Long COVID changes the brains of people differently to those who recover from the virus, reveals new research.
Up to one in four people infected by the virus develop the debilitating condition now referred to as “long COVID.”
People with long COVID may suffer a range of symptoms – including difficulty concentrating, change in sense of smell or taste, tiredness, joint or muscle pain, shortness of breath and digestive issues.
The symptoms may persist for weeks, months, or – as is only now becoming apparent – years after the initial COVID-19 infection.
But the basis of the condition is poorly understood.
Now German scientists have found that people with long COVID exhibit patterns of changes in the brain that are different from fully recovered COVID-19 patients.
They used diffusion microstructure imaging (DMI), a new MRI technique, to detect the changes.
Study lead author Doctor Alexander Rau, of University Hospital Freiburg, said: “To the best of our knowledge, this is the first study comparing patients with long Covid to both a group without a history of COVID-19 and a group that went through a COVID-19 infection but is subjectively unimpaired.”
He explained that DMI looks at the movement of water molecules in tissues.
By studying how water molecules move in different directions and at various speeds, DMI can provide detailed information on the microstructure of the brain.
Scientists say it can detect even very small changes in the brain, not detectable with conventional MRI.
Dr. Rau and his colleagues compared MRI brain scans of three groups: 89 patients with long COVID, 38 who had contracted COVID-19 but did not report any long-term symptoms, and 46 healthy controls with no history of COVID-19.
The research team first compared the cerebral structure of the three groups to test for atrophy or any other abnormalities.
They then used DMI to gain a deeper insight into the brain.
The three groups were compared to reveal group differences in the brain’s microstructure. DMI parameters were read for the gray matter in the brain.
Whole brain analyses were also used to reveal the spatial distribution of alterations and associations with clinical data, including long Covid symptoms such as fatigue, cognitive impairment or impaired sense of smell.
The results showed no brain volume loss or any other lesions that might explain the symptoms of long COVID.
However, COVID-19 infection induced a “specific pattern” of microstructural changes in various brain regions, and the pattern differed between those who had long COVID and those who did not.
Dr. Rau said: “This study allows for an in vivo insight on the impact of COVID-19 on the brain.
“Here, we noted gray matter alterations in both patients with long COVID and those unimpaired after a Covid-19 infection.
“Interestingly, we not only noted widespread microstructural alterations in patients with long COVID but also in those unimpaired after having contracted COVID-19.”
The findings also revealed a correlation between microstructural changes and symptom-specific brain networks associated with impaired cognition, sense of smell and fatigue.
Dr. Rau added: “Expression of post-COVID symptoms was associated with specific affected cerebral networks, suggesting a pathophysiological basis of this syndrome.”
The researchers hope to reexamine the patients in the future, recording both clinical symptoms and changes to the brain’s microstructure.
But the team said that, despite the new brain imaging findings, it remains “unclear” why some people develop long COVID while others do not, although previous studies have identified risk factors including being female, older age, higher body mass index (BMI) and smoking.
The findings are due to be presented at the annual meeting of the Radiological Society of North America (RSNA) in Chicago.
Produced in association with SWNS Talker
