Avipsha Datta, Department of Biophysics, Molecular Biology and Bioinformatics, University of Calcutta
Covid-19 is primarily known to cause respiratory illness, leading to symptoms like cough and breathing difficulties. However, the virus might adversely affect other organs including the heart and brain.
Over the past few months with the increase of the rate of infection, coronavirus patients have reported several neurological symptoms ranging from delirium and confusion to encephalitis and seizures. Loss of smell (anosmia) and taste (hypogeusia), one of the most common symptoms of Covid-19, is due to the malfunctioning of olfactory and taste receptors which is considered to be a neurological symptom. PTSD, anxiety, depression are some of the most prominent after-effects of Covid-19 infection. Many patients have reported these symptoms much later than they are treated for the infections themselves.
How the virus reaches the brain is not known yet for certain. However, several theories have come up to explain the route. Various areas in the brain including the hypothalamus and the cerebral cortex have the ACE2 receptors, the ones which are used by Sars-Cov-2 to infect the cells. The virus may enter the brain through the olfactory bulb or via the GI tract. It might also travel through the vagus or trigeminal nerve or it might reach the brain through the blood circulation as the virus spreads in the body. Autopsy reports of patients from early 2020 suggest that the virus can enter the cerebrospinal fluid which leads to encephalitis.
Till now, the exact causes behind these neurological symptoms remain unknown. A group of researchers at the NYU School of Medicine suggests that the neurological damage is not caused due to the inflammation in the brain or directly by the virus, but rather due to the low oxygen levels in the body associated with Covid-19 infection.
The latest study carried out by them observed 12,900 adults admitted at various NYU Langone centres in the New York City Metropolitan area for a period of 10 days to look for new-onset neurological symptoms.
About 4491 of them were Covid patients, out of whom 666 reported various neurological symptoms like seizures, stroke, encephalopathy, and hypoxic injury 2 days after the onset of symptoms. About 50% of the ones who had neurological symptoms were over 71 years of age, while those without any neurological symptoms had a median age of 63. 66% of the patients with neurological symptoms were men and 35% of all the Covid-19 affected patients with neurological symptoms died.
According to NYU Langone, no cases of brain encephalitis or inflammations were observed in any COVID-19 patients indicating that the virus was not directly affecting the brain tissues. Instead, the damage might be caused due to the low oxygen levels in the body and brain, which was prominent in most critically-ill patients. Low oxygen levels are detrimental to the brain and it leads to confusion, coma, or permanent brain damage. Thus, Covid-19 associated low oxygen levels have more far-reached effects that are yet to be completely understood.
Also read: The stethoscope: A new transmitter of COVID-19?
References:
- COVID-19 may cause neurological injuries, brain damage due to low oxygen levels, finds a new study, https://www.firstpost.com/
- A Prospective Study of Neurologic Disorders in Hospitalized COVID-19 Patients in New York City; DOI: https://doi.org/10.1212/WNL.0000000000010979
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