Is this immune system reaction unique to COVID?
Dr. Merkler: No. Like any virus or bug that gets into our body, the way that we get rid of it is that our immune system takes over and fights it. When that happens, the body destroys the virus through inflammation. Just like if you have a cut in your arm, there can be swelling and redness that arise from the body’s inflammation of that area to make sure that it’s clean. Sometimes, however, the body over-reacts and starts attacking normal, healthy cells in an attempt to get rid of the virus. This has been seen with many other infectious diseases.
Dr. Elkind: We’ve known for a while that when patients have a medical illness that’s severe it can lead to cognitive problems. For instance, with an illness like streptococcal pneumonia, the immune reaction against the strep actually attacks the brain, and these patients can develop movement disorders and other psychiatric syndromes. We call it molecular mimicry because what happens is, the immune system recognizes the viral proteins, but some of the proteins in the brain just happen to be similar enough to those viral proteins that the immune system ends up attacking the brain.
So this is not necessarily specific to COVID. It’s just that there’s more COVID, so we’re seeing more of these aftereffects than we did with any of these other viruses or infections. And the contagiousness of COVID means we might see a lot more of these cases.
What signs should someone look out for? And when should they go to a doctor about brain fog?
Dr. Elkind: If the symptoms are severe or interfere with your life, if they fail to get better after a few weeks, or if they’re associated with any other unusual symptom that the person hasn’t had—like weakness, difficulty speaking, loss of vision, numbness and tingling—you should see your doctor. Those are symptoms that we as neurologists call focal symptoms, implying that there’s damage in one particular part of the nervous system.
Dr. Merkler: We know that COVID does increase the risk of stroke, so it behooves you to see your physician, get scanned, get brain imaging, and do blood work, because it’s important to rule out a brain injury or something completely unrelated to your COVID illness, like a thyroid condition.