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| Meta Title | Long COVID brain fog may be due to damaged blood vessels in the brain | ||||||||||||||||||
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| Boilerpipe Text | Long COVID brain fog may be due to damaged blood vessels in the brain
The result suggests there is a biological basis for this symptom
Brain fog is a debilitating symptom commonly reported by people with long COVID. Now, scientists have linked the symptom to leaky boundaries in the brain.
baona/iStock/Getty Images Plus
Leakiness in the brain could explain the memory and concentration problems linked to long COVID.Â
In patients with brain fog,Â
MRI scans revealed signs of damaged blood vessels in their brains
, researchers reported February 22 inÂ
Nature Neuroscience
. In these people, dye injected into the bloodstream leaked into their brains and pooled in regions that play roles in language, memory, mood and vision.Â
Itâs the first time anyoneâs shown that long COVID patients can have leaky blood brain barriers, says study coauthor Matthew Campbell, a geneticist at Trinity College Dublin in Ireland. That barrier, tightly knit cells lining blood vessels, typically keeps riffraff out of the brain, like bouncers guarding a nightclub.Â
If the barrier breaks down, bloodborne viruses, cells and other interlopers can sneak into the brainâs tissues and wreak havoc, says Avindra Nath, a neurologist at the National Institutes of Health in Bethesda, Md. Itâs too early to say definitively whether thatâs happening in people with long COVID, but the new study provides evidence that âbrain fog has a biological basis,â says Nath, who wasnât involved with the work. That alone is important for patients, he says, because their symptoms may be otherwise discounted by physicians.Â
For some people, brain fog can feel like a slowdown in thinking or difficulty recalling short-term memories, Campbell says. For example, âpatients will go for a drive, and forget where theyâre driving to.â That might sound trivial, he says, but it actually pushes people into panic mode.Â
Campbellâs team studies repetitive head trauma. They knew that traumatic brain injuries can disrupt the blood brain barrier â and that people with these injuries sometimes report having brain fog. That mental muddling reminded the team of what people with long COVID can experience. Maybe the blood brain barrier disruption seen in some concussion patients applies to long COVID brain fog, too, the researchers surmised.
Evidence for SARS-CoV-2âs damaging effects on the brain has been mounting for years. Studies in cells and animals suggest the virus can crumble components of the blood brain barrier. And autopsies of people who have died from COVID-19 reveal barrier breakdowns, Nath and others have shown.
In long COVID patients with brain fog (brain scan at right), dye injected into the bloodstream tends to leak into the brain (see colored speckles) more so than in people without brain fog (left).
C. Greene
et al.
/
Nature Neuroscience
2024
But until now, no one knew if this kind of damage persisted long after the initial infection subsided. The team scanned the brains of 32 people, 10 of whom had recovered from COVID-19, and 22 with long COVID. Of those with long COVID,  half reported having brain fog.Â
An injected dye lit up all the participantsâ brains during MRI brain scans. In people recovered from COVID, the dye had trouble crossing the blood brain barrier. Likewise, in long COVID patients without brain fog, the dye mostly stayed put, confined within blood vessels. But in eight of 11 participants with brain fog, the dye tended to escape from blood vessels and enter brain tissue.Â
âIt was just so clear,â Campbell says. He remembers one of the first people scanned, someone with severe brain fog. Their temporal lobes, brain regions that sit behind the eyes, were âjust flooded with this dye,â he says. The researchersâ work suggests that âbrain fog wasnât just a figment of [patientsâ] imagination,â Campbell says. âIt was a very, very real thing that they were reporting.â
The new findings offer an opportunity to think about potential therapies, Nath says. Perhaps researchers can find a way to slow down the blood brain barrierâs breakdown â or reverse it.
