When the COVID-19 outbreak was in full swing, primary care physicians reported that an increasing number of virus-infected patients came to the office complaining of attention difficulties and memory loss. These cognitive problems have always been mainly attributed to fatigue.
However, now another hypothesis arises: these symptoms could also be directly related to the presence of the SARS-CoV-2 coronavirus in the central nervous system, that is, the brain and spinal cord.
Coronaviruses can attack various organs
To date, COVID-19 has been primarily associated with breathing difficulties, as the virus primarily affects the lungs. However, some scientific research had already shown that, beyond the respiratory tract, coronaviruses have the ability to spread to other organs, including the brain.
Studies after the severe acute respiratory syndrome (SARS) epidemic in 2003 revealed the presence of viral genomes in the cerebral cortex of patients.
In individuals infected with MERS-CoV, lesions were observed in various brain regions, especially in the frontal and parietal lobes.
However, data on the long-term effects of this family of viruses on the brain, as well as the consequences on cognitive functions, remain incomplete.
To take stock of the available knowledge, we have carried out a study of the bibliography in an article published in the journal Brain Communications . In it, we describe the lines of research that must be followed to better understand the link between the brain, psychiatric and neurological disorders, and coronavirus epidemics.
It is vitally important to focus on this point to improve and strengthen the long-term follow-up of people exposed to SARS-CoV-2 during the pandemic.
The hippocampus, a particularly vulnerable area?
Animal studies show especially the fragility of the hippocampus, an area of the brain that plays an important role in memory and spatial navigation. This vulnerability is not only seen in the context of a coronavirus infection, but also in other respiratory infections. For example, experiments in mice infected with the influenza virus revealed that morphological and functional changes occurred in the hippocampus in these animals. These changes are associated with the deterioration of long-term spatial memory.
In the case of SARS-CoV-2, several questions arise: are these changes observed in the hippocampus of some patients? And, if so, are they a direct consequence of the viral infection? Further studies are needed to find the answers.
It will also be necessary to determine whether these brain changes could accelerate the development of other pathologies, such as Alzheimer’s disease, which is characterized precisely by causing damage to the hippocampus and deterioration of spatial memory.
Ventilated patients are the most affected
Severe acute respiratory syndrome, which occurs in the most severe cases of COVID-19 and requires mechanical ventilation to help patients breathe, is another cause for concern.
In fact, it is known that more than 70% of hospitalized patients whose condition requires mechanical ventilation, due to some respiratory pathology, their cognitive faculties, their ability to concentrate , their memory and their verbal fluency are affected, and this even up to a year after being discharged.
On the other hand, it has been suggested that certain cerebral alterations (especially cerebral atrophy) associated with problems of attention, verbal memory and executive functions (logic, planning, reasoning …) that affect patients with severe acute respiratory syndrome could be due to to a lack of oxygen (hypoxemia) produced before proceeding to ventilation.
Psychiatric disorders of viral origin?
We have also reviewed the scientific literature that studies the relationship between psychiatric illnesses and human coronavirus infections.
A small study, carried out with 40 patients suspected of being infected with MERS-CoV and quarantined for this reason, revealed psychiatric disorders, including psychotic outbreaks and hallucinations in 70.8% of the cases. The fact that, in this research, all patients who suffered from these disorders subsequently tested positive for the virus (compared to suspected cases that tested negative, which did not show cognitive symptoms) points to the existence of a viral mechanism.
As a consequence of the COVID-19 pandemic, of an unprecedented magnitude, an increase in the number of psychiatric disorders in the general population is expected, due to the trauma caused by this period. However, it cannot be ruled out that some of these cases have been caused directly by the viral infection, which would have been responsible for the brain changes, and not by environmental factors such as the climate of anguish in which we have lived for several months .
There is increasing evidence of the ability of the new coronavirus to spread to the central nervous system, and the risk of long-term detrimental consequences for the brain appears to be confirmed. Therefore, it is urgent to strengthen research on this topic. Specifically, larger studies are needed on brain dysfunctions that affect people who have been exposed to previous coronavirus outbreaks.
In the coming months, it will also be necessary to pay special attention to the cognitive manifestations related to SARS-CoV-2 infection: assess their diversity, establish the duration of possible cognitive symptoms in former patients, identify the links between the severity of the disease. infection and the extent of cognitive impairment, etc.
For this, the participation of primary care physicians will be essential. They are the most suitable for monitoring patients and identifying those with long-term cognitive problems.
Karen Ritchie, University of Edinburgh
This article was originally published on The Conversation. Read the original.
