Discussion
As scientists and clinicians concentrate on the complexities of the SARS-CoV-2 virus and better treatment strategies for COVID-19, it is possible that neurological manifestations of COVID-19 are being overlooked or misinterpreted [117]. In general, neurological symptoms can be under-diagnosed or even entirely overlooked as neurological manifestations, such as delirium in the critically ill COVID-19 patients or infected outpatients who do not consider a loss of the sense of smell or taste related to COVID-19. As such, clinicians on the front lines of COVID-19 care should be cognizant of possible neurological manifestations of this novel virus. Patients with suspected or diagnosed COVID-19 should be asked about the loss of smell and taste and educated that this is an important symptom to bring to the attention of the provider.
Neurological symptoms of COVID-19 have to date mainly be described within the trajectory of the infection. However, it is plausible (although far from established) that neurological sequelae from COVID-19 may emerge after the patient has recovered from the primary infection and persist for long periods after recovery. For example, it is not known if an elderly patient who recovers from a severe case of COVID-19 with cognitive dysfunction will suffer persistent cognitive deficits. The long-term burden on both caregivers and the healthcare system that might be posed by COVID-19 survivors with neurological or cognitive impairment may turn out to be very important, although it is one that is rarely discussed, even hypothetically [123,124].
There is evidence of neurological complications with SARS and MERS, and a growing body of evidence for neurological complications with COVID-19. The etiology of these neurological symptoms is less clear; they may be directly caused by the viral infection or they could be due to other conditions, such as sepsis, coagulation disorders, cytokine release, and vasculitis, all of which have been reported in COVID-19 patients. Much more needs to be learned, but clinicians must be aware and prepared for the possibility and potentiality of COVID-19 neurological symptoms.
The evidence that the SARS-CoV-2 can enter the CNS is alarming. While autopsy studies show definitive proof that the earlier SARS-CoV was found in brain tissue, viral levels were lower in the brain than in the lungs [125]. The route by which the SARS-CoV-2 virus enters the CNS and its effects on the CNS remain to be elucidated.
It is important to learn more about chronic neurological complications related to COVID-019. The blood-brain barrier, which may protect patients from invading pathogens, is a two-way street and could in theory at least prevent viruses from being expelled from the brain [50]. Further study is needed, particularly as the population of COVID-recovered patients grows and may have to manage long-term consequences of the infection.