain tissue samples from 16 patients in New York City and from three patients in Iowa City who had died between March and July 2020 and tested positive for COVID-19 before or after death.

Patients ranged in age from 5 to 73 years, and their medical history commonly showed preexisting conditions, including obesity, heart disease or high blood pressure, and diabetes.

Before death, treatment was mainly geared toward respiratory infection, and only two patients exhibited agitated delirium.

The researchers also used MRI images to detect any abnormalities in the brain tissue. This included the olfactory bulb, a brain area involved in the sense of smell, since loss of smell is known to be one of the first symptoms of COVID-19.

Another brain region they examined was the brain stem, which is crucial for human survival. It regulates sleeping and eating habits and controls heart rate and the rate of breathing.

To asses the relevant brain tissues, the researchers used a staining method called immunohistochemistry, which allows the visualization of proteins within cells and tissues.

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Results

Of the 19 brain tissue samples, 13 were imaged, and 10 showed brain anomalies. Further analysis showed blood vessel damage.

In nine patients, the presence of lesions suggested they were leaky brain vessel injuries. There were also signs of a leaking blood protein called fibrinogen in the brain. The authors suggest that this is evidence of inflammation that arises from an overreactive immune system fighting infection.

In 10 patients, MRI images showed hypointensities corresponding to congested blood vessels, and an accumulation of fibrinogen around the area.

“Our results suggest that this may be caused by the body’s inflammatory response to the virus,” says Dr. Avindra Nath, clinical director of the NINDS at the National Institutes of Health (NIH) and senior author of the study.

Interestingly, the SARS-CoV-2 virus was not found in any of the patients’ brain tissue. However, the authors write that there is no way of knowing whether the virus was present at one point:

“It is possible that the virus was cleared by the time of death or that viral copy numbers were below the level of detection by our assays.”

When looking at the spots of injury more closely, the researchers found that immune cells, such as T cells, were present around the brain, further supporting evidence of an inflammatory response in the brain.

“We were completely surprised. Originally, we expected to see damage that is caused by a lack of oxygen,” says Dr. Nath. “Instead, we saw multifocal areas of damage that is usually associated with strokes and neuroinflammatory diseases.”

Because the novel coronavirus was not detected in the brain tissue of the deceased patients, the authors say it is too early to tell whether there is a link between the neurological effects associated with COVID-19 and the blood vessel injuries observed in this study.

“In the future, we plan to study how COVID-19 harms the brain’s blood vessels and whether that produces some of the short- and long-term symptoms we see in patients,” says Dr. Nath.

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Minimizing the risk of spread

As scientists continue to investigate all the effects of SARS-CoV-2 infection, it is important to slow the spread of the virus.

The public can do their part in minimizing the risk of transmission by wearing a face mask, practicing social distancing, and staying home whenever possible.

Following these guidelines is essential as vaccination efforts continue to roll out worldwide.

For live updates on the latest developments regarding the novel coronavirus and COVID-19, click here.

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Infectious Diseases / Bacteria / VirusesNeurology / NeuroscienceCOVID-19

Written by Jocelyn Solis-Moreira on January 6, 2021 — Fact checked by Alexandra Sanfins, Ph.D.

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Why does the coronavirus cause blood clots?

What is a blood clot?

Theories

Blood clots in the lungs

Complications

Risk factors

Treatments

Outlook

Prevention

Summary

Emerging evidence indicates that COVID-19, which is the disease that SARS-CoV-2 causes, leads to blood clots in an estimated 30% of critically ill patients.

A blood clot, or a thrombus, increases the risk of complications and death among those who have COVID-19. This disease causes blood clots in 20–30% of critically ill patients.

This article will look at the link between the novel coronavirus and blood clots and discuss some potential treatments and methods of prevention.

What is a blood clot?

A person with a blood clot may experience a cough and sharp chest pain.

Blood clotting is one of the body’s natural responses to injury. It occurs when a volume of blood changes to a semi-solid state in order to prevent excessive blood loss. Several chemical reactions in the body facilitate this change.

Clots that form inside a deep vein, however, can be extremely dangerous. These clots may not dissolve on their own, and they can stop blood flow. This can be fatal.

In some situations, a clot can break off and travel to another part of the body. This thrombus becomes known as an embolus.

If the embolus reaches the brain, heart, or lungs, it can result in a life threatening condition, such as a heart attack or stroke.

The symptoms of a blood clot include:

a cough

coughing up blood

a throbbing or cramping pain in the limbs

sharp chest pain

sudden breathlessness

swelling, skin darkening, and warmth around the clot

Theories about how the new coronavirus causes blood clots

According to a Nature article, researchers are not sure why COVID-19 causes blood clots.

One theory is that the clotting occurs when the novel coronavirus attacks the endothelial cells that line the blood vessels. The virus does this by binding to the ACE2 receptors, which are present in the endothelial cell membrane.

Once the virus binds to these receptors, the blood vessels start releasing proteins that trigger blood clotting.

Another theory is that COVID-19 causes the body’s immune system to trigger a hyperactive inflammatory response. This inflammation may then trigger clotting.

