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Could brain plaques in long COVID patients explain some of their symptoms

A team of researchers at the Indian Institute of Technology in Delhi have used a type of MRI analysis called ‘susceptibility-weighted imaging’ to uncover brain changes in patients up to six months after they recovered from COVID-19. Results from the study will be presented next week at the annual meeting of the Radiological Society of North America.

The researchers collected data from 46 patients who had COVID-19 in the past six months and 30 people who had never been infected with the virus, and found that the patient group had pathological changes in the small blood vessels in the frontal lobe and brain stem regions. These regions of the brain are involved in higher-order cognitive skills such as language expression and voluntary movements.

What is particularly interesting is that the scientists also found deposits in the brainstem, specifically the right ventral diencephalon region which is associated with many crucial bodily functions, including coordinating with the endocrine system to release hormones, relaying sensory and motor signals to the cerebral cortex, and regulating circadian rhythms (the sleep-wake cycle).

Many other studies have shown that the SARS-CoV-2 virus (which causes COVID-19) can cause pathological changes in other organs such as the heart and lungs, so the brain is not the only site of tissue damage. However, an insult to the brain is likely to be linked with complaints such as memory loss, cognitive decline, and possibly physical and mental fatigue.

Research in brain plaques in other disorders often look for the presence of amyloid plaques, which are collections of misfolded proteins that form in the spaces between nerve cells, with deposits of the amyloid beta protein mainly in the grey matter of the brain.

Scientists also look for neuron degeneration and the presence of specialised cells called microglia and astrocytes (brain immune and repair cells) which are often associated with amyloid plaques. Astrocytes respond to all forms of central-nervous-system (CNS) insults (like infections) through a process referred to as reactive astrogliosis, which has become a pathological hallmark of CNS structural lesions.

These amyloid plaques can develop in the areas of the brain concerned with memory and other cognitive functions, as in Alzheimer’s disease. The scientists in India were looking closely for these same signatures in long COVID, to account for changes in cognitive function. 

Researchers are seeking to understand the exact ways in which the COVID-19 virus causes damage to brain cells. One mechanism may be via inflammation of the small blood vessels in the brain, potentially restricting blood flow, perhaps via micro-clotting of small vessels. Another possibility is damage induced by a heighted immune response.

Research on pathological brain changes in COVID-19 sufferers, lesions in more severe cases and possible plaques in less severe cases will hopefully pave the way for a renewed exploration of brain pathology in ME/CFS patients. ME Research UK is currently funding brain imaging studies in ME/CFS (including in the USA and Australia) and will continue to report on research in this field.

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