Emerging new data has confirmed a year-old suspicion that the Covid-19 infection causes neurological disorders. This view first emerged in the summer of last year, during the first wave of the pandemic. Now, it is pretty much confirmed, according to a preprint (yet to be peer-reviewed) paper of four scientists of the Imperial College, London.

The first inkling of the neurological manifestations of the infection arose back in March 2020, when a 56-year-old patient in Beijing was diagnosed with viral encephalitis, suggesting that the SARS-CoV-2 virus could potentially invade the central nervous system. Subsequently, the virus has also been observed in the endothelial cells that line the inner surfaces of blood vessels. (The patient died.)

The preprint — authored by Jiabin Tang, Shivani Patel, Steve Gentleman and Paul M Matthew — outlines a “potential route” for the virus to get into the neural system. The brain, a special organ, is protected by the rest of the body by the ‘blood-brain barrier’ or BBB — a semi-permeable lining of endothelial cells. When the SARS-CoV-2 enters the bloodstream, monocytes, a kind of white blood cells, get activated as part of the body’s defence mechanism. A complex mechanism gets triggered to allow the monocytes to cross the BBB. “This eases the passage of the infected and activated monocytes into the central nervous system, and the SARS-CoV-2 virus is then able to pass through the loosened BBB,” the paper says.

“With higher case numbers, a range of neurological symptoms are becoming apparent,” it notes. The authors speculate that sustained systemic immune activation due to the infection could cause “secondary auto-immune activation in the central nervous system”.

Higher risk profile

The authors say that patients with chronic neurological diseases could be at a higher risk and express concern about a pandemic of neurodegenerative disease.

In an emailed response to a query from Quantum , Matthew observed that “new data has confirmed a wide range of neurological manifestations of Covid-19 and the long Covid syndrome, following the acute infection in some people”.

He further notes that “the causes for these are still not well understood” and “further studies of brains from people with Covid-19 are underway and we await their results”.

The paper draws a parallel between the previous SARS and MERS pandemics and the current one, and observes that even in the previous outbreaks the viral infection had been reported to contribute to brain disorders like encephalopathy, dementia, neuropathy and psychosis.

“Because of the nature of chronic diseases, the symptoms may appear years after patients have recovered from viral infection, which makes it easy to overlook the connection,” it says. Patients with diabetes appear predisposed to Alzheimer’s disease. Also, the rate of central nervous system disorders is “concordant with the respiratory problem status”.

On the positive side, the paper notes that the drug memantine, commonly used for Alzheimer’s disease, “appears to have antiviral potential against SARS-CoV-2, indicating the connection of the underlying mechanisms between Covid-19 and AD”. It is also necessary to know whether any neurological symptom is due to the virus or the secondary immune response, “since the treatment scenarios could be completely different”.

The paper calls for attention to the relationship between Covid-19 and neurodegenerative diseases for two main reasons: One, SARS-CoV-2 infection may cause neuroinflammation, which, in turn, may hasten the progression of some neurodegenerative disorders; and, two, as neurodegenerative patients cannot take care of themselves, the quarantine itself may have negative consequences for the cognition and function, potentially contributing to their vulnerability to SARS-CoV-2 infection.

Psychiatric complications

“Doctors should be aware of neurological and psychiatric complications of Covid-19 in the acute and chronic phases,” Matthew said in his email. However, he adds, “we are not aware of specific treatments for neuro-Covid.”

Dr Sridhar Nagaiyan, who treats Covid-19 patients at the Kauvery Hospital, Chennai, is in agreement with the paper. “Yes, we have seen encephalitis, neuropathy, strokes, etc (in Covid-19 patients),” he told Quantum .