Other factors may also play a role in blood clotting in people with COVID-19. For example, many people who require hospital care due to the disease also have other risk factors for blood clots. These include:

being older

having overweight

having hypertension, or high blood pressure

having diabetes

taking medications that increase the risk of blood clotting

Other viruses, including swine flu (H1N1) and SARS, also increase the risk of blood clots.

Blood clots in the lungs

Blood clots in people with COVID-19 tend to differ from those present in people without the disease who have strokes or clots in the lungs.

According to a paper in the British Journal of Haemotology, in people with COVID-19, the clots appear to form within the lungs. Typically, however, clots tend to form in other areas of the body before breaking off and traveling to the lungs.

Also, in those with COVID-19, the clots seem to form in the tiny vessels of the lungs, rather than the major vessels, as is the case in typical strokes.

One small autopsy study in the Annals of Internal Medicine examined 11 deceased COVID-19 patients. The researchers report that all of them had evidence of varying degrees of blood clots. None of these people received a diagnosis of blood clots while they were alive.

The researchers hypothesize that the blood clotting was the cause of death, despite the fact that 10 of the 11 the patients received anticoagulation, or anti-clotting, treatment.

A 2020 study in the New England Journal of Medicine compared the lungs of seven people who died from COVID-19 with the lungs of seven people who died from H1N1.

The researchers found that the lungs of those with COVID-19 had nine times the number of clots than the lungs of those with H1N1.

Learn more about blood clots in the lungs here.

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Other complications from blood clots

Excessive blood clotting in people with COVID-19 may be responsible for several complications arising from the disease.

Research indicates that people with COVID-19 who have a higher rate of blood clotting activity tend to have a significantly worse outcome than others. They are also more likely to require treatment in the intensive care unit.

Some potential complications of blood clots include:

Stroke

When a blood clot blocks an artery in or around the brain, it can trigger a stroke.

A preliminary observational study indicates that younger COVID-19 patients with no other risk factors for stroke have an increased risk, even if they do not have symptoms of the disease.

The researchers also report seeing strokes in people in their 30s, 40s, and 50s that tend to be typical of people in their 70s and 80s.

Heart damage

A blood clot in the arteries can cause a heart attack or other cardiac issues. According to a study of 187 patients with COVID-19 at a hospital in Wuhan, China, 27.8% of the patients developed damage to the heart.

Pulmonary embolism

Blood clots that travel to the lungs cause pulmonary embolisms, which can be fatal. Prompt treatment significantly reduces the risk of death.

Deep vein thrombosis

Deep vein thrombosis (DVT) occurs when a blood clot forms in a vein deep in the body, such as in a leg or an arm.

In the autopsy study, DVT was present in almost 60% of those who died from COVID-19. Without treatment, DVT can lead to pulmonary embolism, amputation, or death.

Kidney damage

Some people with severe COVID-19 develop kidney damage, even if they did not have kidney issues before contracting SARS-CoV-2. In some cases, the damage is so severe that people require dialysis treatment.

Blood clots may play a role in kidney damage because they can clog the tiny blood vessels in the kidneys, reducing their ability to function.

Risk factors

Some factors that increase the risk of developing blood clots include:

being older

carrying excess weight

having hypertension

having diabetes

having heart failure

taking medications that increase the risk of blood clotting

having periods of inactivity, such as prolonged bed rest

undergoing surgery

smoking

having a personal or family history of DVT or pulmonary embolism

having a blood clotting disorder

Current and developing treatments

Doctors may treat or prevent blood clots by prescribing blood-thinning medications. Many doctors will start this treatment during a person’s hospital stay and continue it for 2 weeks after discharge to reduce the risk of blood clots.

However, taking blood thinners also increases the risk of bleeding, which may make them unsuitable for high risk patients. There are some reports that people on mechanical ventilation with COVID-19 who took blood thinners had a lower mortality than those who did not take the medication.

Researchers are also testing new therapies to help treat and prevent blood clots.

Some scientists are comparing standard doses of blood thinners with higher doses in critically ill people. Others are testing the effects of more potent medications, such as tissue plasminogen activator.

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Outlook

According to the World Health Organization (WHO), most people who develop COVID-19 will experience mild-to-moderate respiratory symptoms. They are also unlikely to require any special treatment.

Those with additional risk factors are more likely to develop severe illness, including blood clots.

Prevention

The best way to prevent infection with the novel coronavirus is to practice good hand hygiene and physical distancing.

People at increased risk of blood clots should speak to their doctor. In some cases, the doctor may recommend using a blood-thinning medication. However, these medications are not suitable for everyone.

Some other ways to reduce the risk of blood clots include:

staying active as much as possible

wearing special stockings to improve blood flow

drinking plenty of water to prevent dehydration

losing weight, if necessary

avoiding alcohol and tobacco use

Summary

Experts do not fully understand why the novel coronavirus causes blood clots in some people. These clots typically develop in the lungs, but they may also develop in other areas of the body.

Blood clots increase the risk of complications, including stroke, heart problems, and death.

People who have concerns about their risk of blood clots should speak to their doctor. However, it is important to remember that most people who develop COVID-19 will develop mild-to-moderate symptoms and recover without complications.

Source :https://www.medicalnewstoday.com/articles/coronavirus-and-bloodclots#summary