COVID-19 and the nervous system: pathogenesis, mechanisms, and outcomes

In the acute period of COVID-19, more than 1/3 patients develop neurological symptoms, 25% of which can be attributed to direct damage to the central nervous system. Most often, all these complications arise due to the penetration of the virus into the systemic circulation, its dissemination and damage to the vascular endothelium. All clinical manifestations associated with the penetration of COVID-19 into the nervous tissue can be divided into several groups:1) signs of damage to the central nervous system, including headache, impaired consciousness, encephalitis, cerebrovascular diseases, seizures and ataxia; 2) signs of damage to the peripheral nervous system, such as anosmia/hyposmia, dysgeusia, visual disturbances, neuralgia and Guillain-Barre syndrome; and 3) signs of damage to the musculoskeletal system, such as myopathy, myalgia and fatigue.The aim of the review was to identify the main sources and mechanisms of nerve tissue damage in COVID-19 disease.Literature search was conducted in the Web of Science, PubMed and Scopus databases. The search was carried out by the following keywords: «COVID-19», «nerve tissue», «endothelial dysfunction», «oxidative stress», «neuroinflammation». The literature search yielded 329 results, of which 234 articles.As a result of the analysis of the articles, 2 main groups of studies were identified: descriptive and experimental. The pathogenesis of damage to the nervous system by the COVID-19 virus has two sources: by infecting nerve endings, such as olfactory sensory neurons, and retrograde penetration of the virus into the brain.