Can COVID-19 lead to a stroke?
People who are critically ill with COVID-19 can have an increased tendency to form blood clots, which can cause stroke. That has been scary and surprising to see, but it wasn’t entirely unexpected. Now what seems to be happening is that even people who are only mildly affected by the virus, people who have a cough and sore throat and mild fever, or maybe even people with no fever, come in with their initial presentation being a heart attack or stroke. We’ve seen these reports in the New England Journal of Medicine and in the media about people who are relatively young, in their 30s, 40s, and 50s, who have little in the way of risk factors and who come in with a big stroke or a heart attack.
Among any age group, it’s hard to know if COVID-19 caused their stroke or if this person was going to have a stroke because they tore a blood vessel exercising or have some other underlying condition. But when we start to see several young people with strokes over a short period of time, that’s what raises the question of whether it’s related to the virus. The only way to know for sure is to do epidemiologic studies and compare cases to see if people with the virus were more likely to have strokes than people who didn’t have the virus. That kind of research takes a while, and it’s ongoing, but hopefully we’ll get some answers to those questions.
What would cause a stroke in patients with COVID-19?
Any infection revs up the immune system, and the immune system is also linked to the blood clotting system. An infection can activate white blood cells and platelets, the cells that are responsible for clotting in the blood, and then they are more likely to form clots, which can cause a stroke or heart attack.
Isn’t COVID-19 a respiratory disease?
COVID-19 is primarily a respiratory disease that causes acute respiratory distress; for most people the major problem is respiratory. But COVID can also infect heart tissue and other organs, like the kidneys and the blood vessels. There’s even evidence that it can infect the brain directly. That’s because the receptor that the virus uses to enter cells is present on many different tissues. It’s in the lung cells, but it’s also in heart, nerve cells, kidney cells, intestinal cells, and other tissues.
People who are critically ill with COVID-19, such as those who end up in the intensive care unit or on a respirator, can have a phenomenon called “cytokine storm.” It’s basically when the immune system overreacts to the virus. As the immune system responds to the virus, it sends inflammatory molecules throughout the body. That hyperactivity leads to damage, which means the increased tendency to form clots may be even greater, which may be more likely to cause stroke. But this is a new disease, so we’re still discovering things.