Covid-19 can usually be clearly felt: headache and body aches, breathing problems, thrombosis, fever. The symptoms vary depending on the severity of the infection and probably also depending on the virus variant. A worrying and as yet little researched phenomenon in connection with a coronavirus infection is its consequences for our brain. A third of those affected report some form of neurological symptoms: those affected have severe headaches, vomit, suffer from dizziness and poor concentration. The loss of the sense of smell and taste are also signs that the brain as well as the lungs and other organs are infected by Sars-CoV-2.
Well, but not healthy
The neural symptoms often also affect people who were originally “symptom-free” because they can still occur after an acute illness has been overcome. They belong to the syndrome also known as “Long Covid”. Between fifty and 80 percent of all Covid-19 sufferers report that they still do not feel healthy months after their recovery, when no virus is detectable in their body. The most common complaints include tiredness, exhaustion, numbness in the limbs and fingers, but also conditions that indicate neuronal damage, such as persistent lack of concentration, anxiety, depression, psychotic states.
“The brain damage happens regardless of the respiratory failure,” says a study that examined how Sars-CoV-2 actually gets into the brain. The fact that the coronavirus also penetrates the brain is known from studies that have been carried out around the middle of last year due to the noticeable loss of the sense of taste and smell. Only now are the mechanisms a little clearer.
As a respiratory virus that can be transmitted through the air, Sars-CoV-2 benefits from the connection of the airways, especially the nasal cavity, with the brain. There is an interface through which the virus finds its way into the brain. The ACE2 receptors to which the virus can easily bind can also be found in the nasal mucosa, so that the virus also easily reproduces there. Other coronaviruses, such as the Mers virus or Sars-CoV-1 – both led to epidemics and are closely related to the current coronavirus – probably infect the brain in this way. The exact path is still the subject of research. What is certain is that the coronavirus can cross the blood-brain barrier – probably by destabilizing this barrier with certain proteins, cytokines, that are formed in the course of inflammation. Again, this is a consequence of the immune response to the virus.
Once in the brain, Sars-CoV-2 can cause thrombosis, inflammation and other brain damage, including neuropsychological damage. Existing illnesses can be aggravated or newly developed. As the study led by Maura Boldrini from New York State University shows, it is primarily the inflammatory cascades triggered by the cytokines that lead to lasting damage and, in particular, to neuropsychic symptoms: The cytokines activate certain cells in the Central nervous system, which includes the brain as well as the spinal cord. This activation of microglia or Hortega cells and of the so-called astrocytes upset the biochemical balance of those neurotransmitters that are responsible for our wellbeing. The levels of quinolinic acid and glutamate increase significantly. Both substances are associated with the development of depression and anxiety disorders. Hallucinations, nightmares and memory loss can also be a consequence of the downright biochemical poisoning.
The tragic thing about the already bad news is that it is not yet known how long the Long Covid symptoms can actually last. One study reported cognitive deficits that persist for up to six weeks.
However, those affected also report that the conditions appear again and again quite arbitrarily. Even in patients who have not previously had any mental illness or complaints. The mental suffering is independent of whether the course was difficult or easy.
In February of this year, the WHO started a standardized survey to research Long Covid.