Neuro-COVID-19: An insidious virus in action

Abstract

Introduction. The punishing effect of the pandemic outbreak of the disease termed COVID-19 (coronavirus disease-19) caused by severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) impelled the author to gather the facts about the nature of this new pathogen. The aim of this paper was to discuss the mechanisms involved in the pathogenesis of neurological complications during the course of COVID-19. State of the art. Neurological symptoms, such as impairment of taste or smell, headache, nausea and/or altered consciousness, are commonly described in COVID-19 patients, although there are emerging clinical reports of more serious conditions such as acute cerebrovascular accidents, encephalitis and demyelinating disease. Whether these manifestations are the direct consequence of viral invasion of the central nervous system, or are caused by indirect mechanisms, is yet to be established. Studies to date have indicated that neurological lesions found in the brains of COVID-19 patients are a combination of direct cytopathic effects caused by SARS-CoV-2 replication and indirect effects due to hypoxia, excessive cytokine reaction, impaired immune response, and cerebrovascular injury induced by viral infection. Studies are still pending into possible routes of SARS-CoV-2 neuroinvasion encompassing the haematopoietic pathway via the blood-brain barrier and retrograde axonal transport through the cranial nerves. Clinical implications. A thorough understanding of SARS-CoV-2 involvement in neurological complications is still lacking. However, our knowledge about SARS-CoV-2 virulence is rapidly expanding, and that has inclined the author to prepare this comprehensive review in the hope that it will improve understanding about the molecular mechanisms underlying neurological abnormalities associated with COVID-19. Future directions. A future detailed study should explore the diagnostics and disease mechanisms so as to enable the development of better therapeutic strategies to reduce the severity of COVID-19 neurological complications.