Canadian study finds brain structural changes in Long COVID patients that are possibly induced by edema or gliosis

Long COVID News: A new study conducted by researchers from various prestigious Canadian institutions has unveiled striking brain structural changes in patients suffering from long COVID. This groundbreaking research provides fresh insights into the lingering effects of COVID-19 on the brain, shedding light on possible causes such as edema or gliosis. The study could pave the way for new treatment approaches and better understanding of the mysterious long COVID condition, which continues to affect millions worldwide.


Tract-based spatial statistics results for long-COVID and normal recovery comparison for mean diffusivity (MD). Green represents the white matter skeleton. Blue voxels represent regions where the long-COVID group had a significantly lower MD than the normal recovery group. LC=long-COVID; NR=normal recovery

The research delved into the neurobiological mechanisms that might be responsible for the symptoms observed in long COVID patients. Long COVID, or post-COVID syndrome, refers to the persistence of symptoms for weeks or months after the acute infection has resolved. Some of these symptoms include brain fog, fatigue, memory problems, and even more serious neurological issues. This Long COVID News report will explore the study’s findings, which focus on changes in brain structure detected through advanced imaging techniques.
 
The Research and Institutions Involved
The study involved 56 participants with long COVID and 35 individuals who had a normal recovery. Researchers from University of British Columbia’s Department of Psychiatry, Department of Medicine, and Department of Radiology, alongside Vancouver General Hospital, collaborated on this extensive project. The team utilized diffusion tensor imaging (DTI), a form of magnetic resonance imaging (MRI), to observe microstructural changes in the brain.
 
By examining these brain scans, the researchers found significant differences in white matter between the two groups. The most notable difference was the lower mean diffusivity in the long COVID group across several regions of the brain. Mean diffusivity is an indicator of water molecule movement in the brain, and changes in this measure can signal potential underlying pathology such as gliosis, a process where glial cells (support cells in the brain) react to injury, or edema, which involves swelling due to fluid accumulation. The study further highlighted how these structural brain changes could explain some of the cognitive difficulties experienced by long COVID patients.
 
Key Findings of the Study
One of the most compelling discoveries in the study was the widespread reduction in mean diffusivity in long COVID patients. This reduction was particularly evident in regions responsible for cognitive and motor functions, such as the internal capsule, corpus callosum, anterior thalamic radiation, and corona radiata. These areas are critical for the brain’s ability to transmit signals and maintain proper function.
 
Interestingly, while structural changes were evident, the study did not find a direct correlation between these brain changes and cognitive performance scores. Particip ants in both the long COVID and normal recovery groups performed similarly on objective cognitive tests. This finding raises the question of whether the cognitive symptoms reported by long COVID patients are more related to functional cognitive disorders, as suggested by the researchers. These functional disorders can occur when individuals perceive cognitive difficulties even in the absence of significant impairments on standardized tests.
 
The authors noted that despite the small effect sizes of the diffusion imaging differences, the findings could be indicative of subtle pathological processes, such as lingering inflammation or mild brain injuries. This could explain why many long COVID patients report ongoing symptoms like brain fog, fatigue, and difficulty concentrating.
 
Potential Mechanisms Behind Brain Changes
The reduction in mean diffusivity observed in long COVID patients may be a result of two key processes: edema and gliosis. Edema refers to the swelling of brain tissues due to fluid accumulation, which can disrupt normal brain function and cause a range of symptoms. Gliosis, on the other hand, is a form of scarring in the brain that occurs in response to injury. Both of these processes can lead to structural changes in the brain and are commonly seen in conditions involving brain inflammation or injury.
 
The study authors suggest that these changes in brain structure could be related to the body’s prolonged inflammatory response to COVID-19. Even after the acute phase of the infection, the body’s immune system may continue to affect the brain, leading to the symptoms observed in long COVID patients. This prolonged inflammatory response may also explain why long COVID symptoms can persist for months after the initial infection has cleared.
 
Further supporting the hypothesis of persistent inflammation, the researchers referenced animal studies and post-mortem human studies that have demonstrated gliosis in individuals who have had COVID-19. Gliosis has been shown to persist long after the virus has been cleared from the body, potentially contributing to the ongoing neurological symptoms experienced by long COVID patients.
 
Implications and Future Directions
The findings of this study offer crucial insights into the long-term effects of COVID-19 on the brain, providing a possible explanation for the neurological and cognitive symptoms reported by many long COVID patients. While more research is needed to fully understand the mechanisms driving these changes, the study’s authors believe that their findings could have significant implications for the treatment and management of long COVID.
 
One important consideration is the potential for these brain changes to be reversible. If the structural alterations are caused by processes like edema or gliosis, treatments aimed at reducing inflammation or promoting brain healing could potentially alleviate some of the symptoms of long COVID. Further studies will be needed to explore these possibilities and determine whether interventions such as anti-inflammatory medications or cognitive rehabilitation therapies could benefit long COVID patients.
 
Moreover, the study highlights the need for continued research into the long-term effects of COVID-19 on the brain. As more people recover from the acute phase of the infection, it is becoming increasingly important to understand the potential long-term consequences of the virus, particularly for those who experience prolonged symptoms.
 
Conclusion
In conclusion, this Canadian study provides compelling evidence that long COVID patients exhibit subtle but significant changes in brain structure, likely caused by edema or gliosis. These structural changes may be responsible for some of the cognitive and neurological symptoms reported by individuals with long COVID, though further research is needed to fully understand the mechanisms behind these changes. The study’s findings underscore the importance of continued investigation into the long-term effects of COVID-19, particularly as the pandemic continues to affect millions of people worldwide.
 
The study findings were published in the peer-reviewed journal: NeuroImage.
https://www.sciencedirect.com/science/article/pii/S1053811924003562
 
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