More Stories from Science News on
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# Long COVID brain fog may be due to damaged blood vessels in the brain
The result suggests there is a biological basis for this symptom

Brain fog is a debilitating symptom commonly reported by people with long COVID. Now, scientists have linked the symptom to leaky boundaries in the brain.
baona/iStock/Getty Images Plus
By [Meghan Rosen](https://www.sciencenews.org/author/meghan-rosen "Posts by Meghan Rosen")
March 15, 2024 at 8:30 am - More than **2 years ago**
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Leakiness in the brain could explain the memory and concentration problems linked to long COVID.
In patients with brain fog, [MRI scans revealed signs of damaged blood vessels in their brains](https://www.nature.com/articles/s41593-024-01576-9), researchers reported February 22 in *Nature Neuroscience*. In these people, dye injected into the bloodstream leaked into their brains and pooled in regions that play roles in language, memory, mood and vision.
Itâs the first time anyoneâs shown that long COVID patients can have leaky blood brain barriers, says study coauthor Matthew Campbell, a geneticist at Trinity College Dublin in Ireland. That barrier, tightly knit cells lining blood vessels, typically keeps riffraff out of the brain, like bouncers guarding a nightclub.
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If the barrier breaks down, bloodborne viruses, cells and other interlopers can sneak into the brainâs tissues and wreak havoc, says Avindra Nath, a neurologist at the National Institutes of Health in Bethesda, Md. Itâs too early to say definitively whether thatâs happening in people with long COVID, but the new study provides evidence that âbrain fog has a biological basis,â says Nath, who wasnât involved with the work. That alone is important for patients, he says, because their symptoms may be otherwise discounted by physicians.
For some people, brain fog can feel like a slowdown in thinking or difficulty recalling short-term memories, Campbell says. For example, âpatients will go for a drive, and forget where theyâre driving to.â That might sound trivial, he says, but it actually pushes people into panic mode.
Campbellâs team studies repetitive head trauma. They knew that traumatic brain injuries can disrupt the blood brain barrier â and that people with these injuries sometimes report having brain fog. That mental muddling reminded the team of what people with long COVID can experience. Maybe the blood brain barrier disruption seen in some concussion patients applies to long COVID brain fog, too, the researchers surmised.
Evidence for SARS-CoV-2âs damaging effects on the brain has been mounting for years. Studies in cells and animals suggest the virus can crumble components of the blood brain barrier. And autopsies of people who have died from COVID-19 reveal barrier breakdowns, Nath and others have shown.

In long COVID patients with brain fog (brain scan at right), dye injected into the bloodstream tends to leak into the brain (see colored speckles) more so than in people without brain fog (left).
C. Greene *et al.*/*Nature Neuroscience* 2024
But until now, no one knew if this kind of damage persisted long after the initial infection subsided. The team scanned the brains of 32 people, 10 of whom had recovered from COVID-19, and 22 with long COVID. Of those with long COVID, half reported having brain fog.
An injected dye lit up all the participantsâ brains during MRI brain scans. In people recovered from COVID, the dye had trouble crossing the blood brain barrier. Likewise, in long COVID patients without brain fog, the dye mostly stayed put, confined within blood vessels. But in eight of 11 participants with brain fog, the dye tended to escape from blood vessels and enter brain tissue.
âIt was just so clear,â Campbell says. He remembers one of the first people scanned, someone with severe brain fog. Their temporal lobes, brain regions that sit behind the eyes, were âjust flooded with this dye,â he says. The researchersâ work suggests that âbrain fog wasnât just a figment of \[patientsâ\] imagination,â Campbell says. âIt was a very, very real thing that they were reporting.â
The new findings offer an opportunity to think about potential therapies, Nath says. Perhaps researchers can find a way to slow down the blood brain barrierâs breakdown â or reverse it.
Questions or comments on this article? E-mail us at [feedback@sciencenews.org](mailto:feedback@sciencenews.org) \| [Reprints FAQ](https://www.sciencenews.org/permission-republish)
A version of this article appears in the [April 6, 2024](https://www.sciencenews.org/sn-magazine/april-6-2024) issue of Science News.
