Possible cause of brain fog in Long COVID patients could be related to impaired blood vessels in the brain

Deterioration in the brain may be the cause of memory and concentration issues associated with long COVID.

Researchers have found through MRI scans in patients with brain fog, indications of damaged blood vessels in the brain, according to a study published on February 22 in Nature Neuroscience. A dye, which was injected into the bloodstream of these individuals, was seen leaking into their brain and accumulating in areas that control language, vision, mood, and memory.

The paper's co-author, Matthew Campbell, a geneticist from Ireland's Trinity College Dublin, points out that this is the first time it has been shown that patients with long COVID can have leaky blood brain barriers. Normally, this barrier consists of tightly woven cells lining the blood vessels, acting as a protective guard for the brain.

Any breakdown in this barrier might allow viruses, cells, and other harmful substances transported by blood to infiltrate brain tissues, according to Avindra Nath, a neurologist at the National Institutes of Health in Bethesda, Md. Though it's premature to confirm if this is indeed happening in individuals suffering from long COVID, the study does lend evidence to the view that brain fog has an organic cause. Nath, who was not related to this study, asserts that this is a significant finding to patients, whose symptoms might often be overlooked by physicians.

Brain fog, described by Campbell, can manifest itself as slowed thought processes or problems with remembering recent memories. A common example would be patients forgeting their intended destination while driving. While this example may seem trivial, Campbell explains that it can actually trigger panic in people.

Campbell's research team specializes in consistent head trauma. They are aware that traumatic brain injuries can interfere with the blood-brain barrier and these injuries often result in reports of brain fog. This led the team to consider whether this barrier disruption seen in concussion patients might also apply to long COVID brain fog.

There has been growing evidence of SARS-CoV-2 causing damage to the brain. Findings from animal and cell studies indicate that the virus can erode elements of the blood-brain barrier. Post-mortem examinations of COVID-19 victims have demonstrated barrier failures, according to studies by Nath and his peers.

Until this point, it was uncertain whether this kind of damage continued post initial infection. This study involved brain scans of 32 individuals, 10 of whom had recovered from COVID-19 and 22 still struggling with long COVID. Half of those with long COVID reported experiencing brain fog.

A dye, used for the MRI brain scans, illuminated the brains of all participants. In those who had recovered from COVID, the dye had trouble crossing the blood-brain barrier. Similarly, in long COVID patients without brain fog, the dye was mostly held within the blood vessels. However, in eight out of the 11 participants with brain fog, the dye tended to leave the blood vessels and seep into brain tissue.

Campbell described the situation as "very clear," expressing how a participant with severe brain fog had their temporal lobes, located behind the eyes, heavily filled with dye. This finding implies that patients' reports of brain fog were not imagination but a real and tangible phenomenon.

Nath expressed that these new discoveries have presented an opportunity to explore potential treatments, such as finding a technique to inhibit or reverse the breakdown of the blood-brain barrier.