The COVID19 brain

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Letter by British Rhinological Society and Ear, Nose & Throat UK

Although severe acute respiratory syndrome (SARS) has been the hallmark of severe COVID19 infection, anosmia (lack of smell) and hypogeusia (the reduced ability to taste), headaches/dizziness have also been reported.

Is COVID19 neurotropic?

We don’t have hard data to support/refute this beyond history from those so far infected. Unfortunatley, figuring this out will not be a priority for acute physicians or intensivists as they struggle to keep those most severely affected alive – believe me I have already tried; not to mention the governance issues. It may therefore be up to the scientists to go back to their laboratory and animal models to look at this in more detail.

COVID19 shares similarities with SARS-CoV (the previous coronavirus epidemic from Guandong Province, China, late 2002); they are both zoonotic transmissions, with lungs as the major site of infection, infecting their hosts via the angiotensin converting enzyme – 2 (ACE2) receptor that is found in a number of organs including the brain. SARS-CoV virus or its viral products have been found in the brains of some patients and in experimental models, where the brainstem was primarily involved.

Mice transgenic (genetically modified) for the human ACE2 receptor were extremely susceptible to the infection unlike naive mice, with infection involving the lungs and brain (see Figure below) after intranasal innoculation.

Figure: Viral antigen distribution for SARS-CoV following intranasal innoculation in naive control mice in the brainstem (E,G) and hypothalamus (F,H). From Netland J Virology, Aug 2008 p 7264.

Why does it matter if we know whether COVID19 infects the brain or not? Most of the patients admitted to ICU’s cannot breathe spontaneously, this could all be due to respiratory distress – but, what if this is secondary to primary ventilatory failure due to brainstem or hypothalamic involvement? Knowing this may save more lives, by treating the brain infection concurrently (remember not all anti-viral drugs get into the brain in sufficient quantities to have a treatment effect). It also has implications for patients on immunosuppressants.

We require information on this, fast; if there are people working on this please share your data and ideas as open source.

About the author

Neuro Doc Gnanapavan

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  • One researcher who has a longstanding (decades long) interest in the coronaviruses and their possible role in MS is Dr Pierre Talbot director of the Laboratoire de neuroimmunovirologie at Armand-Frappier Santé Biotechnologie in Laval, Québec, Canada. Why don’t you talk to him?

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