COVID-19's impact on the brain: Immune response may cause damage

 Previous research links COVID-19 infection to brain issues, such as “brain fog” and neurological issues.

• In a very small cadaver study, researchers from the National Institutes of Health found that antibodies created by the body in response to COVID-19 infection can cause damage to blood vessels in the brain, causing neurological symptoms.
• Scientists believe the discovery of antibody-driven immune complexes on endothelial cells in the brain suggests immune-modulating therapies may help long COVID patients.

As the COVID-19 pandemic continues, clinicians are learning more about the long-term effects of the disease on a person’s overall health. Some coronavirus patients continue to feel the effects of the condition months after initial infection, experiencing long COVID.

The National Institutes of Health (NIH)Trusted Source recently announced new findingsTrusted Source that may have relevance to our understanding of long-term COVID effects. Their new study states the body’s immune response to infection from COVID-19 damages blood vessels in the brain, causing neurological symptoms.

The study was recently published in the journal Brain.

COVID-19 and the brain: What we know

The new study is not the first time research has looked at the effects of COVID-19 on the brain. A previous studyTrusted Source found prior COVID-19 infection was associated with various brain changes, including a greater reduction in global brain volume. And other research showed having COVID-19 may decrease a person’s gray matter volume in the brain.

Researchers have also connected COVID-19 with neurological and mental health conditionsTrusted Source and brain complications like stroke and brain hemorrhage.

Past research also shows the coronavirus continues to impact the brain in patients experiencing long COVID symptoms, such as “brain fog” and other brain changes

New research findings

Medical News Today spoke with Dr. Avindra NathTrusted Source, clinical director at the National Institute of Neurological Disorders and Stroke (NINDS) at the National Institutes of Health (NIH) and the present study’s senior author.

According to Dr. Nath, an earlier studyTrusted Source found evidence of blood vessel damage in the brains of COVID-19 patients who died shortly after contracting the virus, but no signs of SARS-CoV-2 infections.

“This study was undertaken to explore how COVID-19 harms the brain’s blood vessels,” Dr. Nath said.

For this study, Dr. Nath and his research team examined the brain tissue of nine COVID-19 patients who died suddenly after contracting the disease. The scientists observed evidence that antibodiesTrusted Source created by the body in response to COVID-19 infection attacked the brain’s blood vessels, causing inflammation and damage.

“Our findings suggest that the damage to the brain’s blood vessels results from the body’s natural inflammatory response to SARS-CoV-2,” Dr. Nath explained. “For the first time, we observed deposits of immune complexesTrusted Source — molecules formed when antibodies bind antigens — on the surface of cells that make up the blood-brain barrier.”

“We hypothesize that an antibody-mediated attack triggered by the virus damages the blood-brain barrier, causing blood to leak from blood vessels in the brain,” he continued. “This, in turn, triggers inflammation that damages and destroys neuronsTrusted Source.”

Why would these antibodies attack the lining of the blood vessels? Dr. Naths says they do not yet know. “One possibility might be that they are targeted against the ACE2 receptorTrusted Source of the virus, which is highly expressed in these cells,” he said.

While the study only looked at neurovascular damage in fatal cases of COVID-19, Dr. Nath said his team suspects that had these individuals lived, they would have had neurological symptoms of long COVID, including headaches, memory impairment, and brain fog.

“Those with long COVID may have a similar immune response that lingers and damages neurons,” he added. “The discovery of immune complexes on endothelial cellsTrusted Source suggests that immune-modulating therapiesTrusted Source may help.”

More long COVID research needed

As for the next steps to this research, Dr. Nath said the pathology of long COVID still needs studying.

“It’s very hard to study the brain changes driving long COVID without access to brain tissue at autopsy, but long COVID is not a fatal disease,” he explained. “Therefore, we must explore other approaches to deciphering the causes of long COVID. High-resolution MRI scans may provide insight into the neurological symptoms experienced by individuals with long COVID.”

