What effect does covid have on our brain? This is the question that scientists have been asking themselves since the start of the epidemic in the face of the neurological symptoms that patients report.
Loss of consciousness, confusion, encephalitis, Guillain-Barré syndrome and even cerebrovascular accidents (stroke) have thus been recorded.

Infectious or neurological cause?

Not all neurological symptoms indicate damage to the nervous system by the virus“temper infectiologist Pierre Tattevin and neurologist Elodie Meppiel in an article they sign on the site The Conversation. For them, the headaches and dizziness often described in patients make “part of the flu-like syndrome associated with coronavirus infection“.

Likewise, extremely frequent anosmia (loss of smell) is more likely to be linked to inflammation of the olfactory tissues than to neurological damage.

On the other hand, the more severe symptoms such as confusion, strokes, encephalitis and the occurrence of Guillain-Barré syndrome reflect damage to the nervous system by the virus.

Read also: Brain: when covid attacks the nervous system

The virus infects neurons well

A lead confirmed by an international study involving the brain institute (Inserm) published on January 12 in the Journal of Experimental Medicine. This validates the hypothesis that SARS-CoV-2 is attracted to brain cells, that it is able to infect them and multiply there, as with any other target cell. The route of entry of the virus into neurons would be, as for other cells, the ACE2 receptor located on their surface.

But researchers do not yet know the path that the virus takes to reach the brain, knowing that it is protected by a blood-brain barrier. According to a German study published in November 2020 in Nature neuroscience, the most likely lead is that of a passage of the virus via the olfactory mucosa and the olfactory bulbs.

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Explain the symptoms

While waiting to confirm this hypothesis, the results of the Inserm study suggest that the brain damage is indeed the cause of the neurological symptoms observed in covid patients.

And that’s not all: researchers also observe a “significant remodeling of the cerebrovascular network in infected regions of the brain“in mice, details a Inserm press release. It remains to be understood how these changes are linked to the neurological symptoms observed.

The fear of long-term sequelae

And in the long term, what are the risks? It is for the moment the greatest unknown, to which NeuroCOVID, the French register of events associated with covid is trying to respond in the coming months.

The main fear is of course the occurrence of “long-term neurological sequelae“, note Professor Tattevin and Doctor Meppiel. In October 2020, already, the Director General ofWorld Health Organization (WHO) Tedros Adhanom Ghebreyesus warned: “For a significant number of people, this virus causes a series of serious, long-term effects “, including neurological effects.

Here again, current research should provide more information. A small study1 French published in the Journal of Infection December 4, 2020 already provides some answers. According to this publication, 54% of former covid patients presented with persistent symptoms. And for 77% of them, it was neurological symptoms. Results which will need to be confirmed in larger studies but which already confirm the possibility of a long-term neurological risk.

1 The study only involved 70 patients cured of covid-19, six of whom had been hospitalized.