Covid-19 and the brain: collateral damage to explore
While primarily infecting the upper respiratory tract, SARS-CoV-2 also attacks other organs. The brain would be part of it, which could explain certain cognitive disorders.
With the Covid-19 epidemic in full swing, general practitioners reported that an increasing number of patients with the virus came to their offices complaining of inattention and memory loss. These cognitive problems have been largely attributed to fatigue.
However, another hypothesis is emerging: These symptoms could also be directly related to the presence of the SARS-CoV-2 coronavirus in the central nervous system, in other words, the brain and spinal cord.
Coronaviruses can attack various organs.
Until now, Covid-19 has been mainly associated with respiratory difficulties, and the virus mainly affects the lungs. However, scientific work has already revealed that beyond the respiratory tract, coronaviruses have the ability to spread to other organs, including the brain.
Studies carried out after the epidemic of severe acute respiratory syndrome (SARS) in 2003 have highlighted the presence of the viral genome in the cerebral cortex of patients. In individuals infected with MERS-CoV, lesions have been observed in various brain regions, especially in the frontal and parietal lobes. However, data on the long-term effects of this virus family on the brain, and the consequences on individuals' cognitive functioning, remain patchy.
Is the seahorse a particularly vulnerable region?
Animal model studies in particular highlight the fragility of the hippocampus, an area of the brain that plays an important role in memory and spatial navigation. This vulnerability is seen not only in the context of a coronavirus infection, but also in the context of other respiratory infections. For example, work in mice infected with the influenza virus has revealed the appearance of morphological and functional changes in the hippocampus in these animals. These are associated with a degradation of long-term spatial memory.
In the case of SARS-CoV-2, several questions arise: Can such changes be observed in the hippocampus of certain patients? If so, are they a direct result of the viral infection? Research is still needed to find the answers.
It will also be necessary to determine if these brain changes could accelerate the development of other pathologies, such as Alzheimer's disease, which is characterized precisely by a deterioration of the hippocampus and a deterioration of spatial memory.
Patients requiring ventilation are more affected
Another source of concern is severe acute respiratory syndrome, which occurs in the most severe cases of Covid-19 and requires the use of mechanical ventilation to aid breathing in patients.
We know that more than 70% of hospitalized patients whose condition requires mechanical ventilation, due to various respiratory pathologies, are affected by cognitive performance, attention span, memory, and language fluency, and this up to a year after discharge. of the hospital.
Furthermore, it has been argued that certain brain disorders (especially brain atrophy) associated with attention problems, verbal memory, and executive functions (logic, planning reasoning, etc.) affect patients with a syndrome. Severe acute respiratory failure could be explained by lack of oxygen (hypoxia) before ventilation.
Viral psychiatric disorders?
A small study, conducted in 40 patients suspected of being infected with MERS-CoV and quarantined for this reason, revealed psychiatric disorders, including psychotic events and hallucinations, in 70.8% of cases. they. All patients suffering from these disorders were later positive for the virus (while suspicious cases with negative results did not show any cognitive signs) suggest the existence of a possible viral mechanism.
After the Covid-19 pandemic, of unprecedented magnitude, an increase in the prevalence of psychiatric disorders in the general population is expected, due to the trauma caused by this period. However, it cannot be excluded that among these cases, some were directly caused by the viral infection, which would have been responsible for the brain changes, rather than environmental factors, such as the anxiety-inducing climate in which we lived for several months.
Data is accumulating on the ability of the new coronavirus to spread to the central nervous system, and the risk of long-term adverse effects on the brain appears to be far from zero. Therefore, it is urgent to consolidate the researchion on this subject. In particular, larger studies are needed, focusing on brain dysfunctions that affect populations that have been exposed to previous coronavirus epidemics.
In the coming months, special attention should also be paid to cognitive manifestations related to SARS-CoV-2 infection: assess its diversity, establish the duration of any cognitive symptoms in previous patients, identify the links between the severity of the infection and the severity of cognitive decline, etc.