COVID-19 infection impacts brain's grey cells, affects memory, cognition, smell and taste functions: UK Study - Times Now

Brain scan (Representative images)&nbsp | &nbspPhoto Credit:&nbspiStock Images

Key Highlights

• A study carried out by a UK university using before-after images of brain scans of COVID-19 recovered patients has made a stunning discovery.

• Though patients recover from SARS-CoV-2 infection, the imprint of several key organs stays.

• The study finds that there is strong evidence for brain-related pathologies in COVID-19, some of which could be a consequence of viral neurotropism. 

A study in the UK looked into the long-term impact of the novel coronavirus infection on the human brain, post-recovery - and has made some stunning findings. Patients who had recovered from mild or moderate SARS-CoV-2 infection were seen to have suffered some loss of grey matter in the areas that govern cognitive skills, memory-making, sensory functions like smell and taste.

The study and its findings are yet to be peer-reviewed. This means the journal’s editors are yet to take advice from various experts—called “referees”—who have assessed the paper and may identify weaknesses in its assumptions, methods, and conclusions. While the peer-review is awaited or in progress (a process that can be lengthy), authors use the medRxiv service to make their manuscripts available as “preprints” before certification by peer review.

How was the study conducted?

1. UK Biobank scanned over 40,000 participants before the start of the COVID-19 pandemic, making it possible to invite back in 2021 hundreds of previously imaged participants for a second imaging visit. 
2. With that in mind, they studied the effects of the disease in the brain using multimodal data from 782 participants from the UK Biobank COVID-19 re-imaging study, with 394 participants having tested positive for SARS-CoV-2 infection between their two scans. 
3. They used structural and functional brain scans from before and after infection, to compare longitudinal brain changes between these 394 COVID-19 patients and 388 controls who were matched for age, sex, ethnicity and interval between scans. 

Researchers involved in this study say that the vast majority of brain imaging studies so far have focused on qualitative, gross pathology of moderate to severe cases, often carried out on hospitalised patients. It remains unknown however whether the impact of COVID-19 can be detected in milder cases, in a quantitative and automated manner, and whether this can reveal a possible mechanism for the spread of the disease. 

What did they find?

1. The study team identified significant effects of COVID-19 in the brain with a loss of grey matter in the left parahippocampal gyrus, the left lateral orbitofrontal cortex and the left insula. 
2. The findings consistently relate to a loss of grey matter in limbic cortical areas directly linked to the primary olfactory and gustatory system. Unlike in post hoc disease studies, the availability of pre-infection imaging data helps avoid the danger of pre-existing risk factors or clinical conditions being misinterpreted as disease effects. 

"Since a possible entry point of the virus to the central nervous system might be via the olfactory mucosa and the olfactory bulb, these brain imaging results might be the in vivo hallmark of the spread of the disease (or the virus itself) via olfactory and gustatory pathways," said the study authors.

Medical experts in the US carried out brain studies on deceased COVID patients in 2020, says a report in the Washington Post.

No virus enters the brain, yet an untold amount of damage occurs:
Although there wasn’t much virus to be found, the brains of people killed by the coronavirus weren’t unscathed. The Columbia researchers, looking at thin slices of brain tissue under microscopes, found two main types of problems in patients who died of covid. First were infarctions, dead tissue surrounding blocked blood vessels, found in the brain’s grey matter. Without oxygen, the tissue dies. The second issue, appearing in the brainstem, cerebellum and other areas, involved swarms of immune cells. Those cells often converged around dead or dying neurons. “They’re actually attacking and eating the neurons,” one of the study authors told Washington Post.

In this article in the Washington Post by its Science Reporter Ben Guarino, Joanna Hellmuth, a cognitive neurologist at the UCSF Memory and Aging Center, tells him that previously healthy young adults tell her that after even a mild case of covid they have found their brain function slipping. None of these was previously diagnosed with depression or another psychiatric problem. 

Hellmuth rues lack of intensive research by medical authorities in the years between earlier large scale outbreaks. “In SARS and MERS, there were neurological issues,” she said, referring to outbreaks in 2003 and 2013 involving diseases caused by other coronaviruses.

“We didn’t come into this pandemic with a good understanding of the neurological issues of coronaviruses.” Hellmuth hints that unless more research is done this time around, clinicians will be ill-prepared when the next pandemic hits.

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COVID-19 infection impacts brain's grey cells, affects memory, cognition, smell and taste functions: UK Study - Times Now
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