Although coronavirus disease 2019 (COVID-19) is known mainly as a respiratory illness, new research suggests the disease may also affect the central nervous system and cause corresponding neurological disorders, including ischemic stroke, encephalitis, encephalopathy, and epileptic seizures.

According to a data review published in Cells, the symptoms of COVID-19-related neurological manifestations may include dizziness, headache, a loss of consciousness, and loss of balance and muscle control. The virus accesses the body by attaching to angiotensin-converting enzyme 2 (ACE2) receptors, which are most often found on cells that line many organs and tissues in the respiratory system.

ACE2 can be found less often on cells in other parts of the body, including the heart, esophagus, kidneys, and bladder. These areas increase the chances of viral infection, including through the central nervous system.

According to the study authors, COVID-19 may enter the central nervous system either through a porous bone in the nasal cavity—causing the loss of smell and/or taste commonly experienced with COVID-19—or through the body’s circulatory system, thus crossing the blood-brain barrier.

“Ordinarily, the blood-brain barrier allows nutrients to reach the brain while protecting it from circulating toxins or pathogens that could cause infections,” said author Chaitali Ghosh, PhD, in a press release. “However, the exact mechanisms underlying COVID-19-associated neurological disorders remain unknown. Such viral infectivity could alter blood-brain barrier function, which may influence disease progression.”

Ghosh said that once in the central nervous system, the virus activates proteins called cytokines and initiates a cytokine storm, which can cause inflammation in the central nervous system and affect blood-brain barrier integrity. Furthermore, although cytokine storms are usually associated with severe COVID-19, Ghosh said less severe disease may also be at risk of cytokine storm.

“Central nervous system disorders can occur in patients who have only mild or moderate COVID disease,” Ghosh said in the press release. “In fact, they can also come about even before the patient has any respiratory symptoms.”

Although the data on long-term consequences of COVID-19-associated neurodegenerative and inflammation-mediated brain diseases are still limited, Ghosh said further research into whether these comorbidities are risk factors for COVID-19 could be critical.

“I am eager to define and learn more about which signaling pathways are linked to which neurological disorders and think this will be an exciting new frontier in COVID-19 research,” Ghosh concluded.

REFERENCE
COVID-19 may also invade the central nervous system, cause neurological illnesses [news release]. EurekAlert; December 10, 2020. https://www.eurekalert.org/pub_releases/2020-12/cc-cma121020.php. Accessed December 14, 2020.