Covid-19's 'striking' impact on brain includes inflammation, blood vessel damage

A Kiwi scientist is helping to unravel the mysteries of how Covid-19 impacts the brain, including how it affects sense of smell.
University of Auckland neuroscientist Dr Helen Murray joined forces with scientists at the United States government research agency National Institute of Health (NIH), to pour over samples of brain tissue from deceased Covid-19 patients.

While Covid-19 is primarily a respiratory disease, estimates show a third of hospitalised patients have neurological symptoms, including dizziness and headache. Stroke may occur in as many as 5 per cent of hospitalised patients, studies suggest.

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Murray, a research fellow at the Centre for Brain Research in Grafton, was surprised by the severity of the changes in brain tissue in Covid-19 patients.

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They looked at brain tissue from patients who died aged 5 to 73, between a few hours and two months after reporting Covid-19. Samples were collected in Iowa and New York City.

Murrays involvement was because of her expertise in dealing with the olfactory bulb: the tiny part of the brain which enables us to smell.

This part of the brain is not routinely collected by brain banks worldwide, but is collected from donor brains in Auckland.

The olfactory bulb is the only part of the brain connected via the nose to the outside world, making it vulnerable to pollutants and viruses.

In the image above, blood vessels are greeny-blue, microglia (immune cells) are magenta and the blood protein fibrinogen is yellow. In the brain tissue of a Covid-19 patient, below, the fibrinogen has leaked out of the blood vessels, and the extra microglia indicate an immune response.

MRI scans taken by the NIH scientists showed spots in the tissue of the olfactory bulb and brain stem in Covid-19 patients that resembled bleeding.

They examined this further by adding fluorescent antibodies to the tissue binding to proteins to show where blood vessels were thinner than normal and where blood proteins had leaked into brain tissue.

Immune cells surrounded the leaks, indicating an inflammatory response typically associated with stroke, neuro-inflammatory diseases such as Alzheimers and Parkinsons, and multiple sclerosis.

Pre-Covid Murray split her time 50/50 between Auckland and NIH in the US, where she previously looked at the role of the olfactory bulb in Alzheimers.

Murray said the findings were striking but more work was needed to find out exactly what was happening in the olfactory bulb and brain stem.

Unable to travel, Murray helped the team from her home in Botany, advising on preparations and examining high-resolution brain scans in microscopic detail.

The amount of inflammation and blood vessel damage was surprising, Murray said.

It was striking. Ive looked at tissue from Alzheimers patients for years now, but I have never seen changes as severe as these in the olfactory bulb, she said.

Murray said she would be very surprised if the changes werent causing an effect, such as contributing to a loss of a smell, but we still don't know.

Abigail Dougherty/Stuff
The Centre for Brain Research at the University of Auckland contains a human brain bank, storing samples of brain tissues from donors. This includes the olfactory bulb, which is not routinely done in most countries, Murray said.

She said its not often scientists can look at brain tissue from a person who had a virus such as Covid-19, and they were looking to get more tissue to drill down into the specifics of what was happening and why.

We want to understand if the inflammation and the leaks from blood vessels are near these structures and contribute to the loss of smell.

Murray said the key take-home from the research is there are clear neurological effects happening to people infected with Covid-19.

It highlighted for us there are some real key changes that need to be paid attention to.

Murray said there is a working theory that Covid-19 patients could have an increased risk of later developing Parkinsons, Alzheimers, multiple sclerosis or stroke.

Following the 1918 Spanish flu pandemic there was an increase in Parkinsons-like encephalitis among those infected, she said.

Given more than 120 million people have contracted Covid-19, these potential knock-on effects were worth paying attention to, she said.


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