Possible mechanism of central nervous system targeting and neurological symptoms of the new-coronavirus (COVID-19): literature review.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that caused the 2019 Coronavirus Disease (COVID-19) has been associated with several neurological symptoms. This review aimed to highlight the possible mechanism of central nervous system (CNS) targeting and the neurological symptoms that may occur with the COVID-19 infection. The case reports containing the keywords "neurological symptoms" and "COVID-19" were thoroughly reviewed to identify possible mechanisms of CNS targeting and neurological manifestations associated with COVID-19 infection. The angiotensin-converting enzyme-2 (ACE2) receptors have been identified as the functional receptor for SARS-CoV-2. SARS-CoV-2 can affect the CNS through the following mechanisms: 1) Direct infection. 2) Blood pathway. 3) Neuronal pathway. 4) Immune-mediated injury/pathway (Cytokine Storm Syndrome). COVID-19 virus, a neurotropic virus, was isolated from the cerebral fluid (CSF) and responsible for several neurological manifestations. The COVID-19 infection primarily affects CD4+ and CD8+ T-lymphocytes and it induces a surge of inflammatory cytokines, known as Cytokine Storm Syndrome (CSS). The Interlukine-6 (IL-6) is the primary CSS component. The IL-6, interferon-γ and endothelial growth factor were significantly higher in COVID-19 infected compared to non-infected individuals. The improvement of the COVID-19 patients after interleukin receptor blockers supports the CSS theory. The spectrum of SARS-CoV-2 neurological manifestations includes encephalitis, viral meningitis, post-COVID-19 infectious acute disseminated encephalitis, Guillain-Barré Syndrome (GBS), Miller-Fisher syndrome (MFS) and acute cerebrovascular disease (CVD). Several COVID-19-associated neurological manifestations have been reported. Thus, it is important to identify and treat neurological symptoms as soon as possible to avoid long-term effects. The care providers should take the appropriate preventive precautions because patients can present with neurological manifestations of COVID-19 without any respiratory symptoms. Future research is warranted to confirm the relationship between SARS-CoV-2 and the development of neurological manifestations.