People who have been infected with COVID-19 may experience loss of smell and taste, headaches, fatigue, dizziness, memory loss, confusion, difficulty focusing, slower processing speeds, and “brain fog.” For some people, these symptoms may clear up with the virus. For others, they may remain indefinitely.

More serious effects have included loss of consciousness, strokes, seizures, encephalopathy, encephalitis, and Guillain-Barre syndrome.

While the loss of taste (hypogeusia) and smell (anosmia) may seem like mild and even humorous symptoms, we must be aware of what it may suggest. Some scientists hypothesize that this is caused by the virus inhibiting olfactory neurons. Others, however, believe it is only olfactory cells in the upper nasal cavity that are being affected.

While COVID-19 is considered a lung infection, it has also been found to cause blood clots, which can lead to severe stroke. This has been experienced by people as young as 30, and by those experiencing few or no other COVID symptoms.

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Cytokines are substances that are released by the immune system and affect other cells. In cases of infection, the immune system releases pro-inflammatory cytokines. These are meant to help fight off infection; however, high levels of cytokines can cause a breakdown in the blood-brain barrier, which normally protects our brain from viruses and bacteria. This collapse can result in seizure or epilepsy. Seizures can cause neurovascular decoupling, which we will discuss below.

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In rare cases, people with no history of mental illness have developed psychosis weeks after contracting COVID-19, even if their other symptoms had been mild. One theory is that their immune system may remain engaged due to small amounts of lingering virus. Another is that some of the neurotoxins released by the immune system can pass through the blood-brain barrier and cause damage to the brain.

Possibly. Autopsies of the brains of COVID-19 patients revealed leakage of small blood vessels in different areas of the brain, as if the patient had suffered mini-strokes. Brain inflammation and mini-strokes may place a person at increased risk of developing Alzheimer’s disease and other dementias.

One study found that the gene ApoE4, which increases the risk for Alzheimer’s disease, can also increase risk of catching COVID-19 and of having a higher severity of infection.

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.

By itself, no. However, having a brain injury may lead to circumstances that do put a person at higher risk, such as living in a long-term care facility.

Yes, COVID-19 can directly or indirectly induce or worsen an acquired brain injury. Much of the damage from a traumatic brain injury is caused by the brain’s inflammatory response. A COVID-19 infection can also cause inflammation in the brain, which can then exacerbate a brain injury*. COVID-19 also impacts neural function and supply of blood and oxygen to neural tissue**.

All of the effects outlined in the above sections can disrupt a person’s recovery from a brain injury and intensify their symptoms.

What’s more, individuals taking medications, such as survivors of traumatic brain injury, may be more at-risk, as their liver is put under more strain to process additional medications.

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No, please continue to take precautions until public health experts advise otherwise. While the vaccines were granted Emergency Use Authorization by the FDA for their ability to prevent illness and death, we do not know yet if the vaccines also prevent an asymptomatic person from spreading the virus to others. Please continue to social distance, mask up, and wash your hands frequently to help protect others who may not be vaccinated.

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