COVID-19 may not actually infect the brain, but neurological damage persists: study

Does Toronto-COVID-19 affect the brain? The answer is both yes and no, according to a new study that suggests that the virus is unlikely to infect the brain itself.

This study was conducted by experts and surgeons at Columbia University Vagelos College of Medicine. Published in Journal Brain on ThursdayIt was found that the patient examined had no significant evidence of the virus in the brain cells, but still suffered neurological damage from the virus.

“We couldn’t find any signs of the virus in the brain cells of more than 40 COVID-19 patients,” said James E. Goldman, a professor at Columbia University and lead author of the study. .. Said in a press release.

“At the same time, we saw many pathological changes in these brains, which is why critically ill patients experience confusion, delirium, and other serious neurological effects, and mildly ill patients from weeks to on. Explain why you are experiencing “brain fog” for several months. “”

Since the onset of the pandemic, many patients have been observed to develop neurological symptoms after being infected with COVID-19, but little research has been done on the virus in the brain.

This recent study examined 41 people who died from the virus at a medical center in New York City. The average age was 74 years, and researchers agreed with their families to perform an autopsy to study the brain.

One-fifth of the study subjects died of the virus within 24 hours of arriving at the hospital, and many patients had comorbidities such as Parkinson’s disease, dementia, and mild cognitive impairment (MCI). ..

All brains were examined by at least two neuropathologists. Researchers used different methods to study the brain for viral RNA and proteins, focusing on different parts of the brain.

One of the areas they examined was the olfactory part of the brain to investigate the theory that the virus could be transmitted through the nasal passages to the brain. Viral particles were found in the nasal passages, but researchers did not find anything that had invaded the brain.

Goldman said in a release that several other studies examining a small number of brains claimed to find traces of the virus in brain cells, but their findings were “the virus is present in brain tissue.” If so, it is in very small amounts and does not correlate with the distribution or abundance of neuropathological findings. “

Why do victims of COVID-19 have these neurological effects if the virus has not reached enough to affect the brain itself?

Researchers say the damage results in several factors. One major problem is hypoxia. When the body struggles to get oxygen, various areas of the body lack the right amount of oxygen. This can occur in the brain as a result of severe COVID-19.

All the brains studied had hypoxic disorders, the study said.

“The first thing we noticed was in many areas damaged by lack of oxygen,” says Goldman. “It’s not surprising that there is hypoxic damage in the brain, as they all had severe lung disease.”

Other things related to severe COVID-19, such as strokes and blood clots, can also block oxygen to the brain.

However, another finding was that specific immune cells in the brain called microglia were activated in these COVID-19 patients. Researchers believe that these immune cells are attacking neurons illegally, and theorize that they may be due to inflammatory proteins associated with viral infections.

“At the same time, hypoxia can induce the expression of” eating “signals on the surface of neurons, making hypoxic neurons more vulnerable to activated microglia,” said pathology and cell biology. Professor Peter D. Canor said in the release. “Therefore, COVID-19 can damage the brain without directly infecting brain cells.”

The parts of the brain most affected by microglia were the area of ​​the lower brainstem that regulates the rhythm of the heart and breathing, and the hippocampus, which controls memory and mood.

If neurons are attacked by microglia, their loss is permanent, which can cause memory problems in the future, Goldman said.

Interestingly, “neuropathological findings correlate with admission time, even though the study included people who fought the virus for different periods of time, including days and weeks, to death. It didn’t seem to be, “the study suggests. Hospital intervention did not significantly affect the type of neurological injury the researchers were seeing.

Many COVID-19 long-haul carriers report experiencing neurological symptoms such as “brain fog” for several months after other symptoms have subsided.

“If such changes are present in the brains of patients who survive COVID-19, it is important to consider the potential effects of neuropathological changes that we and others have discovered at autopsy.” The study stated.

Since the study was conducted by autopsy, researchers acknowledge that this means that the findings reflect severe cases of COVID-19 and may not be directly applicable to milder cases. I will.

In the future, researchers will find COVID-19 patients who died of the virus in a variety of situations, including those who died months after recovery from COVID-19 and those who had previously experienced acute respiratory distress syndrome (ARDS). I plan to investigate my brain. Their death to better understand how the virus affects the brain.