What causes a person to have long-term sequelae due to COVID-19, while another will show nothing but mild flu-like symptoms for a few days? What are the consequences on our body of this viral infection? Researchers provide an overview of current data and global public health issues, focusing in particular on post-COVID neurological symptoms.
COVID-19 is described as an acute respiratory syndrome manifested by symptoms more or less typical of a bad flu (cough, fever, fatigue, sore throat, etc.), often associated with various neurological symptoms ranging from taste and smell, fatigue, pain, headaches, up to psychological effects such as depression or psychosis.
Our brain on the front line
However, not all individuals are equal in the face of this virus, which can affect some people more severely, either in a brutal and intense manifestation, or in a form commonly called “long Covid”, persisting for months or even years after infection. , with a constellation of neuropsychiatric symptoms.
This is what Avindra Nath, clinical director of the National Institute of Neurological Disorders and Stroke (NINDS) and Serena Spudich, of Yale School of Medicine in Connecticut, have looked into, publishing a study on the state of knowledge and understanding of symptoms affecting the nervous system in particular. In particular, they compare the symptoms of long Covid to those of patients suffering from chronic fatigue or having contracted Lyme disease.
Like any severe disease with respiratory and metabolic disorders, patients may experience a long recovery time with headaches, difficulty concentrating and general weakness. However, strokes have been reported, as well as specific damage to cerebral and neural tissues, ie tissues that make up our nervous system.
These neurological conditions lead us to believe that the virus manages to penetrate the brain and the nervous system, like viral encephalitis. Small aside: viral encephalitis is an inflammation of the cerebral tissues of the brain caused by a virus, leading among other things to more or less serious motor problems that can induce death by respiratory arrest in the most severe cases. However, as the authors point out, analyzes of brain tissue and cerebrospinal fluid (to find out what is hidden in the brain…) of patients infected with SARS-CoV-2 and who died could not demonstrate the presence in large number of viral molecules.
However, this coronavirus causes neuro-inflammation and aberrant neuro-immune responses. This could be explained by the fact that neurological conditions do not all appear at the same time, those affecting the brain are the first, then those affecting the rest of the nervous system (in short everything that controls our body: muscles , organs, processing of visual/olfactory/sensory/auditory data).
Thus, the viral infection could start with a transient infection of the brain very early, facilitating traffic in the nervous system. That is to say that the molecules mediating inflammation and navigating in the vascular system (the blood and the canvas of the vessels) for example will be able to venture into various cerebral and nervous regions, without there being a customs, shall we say. ” It is plausible that subtle forms of generalized vascular dysfunction, including thrombotic microangiopathy (microscopic blood clots) in the brain, may lead to neurological symptoms even in the absence of clinically apparent stroke ».
A real public health issue
What is particularly worrying is the fact that long-term conditions affect people under the age of 50 who have contracted COVID-19 in a mild way, without medical history, with a very healthy lifestyle.
Some of the symptoms are similar to myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), but also to Lyme disease (an infection caused by a tick bite). The various studies concerning the long Covid will be beneficial to research concerning these diseases, because no effective treatment yet exists for them.
However, at present, there is no data to conclude on the mechanism leading to these symptoms, the neurological analyzes of the patients being incomplete or even absent. There is an urgent need to fill these gaps, as there is a “possibility that the infection could accelerate or trigger the future development of neurodegenerative diseases such as Alzheimer’s or Parkinson’s disease”, the authors state. In the case of children, the consequences on their development are still not clearly determined, even if the conditions are benign, some present a multisystem inflammatory syndrome (MIS-C) with serious neurological consequences.
The conclusion of the study is clear, the search for the causes and mechanisms linked to infection by SARS-CoV-2 is a real public health issue, due to the neurological consequences that can lead to the disruption of our immune system. and vascular more or less permanently.
These results, and those of other similar research, will make it possible to develop tools to identify people at risk of neurological complications, but also to reduce or reverse the effects of COVID-19 on the nervous system, from which many now suffer. of people around the world. This is what is trying to do RECOVER, an unprecedented research initiative of the National Institutes of Health (NIH) in the United States.