Dr. Santosh Kesari, a neurologist at Providence Saint John’s Health Center in Santa Monica, CA, and regional medical director for the Research Clinical Institute of Providence Southern California agreed more research is required surrounding long COVID and its effects on the brain.

“We worry about the lungs and the damage that COVID causes to lungs, but COVID is actually causing inflammation and organ dysfunction elsewhere in the body that’s unappreciated,” Dr. Kesari told MNT.

“This report and others like this since the pandemic show that there also is a direct injury in the brain. That has implications for treatment approaches when we see these brain problems in our patients acutely, but also now chronically. Some long COVID patients may be having symptoms — short-term memory loss, brain fog, etc. — because of some inflammation that occurred in the brain of these patients, whether we knew it early on or not,” Dr. Kesari explained.

“And the question really is how can we understand that better?” Dr. Kesari added. “We really need to study it a lot more and understand the timing of COVID infection, the severity of the initial infection, and how that relates to brain inflammation, and the severity and duration of cognitive issues that occur in long COVID patients.”

Long COVID: Antibodies in cerebrospinal fluid linked with brain fog

• Researchers do not fully understand the underlying mechanisms and risks factors associated with the occurrence of brain fog, or cognitive symptoms, in individuals with long COVID, or post-COVID conditions.
• A recent study found that individuals with a higher number of preexisting cognitive risk factors, such as diabetes, anxiety, or depression, were more likely to develop post-COVID cognitive symptoms.
• The study authors also found an association between the development of post-COVID cognitive symptoms and abnormalities in the cerebrospinal fluid.
• These abnormalities generally included the presence of antibodies, suggesting that post-COVID cognitive symptoms could be due to an increase in inflammation.

All data and statistics are based on publicly available data at the time of publication. Some information may be out of date. Visit our coronavirus hub for the most recent information on the COVID-19 pandemic.

Brain fog, or cognitive dysfunction, is one of the most commonTrusted Source symptoms that health professionals observe in individuals with long COVID, or post-acute COVID-19Trusted Source.

A recent study by researchers at the University of California, San Francisco (UCSF) suggests a link between the presence of persistent cognitive symptoms several months after a SARS-CoV-2 infection and the presence of abnormalities in the cerebrospinal fluid.

The study also found that individuals with persistent cognitive symptoms were likely to have a higher number of preexisting risk factors associated with cognitive dysfunction before the SARS-CoV-2 infection.

These results may provide a clue for understanding the mechanisms and predisposing factors that lead to cognitive dysfunction in individuals with long COVID.

The study appears in the journal Annals of Clinical and Translational NeurologyTrusted Source.

Cognitive interviews

A substantial minority of individuals with SARS-CoV-2 infection continue to experience symptoms beyond the initial 3–4Trusted Source weeks after contracting the virus. Health experts describe these persistent COVID-19 symptoms as long COVIDTrusted Source or post-acute COVID syndrome.

Cognitive symptoms — such as difficulty maintaining attention, as well as deficits in memory and executive function — are some of the most common symptoms individuals experience beyond the acute phase of the infection.

The researchers conducted the present study to better understand the mechanisms behind and risk factors for post-COVID cognitive symptoms.

This small study was a part of the Long-term Impact of Infection with Novel Coronavirus (LIINC) study, which is a collaboration among researchers at UCSF to understand the long-term effects of a SARS-CoV-2 infection.

The present study involved 32 participants who had experienced mild COVID-19 symptoms during the acute phase of the infection. A cognitive neurologist interviewed them using a standardized questionnaire to determine whether they had developed cognitive deficits after contracting SARS-CoV-2.

Based on the interviews, the researchers determined that 22 participants had experienced cognitive symptoms after the acute phase of the SARS-CoV-2 infection. The remaining 10 participants were in the control group.

The questionnaire also helped determine the presence of risk factors, such as a history of anxiety, depression, high blood pressure, or diabetes, before the infection that would predispose the participants to cognitive dysfunction.

Source - Medical News Today