COVID19 påverkar hjärnan på flera sätt. Det finns även belägg för att viruset direkt infekterar hjärnceller men det verkar föredra astrocyter. En typ av celler i hjärnan:
COVID and the brain: researchers zero in on how damage occurs
Growing evidence suggests that the coronavirus causes ‘brain fog’ and other neurological symptoms through multiple mechanisms.
/.../One way in which SARS-CoV-2 might be accessing the brain, experts say, is by passing through the olfactory mucosa, the lining of the nasal cavity, which borders the brain. The virus is often found in the nasal cavity — one reason that health-care workers test for COVID-19 by swabbing the nose.
Even so, “there’s not a tonne of virus in the brain”, says Spudich, who co-authored a review of autopsies and other evidence that was published online in April4.
But that doesn’t mean it is not infecting any brain cells at all.
Studies now suggest that SARS-CoV-2 can infect astrocytes, a type of cell that’s abundant in the brain and has many functions. “Astrocytes do quite a lot that supports normal brain function,” including providing nutrients to neurons to keep them working, says Arnold Kriegstein, a neurologist at the University of California, San Francisco.
Andra sätt som viruset påverkar hjärnan är via blodkärlen. Intressant här att man tror att Losartan, ett av de blodtryckspreparaten man i början misstänkte kunde ha en negativ effekt på sjukdomsförloppet, kan användas för att lindra effekterna på blodkärlen:
/.../Evidence has also accumulated that SARS-CoV-2 can affect the brain by reducing blood flow to it — impairing neurons’ function and ultimately killing them.
Pericytes are cells found on small blood vessels called capillaries throughout the body — including in the brain. A February preprint reported that SARS-CoV-2 could infect pericyte-like cells in brain organoids.
/.../
Attwell suggests that drugs used to treat high blood pressure, which involves blood-vessel restriction, might be useful in some cases of COVID-19. Two clinical trials are currently investigating the effect of the blood-pressure drug losartan to treat the disease.
Även autoimmuna reaktioner misstänker man ha en inverkan:
/.../In the past 15 years, it has become clear that in response to infection, some people’s immune systems inadvertently make ‘autoantibodies’ that attack their own tissue, says Harald Prüss, a neuroimmunologist at the German Center for Neurodegenerative Diseases in Berlin. This can cause long-term conditions such as neuromyelitis optica, in which people experience symptoms such as loss of vision, and weakness in their limbs. In a review published in May10, Prüss summarized evidence that these autoantibodies can pass through the blood–brain barrier, and contribute to neurological disorders ranging from memory impairment to psychosis.
Allt detta gör att det inte finns några enkla svar på hur COVID19 påverkar hjärnan:
/.../These pathways — astrocytes, pericytes and autoantibodies — are not mutually exclusive, and are probably not the only ones: it is likely that people with COVID-19 experience neurological symptoms for a range of reasons. Prüss says a key question is what proportion of cases is caused by each of the pathways. “That will determine treatment,” he says.
https://www.nature.com/articles/d41586-021-01693-6
Skulle inte tro det!
