Searching for signs of COVID-19 infection in the brain
Although COVID-19 is primarily a disease of the lungs, patients often experience neurological problems, including loss of taste and smell, headaches, debilitating fatigue, and “brain fog.” However, it was not known whether the virus responsible for COVID-19, called SARS-CoV-2, is present in the brain and, if so, what type of damage it can cause there.
IRP researchers led by research fellow Myoung Hwa Lee, Ph.D., looked for signs of virus-induced damage in the brains of people who died from COVID-19 by examining magnetic resonance imaging (MRI) scans of their brains and directly examining their brain tissue. The research team found no molecular traces of the virus in the patients’ brains at the time of death, suggesting that the virus may have been cleared from the brain by the immune system and, therefore, was not directly responsible for causing the neurological symptoms experienced by the patients around the time of death. However, the team did find evidence of microscopic blood vessel injuries in some of the patients’ brains, as well as highly active immune system cells around the blood vessels. The researchers also discovered immune cells that appeared to be attacking nerve cells in parts of the nervous system that control the lungs and the sense of smell.
Taken together, these results provide evidence that microscopic blood vessel injuries and a persistent attack on nerve cells by overly activated immune cells may be responsible for the neurological symptoms observed in some patients with COVID-19. The findings also suggest that active COVID-19 virus infection may be rapidly cleared from the brain, which could explain why anti-viral therapies are ineffective late in the course of disease, while anti-inflammatory treatments have provided some degree of relief for some patients.
Lee MH, Perl DP, Nair G, Li W, Maric D, Murray H, Dodd SJ, Koretsky AP, Watts JA, Cheung V, Masliah E, Horkayne-Szakaly I, Jones R, Stram MN, Moncur J, Hefti M, Folkerth RD, Nath A. (2021). Microvascular Injury in the Brains of Patients with Covid-19. N Engl J Med. Feb 4;384(5):481-483. doi:10.1056/NEJMc2033369.