This is how the brain changes when the smell is lost through COVID-19

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This is the story of a 25 year old Italian radiologist who One day he lost his sense of smell. Nothing unusual for someone who had a cold in March. Cold, the symptoms of which lasted barely a day.

However, the data from Germany made him suspicious: they discovered some mild COVID-19 patients who had lost their sense of smell and taste (anosmia and dysgusia).

He decided to have an X-ray. After all, he would be able to interpret it almost immediately. And found no strange sign no signs of pneumonia bilateral, characteristic of new coronavirus infections. There was also nothing unusual to see in a fibroscopy of a nasal specimen.

But since he had it on hand, he did an MRI of the brain in 2D and 3D. And then the surprise jumped. Something was going on in the olfactory bulb. A significant change in the cortex it revealed that an infection could happen.

Immediately a PCR that was positive. With no more symptoms than loss of smell, our protagonist had a viral load in the throat and was possibly contagious.

“To the best of our knowledge, this is the first report of in vivo human brain involvement in a COVID-19 patient that shows a change that is compatible with the brain viral invasion into a cortical region that is associated with odor,” explains the doctors. Letterio S. Politi, Ettore Salsano and Marco Grimaldi, authors of an article in JAMA Neurology reviewing the radiologist’s case.

This opens the way to the hypothesis that the loss of smell characteristic of COVID-19 is not necessarily due to blockage of the nasal passages by the mucous membrane or the destruction of cells in the pituitary gland. Rather, there is one direct virus involvement in the brain.

Coronavirus Pathways to the Brain

“SARS-CoV-2 could enter the brain via the olfactory pathway and cause sensorineural dysfunction,” they point out, although they acknowledge that “pathology and CSF studies are required to confirm this hypothesis. »

These are the possible entry points of the virus thanks to its protein S (its “spikes”), which can open the ACE2 barrier of some cells M. V., Politi et al.

Could it be that the patient’s case was confused with another pathology in parallel with COVID-19? Alternative diagnoses (epileptic status, posterior reversible encephalopathy syndrome, encephalitis of a receptor type …) are unlikely given the clinical context, the authors of the study affirmed.

Of course, this does not mean that this change occurs every time the COVID-19 is developed. They looked into other patients’ brains and found nothing. It may be that Resonance too late, up to 12 days after symptoms appear.

The radiologist’s brain had returned normal 28 days later the first response. Just like the sense of smell. “The disappearance of cortical anomalies from the MRI in the follow-up study suggests that imaging changes in COVID-19 are not always present or may be limited to the very early stages of the infection,” the doctors believe.

Of course, they emphasize the importance of considering odor loss as a characteristic feature of this disease, although it is not uncommon to lose it even when you catch a cold. Although the physical causes of anosmia are completely different.

A virus beyond the lungs

There is growing evidence that the SARS-CoV-2 coronavirus may nest in non-respiratory organs. Although its typical manifestation is widespread in the throat and lungs, it has been found in samples from the kidneys, heart, brain and blood vessels.

COVID-19 is a disease that may be as serious as bilateral pneumonia, but sometimes leads to an overreaction in the immune system. Less specialized defenses attack healthy cells and cause the call Cytokine storm, which in the end is worse than the effects of the virus itself.

However, changes in relative frequency in organs where the virus multiplied have been documented, destroying cells just to be able to multiply using its chemical compounds.

In the case of neurological manifestations, a group of researchers from Yale University (USA) compiled the available evidence in JAMA:

Viral neuroinvasion can be achieved in a number of ways, including transsynaptic transfer (connections) of infected neurons, entry through the olfactory nerve, infection of the vascular endothelium (internal coverage) or migration of leukocytes through the blood-brain barrier (blood from the Brain), ”they point out.

The most common neurological complaints with COVID-19 are anosmia, ageusia and headache. However, other diseases such as accidents have also been reported. cerebrovascular, impaired consciousness, seizures and encephalopathy.


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