We don’t know yet if COVID-19 can directly infect brain cells. However, there are many indirect ways that COVID-19 can impact the brain.
Researchers who examined the brains of people who died after contracting COVID-19 determined that many neurological symptoms are likely due to the body’s immune response. Widespread inflammation that the body uses to try to fight the virus (and the associated blood vessel injury) is what may be harming the brain, rather than the brain tissue itself being infected with the virus. Inflammation of the brain is called encephalitis.
Swelling and inflammation can interfere with neurovascular coupling (NVC), which is the connection between brain cells and the blood vessels that supply them. This neurovascular decoupling may be the main cause of lingering symptoms after the virus is gone.
Hypoxic injury, which is caused by a lack of oxygen, has also been found in the brains of those who died from COVID-19. When a virus replicates and proliferates in the lungs, it causes inflammation and issues with gas exchange, which can develop into hypoxia in the central nervous system.
Cytokine storms can occur when the body’s immune system overreacts, and the chemicals meant to fight infection (cytokines) end up causing harm by latching onto and killing healthy brain cells. This can lead to symptoms similar to concussion.
As with any threat, COVID-19 can activate our sympathetic nervous system (flight-or-flight response). Even after the virus is gone, our overactivated nervous system may not relax. This can result in headaches, blood pressure issues, heart palpitations, gastrointestinal issues, light and noise sensitivity, and more.
COVID-19 may cause coagulopathy – the blood’s clotting ability is impaired. One study revealed that COVID-19-related coagulopathy can lead to cerebral venous thrombosis. This is when a blood clot forms in the brain’s venous sinuses, prevents blood from draining out of the brain, and causes blood cells to break and leak blood into the brain tissues, forming a hemorrhage.