New research from Louisiana State University was presented at Experimental Biology 2021, an annual conference of the American Physiological Society. Findings show that some neurological symptoms—including changes in cognition, mobility, and sensory experiences—could be attributed to the virus’s presence in the brain and spinal cord, known together as the central nervous system, the body system responsible for processing and responding to sensory input. These new findings could inform preventative care and approaches to recovery and treatments, but those who have recovered from the illness could still have a long road ahead. Many who live with “long-haul” neurological symptoms are learning to live with more persistent changes in function and mobility or senses and perception.
How Does COVID-19 Attack the Central Nervous System?
Ricardo Costa, PhD, and Diana Cruz-Topete, PhD, of Louisiana State University have been investigating how COVID-19 enters the central nervous system. There are multiple pathways the virus takes to reach the brain and spinal cord, and their research demonstrates that one route is through the blood-brain barrier—a semi-permeable border that selectively allows nutrients to flow to and from the brain. The blood-brain barrier exists to prevent any pathogens and toxins present in the bloodstream from reaching the brain in order to stop the spread of disease or illness. In the blood-brain barrier, glial cells support homeostasis and take on the role of protecting and defending the brain and neurons. A sub-type of glial cells, astrocytes, are the most abundant glial cells in the central nervous system and the brain. In the respiratory system, the COVID-19 virus grabs hold of a specific protein on the surface of each cell. This research team discovered that brain cells have also this protein, which experts hadn’t previously confirmed. Astrocytes, which defend the blood-brain barrier and neurons from infection, are more resistant to COVID-19 than neurons, the cells which receive sensory input and send messages from the brain to other parts of the body. But it only takes a few infected astrocytes to spread the virus to adjacent neurons. Costa says that astrocytes are infected within a few days of exposure and the team has yet to determine how long it takes for the infection to spread to neurons, but because neurons are more susceptible to infection, the virus is likely to spread more rapidly once it reaches them. Viruses rely on the support of the cells they infect to multiply. Once the neurons and astrocytes are infected, the COVID-19 virus copies the genetic material of the cells, mimicking its physical and chemical components to trick neighboring cells in order to infect them. This continues the spread of infection—the same way the virus replicates in the respiratory system.
What Neurological Symptoms Could COVID-19 Cause?
Neurons play a vital role in the body’s internal communication system. As part of their role defending the blood-brain barrier, astrocytes support neurons by helping to guide messages to their intended targets, supporting communication between neurons, and regulating inflammation in the brain. Each of these processes helps to maintain an optimal environment for neurons to signal and function appropriately.If neurons aren’t functioning appropriately, neurological challenges are likely to arise. For COVID-19 patients, neurological symptoms tend to include muscle aches and pains, headaches, confusion and disorientation, dizziness, and changes in sensory experiences—such as taste or smell. Strokes, changes in movement and motor function as well as perception, and seizures have also been reported, but these experiences are less common. Long-haul or post-COVID-19 conditions are a range of ongoing or regularly returning symptoms—many neurological—that patients experience as a result of COVID-19 infections. According to the Centers for Disease Control (CDC), symptoms are considered part of a post-COVID-19 condition if health problems persist for longer than four weeks following the initial infection.
How Do Patients Know If the Virus Has Reached the Central Nervous System?
Patients should monitor disease progression to look out for neurological symptoms they didn’t have before they were diagnosed with COVID-19. New symptoms are likely linked with infection. Costa says that some people could be at greater risk, explaining, “There are certain conditions, such as multiple sclerosis, where the blood-brain barrier is usually compromised. This, in principle, could make the central nervous system more susceptible to viral infection.” Costa says that it’s unclear how long the virus stays active within the central nervous system, but that the virus may change the way cells behave for a considerable amount of time, causing inflammatory factors that counteract health and harm cells. This could lead to longer recovery times or long-haul experiences. The central nervous system, while at risk, will not always become infected if someone contracts COVID-19. Some neurological symptoms might not even be caused by the infection reaching the brain and spinal cord. Instead, it could be inflammation. If someone who has contracted COVID-19 loses the sense of taste or smell, for instance, it could be because neurons are infected, impacting the way the sensory messages are sent and received t. Or it could be due to systemic inflammation, which impacts the brain without ever infecting it. Currently, more research is needed to know which of these two possible causes is leading to neurological symptoms in individual patients.
How New Findings Impact Prevention and Recovery
Because astrocytes are more resistant to infection, Costa says these cells could play a key role in developing protective measures for the central nervous system. Researchers explain that astrocytes are known to be impacted by other viruses, including HIV, and cautiously explain that this new data is just one preliminary part of the puzzle. It’s still too early to tell how this study will impact the way neurological symptoms can be treated in COVID-19 patients. Experts have yet to determine if it’s more difficult to recover from these neurological symptoms than the respiratory effects of the illness. They note that more evidence is needed to understand the best options for preventative therapies and treatment. For now, Costa explains that some patients respond well to steroid treatment. This group of medications mimic the hormone cortisol to rapidly reduce inflammation during overproduction. Costa says that it’s not clear if current vaccines will help to protect those who encounter the virus from neurological symptoms or prevent the infection from spreading to the central nervous system, but Cruz-Topete hopes that clinical data from ongoing trials will provide more clarity. The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page. It’s also important to also consider the mental health tolls you might encounter as you adjust to your body’s changes. Establish a support network and reach out for help as you navigate your health journey.
