COVID-19, the virus that has been encompassing our world for the past two years, has been known to affect us in various ways. It can be deadly or merely cause patients to show cold-like symptoms. Specific symptoms that have been spiking curiosity in scientists lately relate solely to the brain; “headaches, confusion, hallucinations and delirium… depression, anxiety, and sleep problems”, and the non-medical term; brain fog. What Laura Sanders aims to answer in her article from ScienceNews is: what have scientists discovered so far that can possibly link COVID-19 to neurological problems? Can COVID-19 alone be attributed to these problems? Why or why not?
The first step in understanding if COVID-19 really has an effect on the brain is gathering data. Scientists completed a study that reported a very alarming answer; “in the six months after an infection, one in three people had experienced a psychiatric or neurological diagnosis”. This study was published last spring and included those who had experienced mental illnesses, strokes, brain bleeds and other neurological events after six months of COVID-19 infection. The issue with this study is that the connection between COVID-19 and these events is not 100% solidified so it is still unclear whether COVID-19 itself is the cause of these problems. However, Avindra Nath, a neurologist who studies central nervous system infections at the National Institutes of Health in Bethesda, has been trying to find traces of the virus inside of the brain to prove this theory. Nath and his team, after failing several times to find virus in the brain, hypothesized that the virus may not be targeting the brain itself but the blood vessels inside it. They examined blood vessels of post-mortem brains of those who suffered from COVID-19 with an MRI machine so powerful it couldn’t be used on living COVID-19 patients. The MRI machine that they used allowed them to see the blood vessels in a way that they were never able to see before, due to its strength. With the machine, they were able to see that there were clots in the blood vessels, that the walls were alarmingly thick and inflamed and that some blood was leaking out of the actual blood vessels and into the post-mortem COVID-19 victims’ brains. According to Nath, “These results suggest that clots, inflamed linings, and leaks in the barriers that normally keep blood and other harmful substances out of the brain may all contribute to COVID-related brain damage”. But, like before, no solidified conclusions can be made from Nash’s study alone due to several unknowns.
Inflammation and its effects on the human body is another concern related to COVID-19. Any inflammation in the body can cause the brain to make and use chemical signaling molecules differently. Neurotransmitters are key signaling molecules in helping nerve cells communicate and can be disrupted by inflammation. Other key communication molecules like serotonin, norepinephrine, and dopamine can get scrambled up when there is a lot of inflammation, causing further problems. As we learned in AP Biology this year, innate cellular defenses within the body usually lead to an inflammatory response. This happens when the pathogen is able to get past the barrier defenses: our skin and mucous membranes. In the area where the pathogen enters, mast cells will release histamine and macrophages will secrete cytokines. The histamines boost blood flow in the area causing inflammation and allowing the inflammatory process to progress. The cytokines attract neutrophils which digest pathogens and dead cell debris contributing to inflammation and the completion of the innate response. Microglia are cells found in the brain that release inflammatory cytokines to amplify the inflammatory response by activating and recruiting more cells to the specific area in the brain. The microglia are the brain’s version of the body’s immune system. Now you may ask what do microglia and inflammation have to do with COVID-19? Well, in 43% of 184 COVID patients and 34 of 41 post-mortem COVID patients, active microglia was found. This means that microglia had initiated an inflammatory response within the brain as a result of SARS-COV-2 entering the body, proving that COVID causes inflammation in the brain and that it can possibly be the cause of the neurological events mentioned earlier.
Nevertheless, there are still many unanswered questions about the virus’s effects on the brain and if we will ever know who is most susceptible to this concerning response. One important factor contributing to brain functioning that we can not forget is lockdowns. COVID-19 lockdowns have been connected to mental health disorders and according to psychiatrictimes, mental illnesses can activate inflammation in the body. This tells us that COVID-19 may create inflammation indirectly through mandated lockdowns. Another thing to note is the term ‘brain fog’ that so many patients have used, including me when I had COVID-19 last spring, is nonmedical. Though it is listed as a symptom, it can not be attributed to SARS-CoV-2 affecting our brain’s functioning until we research more thoroughly. So, for now, we can not 100% attribute COVID-19 to attacking the brain alone but we know that it has the potential to have a very alarming effect on our brains and our body as a whole.