One year after the start of the COVID-19 pandemic , we are getting closer to understanding the complexities of this disease. Despite being a respiratory disease, the neurological symptoms that have emerged in COVID-19 patients initially puzzled doctors.
The neurological symptoms most commonly associated with COVID-19 are headaches, loss of smell, confusion, and dizziness. In more severe cases of the disease, neurological complications can include heart attacks, encephalitis or severe inflammation of the brain, and the development of neurological conditions.
Beyond these severe symptoms, studies have found that infection with the virus that causes COVID-19 can impact brain aging. A study conducted by Imperial College London, which has not yet been peer-reviewed, looked at the cognitive functioning of around 85,000 recovered COVID-19 patients. The preliminary study, which uses cognitive tests like word association, found that compared to people who did not have COVID-19, these patients suffered from cognitive deficits equivalent to aging 10 years.
These tests of functioning seek to identify the different aspects of cognition that could be affected, such as being able to solve problems, direct attention, and learn new things. Studies have begun to elucidate what aspects COVID-19 affects. For example, according to a study carried out in China with 29 recovered patients, they have problems maintaining care. This indicates that infection with SARS-CoV-2 can lead to long-term mental and neurological health consequences, months and possibly years after patients recover. More research on these chronic effects will have to focus on identifying which aspects of cognition are most affected.
Many studies have sought to shed light on the cause of these detrimental effects on the brain. In some cases, the virus has been found in the brains of COVID-19 patients, however, it is an unusual occurrence. This is because the brain is not particularly vulnerable to infection by the virus. Studies have revealed that neurons in the brain probably do not express the receptors necessary for the virus that causes COVID-19 to infect them.
In addition to direct infection of neurons, there are other processes by which the virus can affect the brain, including inflammation, through viral proteins that damage brain cells and damage to vascular structures in the brain.
For example, a study at the University of Washington found that certain proteins in the virus can cross the barrier that protects the brain from the rest of the body’s circulation, called the blood-brain barrier.
Another study published recently in the New England Journal of Medicine found those blood vessels that are part of the nervous system could be damaged. Using techniques to view tissue, the researchers saw that the blood vessels were thinner than usual and that there were areas of bleeding in patients who had died of COVID-19. They also found that these areas were surrounded by cells of the immune system, pointing to a possible connection between vascular problems and inflammation. Importantly, these damages were seen without the presence of viruses. This indicates that the brain had vascular lesions that possibly contribute to neurological symptoms.
Most of the evidence seems to indicate that direct invasion of the virus into the brain is uncommon and that the neurological and psychiatric symptoms observed are due to side effects of SARS-CoV-2 infection. Among these, it is important to highlight inflammation and vascular damage as possibly key factors in the pathology of COVID-19 and its effects on the brain. Further studies will seek to identify how these processes could be working together to result in neurological problems in COVID-19 patients.
* The author is a doctoral student in neuroscience at the University of Pennsylvania and a member of Ciencia Puerto Rico.
For article’s original version (Spanish), click here.
López, C. (January 13, 2021). COVID-19 y su impacto en el cerebro. Es Mental . https://www.esmental.com/covid-19-y-su-impacto-en-el-cerebro/
López, C. (2020). About me: Claudia López Lloreda.. Science Writer & Neuroscientist. https://www.claudialopezlloreda.com/about-me