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January 26, 2021

How COVID-19 Affects the Brain

How COVID-19 Affects the Brain

Updated on January 26, 2021 at 3:00pm EST.

After battling COVID-19 for the past year, scientists around the world have learned that this coronavirus doesn’t just attack the lungs.

COVID-19 may involve damage to the heart, the kidneys—and the central nervous system.

In addition to the commonly reported respiratory symptoms among patients, doctors have documented that many people lose their sense of taste or smell. These neurological effects can develop days before a cough, fever or other symptoms set in. And in some cases, these lost senses don’t return immediately after recovery.

Other worrisome neurological symptoms—which are more likely to develop in patients with severe cases of COVID-19—include confusion, headaches, a burning or prickling sensation in the hands, arms, legs, or feet, numbness and seizures.

Scientists are still working to understand how COVID-19 may affect the brain but an April 2020 study published in JAMA Neurology found that more than 36 percent of 214 patients in Wuhan, China, experienced neurologic symptoms during the course of their COVID-19 illness.

How COVID-19 could infiltrate the brain
In general, serious viral infections can affect the central nervous system. This can happen directly if the virus damages the blood-brain barrier—a layer that helps protect the brain from potentially harmful substances in the blood, including germs.

Research on how SARS-CoV-2, in particular, may affect the central nervous system is ongoing but the coronavirus has been found in the brain or cerebrospinal fluid of some patients.

SARS-CoV-2 invades the body with the help of the ACE2 receptor—an enzyme located on the outer surface of cells in the lungs, heart, kidneys and blood vessels. ACE2 receptors are also found in the brain.

Research on the coronavirus that causes severe acute respiratory syndrome (SARS), which is closely related to SARS-CoV-2, found that this infection could also reach the brain. In some cases, this could lead to inflammation.  

Other indirect effects on the brain
Inflammation triggered by the immune system’s response to SARS-CoV-2 can also affect the brain.

For some people, COVID-19 has triggered a dangerous immune system response called a cytokine storm. The infection can lead to inflammation that triggers an overwhelming release of proteins called cytokines.

Normally, cytokines help coordinate the body’s response to infection. But in some cases, this response can range out of control, doing more harm than good. This so-called cytokine storm can damage blood vessels and organs and lead to blood clots, which may lead to brain swelling and strokes.

Patients with severe COVID-19 may also develop respiratory distress, which deprives the body of the oxygen it needs. Brain cells can tolerate low oxygen levels for a short period of time. If this persists, however, brain injury can result.

There is also evidence of brain tissue swelling and some brain cell degeneration in patients who died from COVID-19. It’s still unclear if this could be due to direct infection of the central nervous system or a lack of oxygen.

In general, neuromuscular weakness and dysfunction are also common among patients who are critically ill or admitted to intensive care units (ICUs). This may help account for neurological symptoms among some COVID-19 patients who are hospitalized with severe infections.

Recognize serious warning signs
If you develop symptoms of COVID-19 or believe you may be infected, call your healthcare provider.

These symptoms may include:

  • Fever or chills
  • Wet or dry cough
  • Shortness of breath
  • Fatigue
  • Muscle or body aches
  • Headache
  • New loss of taste or smell
  • Sore throat
  • Congestion or runny nose
  • Nausea or vomiting
  • Diarrhea

Your doctor can advise you on whether or not you should be tested for the disease, how to monitor your symptoms at home and if you need to be hospitalized for more specialized care.

But if you develop more serious warning signs of a stroke or other brain involvement, you should seek immediate medical attention. The Centers for Disease Control and Prevention includes two neurological symptoms among the following list of emergency warning signs of COVID-19:

  • Trouble breathing
  • Persistent pain or pressure in the chest
  • New confusion
  • Inability to wake or stay awake
  • Bluish lips or face

Warning signs of stroke also include:

  • Sudden numbness or weakness of the face, arm or leg, particularly on one side of the body
  • Sudden confusion or trouble speaking
  • Vision loss in one or both eyes
  • Loss of balance or coordination
  • Sudden and severe headache

If you develop any of these warning signs, call 911. If you suspect that you have COVID-19, let the operator know and put on a face mask before help arrives.  

Medically reviewed in May 2020.

Sources:
Wu Y, Xu X, Chen Z, et al. “Nervous system involvement after infection with COVID-19 and other coronaviruses.” Brain, Behavior, and Immunity. March 2020.
Harvard Medical School. “COVID-19 basics.”
Mao L, Jin H, Wang M, et al. “Neurologic Manifestations of Hospitalized Patients With Coronavirus Disease 2019 in Wuhan, China.” JAMA Neurology. Published online April 10, 2020.
Abdul Mannan Baig, Areeba Khaleeq, Usman Ali, and Hira Syeda. “Evidence of the COVID-19 Virus Targeting the CNS: Tissue Distribution, Host–Virus Interaction, and Proposed Neurotropic Mechanisms.” ACS Chemical Neuroscience. March 2020.
Andreas Raabe, Heimo Wissing, Bernhard Zwissler. “Brain Cell Damage and S-100B Increase after Acute Lung Injury.” Anesthesiology. April 2005.
Centers for Disease Control and Prevention. “Symptoms of Coronavirus.”
American Stroke Association. “Learn More Stroke Warnin.g Signs and Symptoms.”

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