Brain fog, a complication of SARS CoV2

Replacing the delta variant, the omicron variant of SARS CoV2 has become fiercely epidemic all over the world now. So far, the latter is more contagious but is seemingly less virulent than the delta and the former ones. The omicron variant is apt to be regarded as a mild form of SARS CoV2. The governments tend to be less enthusiastic implementing measures against this variant. Actually, our government seems to omit the PCR test for the diagnosis and not to have the infected people isolated from the society for certain period. Notwithstanding early diagnosis and isolation of the infected one is the basic rule to deal with such contagious infections.

It is well known that RNA viruses are liable to mutate frequently and, with certain mutation, are often evasive from the immunity. So called herd immunity must be hard to be acquired, I am afraid. Even though the fight against this pathogen would not last forever, no one knows when and how it ends up. 

There is another point with this species of virus to be be emphasized. It is so called the brain fog as a complication or a sequel of COVID 19. A kind of cognitive impairment which lasts months or even longer. A large scale review with metanalysis says it amounts up to 22% of all infected cases. It must depend on the diagnosis criteria and knowledge of this complication among clinicians how frequent it is recognized in the clinical sites. It is, however, so common that the patients, however serious their illnesses might be, often could not return to the social life due to it.

https://www.sciencedirect.com/science/article/pii/S0889159121006516?via%3Dihub

It should not be looked down because of the rather large number of cases but also of its pathophysiology. An article in Nature last year has revealed it is due to endothelial cell apoptosis of the small vessels in the brain caused with the viral main protease. Pathologically, it takes the form of the string vessel. The viral main protease causes cleavage of NEMO which adjusts the function of nuclear factor k-B. It results in the inflammation and apoptosis of the endothelial cells. In an animal model, the apoptosis antagonist RIPK3 has blocked this process. This seems to be a process of permanent damage to the brain. 

https://www.nature.com/articles/s41593-021-00926-1

An article in the recent issue of Eur. J. Neurol. says the brain fog won't be ever lasting but tends to recover in the span of months. It is an epidemiological finding. We should wait further study on its prognosis. The above mentioned pathophysiological research in Nature should be an important finding and tells us the brain fog should not be paid little attention.

There are a number of reports depicting the neurological sequelle by SARS CoV2 other than the above mentioned article on the brain fog. 

This must be related with the pathophysiology of the brain fog. It says the COVID 19 neurophysiology resembles cancer treatment related cognitive impairment.

https://www.biorxiv.org/content/10.1101/2022.01.07.475453v1

Some patients of COVID19 show the Parkinson's syndrome like symptoms. This could be comparable to the pathophysiology of the brain fog. 

https://www.biorxiv.org/content/10.1101/2022.01.11.475947v1

Less is known about the long sequel by the omicron variant. We should keep eyes wide open for the further reports about it. It is, needless to say, important for us to take precautions against COVID19 however mild in the acute phase it may look like.