Research review looks as COVID-19 impacts on central nervous system
Researchers from Cleveland Clinic's Department of Biomedical Engineering said that infection with the novel coronavirus (COVID-19) may also affect the central nervous system and cause corresponding neurological disorders, including ischemic stroke, encephalitis, encephalopathy, and epileptic seizures, in a recent review published in the journal Cells.
COVID-19 is known primarily as a respiratory disease, with symptoms that include cough, shortness of breath, and, in severe cases, acute respiratory distress syndrome and pneumonia. According to the new review, the symptoms of COVID-19-related neurological manifestations include dizziness, headache, a loss of consciousness and ataxia or loss of balance and muscle control.
The researchers said COVID-19 gains access to the body by attaching to a specific receptor most abundantly found on cells that line many organs and tissues throughout the respiratory system, called the angiotensin-converting enzyme 2 (ACE2) receptor. ACE2 can be found less abundantly on cells in other areas of the body, including the heart, esophagus, kidneys, and bladder, which increases the chances of viral infection, including through the central nervous system.
As reported in the review, COVID-19 may enter the central nervous system either through a porous bone in the nasal cavity, which causes the loss of smell or taste commonly experienced with COVID-19, or through the body's circulatory system, subsequently crossing the blood-brain barrier.
Once in the central nervous system, the virus activates proteins called cytokines (central players in the body's immune response) and initiates a "cytokine storm." This can cause inflammation in the central nervous system and affect blood-brain barrier integrity, according to the review.
What's more, the researchers said, while cytokine storms are usually associated with severe cases of COVID-19, central nervous system disorders can occur in patients who have only mild or moderate COVID disease, and occasionally even before the patient has any respiratory symptoms.
While there is currently limited evidence on long-term consequences of COVID-19-associated neurodegenerative and inflammation-mediated brain diseases, the researchers said investigations into whether these comorbidities are risk factors for COVID-19 would be critical to follow.
“The exact mechanisms underlying COVID-19-associated neurological disorders remain unknown,” Chaitali Ghosh, PhD, co-author of the study, in a statement. "Such viral infectivity could alter blood-brain barrier function, which may influence disease progression. 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.”