### Citations
C. Greene *et al*. [Bloodâbrain barrier disruption and sustained systemic inflammation in individuals with long COVID-associated cognitive impairment](https://www.nature.com/articles/s41593-024-01576-9). *Nature Neuroscience*. Published online February 22, 2024. doi:10.1038/s41593-024-01576-9.
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| Readable Markdown | ## Long COVID brain fog may be due to damaged blood vessels in the brain
The result suggests there is a biological basis for this symptom

Brain fog is a debilitating symptom commonly reported by people with long COVID. Now, scientists have linked the symptom to leaky boundaries in the brain.
baona/iStock/Getty Images Plus
Leakiness in the brain could explain the memory and concentration problems linked to long COVID.
In patients with brain fog, [MRI scans revealed signs of damaged blood vessels in their brains](https://www.nature.com/articles/s41593-024-01576-9), researchers reported February 22 in *Nature Neuroscience*. In these people, dye injected into the bloodstream leaked into their brains and pooled in regions that play roles in language, memory, mood and vision.
Itâs the first time anyoneâs shown that long COVID patients can have leaky blood brain barriers, says study coauthor Matthew Campbell, a geneticist at Trinity College Dublin in Ireland. That barrier, tightly knit cells lining blood vessels, typically keeps riffraff out of the brain, like bouncers guarding a nightclub.
If the barrier breaks down, bloodborne viruses, cells and other interlopers can sneak into the brainâs tissues and wreak havoc, says Avindra Nath, a neurologist at the National Institutes of Health in Bethesda, Md. Itâs too early to say definitively whether thatâs happening in people with long COVID, but the new study provides evidence that âbrain fog has a biological basis,â says Nath, who wasnât involved with the work. That alone is important for patients, he says, because their symptoms may be otherwise discounted by physicians.
For some people, brain fog can feel like a slowdown in thinking or difficulty recalling short-term memories, Campbell says. For example, âpatients will go for a drive, and forget where theyâre driving to.â That might sound trivial, he says, but it actually pushes people into panic mode.
Campbellâs team studies repetitive head trauma. They knew that traumatic brain injuries can disrupt the blood brain barrier â and that people with these injuries sometimes report having brain fog. That mental muddling reminded the team of what people with long COVID can experience. Maybe the blood brain barrier disruption seen in some concussion patients applies to long COVID brain fog, too, the researchers surmised.
Evidence for SARS-CoV-2âs damaging effects on the brain has been mounting for years. Studies in cells and animals suggest the virus can crumble components of the blood brain barrier. And autopsies of people who have died from COVID-19 reveal barrier breakdowns, Nath and others have shown.

In long COVID patients with brain fog (brain scan at right), dye injected into the bloodstream tends to leak into the brain (see colored speckles) more so than in people without brain fog (left).
C. Greene *et al.*/*Nature Neuroscience* 2024
But until now, no one knew if this kind of damage persisted long after the initial infection subsided. The team scanned the brains of 32 people, 10 of whom had recovered from COVID-19, and 22 with long COVID. Of those with long COVID, half reported having brain fog.
An injected dye lit up all the participantsâ brains during MRI brain scans. In people recovered from COVID, the dye had trouble crossing the blood brain barrier. Likewise, in long COVID patients without brain fog, the dye mostly stayed put, confined within blood vessels. But in eight of 11 participants with brain fog, the dye tended to escape from blood vessels and enter brain tissue.
âIt was just so clear,â Campbell says. He remembers one of the first people scanned, someone with severe brain fog. Their temporal lobes, brain regions that sit behind the eyes, were âjust flooded with this dye,â he says. The researchersâ work suggests that âbrain fog wasnât just a figment of \[patientsâ\] imagination,â Campbell says. âIt was a very, very real thing that they were reporting.â
The new findings offer an opportunity to think about potential therapies, Nath says. Perhaps researchers can find a way to slow down the blood brain barrierâs breakdown â or reverse it.
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