Over the months since the beginning of the pandemic, several recovering patients’ data had been complaining of neuronal affections after being infected by the Covid-19 virus. All around the world, reports neurologic and psychiatric disorders going from headaches, memory problems, to rare psychosis and even encephalitis (which is an inflammation of the cerebral tissue).

• 1/3 of patients were left with neurological or psychiatric disorders 6 months following infection

An American study, published in The Lancet Psychiatry followed a large cohort of 236 379 patients recovering from Covid-19 patients and measured the incidence of 14 neurological and psychological impairments. The study revealed that 34% of patients presented diagnostics for neurological or psychological disorders 6 months after infection. Amongst the diagnosed, 13% were receiving their first diagnostic of the sort. The most represented disorders were anxiety (17%), and mood disorders (14%) followed by disorders incident to the use of psychoactives (7%) and insomnia (5%). However, there was a decreased incidence for neurological disorders such as strokes, cerebral hemorrhage, and dementia though they were more frequent in more severe forms of Covid-19. This risk of developing neurologic or psychiatric disorders was reported as being 44% higher in patients infected with Covid-19 compared to the regular flu.

• The virus enters the brain through the olfactive nerve

A Dutch team at Erasmus MC hospital, Rotterdam, recently published a study investigating the origins of the neurologic and psychologic complications due to Covid-19. The study published in mSphere exposes that the virus propagates to a limited number of cells in the brain but this minimal infection generates a response from “cytokines”, the immune cells responsible for local inflammation.

Dr. Debby van Riel, a virologist at Erasmus MC hospital, emphasized that severe encephalitis due to the uncontrolled propagation of the SARS-CoV-2 virus was rarely observed. “Nevertheless, SARS-CoV-2 can potentially enter the brain through the olfactive nerve and locally infect cells, leading to an inflammatory response, undoubtedly contributing to neurological disorders” Dr. van Riel continued.

As more and more data are pointing at the implication of the olfactory nerve to facilitate the virus entry in the brain, the underlying mechanisms involved in the inflammatory process remain unclear.

• More research is needed on the role of the immune system and covid-related disorders

The study doesn’t give a clear insight into the role of the immune system in the process. Researchers used induced pluripotent stem cells (iPSC) to model neuronal cells in the laboratory. These cells were only cultured for a short time frame and only limited neuronal cell types were generated from the IPSCs. Dr. Femke de Vrij from the psychiatry department of the Erasmus hospital believes more studies are necessary to determine the short and long-term effects of a viral infection on the different brain structures.

Questions: Have you ever experienced neurologic problems while recovering from Covid-19? Which symptoms did you experience?

All in all, don’t forget the protective measures to prevent Covid-19 from spreading: practice social distancing, wash your hands regularly, cough or sneeze in your elbow, use disposable tissues, wear a facemask in public.

Keep safe and remember, this too shall come to pass.

Source: 6-month neurological and psychiatric outcomes in 236 379 survivors of COVID-19: a retrospective cohort study using electronic health records. Taquet et al., Lancet Psychiatry, Avril 2021.

Replication kinetics, cell tropism, and associated immune responses in SARS-CoV-2 and H5N1 Virus-infected Human induced pluripotent stem cell-derived neural models. Bauer et al., mSphere, June 2021

Photo credit: lemonde.fr