The causes of long COVID, which disables millions, may come together in the brain and nervous system
This is a fascinating and very long article from Scientific American that summarises nicely the research and clinical evidence surrounding Long Covid. It's recommended reading if you have ME/CFS or Long Covid, but please take your time with it and don't push yourselves.
Extracts
A chronic fatigue connection?
“Post-viral syndromes have been documented for more than a century, arising after infection with viruses from HIV to the flu. Epstein-Barr virus, which causes mononucleosis, is one of several viruses linked to a condition called myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), which is estimated to affect at least one and a half million people in the U.S. ME/CFS bears striking resemblances to long COVID, with symptoms such as immune system dysregulation, fatigue and cognitive dysfunction. “One of the patterns we see is patients who definitely meet the criteria for ME/CFS. This is something we are seeing and treating all the time” in long COVID patients, Pittman says. ME/CFS can be severe, with some people losing mobility and becoming bedbound.
“Nath, who also studies ME/CFS, says that “we think mechanistically they are going to be related.” Researchers suspect that ME/CFS, like some cases of long COVID, could be autoimmune in nature, with autoantibodies keeping the immune system activated. ME/CFS has been difficult to study because it often arises long after a mild infection, making it hard to identify a viral trigger. But with long COVID, Nath says, “the advantage is that we know exactly what started the process, and you can catch cases early in the [development of] ME/CFS-like symptoms.” In people who have had ME/CFS for years, “it's done damage, and it's hard to reverse that.” Nath speculates that for long COVID, if doctors could study people early in the illness, they would have a better chance of reversing the process.
“Torgerson hopes that researchers will ultimately come to better understand ME/CFS because of COVID. “COVID has been more carefully studied with better technology in the time we've had it than any other infectious disease ever. I think we'll learn things that will be applicable to other inflammatory diseases driven by infection followed by an autoimmune process.”
“The most common, persistent and disabling symptoms of long COVID are neurological. Some are easily recognized as brain- or nerve-related: many people experience cognitive dysfunction in the form of difficulty with memory, attention, sleep and mood. Others may seem rooted more in the body than the brain, such as pain and postexertional malaise (PEM), a kind of “energy crash” that people experience after even mild exercise. But those, too, result from nerve dysfunction, often in the autonomic nervous system, which directs our bodies to breathe and digest food and generally runs our organs on autopilot. This so-called dysautonomia can lead to dizziness, a racing heart, high or low blood pressure, and gut disturbances, sometimes leaving people unable to work or even function independently.
“The SARS-CoV-2 virus is new, but postviral syndromes are not. Research on other viruses, and on neurological damage from the human immunodeficiency virus (HIV) in particular, is guiding work on long COVID. And the recognition that the syndrome may cause its many effects through the brain and the nervous system is beginning to shape approaches to medical treatment. “I now think of COVID as a neurological disease as much as I think of it as a pulmonary disease, and that's definitely true in long COVID,” says William Pittman, a physician at UCLA Health in Los Angeles, who treats Ghormley and many similar patients…
Roots of dysfunction
One study found that in people with neurological COVID symptoms, the immune system seems to be activated specifically in the central nervous system, creating inflammation. But brain inflammation is probably not caused by the virus infecting that organ directly. Avindra Nath, who has long studied postviral neurological syndromes at the National Institutes of Health, found something similar in an autopsy study of people who died of COVID. “When you look at the COVID brain, you don't actually find [huge amounts of virus, but] we found a lot of immune activation,” he says, particularly around blood vessels. The examinations suggested that immune cells called macrophages had been stirred up. “Macrophages are not that precise in their attack,” Nath says. “They come and start chewing things up; they produce all kinds of free radicals, cytokines. It's almost like blanket bombing—it ends up causing a lot of damage. And they're very hard to shut down, so they persist for a long time. These are the unwelcome guests” that may be causing persistent inflammation in the brain…
“What keeps the immune system in attack mode? According to Torgerson, “one option is that you've developed autoimmunity,” in which antibodies produced by the immune system to fight the virus also mark a person's own cells for immune attack. The response to the virus “turns the autoimmunity on, and that doesn't get better even when the virus goes away,” he says. Several studies have found evidence of autoimmune components called autoantibodies that interact with nerve cells in people with long COVID.
“Clues about the inflammatory processes at work could point toward treatments for neurological symptoms. “If it's a macrophage-mediated inflammatory process … intravenous immunoglobulin could make a difference [to] dampen the macrophages,” Nath says. The treatment, referred to as IVIg, contains a cocktail of proteins and antibodies that can mitigate an overactive immune response…
“IVIg can also be used to block autoantibodies. And a therapy called rituximab that targets antibody-producing B cells provides “a time-tested therapy for a lot of autoantibody-mediated syndromes,” Nath says. Another strategy is to use corticosteroids to dampen immune activity altogether, although those drugs can be used for only a limited time. “That's a sledgehammer approach, and you can see if it makes a difference. At least it gives you an idea that, yes, it's an immune-mediated phenomenon, and now we need to find a better way to target it,” Nath says.
“If the virus does hang around in some form, antiviral medications could potentially clear it, which might help resolve neurological symptoms. That's the hope of scientists running a clinical trial of Paxlovid, Pfizer's antiviral drug for acute COVID…