Does COVID-19 Affect the Brain? Neurological Symptoms Could Be Due to Inflammation

There has been a debate on how COVID-19 affects the brain. There has been no evidence that SARS-CoV-2 can persist in the brain, but there were reported neurological symptoms.

Does Corona Virus Invade the Brain?

Researchers are still unsure of how COVID-19 causes neurological symptoms to manifest, so they investigated it in a new study. A coronavirus infection can have neurological effects that extend well beyond the acute phase, including headaches, memory issues, and exhaustion. Early in the epidemic, scientists hypothesized that a direct brain infection would be the root cause.

Dr. Helena Radbruch, head of the Chronic Neuroinflammation working group at the Department of Neuropathology at Charité, noted that there has been "no clear evidence that coronavirus can persist in the brain" much more grow in it. Thus, they wanted to look for proof of intact virus particles in the brain. According to the researchers, the suggestions that the coronavirus may infect the brain originate from indirect testing techniques, making them inconclusive.

A second theory states that the neurological symptoms could instead be a byproduct of the body's robust immune defense mechanism against the virus. Previous research has shown signs that this could be the case. This notion is now supported by thorough molecular biology and autopsy-derived anatomical evidence in the present Charité investigation.

For the study, the research team examined different brain regions in 21 patients who passed away from severe coronavirus infection while in a hospital, usually in an intensive care unit. As a point of comparison, the researchers looked at nine patients who left critical care and later passed away from different causes. They started by examining the tissue to determine if it had changed in any noticeable ways and searching for any signs of a coronavirus. Subsequently, a comprehensive examination of genes and proteins was carried out in order to pinpoint the precise mechanisms that had occurred within individual cells.

The Charité scientists discovered coronavirus genetic material in the brains of certain individuals, just like other research teams before them.

"But we didn't find neurons infected with SARS-CoV-2," Radbruch said. "We assume that immune cells absorbed the virus in the body and then traveled to the brain. They're still carrying the virus, but it doesn't infect cells of the brain. So coronavirus has invaded other cells in the body, but not the brain itself."

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How Does COVID-19 Affect the Brain?

Nevertheless, the scientists observed remarkable alterations in molecular functions in specific brain cells of COVID-19-infected individuals: for instance, the cells increased the activation of the interferon signaling pathway, which is normally triggered during a viral infection.

"Some neurons evidently react to the inflammation in the rest of the body," said Prof. Christian Conrad, head of the Intelligent Imaging working group at the Berlin Institute of Health at Charité (BIH) and one of the principal investigators in the study, along with Radbruch.

"This molecular reaction could be a good explanation for the neurological symptoms we see in COVID-19 patients. For example, neurotransmitters emitted by these cells in the brainstem could cause fatigue. That's because the brainstem is home to groups of cells that control drive, motivation, and mood."

The vagus nerve nucleus is where the reactive nerve cells were mostly discovered. These are nerve cells that originate in the brainstem and reach the heart, gut, and lungs, among other organs.

To put it simply, their interpretation of the results concludes that the vagus nerve senses the inflammatory reaction in various organs of the body and reacts to it in the brainstem even without any actual brain tissue infection, per Radbruch. This process allows inflammation to go from the body to the brain, potentially impairing brain function.

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