Neurological Manifestations of Covid-19

SARS-Cov-2, commonly known as COVID-19, is a type of positive, single-stranded RNA coronavirus that has rapidly taken over the world, infecting millions of people and resulting in an increasingly large number of deaths (Ciotti et al., 2019). Cases of COVID-19 were first detected in Wuhan, China and were initially labelled as pneumonia without any identifiable cause, until an inoculation revealed that the disease was, in fact, a novel coronavirus (Ciotti et al., 2019). Unsurprisingly, discussion regarding COVID-19 has often revolved around its effect on the respiratory system, for it is typically associated with symptoms such as a cough, difficulty breathing, pneumonia, and fever (Ciotti et al., 2019).

Image: World Health Organization

Although the general public is largely familiar with COVID-19’s respiratory effects, there remains a lack of awareness about its neurological manifestations. These are not only rarer than the aforementioned symptoms, but they have also just begun to gain recognition by clinicians and the scientific community. Recently published literature showed that neurological symptoms were identified in 42.2% of studied COVID-19 patients; that number rose to 62.7% for hospitalized individuals (Liotta et al., 2020). More importantly, it has been noted that 82.3% of people infected with COVID-19 experience neurological complications at some point while infected with the disease (Liotta et al., 2020).

Image: The American Journal of Emergency Medicine

A rapid review that examined COVID-19 patients reported that 93 out of 901 individuals had encephalitis, a type of inflammation in the brain (Ellul et al., 2020). Additionally, 19 patients were found to have Guillain-Barre Syndrome, a disease in which an individual’s nerves are attacked by their immune system (Ellul et al., 2020). Among other frequently identified complications are agnosia—the inability to recognize sound, places, faces or objects—and ageusia—the inability to taste (Ellul et al., 2020). Common neurological manifestations also include headaches, dysgeusia, encephalopathy, anosmia, dizziness, and myalgias (Liotta et al., 2020). Moreover, a small proportion of patients have also reportedly experienced deficits in sensory and motor functioning, strokes, seizures, movement disorders, and ataxia (Liotta et al., 2020). Individuals that are younger in age and experienced especially severe cases of COVID-19 were more likely to develop neurological symptoms, and those with encephalopathy had greater mortality (Liotta et al., 2020).

The COVID-19 virus is speculated to enter the nervous system through many different pathways: invasion through the olfactory nerve, migration of white blood cells across the blood-brain barrier, transsynaptic movement from one affected neuron to another, and vascular endothelium infection (Zubair et al., 2020). In fact, the virus has even been detected inside the cerebrospinal fluid in certain patients (Ellul et al., 2020). The virus may damage the nervous system by directly attacking certain receptors, causing secondary hypoxia (a lack of oxygen in the brain), or damaging cytokines and their signalling pathways (Bridwall et al., 2020). Damage to the nervous system may also come about as a result of retrograde transport or the movement of substances to the cell body from the axon terminals (Bridwall et al., 2020).

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Despite the evidence pointing towards the neurological manifestations of COVID-19, our knowledge of this domain is relatively new and, thus, limited. An improved understanding of neurological symptoms is essential in order for us to provide more effective treatment to COVID-19 patients. Beyond that, further research, using both histological and brain imaging study designs, is required to determine the pathophysiology of these complications.

References

Bridwell, R., Long, B., & Gottlieb, M. (2020). Neurologic complications of COVID-19. The American journal of emergency medicine, 38(7), 1549-e3.

Ciotti, M., Angeletti, S., Minieri, M., Giovannetti, M., Benvenuto, D., Pascarella, S., ... & Ciccozzi, M. (2019). COVID-19 outbreak: An overview. Chemotherapy, 64(5-6), 215-223.

Ellul, M. A., Benjamin, L., Singh, B., Lant, S., Michael, B. D., Easton, A., ... & Solomon, T. (2020). Neurological associations of COVID-19. The Lancet Neurology.

Liotta, E. M., Batra, A., Clark, J. R., Shlobin, N. A., Hoffman, S. C., Orban, Z. S., & Koralnik, I. J. (2020). Frequent neurologic manifestations and encephalopathy‐associated morbidity in Covid‐19 patients. Annals of clinical and translational neurology, 7(11), 2221-2230.

Zubair, A. S., McAlpine, L. S., Gardin, T., Farhadian, S., Kuruvilla, D. E., & Spudich, S. (2020). Neuropathogenesis and neurologic manifestations of the coronaviruses in the age of coronavirus disease 2019: a review. JAMA neurology, 77(8), 1018-1027.

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