COVID-19 is getting on our nerves

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Since its sudden emergence into our lives in late 2019, the SARS-CoV-2 virus has been extensively studied; yet, its effect on the nervous systems of young adults is still unclear. Typically, COVID-19 is thought to affect our cardiovascular health. However, more and more studies point to brain involvement. A new study by Stute et al. (2021) found that healthy, young adults diagnosed with COVID-19 may have problems with their nervous system, and particularly, with their fight-or-flight response, compared to healthy adults who were not infected with the virus.

How did they test this?
To test subjects’ nervous system activity, the researchers used an imaging technique called microneurography, which involves inserting a needle with a specialised electrode into a nerve located in the knee region. Once inserted, the electrode can record the nerve’s electrical impulses, whilst also measuring its electrical activity and strength. The researchers employed this technique in young adults 3-8 weeks after their COVID-19 positive diagnosis. The needle was placed in their knee region, after which, patients were asked to undergo a variety of tests to evaluate their nerve activity and their fight-or-flight response (this included where they had patients place their hand in an ice cold water bath for several minutes). Meanwhile, the electrode is picking up on the nerve’s impulses and monitoring them. Following this cold ice bath test, patients were asked to rate their pain on a scale of 1-10. 

What did they find?
The researchers found that in contrast to healthy adults without COVID-19, young COVID-19 patients exhibited higher nerve activity during resting periods, while standing up and during the ice bath test. This was also accompanied by an increased heart rate, when compared to healthy controls. Furthermore, COVID-19 patients reported less pain following the ice bath test. This may suggest that the COVID-19 virus not only disrupts nervous system activity, but could also have lasting effects on the fight-or-flight response and pain perception following recovery, despite being otherwise healthy and experiencing mild symptoms.

How is COVID-19 affecting our nervous system?
It is presumed to be due to the potentially fatal inflammatory cytokine storm, that is associated with COVID-19. However, even in milder and non life-threatening cases, inflammatory cytokine storms can cause an increase in inflammatory biomarkers. These biomarkers can then cross the blood brain barrier and alter the sympathetic nervous system; the system responsible for the fight-or-flight response.

While the pandemic has devastatingly resulted in over two million deaths worldwide, it is important to remember the virus may also affect the tens of millions that have survived it. Understanding what happens to our nervous system following a COVID-19 diagnosis is a crucial step towards understanding the lasting consequences of the disease.

Study: Stute, N. L., Stickford, J. L., Province, V. M., Augenreich, M. A., Ratchford, S. M., & Stickford, A. (2021). COVID-19 is getting on our nerves: Sympathetic neural activity and hemodynamics in young adults recovering from SARS-CoV-2. The Journal of physiology, 10.1113/JP281888. Advance online publication.

Featured image: Science Photo Library – PASIEKA/Getty Images

Edited by Malavika.

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