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According to estimates, around ten percent of those affected struggle with long-term consequences of corona

Photo: Swen Pförtner / picture alliance / dpa

Doctors have found a physical cause for the so-called brain fog in Long Covid patients.

Accordingly, the viral infection causes a disruption of the blood supply system in the brain.

The blood vessels become more permeable and are less able to protect the brain from pathogens, toxins and other substances in the blood.

This is reported by the research group led by Matthew Campbell from Trinity College Dublin and Colin Doherty from St James's Hospital in Dublin in the specialist magazine "Nature Neuroscience".

"For the first time, we have shown that leaky blood vessels in the human brain, together with a hyperactive immune system, may be the main cause of brain fog associated with Long Covid," explained Campbell.

He and his colleagues had already begun to investigate this form of clouding of consciousness, also known as brain fog, in the initial phase of the corona pandemic in March and April 2020 by analyzing blood samples from 76 Covid patients.

They found increased levels of the protein S100-beta, which is, among other things, a marker for a disturbed blood-brain barrier.

The boundary between the bloodstream and the central nervous system is called the blood-brain barrier.

Thanks to special cells that lie on the outside of the vessel wall, only certain substances can pass into the brain.

This protects the brain from harmful substances and pathogens.

When the blood-brain barrier is disrupted, substances enter the brain that would otherwise be shielded.

The researchers have not yet been able to elucidate the exact mechanism of the weakening of this system.

They also made the disruption of the blood-brain barrier visible using imaging techniques.

To do this, they used a special type of magnetic resonance imaging (MRI), dynamic contrast-based perfusion MRI.

What is measured is the way in which a contrast agent flows through a tissue.

The special MRI images show that in brain fog patients more contrast medium reaches the brain tissue outside the blood capillaries.

Campbell, Doherty and colleagues are convinced that Corona is not the only viral infection that damages the brain in this way.

“The results are now likely to change the way we understand and treat post-viral neurological diseases,” said Doherty.

In recent years it has been shown that in many neurological diseases - such as multiple sclerosis (MS) - a viral infection is probably the triggering factor for the disease, according to a statement from Trinity College.

The study authors are currently examining in more detail what role the blood-brain barrier plays in this.

Since the pandemic, research has been carried out worldwide into the background and forms of treatment for post-Covid diseases.

Post- or Long-Covid refers to longer-term health impairments following a corona infection that extend beyond the acute phase of the illness of four weeks.

The frequency of Long Covid is difficult to measure.

According to estimates, around ten percent of those affected have to struggle with long-term consequences of corona.